Help! '91 Automatic stumbling on 1-2 shift

[Chuck Lewis]

New user, first post and first time Vette owner (4 months now).

My '91 with auto-trans is having trouble on the first to second shift under normal driving conditions. It's like the ignition is totally shut off for a second, the car totally falls on it's face then accelerates normally.

Very easy acceleration it doesn't stumble, hard acceleration it doesn't stumble and manually shifting it at various rpms doesn't stumble, just normal driving. I did notice that the 'first to fourth' light comes on right before first to second shift when it stumbles. The 'first to fourth' light just applies to standards, doesn't it. Why woukd it be coming on with my automatic?

I've been searching and searching, still can't find any answers or even common issues to my problem. Any ideas?
Thanks, Chuck

 

[Hib Halverson]

Obviously the skip shift light (manual trans only) should not be coming on in an automatic trans car.

Is this car modified at all?

 

[Schrade]

Welcome onto the boards there.

You might need input from PeteK - the tranny guru on the boards here...

... although, engine tune problems can manifest as tranny problems.

So as 'Hib' asked, do you have mods? Have you stuck a paper clip into the ALDL socket, to pull codes?

 

[Chuck Lewis]

I don't know of any mods to the car except for muffler eliminators that the PO put on it. I was getting a code 32 and just last weekend replaced the EGR valve and the injectors. This stopped the check engine light from coming on and made the engine run smoother but didn't help the shift issue. The only codes I've gotten out of it was the 32 for the EGR.
Thanks, Chuck

 

[Hib Halverson]

During very easy acceleration, hard acceleration and when manually shifting from 1-2...the times when the hesitation does not occur, does the "one-to-four" light come on?

 

[Chuck Lewis]

No, the 'one to four' light does not come on prior to a good shift.
Thanks, Chuck

 

[Chuck Lewis]

More info

My 17 year old son is driving the car now. He says that the 'one to four' light does not always come on before the stumbling shift.
Thanks, Chuck

 

[Schrade]

If the light came on once, it's probably stored still as 'H' history DTC (although I don't know if OBD I does history coding there). And problems don't usually go away by themself.

Even then, some 'C' Current DTC problems won't light the SES light until Closed Loop. Most trips are short too uh HUH, so you could have many days pass with an active problem, since you take short trips.

This is one reason the shop won't call you after a bogus repair, til AFTER it's cooled off YUp. Whenever they call, tell them to have it warmed up to CLOSED LOOP when you get there.