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I have a 96 GMC Sierra 1500 that has approx 140k miles on it. The check engine light went on so I took it in for service. My mechanic put it on the computer and it said the plugs are misfiring. So we replaced all the plugs, wires, distributor cap & rotor. Well a couple weeks later the check engine light went on again. He checked on the computer and couple of cylinder's are still misfiring. He thinks the injectors might be clogged. Does that sound like that might be the problem or does anyone else know what it could be? Thanks.

He did not diagnose enough. It needs to have a injector balance test performed first.
If you live in the Sacramento area give me a call I can probally help you out.

916 813 0321

Don't waste your time or money chasing missfires on that early vortec FI system. Have it replaced with the updated spyder assenbly and all problems will go away. The early poppet injectors are not worth replacing at $90.00 each. As soon as you replace 1 a different cylinder will give you issues. The updated spyder assembly with small injectors at each cylinder will set you back about $400.00 but you can relax knowing the FI issues are gone. I have done hundreds of them at my shop with great results. Also GM was swaping them out for 10 years and 200K miles due to emission problems at no cost.

Hey Leon thanks for the offer but I'm in SoCal in the L.A. area. So Byron will this spyder assembly replace the current fuel injectors and is it bad to drive it the way it is right now? I use the truck every day and don't want to cause it anymore damage. Thanks guys!

The only further damage could be to the Cata;ytic converter due to overheating caused by the misfire. Yes it is a dirrect replacment for the existing system. The update converts your system from CSFI to MFI. The needed parts are as follows -----

V-6 - 12568332 injector assembly, 88894355 Bracket, 17113215 Seals
V-8 - 93441235 Injector assembly, 93442096 Bracket, 17113206 Seals

If you have an aftermarket Delco source it is avaliable in a kit.

Byron thanks for your help. It is greatly appreciated. We initially thought about replacing the injectors but didn't know about the updated spyder assembly. You definitely saved me some money in the long run. Thanks again!

Byron - I am sort of been having a similar experience in my '95 Ford with the 5.8 "R" engine as far as the Check Engine Light. (152k miles on it)


Last couple of times the auto choke on start up has not been working on a cold start - idles to 500r's and then died. What I do now is push the gas pedal - then key the ignition start the fuel pump up to pressure and press is again before I start it. That seems to be working so far.

Sometimes while driving though with everything "normal" my Check Engine light will come on.

I am thinking to myself that it possibly could be the EGR valve ..... Could I be correct in this or should I put new plugs/wires/roter cap on. They have about 60k miles them withem with 8mm wires and the Bosh Quad Fire Ceramic plugs.

Thanks for your time to reply.

Here is what I would recomend -
For the lousy cold idle - Remove the intake boot from the throttle body, open the throttle and wipe the oil deposits out of the bore with a rag and some carb spray first - that fixes 9 of 10 ford idle issues. Also look for any vacuum caps missing from the intake manifold.
Next - Dump the Bosch plugs - they arn't worth a damn on Fords ignition. I hate to say it but put the correct Motorcraft plugs in it.
For the "Check Engine" light - Get someone to run a KOEO and a KOER test on it with a real scan tool - Not just an Autozone code reader. Oh yea, that means Key on engine off and Key on engine running.
Get me some codes and maybe I can help. Even if the engine light is off there are still codes in the memory.

Thanks Byron.

I'll dedinately check out the throttle body with cleaner.

The plugs, wires I will prolly go back to stock OEM parts. Even though the wires now are shielded ... they still mess up my AM reception on the radio.

I had a similar problem once on my 2001 GMC while camping. Turned out that a rodent had climbed into the engine compartment and cut one of the small wires to an ignition module. It was very hard to locate since it was close to the firewall. I made it to a dealership in Napa and they made a quick repair.