Posted: 9/19/2010 6:41:39 PM EDT
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I've noticed over the past few weeks that my engine is running a bit rougher. Nothing major, but not as smooth a a few weeks ago. doesn't stall, but feels like it might miss a little...slight shudders, but nothing major.
Today, driving back from a road trip, while driving down a long decline (driving downhill), MIL light flashes. no noticeable problems, no rough running when let off the gas. Stopped about 10 seconds after the road leveled out. About 2-3 hours later, hit another long decline, same problem. I'm somewhat puzzled. What could be causing this? There's no MIL currently lit, and thus no code to check. Just changed the air filter and plugs a week ago as a first attempt to resolve the rouger running. Ran a can of sea foam through the gas. specs:02 Chevy Suburban, 1500, L59 V8 5.3L, 167000 miles. plugs, air filter, pcv replaced a week ago. MAF sensor about a year ago. Fuel filter about 4 months ago. |
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Flashing MIL indicates a misfire severe enough to damage the catalyst.
Get your codes checked.You should at least have a "pending" code stored but it will probably be a PO300 random misfire. You will need a decent scan tool that can read GM misfire cycles so you can narrow it down to individual cylinder(s). |
| I will check my codes on my lunch break. It's odd, because it's not a matter of failure, but intermittant problems. This year does have separate coils for each plug, so I guess it's possible that one is bad. Ignition wires are 2-3 year old Lingenfelter Magnacor, and are in good shape. That's not to say it's impossible that there is a problem, but visually they look in good shape. |
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In other news, no problems since. That is, until yesterday. blinking MIL. P0306, Cylinder 6 misfire.
Intermittant at this point. Going to check the plug and ignition wires on my lunch break, and go from there. If that's all good, may be time for a new coil pack, coil over pluyg module doohickey. lol... |
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Flashing check engine light means the computer is detecting a misfire. Yup, this is generally the case. I had a Mitsubishi that did the same thing except only having 4 cyls you KNEW when it was misfiring. Oh yeah... blew an ignition wire in a v6, and you could tell. But in a V8? Nothing. lol.. |
My 2004 Grand cherokee does this, too.
Intermittent flashing, usually on an uphill drive out of Reno to the mountains. Dealership can never isolate or fix the problem. I'll lose power and will be literally standing on the accelerator and barely doing 45 mph. I've asked them to replace injectors, etc to no avail. They say the injectors are fine, engine is fine, it's a computer problem. They clear the codes and tell me to use high grade gas and Lucas fuel products. Nobody seems to be able to fix it here. |
| Well... went to lunch and had the MIL waiting for me. Removed the ignition wire, reseated the coil connector, checked the plug (it was tight) and reattached the ignition wire. No further problems on the lunch break, but the drive home should tell if it's fixed or not. |
| Misfires due to ignition problems will usually show themselves under a load. The heavier the load, the harder the acceleration, the worse the misfire becomes, until the rpms get up there. Intermittent misfires, or at least all the intermittent misfires I have had the headache of diagnosing, have come down to either fuel injector/wiring concerns, or poor quality fuel. And lately we've had a slight bit of a run on the poor quality fuel issues. Given your code isolated the misfire on cyl #6, you most likely have a flow issue in your #6 injector. In your case I would try getting the injectors cleaned out with a pressurized IV canister injector cleaner. |
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Swapped ignition coils this morning. Swapped 4 and 6, so if it's a bad coil, the problem should migrate. 7mm head, so I had to use a driver as I don't have a socket for 7mm. Combine that with 8 degrees ambient, and my hands are killing me. lol....
Edit: had a few blinking MIL lights, but no error codes yet. on my lunch break, added a few bottles of Techron injector cleaner. Seafoam was sold out, and I've heard good things about techron. |
Quote a few blinking MIL lights on my way in this morning. When I got home last night, I swapped ignition wires, and the problem is still on #6. I'm guessing at this point, it's a dirty injector, or a bad plug. Hopefully that cleaner works... I don't want to have to tear down the fuel system and have to manually clean the injector in single digits.
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Did the pressurized IV injector cleaner last night. Seemed to help for about 5-10 minutes, then the problem came right back. Probably going to call the local repair shop and take it in this weekend. If I had a garage, or heated area I could work on, I'd try it myself. But working on an engine in single digit/low teens, with carpal tunnel/wrist problems...not going to happen. Not to mention, I have the horrible habit of snapping off bolts....
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| Fuel Injector toast. Uncleanable, totally fooked per repair place. I've used them before and trust them. 173,000 miles, so I guess it's not so bad. Parts, labor, diagnostic, etc. $303. I know the injector alone is around $150, so that doesn't sound too far off. |