hesitating starts, stumbles before warm

Recently i've been getting hesitating starts. it won't start first go. a lot of the time. it cranks and trys to start, but just chokes and stupbles to a stall. second go it starts fine.

when this happens stumbles on reving. like if i'm in nutral the rmps go down before they go up. and it like almost stalls.

once its warm it runs like a champ. or if i run just down the street it will be good. it i drive for a bit, park. let it sit 3 hours it will start and run fine.


it got way worse the other day when i had 2 days off and didn't drive.

electrical? battery is 2 years old, but a 3 year battery. plugs new, wires who knows. fuel filter new.

ideas?

I'm thinking something like the IAC or TPS sensor. It sounds like something isn't reading right.

I don't think it would be the tps because the tps is only for emissions. I think the iac is possible but i think the fuel system is more likely the problem. If you're car cannot maintain fuel pressure while the car is off it may be trying to get fuel to the engine it it has not been on it a while. I'm thinking this is the cause because you said it was worse the longer it sat.

Since when is the throttle position sensor for emissions?

unplug it see what happens, nothing, it is useful for logging but that it.

The TPS houses the closed throttle position switch, which controls the IAC based on a high and low voltage signal. It's used more than for just logging. And I don't see how it deals at all with emissions.

I'm feeling lazy right now but i'll find th link later. I'm not arguing i'm just saying it doesn't help the performance nor driveability of the car i unplugged mine a few months ago and it has done nothing.

Maybe yours never worked in the first place? I don't know but any car that I've ever dealt with needed the tps to run/drive normally. I'm not arguing, I just stick firm to my knowledge/opinion :thumbsup: I just said to check it because it's one less thing that *could* cause a problem.

Might be a vac leak. My buddy Mike's Olds had the vac hose on the MAP sensor (I think, thats just what he told me) was cut and it stumbled around and idled funny until it was warm.

Maybe yours never worked in the first place? I don't know but any car that I've ever dealt with needed the tps to run/drive normally. I'm not arguing, I just stick firm to my knowledge/opinion :thumbsup: I just said to check it because it's one less thing that *could* cause a problem.
No it worked fine, when i put the smim on i broke the wire connector. Nothing changed in the way it ran, i also have the closed throttle switch disconnected, again it's fine. I read somewhere that the tps sends a signal to the ecu so it can lean out the afr when deccelerating. I can't find the link to where i got that info but i know from experience that it was ok. I think a malfunctioning tps could caue some problems though, i.e. if it was tps was 50% then the iac would not come on. Try unplugging the tps and starting the car.

car sat alll day sunday parked. started right up no problems. sat all night outside got down to about 40. ever so slight start up hesitation, and a little hesitation on acceration.

i had a simualr problem the winter before last. new spark plugs took care of it, and last winter it was fine. now its doing the same thing in the cold.

as it gets warmer this week i'll be able to tell if its outside temperature that causes it.

Mine did the same thing when in cold weather. Took many tried to get it to turn over and stay on. I replaced the TPS and the IAC, and it has worked fine ever since. The IAC is more than likely the problem though. My car refused to run without the TPS plugged in FYI. IDK why.

My car refused to run without the TPS plugged in FYI. IDK why.

420a needs the TPS to run, the 4g63 doesn't "need" it, but it should have it

umm are the TPS and the IAC expensive to replace?

I believe the IAC is ~$100 (give or take 10 depending on where you go) and the TPS i'm not sure. Check ebay.

For the 420a the TPS was $60. The IAC was $50 IIRC at Pep Boys. May be more for you guys though. I dont see why though. EBay is a good place to find them