help with codes

[jayro]

I all of a sudden had some drivability issues. The car is a '94 MTX with 170k on it. All the maintinance is up to date.

I was driving through town and all of a sudden I notices that when i took my foot off the gas it seemed like the rpm didn't drop (like if the throttle was stuck open a little). I pushed in the clutch and the rpms stayed around 3k. I tried giving it a little gas, but the rpm would go up but not down. Then the rpm dropped and the engine died. It started right back up and limped into the gas station like it was going to die agian. Let it sit for a few minutes and it started up and ran fine for about a mile or so and then did it all over agian. I pulled the codes when I got home and came up with this:
511 no power to pin 1
112 air temp sensor low or grounded
121 TPS out of range
412 and 411 Idle speed control too high and low

I also got code 454, but couldn't find it?

Any ideas
Jeremy

 

[Huntervf]

Do you have a chip in that car? 511 usually pops up if you have an LPM.

121 points to a bad throttle position sensor, which can definitely cause your problems. It's the black plug right on the side of the throttle body, held on with just two phillips head screws. As far as SHO problems go, it's about the easiest fix you'll get Given your symptoms, I'd start there first.

That said, was your engine running at low RPM during the self-test? I'm a bit concerned that you might have a bad computer, especially if you're not running a chip. Grounded ACT sensor, no power to pin 1, errant code (454 shows up as a servo leaking, which in this context is part of an automatic trans)... a goofy computer can most definitely make your car run goofy.

I'd suggest pulling codes again. KOER, KOEO and the cylinder balance test. Let the computer do the whole thing, see how it responds and see what kind of codes you get back. Be very mindful not just of the code, but of the tests themselves and if they're being performed correctly. I had a 95 ATX with a low idle problem I couldn't diagnose for the life of me. I'd had problems running the self test the first time around, wouldn't complete the KOER test. I thought it was just a glitch because the second time the test was fine, but I got back a low idle speed code just like you did. Third time (a few days later after replacing the IAC and cleaning the intake) I couldn't get it to run either KOER or cylinder balance test, so on a hunch I swapped computers and all my problems were solved.

 

[tompumped]

I'd check the voltage first at the sensor and make sure it's the sensor itself.
If the screws for the tps give you trouble use an impact driver, that's what I had to do recently. I wasn't having any issues I just decided to waste money but the original had 110k on it. Seems to have better throttle response.

 

[jayro]

Thanks for the feed back. Yes I do have an LPM. I was thinking the TPS could be the problem since all the codes were pointing to that. I ran the codes 2-3 times. I couldn't get it to do the cyl. balance test. I got the 538 code atg the end which is "System didn't recieve the goose test". I reved the engine like I was supposed to, but got nothing. I was thinking that if it requires input from the TPS to start the test then that too would point to the sensor. The first time I had trouble with the KOER codes....I would turn the wheel left/right and step on the brake, but when I would blip the throttle nothing would happen.
How would I test the TPS, I'm kinda ignorant when it comes to testing stuff like that....I usually just replace them as the test.

Jeremy

 

[Huntervf]

Hmmm... your computer probs sound suspiciously like my 95, but you make a good point that the TPS could be messing up the test. It's such an easy swap I'd just replace it, see what happens.

 

[rubydist]

You have to get the rpms up pretty high during the 'goose' test, so you might not have held it quite long enough.

The test of the tps is to measure the resistance across the two outside pins while you turn the shaft - it should range smoothly from high to low and back as you move it - no 'flat' spots or jumps in the resistance.

 

[tompumped]

In school they taught us that most of the time you need an oscilloscope? to measure the drop, it can't be caught with a voltmeter. I don't know how true this is though so I can't say either way.

 

[jayro]

Replaced the TPS (even though the first replacment was broke out of the box....grrrr). It seemes to be fixed. Drove around for about 20 min with no issues and no codes. I'll have to test drive some more tommorrow and pull the codes agian to make sure. I'm a little scared to celebrate it being fixed....just too easy of a fix for the SHO. Thanks for help.

Jeremy

 

[tompumped]

I agree with what I read here and from reading through posts/threads Hunters assumpton might be dead on.