Help please… 1999 Tahoe 5.7 2wd

[86GN-862+2]

It's got 170K miles and was running great. Now it is popping a code 0301 which is a misfire on cylinder 1 according to OBD code booklet. I've replaced plugs and checked for spark and it's all good. Thinking injector may be done for it stumbles at idle but runs strong under load. Another peculiar thing happenings is that all the lights are dimming as it "misses" when idling or under acceleration. Weird as this may sound, it seems to have started after I had it detailed and the detail shop just sprayed the crap out of the engine bay to make it shine more. I don't know what they use but could be that armor-all crap. I have also ran two cans of injector cleaner. B Chem-tool(l think) and after fuel up again I poured some seafoam. I cleared the code several times but it keeps coming back. The wife did run the thing low on gas a few times too. It was so low on fuel that while running some errands, it almost killed the engine as I was making a turn. Maybe it picked up the trash in the tank and plugged up a few injectors… I don't know. I also replaced the fuel filter BTW. Sorry for a long post but just trying to put down everything as it happened. Any help is appreciated.

 

[scot502]

had same problem on 00 Tahoe changed fuel pump and no more problems. A gm tech told me you start having this problem when fuel pump is about to die.

 

[GBGN1]

If the fuel pump was going bad there would not be just a misfire on one cylinder. Get it scanned with a tech 2 and they will be able to see the fuel trim and misfire graph and will be able to diagnose the problem much easier. Stop putting the injector cleaner in it. Waist of money. People need to realize with todays fuels with at least 10% ethanol in it will keep the injector clean that way. If that injector is bad, do a ohm reading and make sure its in spects.

 

[charlief1]

Since you replaced the plugs what brand did you use? This sometimes causes the issue. Also if you have the cap with the wires atached to the side it has a serious issues with creating missfire problems when it gets old.

 

[chopped39]

Wait till its dark and take a spray bottle with water and spray a light mist on cap and look for arcing. I cant remember but I think when the cap archs through inside the cap its the number three thats pathed by the coil contact. You cant see the the carbon track. These are very common for caps. get an ac delco cap. It may also be a poppit valve sticking. Its a pain in the butt but if you pinch off the return line under the truck near the tank for just a couple seconds .This will put 90 psi on the poppit if its stuck that will usually break it loose. If i is the injector swap it out for the multiport set up. Its a little expensive but worth it in the long run. Spray the wires and cap first before anything and do it when its dark so you can see it easier . Good luck

 

[86GN-862+2]

Had to try the fix in a can. Many people swear by sea foam. It actually sorta helped because the engine ran smoother for a few miles with the engine light barely visible then it lit up again as bright as ever. Will try the cap and rotor next. Plugs I got were
Autolites. I know, I know get ACDelco. Next is either injectors or possibly distributor gear if cap rotor doesn't fixt it? All this was done at around 100K miles anyway. Fuel pump has been replaced in the last year. The old one didn't show any trouble codes when it went out. Idle fuel pressure is at around 55lbs and it climbed when I revved the engine up some. Thanks to all replying. Really think it is the fuel injector cause it gets plenty of spark on that first cylinder but engine idle is unchained when. I pull the wire from the plug. It stays stumbling.

 

[chopped39]

If you can get a scanner with bidirectional controls you can shut off injectors one by one. perform a pressure drop test on injectors also. also called a balance test on some scanners. I use ac delco alot but the autolites will be fine.

 

[John Larkin]

If it is not a pain in the ax, move the injector to another cylinder. That would tell you if it is the wiring or the injector.