Cannondaleriders

My wife has a 2002 GMC Yukon that has been giving me problems. The problem is that there is a lot of shaking at idle and when you accelerate it acts like a quad that is to rich. It has a lot of hesitation and clears up when you are at a steady speed. The Service Engine Soon Light is on so I got it scanned at Autozone. It gives a "Misfire on Cylinder 6". I replaced all spark plugs. When I did change them, the spark plug in cylinder 6 was really rich. Took it back and gave same error with no change in problem. I switched a spark plug wire from cylinder 4 and took it back to get scanned hoping that it would give a different code but it didn't. Next thing I was going to do is do the same with the coil. What do you guys think it can be. Maybe an injector? Sorry for asking here but I know there are some real knowledgable guys here.

May be worth you time and money to just take it to a certified dealer to read the code and diagnose it. I have had Autozone and the like check my engine lights before. Told me it was a fuel leak problem and sugested I change the gas cap. Engine light came back on. Did this game for a couple months. Finally had to take it to a dealer for something else and they diagnosed the check engine light and replaced a cracked breather hose. Only cost $80 for part and diagnoses.

You might want to take it to get a better reading the ones at Autozone do always tell you the corect code and they dont give you all the the info that the one at dealer ships gives you. Good look

Sounds like to me you may have the notorious DEX COOL issue. You may want to check your intake gaskets. That is exactly how mine started out and the next thing I know my oil is milky and all of my cylinders are getting a steam cleaning. My yukon is currently in the shop getting a new motor. Try disconnecting your battery and see if the error clears but if it comes back then you might want to check it out.

Sounds like a coil to me. You could swap number 6 coil with say, number 8 and see if it misses on 8.

Just had the same problem with a 99 Jeep, strait 6 had a miss fire in #4 changed the whole coil pack (it's all one piece) and spark plugs, still same problem, so i took all the injectors out and cleaned the ones that i thought were good and put a new one in #4 still the same problem so i switch them out again, still no luck, also did a compresion check all good, so i get a Snap On computer and do the injector test with it and come to find out that the cylinder doesn't go in the same order as what the fireing order is, it goes 1-6 for the cylinder order and the one that i kept putting a different injector in #4 was really #6, what a pain in the butt this has been for the last week or so, so i would say take it to the dealer and get it over with, will save you in the long run, i was all most to the point of getting a new computer at the price of 450.00, or just find out which one is #6 from the start and try the injector swap? Good Luck

5.3? Rough idle, misfire #6 and if it backfires (doesn't sound like backfiring, But I was riding in passenger seat with head out the window and it was defiantly coming from right front fender were intake is ducted thru) thru the intake on hard acceleration. I would say fuel pressure regulator $42 at AutoZone.

Someone at the spring ride at Speed2424's took apart a Cannondale pressure regulator and it looked Identical to the one I just installed on my truck

A quick note. I used to work for Autozone for a time. The ones at Autozone have extensive information describing what the problem is similar to a dealer. Problem? Most the employees don't know how to find that info and will tell you the basics or only one of the problems if there's more than one. Take it somewhere that's certified. You'll be glad you did.

Autozone should stick to selling cheap quality parts and leave diagnosing problems to the mechanics. Their diagnosis of problems is a joke a best.

You need to verify that the coil on that cylinder is actually firing.....(most common problem)
If yes, then check your compression.......
If compression is good, check the EGR Valve for for sticking open (it opens in the intake closest to the #6 cylinder.)
Also, check for intake leaks.

If you need more help, call me at 601-209-3139.

Jimbo

P.S. If your spark plugs are bad enough to need changing, then so are your plug wires. It doesn't do any good to have new plugs and have wires with so much resistance that the plug can't get any fire.

Is it just me or have you not been on here in a while? Where have you been???