1991 GMC 1500 low idle

PJHAFNER

MEMBER
1991 GMC C1500

I have a 1991 GMC pickup with a 5.7 350 with 204,000 miles. Just did tune up and after the idle is around 450. The truck now stalls at times when put in gear and at lights. But when cold it idles fine, and when in park any help would be great thanks PJ

1 Reply

KENVCR

MEMBER
105 POSTS

I Need a little more info but. If you have a TBI fuel inj system here are some things to check.
1) EGR valve. While the engine is running pull the small hose off of the valve. Feel the end of the hose for vaccum. Yes vaccum & change in rpm, reattach hose and try to manually move the diaphram slowly. If it moves but sticky or really loose, replace with correct one. You need the original to get the exact replacement. Follow instructions and you should have no problem.
2)Fuel meter cover with pressure regulator. This is a tougher one to diagnos. Is your gas gage working properly? Do you smell raw gas after you shut off engine? When you brake at a stop light does it almost stall and then pick up rpm to about 2 to 2500rpm? Then when you begin to drive again it sputters and just about stalls again? Then you would definitely need this part.

Your tune up, was it just cap & rotor & plugs? Was there any indication prior to this tune up that a problem existed?

Before you go out and start spending a lot of cash on stuff you do not need, answer the questions & I will get you the answer you need.
DID YOU loosen or move the distributor at all?
Is the service engine light on?

Talk to you soon.
Kenvcr