So confused... :(

[Bedwards]

Hey guys. Here's the problem... I have a 2001 Grand Prix GT (with the SS M90 kit), and I'm having a random non-start issue. My car will start fine for like 3 weeks straight, no problem, then all of a sudden it won't start. The first time it does it, the RPM will shoot up to 1000 or so, and it will die instantly. If I try start it again, it will just crank, and the RPM won't move. If I hold my foot on the gas, it will run, but as soon as I let off, it dies. Sometimes later that day, I'll try to start it, and it will fire right up. It just doesn't make sense.

I had an issue like this before, and after replacing the spark plugs, fuel filter, cleaning the MAF and cleaning/adjusting the IAC, it fixed it. It didn't happen for a while, then it started happening again. I changed the IAC from my old L36 throttle body to my current L67 throttle body, and it started up right away. I don't know if it was a coincidence or not. It was working fine for a bit, now it's doing it again. It's kind of hard to believe that both my IAC valves from both throttle body's are worn out, but I guess it could be possible. What do you guys think? Thank you.

[Sinister Drag Designs]

check fuel pressure. Try to prime the pump for a couple seconds before starting it for the first time. Any stored codes when you do get it running?

[copgtp]

x2, sounds like it may be a fueling issue.

[Slick2500]

It almost sounds like the fuel pump, my sisters car did that for months before the fuel pump finally died. But idk they are cheep for these cars and easy to replace so.

[BillBoost37]

I like the fuel pressure thing, but that should become more consistent and progressive. Have seen this on occasion on cars. Almost like the pcm forgets idle etc. Once you get it running and hold it for a min it will idle again on it's own and doesn't happen until a while later?

Check the battery cables along with the rest of the stuff.

[Bedwards]

I always let it prime for a few seconds before I try start it. After priming, my fuel pressure is around 40-43 PSI, so I don't know if that would be the problem. I don't have any stored codes at the moment, but I occasionally see a P0452 code. If I hold my foot on the gas and let it run for a minute, it will still die when I let off.

[BillBoost37]

What is P0452 Bedwards?

[MoarkatsINmuhtrailer]

its an evap code bill. system pressure or leak. changing the pump might be the way to go

[Bedwards]

It relates to the EVAP pressure sensor outputting a lower voltage. Not really sure what that means though... I replaced my fuel pump about a year ago, with a new one from W-Body store. I hope to God it wouldn't have gone bad already.

[Bedwards]

Anyone else have any ideas?

P.S. I'm deleting my EVAP system soon as well.

[BillBoost37]

Go get the code at Gearchatter.com and link it back. I bet the diagnostic aids is key in finding the problem and fixing it.

[Bedwards]

I really don't think this problem is fuel related. I bought a new IAC because my other one was giving values around 200 at idle and the pintle was way too long. So far, so good. The value is around 130 on a cold start an lowers down to about 30 on warm idle. No problems so far.

[real diehl]

My car did this once...wouldn't idle without your foot on the gas. I messed with it all night, went to bed, and it started up fine the next day.

Could the plugs be getting wet somehow?

[BillBoost37]

I tend to be pretty good at diagnosing. It's because I take the time to read up on the code etc and see how the engineers made it interact with other things. Learned a lot of very interesting things over the years and I'd never have thought X and Y act together like they do.

Want to solve this? Go get the info I suggested. Do your research and learn about the issue instead of guessing that it's not fuel related etc. I'm changing my tactics from me doing all the work to having the member with the problem do a certain amount of the legwork. We are here to help, not do all the work.

[Bedwards]

The thing is, is that I haven't seen those codes arise in like 3 weeks. They are gone from the PCMs memory. Yet, I still had the problem happen. I'll look at the code when I get some time to diagnose it. But for now, the IAC seems to have solved it. We will see how it goes.

[L36pro]

sounds like the fuel pump. the surge at start before dying is probably the residual fuel pressure from your last drive. prime the pump and listen for the hum next time this happens. you should get in the habbit of priming the pump before EVERY start to save wear and tear on the starter, pump, injectors, battery etc etc etc.

[Bedwards]

I always prime it before starting. I'm wondering though, if I prime it and let it sit (don't start), should fuel pressure stay the same? Mine slowly starts to decrease. Does this mean I need a new fuel pump?

[matt5112]

Vacuum checked the FPR?

[Bedwards]

Vacuum checked the FPR?

How do I go about doing that?

[L36pro]

check the fpr by pulling the vacuum line off and see if its leaking gas. this would cause a dangerously enriched Air to Fuel Ratio. and pressure should drop, but dont quote me on it. i saw a thread where a dude had a gtp that was really hard starting, but ran fine. then he just replaced the pump anyways and it ran fine ever since. try a junkyard or amazon before you know for sure that it is the fuel pump