Missfire

[fljeeper]

Hi, my son and I have been trying to eliminate a misfire that his 97 SE has. We have reduced the frequency and intensity of the misfire by doing the following: new intake/exhaust manifold gasket - the old one was loose and leaking, tested and repaired as needed all the vacuum lines - a few has suspect connections, new throttle body gasket, new IAC housing gasket - old one was cracked, replaced injector O-rings - old ones were cracked. The Jeep has recent plugs, plug wires, distributor cap, rotor, and coil. I also put a stethascope on the injectors and they all sound the same. Now when running at a steady steady RPM it has no misses, but when accelerating it still misses at times. Any suggestions on what to look at next?

Thanks,

Dan

 

[StG58]

Double check that the plug wires are fully seated and "snap" into place. I put a little dielectric grease on the wires, slip the boots up the wires a bit and then slip the boots down over the plugs once the wires are seated. Same on the distributor side. Sometimes it's a simple thing that bites you. Start there before throwing parts and money at it.

 

[Jerry Bransford]

One temporary problem that plagued 97-98 engines was a bad batch of weak valve springs which caused misfires and repetitive '43' diagnostic trouble codes when the Check Engine light is on. It took the factory quite a while to find the cause. Replacing the springs fixed my '97 TJ's random misfires. Mine was one of the factory test mules for various fixes, they sent me a lot of free parts to install but unfortunately, none of them helps. Fuel injectors, fuel injector wiring harness, clockspring, camshaft position sensor, crankshaft position sensor, new engine computer, ignition wires, distributor cap, rotor, etc. It was terribly frustrating for the factory.

Ultimately it was indeed the batch of weak valve springs that caused my random misfires. Replaced 'em and that was it!

 

[fxrsliberty]

If your not getting a code it's mechanical, anything in the ignition would code out. Even a faulty injector. Run seafoam through the oil for one oil change. If the valves are dirty and stick...... also not a bad idea to ruin seafoam in the fuel to clean the valves on both ends. And by all means, rev the crap out of it once in a while.

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