I have 88 wrangler with a 4.2 and 5 speed. Basically the jeep runs and drives perfect when cold and at operating temp. But after maybe a few minutes once it’ll get going the car starts slowing itself down, kinda like if it was engine braking hard. I have to give it a lot more throttle to even get it moving from a stop. In-between shifts it’ll slow itself down and lose speed and rpms. It won’t make it past third gear and with any amount of throttle rpm’s won’t go up in third. Now the part that’s really confusing me is if I pull over for maybe a minute or two after this happens it’ll start driving even better than before. Shifts feel smoother, pedal response feels better, rpm to mph is better. It does not overheat at all. I’m leaning towards something with the breaks? The PO change out the MC and did mostly the entire brake system. Any one can help me diagnose this or maybe give me some ideas on what it might be. Please and thank you!
Jeep runs perfect, but only when cold
- Thread starter SwazyCakes
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Sounds to me like it may be the choke. Does it by chance have an electric choke? It may just need to be adjusted a little.
Lets say it goes into dying mode. If you can pull over immediately, have it out of gear, P brake off can you push it or if you are on the slightest grade will it freely roll? Point being brakes dragging. Far as choke being stuck on does it blubber black smoke or run horribly? does it idle ok when you pull over, if you hit the gas does it rev cleanly and crisply?
if the 4 wheels are jacked up and the tire/rims spin easy by hand then they are not brakes stuck on.
mine came with both rear parking brake cables rust seized. and stuck engaged ! and dranging
so is the 2v carb still here,???? the horror of electronic controlled carbs?
many were modified, so we look or hacks there first. on all carbs this year. 87 too.
THE CARB IS complex
here is the 88 full carb controller schematic. called the BBD 2v carb.,page B-217 in the FSM manual factory service manual.
258cu-in, or 4.23Liters I-6 engines, the vin codes tell you what was there day 1 new. carb code 8384 (manual trans version)
page B218 shows all settings for the carb, for sure choke setting and be sure it released when engine is hot (180f = hot/normal)
coke 1 notch notch rich it states./
seem to me as the engine warms up to normal and the chock turns off, the carb goes lean and all real power (HP) is not on tap (right foot)
just a guess but IDK blind.
The MMC controls all fuel mix when engine is hot (means normal) it does that by modulations of the metering solenoids on side of carb.
and 1 O2 sensor
the carb this old may be just gummed up inside as they all loved to do 1920 to mid 80s when TBI came to play (EPA mandates)
the carbs then were fully dismantled and cleaned, all fuel paths and air. and jets. (all clean as a whistle)
complex carbs these are, nothing like dad had, in the 70s. or older
most jeeps this old are now modified. just to make it run.
if you take it to a shop and the see the MCU metering carb they RUN for the hills (and justified)
but I can't see under your hood for MODS and hacks or such , not me, all I can do is guess it is still stock and what we see below.
this is out of the Free FSM. 88 YJ,
Many of this electric carbs are now modified, and the 1st clue is the missing marked below metering devices.. wires cut to them a huge clue.
Some of this used vacuum metering device photo 2, that love to gum up.
as you can see last photo is the BBD 1987/89 fuel mixture control stepper motor, device, this is how the MMC controls mixture all the time.
most times we see it missing or wires cut to it and vast posts in calif failing dead hard for this device missing or hacked and failing smob for just the visual inspections in CALIF (< posted as a worst case to learn the ropes here)
mine came with both rear parking brake cables rust seized. and stuck engaged ! and dranging
so is the 2v carb still here,???? the horror of electronic controlled carbs?
many were modified, so we look or hacks there first. on all carbs this year. 87 too.
THE CARB IS complex
here is the 88 full carb controller schematic. called the BBD 2v carb.,page B-217 in the FSM manual factory service manual.
258cu-in, or 4.23Liters I-6 engines, the vin codes tell you what was there day 1 new. carb code 8384 (manual trans version)
page B218 shows all settings for the carb, for sure choke setting and be sure it released when engine is hot (180f = hot/normal)
coke 1 notch notch rich it states./
seem to me as the engine warms up to normal and the chock turns off, the carb goes lean and all real power (HP) is not on tap (right foot)
just a guess but IDK blind.
The MMC controls all fuel mix when engine is hot (means normal) it does that by modulations of the metering solenoids on side of carb.
and 1 O2 sensor
the carb this old may be just gummed up inside as they all loved to do 1920 to mid 80s when TBI came to play (EPA mandates)
the carbs then were fully dismantled and cleaned, all fuel paths and air. and jets. (all clean as a whistle)
complex carbs these are, nothing like dad had, in the 70s. or older
most jeeps this old are now modified. just to make it run.
if you take it to a shop and the see the MCU metering carb they RUN for the hills (and justified)
but I can't see under your hood for MODS and hacks or such , not me, all I can do is guess it is still stock and what we see below.
this is out of the Free FSM. 88 YJ,
Many of this electric carbs are now modified, and the 1st clue is the missing marked below metering devices.. wires cut to them a huge clue.
Some of this used vacuum metering device photo 2, that love to gum up.
as you can see last photo is the BBD 1987/89 fuel mixture control stepper motor, device, this is how the MMC controls mixture all the time.
most times we see it missing or wires cut to it and vast posts in calif failing dead hard for this device missing or hacked and failing smob for just the visual inspections in CALIF (< posted as a worst case to learn the ropes here)
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is hot idle 800 RPM or random or too low. or as the HOOD EPA sticker shows for hot idle.
as you drive and you shift to neutral ,does car now coast easy (normal) ? flat ground???
if not brakes drag or as we say worse (axle bearings shot) or parking brake seized up like mine were (day1 owned ,last summer)
Ive never seen any 30 year old carb , that works right, (I never cured) they do not exist. and parts for them are crazy rare so enforces bad.
my guess no BRAKE issues, do not break the Brakes.
my guess is carb failing.! (lean out caused)
top cause is metering needles jammed on BBD carb (if still has it)
why not post a photo of the carb so we can see the all so common hacks there.
a photos can be worth 1000 words, try it?
I think the next year had the electric metering system. no 87 but , gee car mfg. plants change what it there in July each year. so vin plate covers that.
as you drive and you shift to neutral ,does car now coast easy (normal) ? flat ground???
if not brakes drag or as we say worse (axle bearings shot) or parking brake seized up like mine were (day1 owned ,last summer)
Ive never seen any 30 year old carb , that works right, (I never cured) they do not exist. and parts for them are crazy rare so enforces bad.
my guess no BRAKE issues, do not break the Brakes.
my guess is carb failing.! (lean out caused)
top cause is metering needles jammed on BBD carb (if still has it)
why not post a photo of the carb so we can see the all so common hacks there.
a photos can be worth 1000 words, try it?
I think the next year had the electric metering system. no 87 but , gee car mfg. plants change what it there in July each year. so vin plate covers that.
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the needles fail easy
the vacuum is a fixed amount at a give demand by your right foot (plenum vac)
the needles gum up and the vacuum is hopeless to pull against the gum.
just like those old nasty Rochester quadra-jet carbs (4barrels) did long long ago. just 1 drop of water here and they seize up. (we want to forget it)
the vacuum is a fixed amount at a give demand by your right foot (plenum vac)
the needles gum up and the vacuum is hopeless to pull against the gum.
just like those old nasty Rochester quadra-jet carbs (4barrels) did long long ago. just 1 drop of water here and they seize up. (we want to forget it)
i bet the brakes work hot and cold engine.
so is not the brakes if only hot engine fails.
the I-6 has great engine torque at about 3000 rpm, and is wonderfully flat seen here
see the torque here in RED line (post 29)
so is not the brakes if only hot engine fails.
the I-6 has great engine torque at about 3000 rpm, and is wonderfully flat seen here
see the torque here in RED line (post 29)
the carter BBD was infamous then for not liking E10 Ethonal fuel we have now.
E10 seals melt. and fail.
Carb mods /hacks
many have the SO CALLED NUTTER bypass MOD. <<seen here
Google JEEP nutter bypass like this.(click and read how it looks for identification) the video is here, Youtube (calif not allowed, ) The VIDEO is Grade 10/10 imo
or china carbs there. (ebay and random results )
or was swapped to MC2100(off a ford)
or to webers $$$$$$$$$$$ or weak, funky failing weber fakes.
and more, google this and see vast years of hacks to fix bad BBD, that has no spare parts today.
or switched to CJ carbs 1980 and HEI distributors.?
but clean it first, the carb. all gunk GONE, that GREEN slim is GUNK.
and make sure mod's are not there now (hacks)
inspect the whole carb area for hacks, missing parts, cut wires. or things the FSM shows is wrong there now.
Vacuum lines hacked, missing or sucking air.
that is the short list of what might be there. nothing more,
we cant see what is there,
E10 seals melt. and fail.
Carb mods /hacks
many have the SO CALLED NUTTER bypass MOD. <<seen here
Google JEEP nutter bypass like this.(click and read how it looks for identification) the video is here, Youtube (calif not allowed, ) The VIDEO is Grade 10/10 imo
or china carbs there. (ebay and random results )
or was swapped to MC2100(off a ford)
or to webers $$$$$$$$$$$ or weak, funky failing weber fakes.
and more, google this and see vast years of hacks to fix bad BBD, that has no spare parts today.
or switched to CJ carbs 1980 and HEI distributors.?
but clean it first, the carb. all gunk GONE, that GREEN slim is GUNK.
and make sure mod's are not there now (hacks)
inspect the whole carb area for hacks, missing parts, cut wires. or things the FSM shows is wrong there now.
Vacuum lines hacked, missing or sucking air.
that is the short list of what might be there. nothing more,
we cant see what is there,
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