'97 Tahoe - Misfire diagnosis

[crooner]

I have 1997 Tahoe, bone stock and am getting a 'Service Engine Soon' light. I can feel a very tiny miss at idle only especially on warmer days for some reason (or all in my head). I bought an ODBII scanner from Autozone and it throws a P0306 - Misfire on #6 cylinder.

So far, I've only changed the #6 sparkplug wire, cleared the code then ran it for about 30 miles. The light stayed off, but the scanner picked up a 'pending' P0306 code, then a definite P0306 code and the light came back on the dash. Cleared it and drove it again (as normal) and at first it had a 'random misfire' P0300, then back to the P0306 as a second code.

Just wondering whats the best way to track down this problem. I have a bottle of Seafoam that I am running through it in hopes that if its the fuel spider/distrib, that'll clear it up. Other thoughts I was having are a fresh set of plugs, cap and rotor.

Any insight would be appreciated. Thanks.

 

[SunlitComet]

Inspect plug for cleanliness, type and gap. Also inspect the cap and rotor for deposits or corrosion on terminals. And finally after running those miles what is the misfire history showing for all cylinders?

 

[crooner]

Ok, so I am generally on the right track it sounds like. Will pull plugs in the morning and probably replace them with NGKs. Cap and rotor to follow.

The misfire history? Its never done this since I've owned it (about 20k) or is there a history function on the better ODBII readers? Mine doesn't have it.

One odd thing I've noticed is that the #6 wire is very close to the dipstick tube and appears to have been rubbing on it--evidenced by the wear mark on the old wire that I replaced today. With the wire holders, there is still precious little gap between metal parts. I assumed incorrectly that those were the source of the misfire (arcing).

 

[SunlitComet]

Do not use NGK. Use either Ac delco 41-993 or Autolites APP605. They are also pre-gapped. If you don't have misfire history then you will need a better scanner. You should get one that read Enhanced GM perimeters. Especially Misfire history and CAM_RETARD.

---------- Post added at 05:04 PM ---------- Previous post was at 05:01 PM ----------

I have also moved your thread to the appropriate place.

 

[willxfs]

Anyone have a make and model number of a scanner that can read misfire history and especially cam offset retard. I'm looking for one. Thanks

 

[SunlitComet]

Do you want hand held or pc/laptop based?

 

[willxfs]

Really whichever one is cheaper. I need to adjust the cam offset. Labtop version might be cool. Thanks

 

[SunlitComet]

I use this software in the first link and bought the GM add-on in the second link. There are several different types of hardware interfaces but I chose the one in third link.

http://www.scantool.net/software/scanxl-pro.html

http://www.scantool.net/software/scanxl-gm-enhanced-diagnostics-add-on.html

http://www.scantool.net/scan-tools/pc-based/obdlink.html

I do not use the software that comes with the hardware. That is what the scanXLPro is for.

You can down load the software to check as a demo. Once you purchase it they will email registration key. You just have to wait for hardware in the mail. mine took three days.

Note it will most likely not read ABS for a '97 but you may bee overwhelmed with what is does show so take your time to read it correctly.

 

[willxfs]

Sunlitcomet,
Thanks for the links. Thats just what I was looking for.

 

[Uderro1]

I have the exact same problem in my 96 Hoe except that it is cylinder 5. I replaced cap, rotor, plugs and wires. Flushed the cooling system and used Blockseal to try and seal up any coolant leaks. To no evale I still have the same code being thrown. I am loosing water some where. I fill the radiator and can go about 3 weeks without having to put any in then when I do it is like a quart or two. The one mechanic at work thinks that it is the head gasket leaking into the cylinder but we are not sure. I was told that it could be the plenum also.