2000 Jimmy missing badly

[nlb250]

4.3 V6 began showing engine light when highway use in OD. Still ran but little power in OD. Light went out when parked for a while. Ran fine around the city. OD agian engine light on now missing badly feels like on running on 4 cylinders. Have changed the ignition sensor and catalytic converter in the last couple of weeks. Need your diagnostic advice before i start spending time and $. Thanks

[MT-2500]

Have you checked /replaced plugs with AC delco plugs and checked for dead cylinder miss?
What codes arer you getting?

[nlb250]

Yup changed plugs and wires only 5 weeks ago as well as cap. Shows misfire. Could the tranny going into OD cause the misfire to occur if the tranny needs repair? Really don't want to see an afirmative response.

[Rick Norwood]

Originally Posted by nlb250

Yup changed plugs and wires only 5 weeks ago as well as cap. Shows misfire. Could the tranny going into OD cause the misfire to occur if the tranny needs repair? Really don't want to see an afirmative response.

I had the almost exact same problem with my 2000 Jimmy. What brand of Distributor cap did you buy? I had P0300 (Random Misfire) codes. Have you taken the truck anywhere to get the codes read? Auto Zone will do it for free, but DO NOT BUY THEIR DISTRIBUTOR CAPS.

See this thread:http://www.automotiveforums.com/vbul...d.php?t=975186

My brand new AutoZone distibutor cap went bad in less than 6 months, and BECAUSE I DID NOT BUY AN AC-DELCO CAP, I had to replace my "new" cap with an AC-Delco Cap and my problem went away.

[Darren509]

Ditto. My cap and rotor were less than one year old and looked perfect to the eye, but had many problems and hours of diagnostics done before I bought an AC Delco set, fired right up and no problems since.

[nlb250]

Thanks for the ideas. Had the mechanic here this AM and the code was 0300 which could be any number of things causing the misfires. Checked the EGR and unplugged it and the truck ran the same. Costly little item to replace but it appears it could be the culprit since changing the catalytic converter last week. I will let you know the outcome.

[nlb250]

Replaced EGR unit with used one but made no difference with the missing.
I guess the next will be the cap & rotor. Any thing else?

[old_master]

P0300 is almost always caused by secondary ignition: plugs, wires, cap, rotor, ignition coil. As mentioned, make sure the plugs, cap and rotor are all AC Delco, and the wires either AC Delco or Autolite professional series. Don't spend money needlessly, but spend it on the right stuff!

Insufficient fuel pressure can also cause a P0300 to set, but make sure ignition is good first.

If there was a problem with the EGR valve, it would have set a DTC for it

[nlb250]

Changed rotor and cap checked the new wires out in 6 weeks ago a okay. reolaced the EGR unit still running rough as a tax audit. unburned gas out the tail pipe. Any other ideas?

Norm

[MT-2500]

Originally Posted by nlb250

Changed rotor and cap checked the new wires out in 6 weeks ago a okay. reolaced the EGR unit still running rough as a tax audit. unburned gas out the tail pipe. Any other ideas?

Norm

Proper testing wouyld be in order.

Fuel pressure?

Plugs and wires?
Good AC delco?

Look for what cylinder is missing.

Is it getting good hot blue spark?
Good Compression?
Is plugs wet or dry on ends?

Have you checked the camshaft retard setting?

Mas air flow sensor reading good?

[Darren509]

I know this may sound dumb, but please dont take it that way, but is your firing order correct with the wires? And if so, have you pulled your plugs to see if any are fouling out..

[nlb250]

So heres' the latest. had compression tested and #3 has "0" compression and #5 ain't too much better. Currently the engine is being broken down and having a good look on the inside. I will let you know the outcome soon after my cheques run out.
Norm