GM-GMC: GMC truck, gmc savana, gmc dealer

Question
Hi Dean

I recently purchased a 98 GMC Savana with a 5.7
I took it to a GMC Dealer and had them go through it engine, tranny oil, grease, brake drums, computer updates.

I am presently experiencing a surge when I go on OD and just feather the throttle...It doesn't seem to skip under  any strong acceleration only at a crusing speed...55 ish...

Any thoughts..?

Answer
Hi Ed - I will try to give you a couple of things, but I must warn you, that if you keep searching on AllExperts.com, there are a couple of guys who are in ONLY auto repair, and while I have seen some of this stuff, they are the ones who are the most qualified to check this out.

First, we will have to figure out if there are any other times that the truck does its thing.  Does it make a difference if you are loaded or not.  Will it do it if you have the cruise control on?  Does it make a difference if the tank is full?  Secondly, you have to find out exactly what was done at the dealership.  Did the problem start before or after it was there?

Basically, it could be fuel related, or electrical related.  A shortage or too much fuel can cause the truck to do this, caused by a bad fuel pump, or a bad fuel regulator.  But you have to start pinning down better the circumstances when it "burps".  This will help you or the technician not chase gremlins that aren't there.

When the van was at the dealership, where there any emissions codes stored?  If they reflashed your ECM, they would have cleared any codes that may help you find out what is going on.

It could be a bad plug wire that is arcing across.  It could be something in the ignition like a bad module, or what they use for a distributor now.  Could even be something in the emissions like a EGR.

Whatever it may be, it is prudent to talk to someone more in the know, and that may be someone on the Auto Repair side of AllExperts, or a technician.  Try to have the circumstances pinned down as to when and how the problem occurs and goes away.  All of this auto repair is just a big flow chart, with "if" and "then" so you see the next possible solution - "if" the truck is doing this, "then" replace "...."  

I hope that I have helped to direct you to better information, but if you have something more in line for my expertise, please feel free to drop me a line.

Automotively yours,


Dean