Stan,
I have a 96 GMC with the 5.7 engine. I have had a problem recently with it missing when weather was wet. Once I would drive about 20 miles it would go away. I replaced the plug wires less than 200 miles ago hoping that would clear the problem. I was down with the flu for four days last week. The truck sat the whole time. When I tried to start it the starter wouldn't engage the flywheel. I replaced the starter and that fixed the problem. When I tried to start it it cranked for awhile before it started. When it did fire it backfired and quit. I then started it again and it started right up but it was now missing badly on one cyl. So I went and got new Champion plugs and a Delco rotor and cap. I installed these tonight and the problem has not gone away. Do you think that it is possible that when it backfired it could have damaged an injector. The truck will start almost instantly when I crank it and seems to be missing on just 1 cyl. When I drove it the miss goes away at about 3000 rpm or if I romp on it. I can't drive it like that all the time though. I forgot to mention that I have 248805 miles on it. I have had no problem with the engine prior to this. It uses about a quart of oil after about 2000 miles and I have changed it every 3000 miles since I have had the truck. I bought it in 99 with 66K miles on it.
If you have any ideas I would appreciate your help.
Thanks, HD

hadude,

I can't remember if the trucks were offered with multi-point injection or just throttle-body injection. I believe that most of the the trucks were TBI. A back fire could cause injector problem but very slim.

As for the spark plugs, for Chevy always go with OE AC-Delco plugs. For some reason chevy's are picky when it comes to plugs. They are usually cheap unless they are the platinum AC-Delco, which I believe in 1996 almost all chevys used them. I use to work for Auto Zone and always had complaints about any other plug in a chevy because it will foul out or just not work properly. "Read" the spark plug for rich or lean condition. Look at any repair manual or online to see what each cylinder is doing. I would go ahead and change the wires also if you have not done recently. You would be amazed at how often the wires are the culprit. Good luck

Oh, I forgot to mention if it is a OBD II truck, usually the check engine light will come on. OBD I, than it will it may take a while.

In the dark, see if any spark is arcing any where on the engine.

Ok first of all Silvia240 is correct, you really need to get those Champion plugs out of that Chevy ASAP, the plug you need is a 41-993 which is a plat. plug. You can pick them up at a AC Delco distributor for about 5.00 a plug. I can't count how many GM's we have come in for performance problems and we replaced usually Champion or Bosch plugs and it runs tons better.

Now for the back fire part, usually a back fire means a timing issue, and could be related the hard start problem. I strongly recommend you talk with Stan or get it looked at. If you have the Vortec engine you will need a OBDII "scanner" to check and and set your engine timing, and if the timing is off them find out why your timing is off.

I have the Vortec engine. I couldn't find Delco plugs the other night when I was looking for plugs. Everyone in Terrell was out of them. I did buy platinum Champion plugs. I have always used Champion with no problem and usually change them at 50K miles. The last set I had installed instead of doing it myself and when I changed them last night I saw that they had installed Autolite plugs. The plug wires are only 2 weeks old. I replaced them because I had noticed that the old wires looked like a light show in the dark. They are good now. I think I will take it to O'Reiley tonight and have them put it on a scanner and see what codes it is reading. The check engine light is blinking off and on.

hadude call me at 214-538-9071 cell ok.

Dad you just need to KILL the GMC and get a FORD
Like me and Jerry.








GO ARMY

Your dist. cap could possibly be the problem. Remove the to screws and look inside. If there is any corrosion replace the cap and rotor, and spray a little WD-40.

if it the dist cap the one that looks flat on top iv had those thisgs crack inside where you cant see it i think gm messed up when they changed to the newer style of caps and it could also be a fuel problem like a sticky injector if it if the multi-port
not tbi the vortec 4.3s had the same problem with the injector asmebly its like a octapuss looking asmbley and very expensive also you might check fuel pressure just to be safe..

Stan,
I am off on Friday and would like to meet you and get the injectors if possible. I need to get the truck running right. I need to use it now.
I have now installed new plugs, an OEM cap and rotor and new wires. It still has one cyl not firing.
If it is possible to meet you on Thurs or Fri to get the injectors call my cell 214-505-0519. Fri would be best for me but I could meet you anytime.
Thanks

I will call you later tonight ok

Thanks Stan

Stan,
I am off tomorrow. I am coming into Dallas early. I have to fix a gate for my mother in law. I will be done by 9:00. If I could meet you and get the injectors it would be great. I will be near Buckner and John West. I would like to get my truck running right this weekend.
If another time during the day would be better let me know. I can meet you whenever would be good for you. My cell # is 214-505-0519.
Thanks

Stan,
When could I meet you to get the injectors for my 96 GMC truck. I need to get it running so I can use it.
I have been extremely busy the last 3 weeks so I have put it off. I have a 99 Saturn that I use to get back and forth to work so it hasn't been an issue. With the weather warming up I am needing to use it more and more now. I can pretty much meet you any time now. Just let me know when and I will meet you. The only thing that could be an issue to me is if I have a meeting scheduled at work.
Let me know when.
Thanks,
Harold Duty