Limp mode / TPS
 

I just picked up a 89 GXL with 87,xxx miles. "Motor had been replaced/rebuild by rotary world in SC." Cant tell if thats true, as it runs like crap. I am an ASE certified tech, so feel free to throw out detailed diagnositics :).

Here's how she runs:


Smoke tested. One cracked vacuum line and a check valve were replaced. No change.
UIM and LIM removed/inspected/cleaned. 6PI were hung up as well as VDI from no air pump. I purchased and put on an air pump. No change.
Fuel pump, fuel filter, injectors are new. Grounds cleaned including under the UIM.
Timing is correct, checked with a timing light. All 4 plugs getting spark.
MAF reads 1v-4.5v and IAT pin reads 3.8v @ ~60 degrees F

So far I have adjusted both Narrow and Full range TPS, warm, via backprobing. Narrow range set to .75v at rest, max only read 4.1v
Full range set to 3v at rest, max reads up to 5v.

A far as readings go (with a fluke 233) there were no blips or drops in the voltage while sweeping through the range for either TPS. HOWEVER, when i disconnect the TPS while running the idle no longer fluctuates but stays ~2000-2500rpm.

In my experience working on non-rotarys, if a sensor is unplugged and corrects the issue, TOSS IT THATS YOUR PROBLEM. In this case however, im stumped as my readings were good. Anyone have insight or a similar issue? I might look into the OMP this weekend as I have read s5's will go into limp mode if faulty.

Thanks guys, Blake

from what i've read on the site a bad oil metering pump will cause it to go into limp mode.

bad OMP will DEFINITELY make you go into limp mode LOL

my 90 n/a. does the same thing until its at OT. i have been tryin to figure it out so if you got anything on it let me know. i have been looking at replacing my TPS since it reads pretty much nothing. and i think the omp limp is a different kind of limp. because i can still pull through all gears just fine . . . no fuel cut. not a daily driver just sayin. and when its at OT. it holds ide at 1200 and will drop to 800 and about die until bliped on accasion.

and when i unpluged my TPS while running i was racing to put it back in because it about die LOL. let me know. i have also been lookin for same problem. many hours

The TPS needs to be set to 1 volt on the G/R wire w/key to on and the engine as warm as it can get and the TPS should read about 4.5 volts when the Narrow Range TPS rod is fully extended.

Thanks satch, ill try adjusting the TPS again but to my recollection the max would never go above ~4.1v. If the OMP checks out ok, it might be time to throw another TPS on there..

Ill let you guys know what updates I have with this issue. Have you checked your voltage signal from the TPS with a good Meter? Are you experienced with backprobing? They say the "light" method is the best way to set them but I am used to setting by voltage.

How did you check it to get "no reading"? That might be a easy sign you need to replace it. And mine did not die when i unplugged the TPS, the "hunting" idle stopped but went very high.

I believe the high range is based off the low range thus if you had the low range set to .75 volts then it would make sense that the high end of the range would be affected. Perhaps not but worth a try.

i will also try to reajust. i would like your input on backprobing that could of been my mistake. also when i push in the narrow range plunger with my fingure it smooths out the idle. i have read about having to adusting the BAC valve after ajusting the TPS. havnt really dug into that section yet.

Only turbo BAC's can be adjusted. (not NA's) So, you need to leave yours alone. The Red lead of the meter is backprobed into the G/R wire while the TPS is plugged in and the Black meter lead goes to a suitable ground such as the negative battery terminal and this is done w/the key to on. And the engine needs to be as hot as it can get and usually a twenty minute drive will do this (idling for a few minutes is not going to cut it).

:icon_tup:

Is there a way to test the N/A BAC satch? Frequency? I believe the connector is only 2 pin

i just picked up a TPS from rhinehartsauto.com for 80 buck!!!!!! they have great service and about every thing you need for an fc. any ways i will let you know how it runs after the transplant. and you should of went to diesel mechanics

runs great. still runnin rich but pulls great