going to the crusher

[bowtie44s]

I am going to mess with this car for about one more week then its going to the crusher.

I have an 03 grand prix gtp. I posted a thread a while back about it randomly dieing. It's a lot more consistent now. It will be fine for 20 or 30 minutes then the boost gauge will go crazy, up and down at idle or any throttle speed. When it's having a fit it will idle from 200rpm to 400 up and down the lights will dim and the heater slows down then it dies. If I just barely touch the gas pedal the lights brighten up it will lunge a little sometimes and seem ok at around 1100 rpm. As soon as I take my foot off it goes back to the 200-400. If I do let it die I can put it in neutral hold the pedal half way down and it starts back up. It won't ever stop doing it unless I shut it off and sit about 2 minutes then it's fine for another 20 or 30.

I have changed the crank sensor maf and tps. What operates the boost gauge? I thought it was a combination of the maf and tps. I have no check engine light which makes it a lot harder. I'm tired of shot gunning things.

One last thing. I changed the tps last night. I had the wire unplugged and dropped a bolt. I started it, pulled forward and picked up the bolt and the check engine light was on. I assumed it was a tps code but never read it. This morning on the way to work it ran at about 4000 rpm and would barely go 35mph. That's the only time it was down on power. I pulled over, shut it off and it wouldn't start, just cranked and cranked. I set there for about 2 minutes and it started right back up but my check light was off. I was hoping the computer reset itself but it did it again on the way home. I have been noticing a funny smell, real bad this morning, not exactlly rich but maybe like a rich mixed with sulfur smell. I don't think it's a plugged converter since it runs fine sometimes.

Sorry for the length but somebody please help. I'm out of ideas and this thing is about to go to the crusher.

[MoarkatsINmuhtrailer]

uh have you checked your alternator?

[matt5112]

map signal is what the boost gauge responds to.

have you tested that the cat is good?

so far it seems you haven't tested anything.

[coolone]

Crank sensor, mag and tps... You Checked? How? Scanned for codes? Recent work done prior to issues? Mileage...?

[bowtie44s]

Haven't tested anything, I will check the alternator tomorrow. Just make sure its charging around 14 volts??? No recent work. 151,000 miles. I changed the crank sensor and tps, with no change. I just read I need to do the relearn on the tps, I will try that tomrrow. What else should I check and how? I did have the cat replaced under warranty at around 80,000, I doubt its that since sometimes it runs good but i'm open to anything. How should I check it? the only way I know of is vacuum, is there an easier way? Also, what is the other sensor in the throttle body above the tps? There is another plug in the air boot before the throttle body but doesn't look like any sensor on the other end. I have checked fuel pressure when it was acting up and it was 60 psi.

[bowtie44s]

No codes but haven't put it on a techII or anything like that, thanks for your help guys.

[pontiac4lifesc]

sensor above the TPS is the IAC and i had a similar problem and it was the battery. i could be wrong but having a weak battery can bench test 12V but you put a load on the battery and if it drops below 11V then its too weak?

[bowtie44s]

I'm not used to the new stuff but I would think the battery would cover for the alternator until its too low to start anymore. I did test the alternator, I believe it was putting out 14.9 volts. The battery was 12.5 volts. I turned the head lights and blower motor on full blast with the engine off and it dropped to 11.4 volts. The battery is probablly 4 years old and has some corrosion. Do you think that could be my problem pontiacforlifesc? It's worth a try, I sure hope so.

[coolone]

If you didn't test anything, then you are just shotgunning parts at you problem and guessing! Might as well change your rotors too while your at it!

Youve got to start from scratch, your electrical system is going to have issues regardless if you can SEE corrosion. Disconnect and clean all connections and surfaces they attach to, I.e., grounds, use a dialectric grease when putting it back together and tighten correctly. Check wires from battery to ground, battery to alt., alt ground for continuity, then check while running with volt tester to see if charging properly, have battery tested for dead cells, etc. Then scan for codes... Proceed from there...

[bowtie44s]

I believe you fixed it pontiac4lifesc. I have a tester that measures the voltage and puts a load on the battery. I took the old one out and it read a little over 12volt. I put a load on it and it instantlly dropped to 0. I have no idea how it started the car but it did fine. I drove it about an hour and it hasn't had any fits yet. I hope it's over with. This has driven me nuts for a long time. THANK YOU!!!