1990 YJ 2.5l, my manual says starting input voltage is 5 volts. Mine is 5.13 volts. Out put is suppose to be 4.7 volts. Is 5.23 volts ok. I have changed 3 sensors and still have hesitation at different RPMs with each different sensor?
TPS setting
- Thread starter Eric Haberli
- Start date
Redux 2: TBI pains. French PCM madness.
first off this TBI , set ups are a huge pain, unlike 1991+ zero TPS calibrations and no HUGE ISA(IAC) there and the pain of that too.
91 ended RENIX (made in France) top new SBEC PCM,. (hugely better)
not only that but the FSM calls out a special tool to setup this crazy ISA motor drive setup.
not clear at all is , what part of TPS calibration is the most important , as most cars made with TBI idle is critical.
but wait this car has 2 switches here, WOT and idle,. and both must work and not be dead or set wrong.
My best guess (gee ,im no Jeep TBI programming expert) <<how it really works IDK.
The idle switch is inside the ISA, and this is covered in the free FSM , chapter 14.
chapter 14 covers, wot and idle switches , tests and adjustments. (i bet this is really the first step not TPS calib )
TPS is set, key on, engine off ,
only the TPS output pin is set.pin A.
the procedure can surely fail if the ISA is bad. (idle motor failing in lots of ways it can)
the TPS is set at 17 and 93% 17 is idle and 93 is wot.
but the ISN gets in the way of the TV, keyon, not running, so my guess is, the 93% setting is the critical TPS calibration step.
Again the power pin is not 5vdc, no, it is 4.5 to 5.5Vdc, each PCM sold is in that range it is NOT A PRECISION power supply it is +/- 10% spec.
so we measure that first to compute outcome set TPS calibration, (adjustment/alignment) what ever you want to call it ,IDC
do not use body,battery or engine ground to the meter, only use PIN B for ground or it all fails.
the word INPUT below means the Power pin C,below. one can say Input power pin to be clear.
Now my idea simple
just do the WOT calibration
1: input say is 5.0vdc (it wont be) measure pin C to B (this is a DMM test, using needle probes)
2: .93 % times 5.0vdc = 4.65vdc (computed by you only, , math C TO B times 0.93 = 4.65vdd
3: move TV (throttle valve) by hand to max WOT, and turn TPS to , 4.65vdc at pin A to B.
4: tighen TPS torx T20 screws gently, a done deal; in 4 steps. (by me) call it a day.
FSM actual
SEE IF LIKE THIS,
idle TPS voltage keyon (metered), engine off is not predictable. ISA is crazy device, if you read all about it in the FSM
and easy to break too, see all warnings on it , in chapter 14.
I know why it is so, it is because at key on, it uses stored data to predict, start up air even down to -40F degrees air temps.
it has huge table in ROM. inside the PCM to do that, even my 95 does. as do all cars made EFI (gas)
it open the throttle ,key, to allow a clean fast easy startup at any ambient temp,even in ALASKE or top of Pikes Peak.
reading the wrong books you did, the OEM books is , free.
the real book told you unlike lame ChILL-TONS(sic) told you
the PCM 5vdc pin is not 5vdc, it is 4.5 to 5.5Vdc. this is in the FSM preamble, chapter 14. that CHILL_TONS forgot to keep. (lost it)
never use chiltons to calibrate ANYTHING.
the make great books if reading how now to get injured, this is true, so has some value there.
like dont drink fuel
do not eat a running fan blade.
depressurize the fuel loop first. not spray eyes with fuel, cracking open fuel lines and no eye protection
and more. (never get under any car lacking real jackstands, ever. using only 1 china made jack, omg
good luck and do ask questions for sure how to test parts.
and for sure EFI just hates RUSTY corroded or loose wires and pins,/sockets.
the CEL lamp must go out running,, does it.?
first off this TBI , set ups are a huge pain, unlike 1991+ zero TPS calibrations and no HUGE ISA(IAC) there and the pain of that too.
91 ended RENIX (made in France) top new SBEC PCM,. (hugely better)
not only that but the FSM calls out a special tool to setup this crazy ISA motor drive setup.
not clear at all is , what part of TPS calibration is the most important , as most cars made with TBI idle is critical.
but wait this car has 2 switches here, WOT and idle,. and both must work and not be dead or set wrong.
My best guess (gee ,im no Jeep TBI programming expert) <<how it really works IDK.
The idle switch is inside the ISA, and this is covered in the free FSM , chapter 14.
chapter 14 covers, wot and idle switches , tests and adjustments. (i bet this is really the first step not TPS calib )
TPS is set, key on, engine off ,
only the TPS output pin is set.pin A.
the procedure can surely fail if the ISA is bad. (idle motor failing in lots of ways it can)
the TPS is set at 17 and 93% 17 is idle and 93 is wot.
but the ISN gets in the way of the TV, keyon, not running, so my guess is, the 93% setting is the critical TPS calibration step.
Again the power pin is not 5vdc, no, it is 4.5 to 5.5Vdc, each PCM sold is in that range it is NOT A PRECISION power supply it is +/- 10% spec.
so we measure that first to compute outcome set TPS calibration, (adjustment/alignment) what ever you want to call it ,IDC
do not use body,battery or engine ground to the meter, only use PIN B for ground or it all fails.
the word INPUT below means the Power pin C,below. one can say Input power pin to be clear.
Now my idea simple
just do the WOT calibration
1: input say is 5.0vdc (it wont be) measure pin C to B (this is a DMM test, using needle probes)
2: .93 % times 5.0vdc = 4.65vdc (computed by you only, , math C TO B times 0.93 = 4.65vdd
3: move TV (throttle valve) by hand to max WOT, and turn TPS to , 4.65vdc at pin A to B.
4: tighen TPS torx T20 screws gently, a done deal; in 4 steps. (by me) call it a day.
FSM actual
SEE IF LIKE THIS,
idle TPS voltage keyon (metered), engine off is not predictable. ISA is crazy device, if you read all about it in the FSM
and easy to break too, see all warnings on it , in chapter 14.
I know why it is so, it is because at key on, it uses stored data to predict, start up air even down to -40F degrees air temps.
it has huge table in ROM. inside the PCM to do that, even my 95 does. as do all cars made EFI (gas)
it open the throttle ,key, to allow a clean fast easy startup at any ambient temp,even in ALASKE or top of Pikes Peak.
reading the wrong books you did, the OEM books is , free.
the real book told you unlike lame ChILL-TONS(sic) told you
the PCM 5vdc pin is not 5vdc, it is 4.5 to 5.5Vdc. this is in the FSM preamble, chapter 14. that CHILL_TONS forgot to keep. (lost it)
never use chiltons to calibrate ANYTHING.
the make great books if reading how now to get injured, this is true, so has some value there.
like dont drink fuel
do not eat a running fan blade.
depressurize the fuel loop first. not spray eyes with fuel, cracking open fuel lines and no eye protection
and more. (never get under any car lacking real jackstands, ever. using only 1 china made jack, omg
good luck and do ask questions for sure how to test parts.
and for sure EFI just hates RUSTY corroded or loose wires and pins,/sockets.
the CEL lamp must go out running,, does it.?
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if it TPS was set correctly
then there are other problems. I can not drive the car to see EXACTLY what you are doing at the Hesitation.
all I have are questions, for that. lack of information
nor how long it hesitated, max would be about 1 to 3 seconds, then the MAP sensor wakes up and full power is on tap (right foot)
I presume all hesitations happy moving the right foot, never just cruising steady and right foot steady. is this CORRECT>
please elaborate the good ,bad or ugly as i call it, all that matters driving all actions driving.
then there are other problems. I can not drive the car to see EXACTLY what you are doing at the Hesitation.
all I have are questions, for that. lack of information
nor how long it hesitated, max would be about 1 to 3 seconds, then the MAP sensor wakes up and full power is on tap (right foot)
I presume all hesitations happy moving the right foot, never just cruising steady and right foot steady. is this CORRECT>
please elaborate the good ,bad or ugly as i call it, all that matters driving all actions driving.
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HI Doef, Thanks for all of this information. Unfortunately This is a 1990 YJ with a 2.5L with a single fuel injector mounted in the throttle body. This YJ only has 118,000 miles on it. Being 33 years old I immediately did a major tune up on the engine and replaced all sensors, ignition system, hoses, alternator, water pump and fuel pump with filter.
MY fuel pressure for this unit is 14 PSI. and it doesn't have an engine check light so there is no codes.
I have just changed TPS for the 4 th time this time using a NTK unit and There is a noticeable difference. Now that I have said all this, I was asking if input voltage 5.13 volts was ok? the book says 5 volts. with WOT at 4.6-7 Volts. I have set the TPS 2 ways one is 5.13 X .17 which out put at closed throttle is O.8721. I have also set the TPS at 4.7 volts at WOT. There is no applicable difference in performance other than the hesitation moved from 1600 -1700 RPM to 2300-2400 RPM? Its funny you mentioned, running lean. my MPG has been 14.7. sense playing with TPS the milage is now 16.24 MPH. I did a plug check and I have nice tan burn.
I'm thinking it s the computer !!!!. The engine runs great very smooth with adequate power for a 4 banger.
MY fuel pressure for this unit is 14 PSI. and it doesn't have an engine check light so there is no codes.
I have just changed TPS for the 4 th time this time using a NTK unit and There is a noticeable difference. Now that I have said all this, I was asking if input voltage 5.13 volts was ok? the book says 5 volts. with WOT at 4.6-7 Volts. I have set the TPS 2 ways one is 5.13 X .17 which out put at closed throttle is O.8721. I have also set the TPS at 4.7 volts at WOT. There is no applicable difference in performance other than the hesitation moved from 1600 -1700 RPM to 2300-2400 RPM? Its funny you mentioned, running lean. my MPG has been 14.7. sense playing with TPS the milage is now 16.24 MPH. I did a plug check and I have nice tan burn.
I'm thinking it s the computer !!!!. The engine runs great very smooth with adequate power for a 4 banger.
A=TPS output , aka , throttle angle today. 1V AT IDLE, AND 4V OUT AT WOT (APPROX)<< BUT WE CALIBRATE IT.
B= special PCM ground. (most PCM monitor its own ground here to correct for measured ground errors, (callED kelvin measurements)
C= PCM SPECial, 5vdc, refr. supply to TPS and MAp 4.5V TO 5.5VDC IS Spec, varies by each new PCM Installed, called POWER and does not change.
B= special PCM ground. (most PCM monitor its own ground here to correct for measured ground errors, (callED kelvin measurements)
C= PCM SPECial, 5vdc, refr. supply to TPS and MAp 4.5V TO 5.5VDC IS Spec, varies by each new PCM Installed, called POWER and does not change.
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this TPS must be installed such that there is NO play in the TPS gold level seen here.
not just thrown on, it must be indexed properly. as most cars made same thing. (before TBW throttle -by-wire)
it is not easy to say howto in words.
but the video can help, but turn on, SUBS?CC to understand accent huge here. in YTube settings.
see video turn on CC SUbs.
not just thrown on, it must be indexed properly. as most cars made same thing. (before TBW throttle -by-wire)
it is not easy to say howto in words.
but the video can help, but turn on, SUBS?CC to understand accent huge here. in YTube settings.
see video turn on CC SUbs.
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Dorf: a couple of things come into play.
1. Throttle body has been rebuilt with new regulator and pressure set to 14 psi.
2 I have been going to Battery ground instead of terminal B???
3 This throttle body has an ISA which does not let me put the throttle on the ideal stop.
4. We don't have many hills here in FL but we do have bridges, I have no problem going over a bridge in 5th gear.
I will try and set the differential as you have laid out in this thread. should I back off the ISA to achieve closed throttle?
Yes I'm using a Chilton manual 40650.
1. Throttle body has been rebuilt with new regulator and pressure set to 14 psi.
2 I have been going to Battery ground instead of terminal B???
3 This throttle body has an ISA which does not let me put the throttle on the ideal stop.
4. We don't have many hills here in FL but we do have bridges, I have no problem going over a bridge in 5th gear.
I will try and set the differential as you have laid out in this thread. should I back off the ISA to achieve closed throttle?
Yes I'm using a Chilton manual 40650.
i have the 1990 book OEM ,jeep, FSM
i will now send them to you in chapter 14.
for sure this new passage, preamble page 48
14-22 to 14-63 Throttle body injection pages, TBI, YJ chapters.
HERE IT IS, CHAPTER 14, TBI SECTION. COVERS IT ALL
42 PAGE,EXTRACTED FOR YOU, 2MB SIZE, SMALL.
TBI only .
14-62 is tps calibration, there is TPS flow chart page 47 to test the TSP fully,
i will now send them to you in chapter 14.
for sure this new passage, preamble page 48
14-22 to 14-63 Throttle body injection pages, TBI, YJ chapters.
HERE IT IS, CHAPTER 14, TBI SECTION. COVERS IT ALL
42 PAGE,EXTRACTED FOR YOU, 2MB SIZE, SMALL.
TBI only .
14-62 is tps calibration, there is TPS flow chart page 47 to test the TSP fully,
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Dorf: where can I purchase the OEM FSM?
I'm very confident the ISA is set up correctly. It does what the manual says it to do. I can reach 4,000RPM in 1,2,3, gears easily.
Attached are photo's of the TB. Also not I got rid of that crappy plastic valve cover. Thats a 1994 aluminum I picked up at a junkyard for $20.
I'm very confident the ISA is set up correctly. It does what the manual says it to do. I can reach 4,000RPM in 1,2,3, gears easily.
Attached are photo's of the TB. Also not I got rid of that crappy plastic valve cover. Thats a 1994 aluminum I picked up at a junkyard for $20.
well steady right foot has zero to do with TPS and zero to do with ISA, (if not bad ISA and it is trying to move the throttle as you drive fast, OUCH !)
it is not tip in hesitation (tps dead) (aka, just off idle hesitation)
it is not fast right foot, cruising fast, and the you moving right foot for more speed, hesitation. ( TPS does this for seconds only,, fast enrich mode)
so is is lean burn cruise failure. only. right foot at 1400 3rd gear. (injection rate is dead wrong) try unplugging O2 sensor yet and drive.
so that begs the question , you did not answer my WOT questions, on power to the road, in all gears 1 to 4.
my guess now, is simple lean out. (dynamic on the fly driving fast lean out)
running lean
I have remote fuel pressure gauges in my shop to find , this. Like i said a weak fuel pump or wires to it rusty ,
the TBI has test port for pressure, 14-15psi calibrate what if 14psi is 10 moving fast.
if not 14, moving fast that means the FPR lost control due to a weak fuel pump.
filter is new so not that.
weak pumps happen many times for sure this old car, is bad wiring to the pump (rusty) harness pins, all. or the ground to the pump bad.
11vdc minimum to actual pump is my low spec I ALLOW.
11vdc is cranking voltage. so I expect at least that.
most cars are near 14vdc running so pump sees 13vdc then at pump. (cheap wires on cars love to drop 1volt to pump but is ok)
I have remote reading, DMM to find things that fail like this. (DC power failures)
a new pump does not cure bad wiring ever.
the old PCMs like this were horrible with 02 controls. (had too much .)
classic failures were back then, were this.
exhaust leak any where near that 02 sensor, sucks in 20 % oxygen from earths atmosphere, called air.
20% air landed there, causes 02 to real hard lean. to 0vdc output
and EFI goes hard hard lean.
cranked, exh manifold
missing or bad exh. header donut ring gasket sucking air.
cracked header pipe cat, there must be no cracks there.
also if vacuum gauge bounces at idle. that can be sticking intake valve and misfiring, (I cant hear your engine)_
and each misfire this gross sends a slug of air to the exhaust.
or a burned up head valve.
folks forget how exhaust works
here it is. the Exh pressure wave
see B? that is vacuum in the pipe, real., and if cracked, it does SUCK air. and fails hard.
one way to find leaks
is rubber hose to your ear
and moved end of hose, over all exhaust parts up to the cat, head to cat, for PUTT PUTT sound in the hose to ear, bingo leaking
now lets talk limp home. mode
if the say map goes dead, the PCM fails for dead map and sets DTC error (2digits) 13 or 14 DTC
but the engine doesnt die lacking all MAP data. gone. ( a win) kinda.
no.
it goes to limphome and uses the TPS as crude MAP sensor now dead, it simply simulates a dead map sensors.
so the real cause is not scanning the PCM for DTC errors first. (if true) the CEL must not glow running, same then ,same now 2023.
key on, does the CEL lamp glow as it must for the CEL lamp self test
then goes out running?????????
the check engine lamp. what does it do now
the 90' manual for RENIX PCM shows only DRB-II, scan tools work to read DTC errors. (my old sold 88 same sad story)
1991 up the key on 3 times sets blink codes, for DTC errors. not 90 or older.( french PCM's)
"1991 - Chrysler Corporation (then the owners of the Jeep brand replaced the Renix control system with OBD-I-compliant control electronics, the Chrysler HO EFI. big change in 1991." yours is less smart.
there are 3 oem manuals and 3kinds (full FSM, EFI book and diagnostic book) and 3 forms of books.
on CD + pdf (ebay endless) the RED book is OEM, do not get less.
free, google finds them ever time, PDF
real paper books, seen used on ebay, endless.<< click me
and chilton/haynes junk, I call a door stop. a toxic mix of 10 years of cars, not one good for 1 car. ever. (but great books on how not to get hurt ,etc)
the oem book is 2200 pages long
if the say map goes dead, the PCM fails for dead map and sets DTC error (2digits) 13 or 14 DTC
but the engine doesnt die lacking all MAP data. gone. ( a win) kinda.
no.
it goes to limphome and uses the TPS as crude MAP sensor now dead, it simply simulates a dead map sensors.
so the real cause is not scanning the PCM for DTC errors first. (if true) the CEL must not glow running, same then ,same now 2023.
key on, does the CEL lamp glow as it must for the CEL lamp self test
then goes out running?????????
the check engine lamp. what does it do now
the 90' manual for RENIX PCM shows only DRB-II, scan tools work to read DTC errors. (my old sold 88 same sad story)
1991 up the key on 3 times sets blink codes, for DTC errors. not 90 or older.( french PCM's)
"1991 - Chrysler Corporation (then the owners of the Jeep brand replaced the Renix control system with OBD-I-compliant control electronics, the Chrysler HO EFI. big change in 1991." yours is less smart.
there are 3 oem manuals and 3kinds (full FSM, EFI book and diagnostic book) and 3 forms of books.
on CD + pdf (ebay endless) the RED book is OEM, do not get less.
free, google finds them ever time, PDF
real paper books, seen used on ebay, endless.<< click me
and chilton/haynes junk, I call a door stop. a toxic mix of 10 years of cars, not one good for 1 car. ever. (but great books on how not to get hurt ,etc)
the oem book is 2200 pages long
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does the CEL glow key on, and go out running
how long is that 3gear Hesitation. endless or 1 to 3 seconds and full engine power then resumes, please elaborate this.
"Hesitation is steady right foot at about 1,400 RPM in 3rd gear. this the best it has been."
how long is that 3gear Hesitation. endless or 1 to 3 seconds and full engine power then resumes, please elaborate this.
"Hesitation is steady right foot at about 1,400 RPM in 3rd gear. this the best it has been."
Check engine lamp , glows, key on and goes out running? both>?
the voltage you read is 100% spec,. end story that;.
changed what sensors,?????
the O2 fails or O2 replaced 10 times and exhaust cracks near by make them all fail, (oldest EFI story on earth )
tell parts replaced all is best,a list..
some parts on cars cannot just be thrown on. but most are PNP
Hi Dorf, the 1990 YJ doesn't have CE light.
I think I now I can move on from the TPS and the idle speed actuator (ISA).
When I started working on this project 2 years ago, I did a major tune up on the engine because it sat in a car port for 7 years. I bought it from the original owner.
Changing all the sensors I thought I had covered all the testing and set up. What I didn't do was look into the ISA and the TPS and how they have to work together.
Today I went back to the ISA to make double share it was set up as designed. When it was disconnected the ISA took the RPM to 3500 RPM, and the plunger went to full extension, I then connected the reconnected the ISA and with the engine running the plunger retracted all the way in so that checked out. To make sure the throttle was completely closed I I then remove the ISA from the bracket.
Now I could check the TPS voltages. Input was 5.12V out put was 2.2V which didn't make any sense but never have removed the ISA I'm sure the reading was the problem. Acording the information that I could find, in a perfect world with 5V into terminal C the perfect reading coming out of terminal A should be 0.930. What I did is take the 5.12V input reading and mulitplied by .17 which gave me 0.8704. I set the TPS at close throttle at O.8704. I then put it all back together. All systems seem to come in, Idle was at 810 RPM and great throttle response for a four cylinder. As you mentioned then 1990 2.5 L YJ is a bit of a Rube Goldberg.
I ordered a new Mopar 1990 service manual RED cover from BJ's Full size Jeep Parts. I'm retiring the Chilton!
I think I now I can move on from the TPS and the idle speed actuator (ISA).
When I started working on this project 2 years ago, I did a major tune up on the engine because it sat in a car port for 7 years. I bought it from the original owner.
Changing all the sensors I thought I had covered all the testing and set up. What I didn't do was look into the ISA and the TPS and how they have to work together.
Today I went back to the ISA to make double share it was set up as designed. When it was disconnected the ISA took the RPM to 3500 RPM, and the plunger went to full extension, I then connected the reconnected the ISA and with the engine running the plunger retracted all the way in so that checked out. To make sure the throttle was completely closed I I then remove the ISA from the bracket.
Now I could check the TPS voltages. Input was 5.12V out put was 2.2V which didn't make any sense but never have removed the ISA I'm sure the reading was the problem. Acording the information that I could find, in a perfect world with 5V into terminal C the perfect reading coming out of terminal A should be 0.930. What I did is take the 5.12V input reading and mulitplied by .17 which gave me 0.8704. I set the TPS at close throttle at O.8704. I then put it all back together. All systems seem to come in, Idle was at 810 RPM and great throttle response for a four cylinder. As you mentioned then 1990 2.5 L YJ is a bit of a Rube Goldberg.
I ordered a new Mopar 1990 service manual RED cover from BJ's Full size Jeep Parts. I'm retiring the Chilton!
watch out for the warnings on ISA, when remove (ISA and unplugged IAC) the ISA it says has no spring inside it, and confuses folks
And to never force extened the plunger, key off and disconnected due to it not having limits stops and the end of travel and forcing it wrecks it.
one fussy best that ISA> no wonder they dumped it. for MPI. fast.
as you can see now the ISA the way it works keyon, , the TPS cannot be calibrated for idle position, due to that varies keyon,. so it is only done at
TPS WOT out is 93% of what B>C reads.
most TBI cars on earth TPS set at idle ,but not the bugger.
the lie in chiltons is there is no 5vdc on all TBI, only 1 in 10 cars will it be at 5v, 4.5 to 5.5v all cars. (this model) ( 0.1v resolution)
sure we can use 5.0v as and example sure. and i did below.
chiltons. defeats the end results to dead wrong, due to their error.
they forgot to read the FSM FUELing chapter preamble, it states that clearly. (same power source to MAP too.) <<< yes easy to miss, sure.
the output test is done only WOT< so 2.5v is wrong. key on,. only and not running.
correct is (5.v ) input , wot output is 4.65 (93%) times 5 is that.
the trick is yes strange. due to TPS calibrated at WOT. only, KOEO.
the other 2 possible problems are
1: the wot switch dead.
2 the ISA idle switch failing. inis
yes, keep in mind key on engine off (KOEO) the PCM sends data (motor control) to the ISA, to intelligently set cranking up idle air supplies, for the start.
that is why calibration can not be done using idle. (it is always in-determinant) so is done Chilton step 7 above (dont skip comment there)
the air it send even varies greatly for cold starts. or super cold start ups, using ECT data. TEMPs
or hot starts,small air sent. greatly less hot is the key word.
And to never force extened the plunger, key off and disconnected due to it not having limits stops and the end of travel and forcing it wrecks it.
one fussy best that ISA> no wonder they dumped it. for MPI. fast.
as you can see now the ISA the way it works keyon, , the TPS cannot be calibrated for idle position, due to that varies keyon,. so it is only done at
TPS WOT out is 93% of what B>C reads.
most TBI cars on earth TPS set at idle ,but not the bugger.
the lie in chiltons is there is no 5vdc on all TBI, only 1 in 10 cars will it be at 5v, 4.5 to 5.5v all cars. (this model) ( 0.1v resolution)
sure we can use 5.0v as and example sure. and i did below.
chiltons. defeats the end results to dead wrong, due to their error.
they forgot to read the FSM FUELing chapter preamble, it states that clearly. (same power source to MAP too.) <<< yes easy to miss, sure.
the output test is done only WOT< so 2.5v is wrong. key on,. only and not running.
correct is (5.v ) input , wot output is 4.65 (93%) times 5 is that.
the trick is yes strange. due to TPS calibrated at WOT. only, KOEO.
the other 2 possible problems are
1: the wot switch dead.
2 the ISA idle switch failing. inis
yes, keep in mind key on engine off (KOEO) the PCM sends data (motor control) to the ISA, to intelligently set cranking up idle air supplies, for the start.
that is why calibration can not be done using idle. (it is always in-determinant) so is done Chilton step 7 above (dont skip comment there)
the air it send even varies greatly for cold starts. or super cold start ups, using ECT data. TEMPs
or hot starts,small air sent. greatly less hot is the key word.
I investigated the possibility of switching to 1991 MPI system. It 's a hell of a lot of work. Maybe if I ever have to do a complete engine overhaul someday. If I would use a 91 MPI the head from the 90 will work. Starting in 92 you need a different head also.
We'll, I noticed something interesting today! While driving the YJ and the hesitation was happing as normal, I noticed the Amp meter was dipping in conjunction with the tachometer dipping! After all this pain chasing this gremlin could it be as simple as the Key switch. There seems to be a electrical connection. I have chased this and it all points to the ignition switch.
use a DMM, and measure voltage see of Alternator is acting up. (oddly) 13 to 15vdc is normal running.
the cluster gauges, act up?
Gauges fuses loose or rusty pins.(named IGN LPS >fuse) also run TACHOMeter power. and says Gauge package power. Fuse Keyswitch power IGN RUN. yellow wire. runs IGN module and 02 heater power.(that love to short) this Y , wire run the Alternator regulator sense pin and if not stable so be REG not stable.
the bank of gauges, right is Voltmeter not AMPS, VM connect to IGN power feed.
or is dash modified?
this series 81 jeep (fsm name) has no cruise control option , right? if yes defeat it at its, flex cable to TB.
if battery voltage is good (in range) and IGN is not, the wiring or IGN switch is bad. or some device on IGN is over-loading IGN power feed.
1990/2.5L
uses a real voltmeter in you DMM and monitor the yellow wire. at the fuse box or using fuse extender, at IGN+LPS fuse slot, left dash box.
below 13vdc running is not good.
page 8 FSM your ALT, at battery lugs.
the cluster gauges, act up?
Gauges fuses loose or rusty pins.(named IGN LPS >fuse) also run TACHOMeter power. and says Gauge package power. Fuse Keyswitch power IGN RUN. yellow wire. runs IGN module and 02 heater power.(that love to short) this Y , wire run the Alternator regulator sense pin and if not stable so be REG not stable.
the bank of gauges, right is Voltmeter not AMPS, VM connect to IGN power feed.
or is dash modified?
this series 81 jeep (fsm name) has no cruise control option , right? if yes defeat it at its, flex cable to TB.
if battery voltage is good (in range) and IGN is not, the wiring or IGN switch is bad. or some device on IGN is over-loading IGN power feed.
1990/2.5L
uses a real voltmeter in you DMM and monitor the yellow wire. at the fuse box or using fuse extender, at IGN+LPS fuse slot, left dash box.
below 13vdc running is not good.