20 Most Recent 1988 GMC S-15 Questions & Answers

sounding like a cracked or broken vacuum line, could also be the adjuster screw has a build up on it as well, on the stopper. but sounds like a vacuum leak.could be on the lines or on a diaphragm moving part. you would need to use a leak tester.

1988 GMC S-15 | Answered on Feb 27, 2018

hey there my best bet solution would be to remove the c clip and wrap some wire round it a few times to solve the problem..

1988 GMC S-15 | Answered on Dec 06, 2017

Clearly some fancy diagnosis and testing is needed and checking the fuel pressure will be part of those checks as would testing the injector spray patterns.
If the injectors are producing droplets that are large or are dribbling or leaking the oxygen sensor will see the result as a lean mixture and increase the injector duty cycle making the situation intolerable at idle when the intake air speed is too low to break up large fuel droplets.

Just an idea...

1988 GMC S-15 | Answered on Sep 16, 2017

Hi Chris:
Odds are that the appropriate Haynes Manual would not only have the diagram, but also all of the step by step instructions.

1988 GMC S-15 | Answered on Jan 13, 2016

Blue smoke is almost always oil in the cylinders. It's caused by bad valve seats or bad rings. Timing won't cause blue smoke.

1988 GMC S-15 | Answered on Nov 24, 2015


1988 GMC S-15 | Answered on Oct 25, 2015

Trace the wiring harness at the rear to see if its rubbed through anywhere. Check all plugs are fully home and plugs pins are in good condition, not corroded or wet. Next check the ground leads on both rear lights to see if its an earth fault sending current to both bulbs. Next, remove one bulb and see if the other functions normally. Then try other way round. See if that shows up any fault.
Also, if you have a trailer socket, check that for cross connection etc.

1988 GMC S-15 | Answered on Jun 04, 2014

Short in wire.. look under the rear of the truck.. find the tail light harness.. take your volt meter and see if it is flashing there.. if not than the short is in the harness running up to the rear lights.. If it is flashing there trace forward.. could be anywhere between that connection and the flasher.. Post a comment and let us know what you find..

1988 GMC S-15 | Answered on May 24, 2014

Change the temperature control sensor to the front if the engine near radiator
1 start the truck let it run till you think it is at normal operating temperature
2 unplug the temp sensor if the idle changes then the sensor is bad

1988 GMC S-15 | Answered on Mar 24, 2014

a lot of comments with no answer to the question. you need the steering wheel puller tool. take off the nut holding down the wheel and use the "Teering wheel puller" (peice of metal with 3 bolts) 2 bolts mount to the steering wheel to pull, and one bolt pushes on the rod that the nut was screwed on. that bolt pushes and the other 2 pull the steering wheel off.

1988 GMC S-15 | Answered on Nov 23, 2013

what year, what engines, the blue box , above contradicts.

1988 GMC S-15 | Answered on Oct 08, 2013

I suspect that you have some sort of immobiliser connected to the seat belt system and that area has moved and not allowing the circuit to be made for starting. A sort of can't start the car unless the seat belt has been applied. Try clipping up the drivers seat belt for starters or check if there is such a requirement in the car.

1988 GMC S-15 | Answered on Mar 21, 2013

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