I recently changed the plugs and wires for the first time at 97,000 miles on my 99 manual coupe. They may have been changed before I bought the car at 45,000 miles, although I doubt it. The car was running fine before the change, but since then hesitates badly and backfires when I floor it. If I accelerate gradually there is no hesitation all the way up to 6,000 rpm.

The DIC briefly showed the P0300 C code while the engine was running, but only once, and it has not returned, even when the engine stumbles badly. Other codes it showed were B2605, U1096, U1064 amd U1016. They were all History codes except for B2605 which showed Current briefly, but no longer. I looked these codes up in the repair manual and don't see how any of them could be relevant to my problem, with the exception of P0300 of course.

Naturally, I figured I screwed something up when I changed the plugs and wires, so I took them all out again and put them back in very carefully. I didn't have problems getting any of the plugs out or in and I'm certain that all the wires snapped onto the plugs and coil packs as they should.

Since the engine fires smoothly under mild acceleration, I'm thinking there may be a fuel problem - clogged filter or injectors? Failing fuel pump? If it is a fuel problem it would have to be be a heck of a coincidence happening right after I changed the plugs. One other piece of info - I didn't have a new gasket for the AIR pipe that I disconnected for the plug work. I reused the old one. I don't see how this could cause the misfires, though.

Before I start replacing fuel filter, pump, injectors, etc., is there anything I'm missing? Is there anything I could have screwed up while replacing plugs and wires? It was a pretty simple procedure.

Thanks.

 

If the car ran fine prior to the plug/wire change, check all your plug wires for continuity with a multimeter/ohm meter.

I damaged one of my GMPP Red wires after installing my LTs last fall.
The wire on the connector to the plug failed, but the connector did not come off. It took checking it with the meter to find it.

Check the wire on plug #7, it was the one I damaged and it seems like the one others have had problems with also.

The car ran perfectly and didn't have any codes, but when you went WOT, it would buck, kick and sputter, especially in 6th.

 

If the missfire occured JUST after the plug and wire change, it is the plugs and wires causing it now. Maybe a bad wire (ohm check them) a cracked plug (inspect them) maybe a bad wire connection at the coil or plug.

Don't change any filters or injectors until you fix what is NOW broke.

 

Thanks guys. I know I have an Ohmeter around here somewhere. I'll check the wires tomorrow.

 

Here it is again!
http://forums.corvetteforum.com/c5-t...esitation.html

 

Thanks Jnape and TN Vette, for steering me away from fuel issues. I removed the plug wires again and tested them - they were all fine. I put them back and the car runs great - no missing or backfiring. I can only assume that I had not previously pushed the wires onto some of the plugs fully. Anyway - alls well that ends well.

 

LOL,ALWAYS look at what you just worked on first! Happy ya solved it!