Automobile / GMC / S15

GMC S15 Truck Repair Questions and Answers

Question:  1990 GMC S-15  mileage: 187,000.  I'm having a starting problem with my pickup.  It is an intermittent problem.  The engine cranks with plenty of power all the time.  When the truck acts up...a tiny squirt of starting fluid into the intake (with air cleaner cover removed and then tightened back to normal before cranking) the engine fires right up every time without hesitation.  When the truck is running it responds directly to the throttle and exhibits no signs of sputtering or stalling.  The problem most often occurs after a short drive allowing the engine to get warm...after the truck sits about half an hour it won't start.  It seems not to be receiving fuel...Last spring I replaced the fuel filter and fuel pump.  I live in the Northeast and I am wondering if the thermal changes point to the problem.  Any ideas would be much appreciated. 

Answer:    Your car is equipped with a computer controlled engine management system.  An independent auto service center can scan your computer for fault or error codes.  The information should pinpoint the malfunctioning components.   If a major tune-up has not been done recently, this could be the cause of your problem.  Replace the spark plugs, plug wires, fuel and air filters, etc.  Also, replace the oxygen sensor.  In addition, service the fuel injection system.  Clean the carbon deposits from the throttle bore and idle passages.

Question:  1992 GMC S-15  mileage: 95,000.  Having repeating problem with ECM.  Engine check light comes on.  Engine runs so rough cannot drive.  Original problem occurred driving 60 mph on freeway, engine light came on, lost power but made it 10 miles home.  The computer code is always 2-3 (mixture control solenoid).  Over last 5 months, have replaced: mixture control solenoid, oxygen sensor, ECM (3 times), entire carburetor, added ground wire from ECM to firewall & engine to firewall.  Has been to a local shop and to a Chevy dealer.  The truck has a remanufactured long block with about 5,000 miles on it.  New fuel and water pumps were installed at engine replacement.  Within last 8 months alternator, starter, and battery were replaced.  Truck still does not run reliably.  ECMs have been lasting 3 to 30 days.  I tried to find a replacement wiring harness and its not available from dealer.  Any suggestions?   I have lost faith in local dealer & repair shop.

Answer:    After reading your question, the only thing we can think of is something else is causing the ECMs to fail.  What comes to mind is AC voltage from a bad alternator from a leaking diode, or high voltage (from the coil) somehow is getting back down the wiring harness to the ECM or bad plug wires next to a wiring loom or stray high voltage in the distributor getting into low voltage wiring.

Question:  1994 GMC S-15 4WD  mileage: 80,000.  Where do all these vacuum hoses go? Is it possible to get an on-line map of some kind?

Answer:  Your best bet now is to take your vehicle to your local mechanic, or buy a shop manual. Click here to find out more

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