98 Chevy S10 Misfiring Problem

Posted in Ignition Systems | Asked on Aug 12, 2010

I recently replaced my intake manifold gasket. I forgot to mark the distributor when I removed it (well I didn’t know you had to, and my dad (he was helping me, he’s the certified mechanic, an HVAC mechanic by profession) forgot about it) and so the timing got messed up. I took the spark plug 1 out of its hole, felt for compression, and continued turning the crankshaft to TDC (which was only a very little more). That got the my truck to start but it threw P1345 SGC (Cam Position) Sensor Circuit Malfunction/ Crankshaft Position – Camshaft Position Correlation as well as P0300 Random/multiple cylinder misfire and finally P0304 Cylinder 4 misfire detected all at once. After reseting the computer using my AutoTap the P1345 went away but the other two stayed. Oh, the engine was also ROUGH idlling, it was practically shaking back and fourth and it was hard to start. So I removed the hold down bolt for the distributor, turned it clockwise a tooth or two, bolted it back down.
After bolting the distributor back down, it starts easier and the rumbling is less evident, if at all. But the P0300 and the P0304 OBD II codes keep coming up. I also noted that my exhaust pipe sounds like its “puffing” out the gas. I put paper in front of it to see if it would suck the paper in, and it was blowing out like it was suppose to. It just blows out exhaust in intervals. Any ideas what to do?
Sorry I didn’t give more details about my truck. Here it is

4.3 liter V6 Vortec vin code X
CSEFI fuel injection
EDI ignition

It’s a fresh problem and it’s been running fine on the cheap gas for almost 10 years (it was bought December 1997). If you think my timing is off, do you happen to know how to adjust the timing on the 98 S10 Vin X or can show me a website (I’ve tried google and yahoo and I find useless links)? Everywhere I look (Haynes manual, under the hood, car manual, websites) says timing is preset, do not adjust timing. But if a car has a distributor, it has timing that can be messed up. I doubt it’s a vacuum leak since my MAP (Manifold Absolute Pressure) is at 11″ Hg (11 inches of Mercury) at idle, which is normal MAP. However, I could be wrong, I’m just a shadetree mechanic. And I was EXTREMELY careful (think of a matchstick man in a room of dynamite) with my injectors. I made sure they stayed clean, lined up perfectly, etc..

There are 4 Answers for "98 Chevy S10 Misfiring Problem"

  1. pk112390 says:

    try some premium fuel…the combustion rate is higher so the gas will only ignite with the spark plug’s spark…regular gas can prematurely combust under heat and pressure …causing the engine to misfire or “knock”.

  2. Autoinspector says:

    If it started after the intake gasket replacement, you likely messed something up and there is a vacuum leak. try spraying choke cleaner along the gasket and see if it makes any difference. If the problem is not fresh, I bet this is the “octopus” leak. This thing has a funky injection system that utilizes CPI (Central Port Injection) with hoses for each cylinder. These things leak to the point of hydraulocking cylinders.

  3. studmuffin says:

    did you get the firing order right?,also maybe you got a cracked dist. cap.maybe you still got a vacume leak somewhere,put a vacume guage on it,it might tell you whats wrong.

  4. Mr. KnowItAll says:

    This may sound stupid, …..double check your firing order…….
    You may have two spark plug wires reversed on neighboring cylinders.

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