TPS issues?

G

Gilaguy23

YJ Enthusiast
Joined
Apr 12, 2021
Messages
987
Location
Q town New Mexico
Hey everyone, another newbie here with another TPS question. This is on my 91 YJ with a 4 cyl/5 speed. 140k Miles running good as always. A month or so ago I thought Id treat it to a TB cleaning and new TPS cause it idled a bit low and rough feeling to me @ 500. Pulled the TB, cleaned it, new NTK TPS, o/e AIC still used ,cleared the comp letting it sit for hours with the battery disconnected. Put it back together and the idle is 1100 rpm. Hum, many comment on aftermarket TPS'es and their quality.

OK, I'll try another. Standard brand this time and a new TB gasket and full inspection of vac lines, B booster vac leak, you name it. Same deal. Irritating at best. Locate New Mopar TPS. Looks identical to the NTK as some have mentioned on other forums, however the part number etched in white on it is NOT the same as the NTK unit. Install the Mopar one and still have the 1000/1100 rpm speed. I'll add on each TPS Ive ohmed the ground pin,checked for input voltage of 5V, and checked the voltage at closed throttle and WFO. .7v @ closed and various at wfo in the 4 + or - volt range and after the NTK Ive tried a new and the O/E IAC and new O ring with the same results. Still runs fine but the high idle is pisser of sorts.

Thanks for any input folks.
 
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JKP said:
IAC controls idle speed. Yes, you are correct. As I mentioned directly after installing a new TPS and not touching the IAC the idle went to 1100. I replaced it with a new IAC and still the same 1100rpm. I've pulled the new one and can see that the tip of it is fully seating in the TB as well. Seems fairly common after searching the jeep forums. Most guys are working with TJ's however. Kinda makes no sense as to why the huge change in rpm.
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Ok, missed that you had a new IAC.

Have you pulled up the shop manual for yours? I have only worked on the 6 cyl.

Only things that come to mind are the IAC or a vacuum leak.
 
Vac leak was what I was thinking as well. Been over this thing 3 times with a fine toothed comb so to say and have found nothing in the way of leaks. Even tested the PS pressure switch to see if that had any impact. FYI, the 6cyls dont use one of them, only the 4's. Wish i didnt trash the OE one and might even hit up a junk yard to find one since the 2.5/4.0 and many other DC vehicles used the same one.
 
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