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Car Forum / GMC Cars / March 20052002 Tahoe Rough Idle after changing plugs
I hope soneone has some idea what I may have done wrong here: 2002 Tahoe 4x4, 5.3L PFI Vortec E-85 engine, 65K miles. Ignition type : coils mounted on the valve covers, one per cyl and a short wire to the plug (not a coil pack). I changed the spark plugs (used to do that at 50K on my older vehicles but lost track of time. (Now I hear they're good for 100K but I'm hard to teach new tricks), but sadly used cheap Champion plugs from Meijer and may have mis-read the book at the store and got the wrong ones. It ran like crap, so I immedieatly went to my trusty NAPA and got the correct plugs (double platinum, $63 a set, holy crap!). My wife said it turned on the Check Engine light several times the day she drove it, but it's not on any more and there are NO codes stored, according to my cheap Accton OBDII scanner. The manual and the tag under the hood say to gap at 0.060", but the NAPA computer said don't change from 0.040" pre-gap. I put them in at 0.040" and it runs pretty good, but after a day my wife complained of a rough idle. So I regapped them to 0.060", but it still idles rough. Not too bad, but definitely noticeable, and it hesitates a bit when accelerating from a dead stop. The wire boots were quite difficult to pull off the plugs, could I have damaged one or more to cause this problem? It's another $70 for wires, and I'll replace them if I have to, but seems kind of drastic to have to spend $130 on a set of plugs. My next oldest vehicle is a 93, so I'm not used to working on Vortecs. Is there anything I need to do when changing the plugs? Thanks in advance for any advice, Scott Reese 93 GMC 2500 Suburban, 65K miles 02 Tahoe, 65K miles 89 Caprice Classic, 230K miles > I hope soneone has some idea what I may have done wrong here: > [quoted text clipped - 23 lines] > $130 on a set of plugs. My next oldest vehicle is a 93, so I'm not used to > working on Vortecs. Is there anything I need to do when changing the plugs? The misfire is very likely from the wires, especially if you pulled on the wires or even worse, used pliers to loosen them. I'd pop the hood while it is dark out and see if you can see any arcing at the wires or around the boots. Since it is more likely to misfire under load, have a helper hold the brake and give it a little gas while in drive. Ummm...don't stand in front of it.;-) H Why would you replace the plugs at 65k? Are the Champion plugs platinum? Try putting DELCO plugs back in it. Bret >I hope soneone has some idea what I may have done wrong here: > [quoted text clipped - 40 lines] > 02 Tahoe, 65K miles > 89 Caprice Classic, 230K miles Get somebody with a decent scanner to pull the codes and freeze frame data. If the check engine light came on and went off the codes are still stored in the computer. >I hope soneone has some idea what I may have done wrong here: > [quoted text clipped - 40 lines] > 02 Tahoe, 65K miles > 89 Caprice Classic, 230K miles Scrap the Champion spark plugs, put AC Delco in. Regular style spark plugs are NOT PRE-GAPPED, there is no such thing. Gapping them to vehicle manufacturer's specs was the right thing to do. Change the plug wires. Then it should be back to normal. Next time don't change your plugs until the 100,000 mile mark. ;) Steve > I hope soneone has some idea what I may have done wrong here: > [quoted text clipped - 31 lines] > 02 Tahoe, 65K miles > 89 Caprice Classic, 230K miles Any noticeable misfire should set a code indicating which cyl. , ie: p0301 > Scrap the Champion spark plugs, put AC Delco in. Regular style spark plugs > are NOT PRE-GAPPED, there is no such thing. Gapping them to vehicle [quoted text clipped - 52 lines] >> 02 Tahoe, 65K miles >> 89 Caprice Classic, 230K miles Thanks, everyone for the guidance. I'm a newbie to this NG and was quite happy to see all the helpful responses. The Champions were not platinum, but I had already removed them and the new ones are AC/Delco. I did, in fact, use pliers to get the boots off the plugs. They would not budge by hand. New wires are on order (E-85 engine parts don't seem to be stocked anywhere). I think I'll probably invest in one of the PC-based scanners ($300-$450) for my laptop and scrap the Accton. Watch for it on E-Bay.... And lastly, I'll wait 100K next time. I'm not used to these newfangled motors, I used to be lucky to get 65K out of a set of plugs. I just have to adjust my mind set to the new technology. My thinking was that if 100K on Dex-Cool was partly (or mostly) hype and wishful thinking, then 100K on a set of plugs might be as well. I'll take the word of most of you in this group over GM's marketing department any day. When the wires come in Wednesday, I hope to be able to post a final chapter to this story. Until then, Thanks again,  SignatureScott Reese 93 GMC 2500 Suburban, 65K miles 02 Tahoe, 65K miles 89 Caprice Classic, 230K miles |
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