Throttle Position Sensor & Idling Problems

1997 Pontiac Grand AM SE, 3.1L V6
108,000 miles

Around 6 months or so ago my Grand Am got flooded in a storm. After it dried out I noticed it idled extremely high, around 2000rpms, and it shifted very late, check engine light was also on. My street mechanic replaced the throttle position sensor and the car ran normal, and the check engine light went out. A few months after replacing the TPS, I noticed the check engine light on again, and a slightly higher idle than normal, around 1000rpms at normal operating temperature. This time I went to Aamco because I had ABS, and ETS lights coming on as well as the Check Engine light. They pulled codes indicating a faulty left wheel sensor and throttle position sensor.

After all the repairs were made by Aamco, once again the car ran normal, with no lights, until now. My check engine light recently popped on again, and again the idle is not normal.

I'm thinking TPS again, but I'm also thinking something is causing the TPS to keep going bad on me. I sure hope someone can give me some ideas. I know the flood could have caused more damage than I initially thought. But could that have something to do with this never ending check engine light and idling problems I keep having?

THANKS ALL

could be wet connections shorting the TPS.

did you or someone go through all them and make sure they are dry ?

The first time I changed the tps I had my street mechanic change it and he knew about the flood, because it was the very next day. But I didnt mention it to the guys at Aamco though. I'll be using an extended warranty, so I want to hint around that fact that there may be some moisture causing a short, but I don't want to suggest that I was flooded at one point, that may void my warranty.

Wouldn't all the moisture have dried up by now? It's been over 6 months now.

I've seen cars that sit for over a year after flood damage and some plugs can still have water in them causing shorts.

Compressed air works well to dry them, Q- tips in those tight places.

You could also have water in the vacum lines/system causing some idle issues.
Your IAC has more to do with idle then the TPS.

How deep was the water ??

I just took the car back to Aamco. What is the IAC? And would their computer scans pick up a faulty IAC?

I remember the day after the flood when we changed the TPS, I noticed it was wet. The water level was pretty high. I just barely had clearance to open my doors.

Idle air control -IAC and yes it should pick up a faulty IAC, but it could also need cleaned.

And thats not very much water, last Saturday I drove my SE through water that was about 2 ft deep. It was coming in my doors a little. :eek7:
Plus I drove through other flooded areas, that I knew were safe to drive through, at higher speeds. My engine was soaked ! My CAI was full of water and everything is clean and ran fine... :2cents:

Hope they get you figured out.

Do you know the exact codes? You might have a DTC which refers to the TPS *CIRCUIT* or a code that refers the the TPS *ITSELF*.

My point is you need to know which code it is to know whether the problem lies in the circuit (can be multiple codes) or the TPS itself. DTC's are wonderful at helping properly diagnose a vehicle problem.

If you do get the exact code, look it up here REMOVED BY MODERATOR they cover a lot of codes.

We do have 90% of the trouble codes posted here at AF.

N-Body Trouble Codes (http://www.automotiveforums.com/vbulletin/showthread.php?t=525205)

The exact code the guys at Aamco pulled was P122. It seemed to be a code they weren't to familiar with, so they used some computer system to try and narrow down what could cause this code. The software they used said that a faulty A/C pressure sensor could cause this code. Not to mention the TPS, and O2 sensor. But the guy I was working with wanted to order the A/C pressure sensor and see if that fixes this problem.

I checked out the trouble codes page you posted xeroinfinity, and I noticed that the P122 code mentioned "Throttle Position Sensor (TPS) circuit low input", and didn't mention anything at all about an A/C pressure sensor. So does that A/C pressure sensor make any sense to anyone at all? Now that I think about it, ever since the first time my car got out the shop, I only noticed the check engine light and high idle when the a/c was on and and fully warmed up.

The AC pressure switch would be a more likely cause, since the bottom of the car got wet, it could have shorted it out.

One of these would be something to do with the A/C pressure switch..
P0530 - A/C Refrigerant Pressure Sensor Circuit Malfunction
P0531 - A/C Refrigerant Pressure Sensor Circuit Range/Performance
P0532 - A/C Refrigerant Pressure Sensor Circuit Low Input
P0533 - A/C Refrigerant pressure Sensor Circuit High Input

Well the guy at Aamco did order the a/c pressure sensor from a local gm dealer. Being that today is friday and it is the end of the day, and aamco is only open until noon tomorrow, and closed on sunday, i will have to wait to monday to have the sensor installed. I'm a little skeptical with what i read about that P122 code that this will actually correct my idle problem. But you think that might be the culprit hu? I'll post what happens. Thanks Again.

Well I was doing some research and discovered a thread for a 1993 GM Cadillac El Dorado. I found the P122 code that aamco pulled from my car.

P122 (E122) .................. A/C coolant temperature sensor signal voltage problem.

Now I'm a little more optimistic that the a/c pressure sensor may actually fix my problem. I don't know if the codes have different meanings for Caddys and Pontiacs. But I just remembered I did post another thread along with this one mentioning a/c problems i was noticing along with the high idle. It never occurred to me that the 2 problems may be related. For now, I'm not using any a/c and so far the car runs fine. We'll see what happens in a couple days on Monday.

yes it is probly the trouble as it will make your idle a little higher , just like when the AC is turned on.

actually i noticed yesterday while driving the idle started to get higher little by little. and i didn't run any a/c all day. now i'm back to thinking the a/c pressure sensor may need to be replaced, but being that the car acted up without any a/c being used, i may need to replace something else too. that software that aamco used also mentioned that the tps could be the culprit, but being that they just replaced it not to long ago, they just ruled that out. i wonder if the a/c pressure sensor could have damaged the tps, and i need to replace both.

OK, so Aamco installed the a/c pressure sensor. The car ran good for a couple days, then all of a sudden check engine light, followed by high idle occurs again. At this point I'm getting very frustrated. I have noticed that this problem seems to occur more on days when I start the car a lot. If I only have to start the car a couple times a day, then it seems to be fine. But when I have to disengage the engine and then reengage it, I get stuck with a high idle problem until the car completely cools. I was wondering if the starter can somehow be responsible for the high idle.

Oh and I think I saw EGR Valve on that Aamco list of possible P122 code culprits. Does that make any sense to anyone? I would greatly appreciate any quick inexpensive possible solutions I could try. I think I read IAC, but I have no idea what that is.

Thanks again for all the help.

Since you say its doing the high idle when warm , look for vacum leaks .

But I would get the code(s) exactly other wise you are just guessing.
To test/replace you IAC- idle air control check this link.
Idle Air Control(IAC) Testing Replacing (http://www.automotiveforums.com/vbulletin/showthread.php?t=663849)

Just an update on how the car has been so far. Like I said before after AAmco installed the a/c pressure switch, the check engine light and high idle issues returned. So on friday, june 20th I went back to Aamco to get it scanned again. They pulled the same P122 code as before. The guy in charge there didn't have any idea why I was still having problems, even after I explained the flood damage I had.

That same day I went to my street mechanic. He looked at the throttle body and noticed it was pretty dirty. So he used some throttle body cleaner to clean it, and also picked up some seafoam and somehow feed it through the intake to clean that out. He also looked at the connections and didn't notice any moisture. So I decided to see what happens if I replaced the TPS again. My thinking was that somehow the a/c pressure switched was the main culprit. I don't know if the a/c pressure switch and the tps are on the same circuit. But after the a/c pressure sensor was changed, I thought that maybe the old one already damaged the new tps that aamco installed.

So I changed the tps, used the throttle body cleaner and seafoam to clean up all that build up. And so far so good. If this doesn't work, I don't know what else to do.

well the p122 is low signal input on the TPS, which would lead me to believe theirs a wiring problem within that circuit.

Hopefully you've got it taken care of, good luck.