93 lumina touchy gas in colder weather

[Mediaman67]

Hi all,

I'm in New England, and it's starting to get cooler...

whenever it's about 50 or lower outside, and the car is not warmed up yet, if I hit the gas, about 1/2 the time, it will dip down like it wants to stall, but then usually recover and it's ok...

my wife can get it to stall more than me, but she is a lead foot, and my guess is that she gives it too much gas right away, and it can't always recover.

Again, when it's 65+ outside, doesn't have this problem... and only usually when the engine is colder, before it gets up to temp.

it idles ok, maybe a tad rough at times - when it's cold, I can see the tach quickly bounce sometimes when at a light, or in park, etc... does like a quick little flick thing... don't know if that is related...

any ideas? she is worried that it will strand her. I have replaced the Ign module, newer plugs and wires (runs great other wise anyway)

I was thinking of cleaning the TB, but I know it can be screwed up if I am too agressive, so I wonder if it's that at all, or something else, like a faulty EGR value or whatnot...

Or vacuum? but how can I test that?

Thanks to all

[jeffcoslacker]

I think you are on the right track, personally with complaints of stalling or hesitation when cold my thoughts go straight to overly lean idle...

The EGR is not active until the motor is fully warmed up, so I doubt it's involved. But you have an IAC (idle air control) that may be the cause...

It's job is to meter how much air bypasses the closed throttle plate. By doing so it basically becomes the replacement for the choke on a carb, the fuel injection equivalent. If it's having problems seating, it won't be able to precisely meter for the kind of rich mix the motor requires when cold.

Symtoms are usually stalling or hesitation coming off idle and "hunting" for idle speed when cold...sound familar?

Also your idea abount the throttle body is sound...if the plate gets varnished up too much it can get stuck open slightly at rest when it should be fully closed. A quick spray with some cleaner will take care of that possibility...

Vacuum leaks you can check by spraying starting fluid, WD-40, cleaner, or even water around any suspect areas...if it gets drawn into a leak the motor's idle will react suddenly by either picking up faster or bogging down, depending on what you're spraying and how large the leak is...

Other things to check would be...I think you have a MAP sensor rather than MAF on that year? MAF is in the duct entering the motor, halfway between the airbox and the throttle plate, so it splices the duct together and has an enclosed circuit board and wires coming out of it...MAP will usually be on top of the motor or on the firewall, a black plastic rectangle maybe 2.5" long with a vacuum line and some wires going to it...it tells the computer about the density of the air charge going into the motor...and air density changes with temperature sooo...make sure the vacuum line is solid all the way and not spongy or cracked...

I don't know if you have an IAT (intake air temp) sensor...I think it's in the airbox if it does...

Anyway, that should keep you busy for a while...I'll try to think of anything else. Someone will be along to mention all the stuff I forgot too...

[Mediaman67]

the situation gets worse...

This morning, on her way into work, the car stalled when she was slowing down... it didn't shudder, she said it just died, so I don't think it was the TC sticking, but could have been.

so, to check if it is the TC, if she drove it in D (not lock up) the car should never stall then, correct? (if this is the problem)

I'm just trying to either duplicate the problem, or elimate things...

Also, recently, I had the tranny pan pulled for just a drain and a filter change, as part of having some of the rusty brake lines fixed...

I hope this is upper intake related, and not tranny related... would a bad/failing IAC cause the car to stall if you take your foot off the gas?

BTW - no check engine light or anything like that... oh, and the other thing to mention, this was when the car was fully warmed up (she was almost to work)

I feel like this thing is starting to nickle and dime me to death... and I really don't want to guess at why it stalls, so any help you all can give us would be great...

Thanks