Questions and Answers

GMC Sonoma Jerking Around Q. Hello Vincent, I've been reading your Q&A section for General Motors and found a few hits on my problem. I think I need to replace my PCM, but I wanted to ask you first for other possibilities. 1995 GMC Sonoma Manual Transmission 4 Cylinder

I am getting hesitation/jerking during acceleration (hot or cold). It occurs in all gears and especially when I am going uphill.

The problem occurs mostly when the engine is under "load" (yes I'm learning). I went out and did some driving tests uphill and found these problems.

Anywhere from 1,000 RPM to 3,000 RPM the hesitation and jerking occurs. I drove uphill in third gear and put the gas pedal to the floor. The engine extremely hesitated and jerked while trying to gain speed. Once I got to a high RPM the hesitation stopped. But when I changed gears to fourth gear, the RPM's dropped and the hesitation started again.

I went down to the local parts store and asked three auto guys on what my problem may be. Because I haven't changed my fuel filter ever, they agreed that was my problem. I bought a fuel filter and some injector cleaner. So I went home and got fuel all over my face, got greasy fingers and can't seem to get the grease out from my nails! haha. Anyway, I successfully changed the fuel filter. I noticed the fuel that poured out of my old filter was brown! I went down to the gas station and filled up with premium gas and mixed in my injector cleaner.

I thought my problem would be solved but no luck. I drove around again and found mild hesitation in normal conditions. I went on an uphill test and received the same symptoms.

Is this related to the TSB: 67-65-37 JUN 97 Engine - Intermittent Hesitation/Low Power/Rough Running?

Or is it something else? I'm looking for anything other than the wires/plugs solution.
Thank you so much for reading,
Mark

A. The "jerking" that you describe would almost always be related to plugs or wires. These four cylinders are prone to having bad wires. If they are numbered they are the original wires. You didn't mention if you replaced them. A fuel related problem is a smooth hesitation. Like it runs out of gas. A jerk is almost always spark related. Could also be a coil or module problem. The jerking you feel is a cylinder dropping out momentarily. If you could isolate it the fix would be simple. Try misting the wires with a light spray of water to simulate a rainy day. You may just see the spark jumping from a plug or wire to ground.