Limp Mode? Not sure whats wrong, need help! - Third Generation F-Body Message Boards

camaro1185 · 08-24-2009, 08:06 AM

Bit of a (long) back-story.
Friday, I was determined to get rid of my code 34 problem. I replaced the burn off relay, the power relay, and cleaned the crap out of my MAF with the MAF cleaner stuff. I cleared the codes and started it; it ran great, no codes etc. The next morning I took it for a drive since Friday night it poured, and the second I started it in the morning, the CEL was on with the same code 34.

So code 34 is not fixed, but I don’t care, I have another bigger problem.

Sat night, was on the highway and the alternator died on me. After 4hrs of waiting for the flat bed, I got it home. Now Sunday morning, I replaced the alternator and got the car started.
After I started it I noticed it running weird, I think I may be in limp mode. From trying to start it and from the tow truck guy wanting to see if I could get it started to move it closer to the truck, I completely killed my battery. I’m thinking that since the battery was so dead that I did something to the ECM.

Here is how my car acts:
Idles fine, but when I give it a slight rev, it seems to be choppy. When I drive it, it seems to be VERY underpowered and won’t go past 3K rpm. It also seems to up shift, but if I get on the gas it won’t downshift.

I know this is long, but I have NO CLUE what’s going on.

Is my ECM shot?

Is there a way to reset it?

Is something else wrong?

Any help would greatly be appreciated.

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KnottyBuoyz · 08-24-2009, 08:52 AM

I've just gone down a similar road troubleshooting a code 33. I had a similar incident where the alt died and stranded us along the highway at rush hour. I don't think loosing the battery will hurt the ECM but I'm not totally positive on that point. I would think a voltage spike would do damage but not a loss in charge.

I started replacing parts (yeah I know wrong way $$$) to try to clear the code. In the end it was the TPS adjustment and should have checked that first. I also traced and cleaned every ground wire (having experience on boats) as this causes a lot of problems. You mentioned it rained so humidity can screw royally with grounds. Boats live in the water so humidity is always a major problem.

There's some good diagnostic charts on here, download them, print them and follow them. That's the best advice I can give.

Good luck.

camaro1185 · 08-24-2009, 09:32 AM

Could I have some how done damage if i changed the alt. with out disconnecting the battery? When i finally got the alt. replaced, i noticed i had forgot to disconnect the battery.

I may try undoing the battery for 5 mins to see if that will reset the computer parameters.

Thanks for the info. though. Not only the humidity from the rain, but it has been crazy humid the past week(80% humid).

transam85dudeman · 08-24-2009, 01:11 PM

TPI rite? try pressing down the injector connectors, Does it sound like a miss? do you have a K and N filter? check every sensor connector. press down on every spark plug wire. Limp mode huh, check for fryd wires/ fuses. does the pump prime?

camaro1185 · 08-24-2009, 02:17 PM

Quote:

Originally Posted by transam85dudeman

TPI rite? try pressing down the injector connectors, Does it sound like a miss? do you have a K and N filter? check every sensor connector. press down on every spark plug wire. Limp mode huh, check for fryd wires/ fuses. does the pump prime?

Nope, it doesn't sound like a miss. No K and N.

The more I read about limp mode, the more I think thats not whats going on.

When reving, it runs a little rough (almost like when your about to run out of gas, where you get spirts of rpms.) The other thing it does is that it seems to be only going to 3k rpm when driving (when parked i can rev to the redline).
Thats the thing, it idles well, to someone who wasnt used to the car they would never notice it (except for not going past 3k when driving)

The CEL is on, but i think its because of the code 34 i was trying to fix.

Im going to try and unplug the batt to clear the codes, then search for other codes.

astrosurfer · 08-24-2009, 09:03 PM

almost sounds like a clogged catalyst...but I don't know if you have one.
I've had same issue with same symptoms.
Good luck.
Hope I was the one who helped...lol.

camaro1185 · 08-24-2009, 10:18 PM

Quote:

Originally Posted by astrosurfer

almost sounds like a clogged catalyst...but I don't know if you have one.
I've had same issue with same symptoms.
Good luck.
Hope I was the one who helped...lol.

You mean cat right? its funny you mention that, that has been what i have been saying since i got the car.

astrosurfer · 08-24-2009, 11:45 PM

yeah I mean the cat.
strangely enough I did not get a check engine light til I was taking it to the shop.
This was on my Malibu....had only 42000 on mileage.
Fortunately it was covered under warranty.
Exact same symptoms....
Started fine...
Revved no problem in park....
Put it into drive and get 0-60 in like 10 minutes.
A little exaggerated but it did take a few minutes to hit speed limit when taking it on I12 to the shop.
Still wish you the best of luck....This may not in fact be the problem. Just a possibility based on personal experience.
Easy to throw money at it in the wrong place.

I'm told the rotten egg smell is more prominent...but I did not notice it on my car.