1989 GMC C1500 Stalling, Hesitation and Rough idle

MOTORMANIA15

MEMBER
1989 GMC C1500
V8
2WD
AUTOMATIC
249,000 MILES

I have an 89 GMC C1500 with a 305.When I bought it the guy said it had been sitting for 2 years. So I had to take the heads and intake manifold off for cleaning. I have it back up and running, but it runs rough, stalls often, and hesitates under acceleration. I ran a compression test and it reads 200 and above for all cylinders, I adjusted the timing, ran an OBD 1 on it and it says everything is fine, there is just one thing though, the check engine light keeps going on and off. I replaced the air filter, fuel filter, fuel pump and sending unit, spark plugs and I drained the old fuel and added fuel treatment, but it hasnt improved in any way. So any comments would be greatly appreciated.

2 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

Try this take some cabr cleaner spray around intake see if idle improves if sprayed in a certain spot. May have intake leak. Was the condition there before repairs?

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Thursday, June 25th, 2009 AT 4:19 PM

MOTORMANIA15

MEMBER
15 POSTS

I already tried the carb cleaner it didnt work, and I made sure the intake bolts are tightened. OK this is how it went, my automotive teacher got a donation from some guy and he told my teacher it barely ran, so my teacher drove it back and it took him an hour to drive it about 3 miles so before I started to work on it I heard it run, it sounded like crap, so I ran a compression test and over half of the pressures were below 140 so I took the valve covers and intake off and found a broken push rod