2002 996 misfire

Ken911 · 11-03-2009, 05:55 PM

Has anyone been able to diagnose misfires on cyl 1 and 2 ? we've tried coils, lifters, plugs, and air/oil separator....to no avail . thanks for helping.

peavynation · 11-03-2009, 06:22 PM

It's the IMS letting go and the RMS leaking.

Lol!!
Sorry Ken911.

And welcome!

Macster · 11-03-2009, 06:54 PM

Quote:

Originally Posted by Ken911

Has anyone been able to diagnose misfires on cyl 1 and 2 ? we've tried coils, lifters, plugs, and air/oil separator....to no avail . thanks for helping.

Misfires -- CEL blinking or just on steady? -- on one side can be a failing or failed VarioCam acutator, solenoid. I mean you've eliminated the most common causes, assuming the new coils/plugs are good, correct, and all the hook up and connections are good.

If a VarioCam actuator or solenoid bad enough this might generate an error code in its own right. In the meantime, it might just generate a misfire.

A misfire in just one cylinder can be a bad injector but engine controller will attempt to adjust/adapt by if injector blocked injecting more fuel in the other cylinders. Long term fuel trim on this bank will reflect any enrichening or leaning (if the bad injector leaking) of the air fuel mixture.

Another source of a misfire can be a burned valve. I've seen this happen on just one valve -- exhaust -- in an engine but if one cylinder can experience a burned valve, two cylinders can.

Adjacent cylinders experiencing the same symptom suggests a common failure between them: intake manifold leak; head gasket leak; or cracked head; porous head or block.

What do long term fuel trims look like?

What did the old plugs look like from these cylinders? Exceptionally clean, dirty, oily, dark with carbon or other deposists; or just normal?

What do the new plugs look like?

And of course the misfire can be an early sign of more serious troubles with the camchain drive. What is engine noise like?

Sincerely,

Macster.

garrett376 · 11-04-2009, 12:38 AM

When does the misfire and CEL happen? Right at startup? A worn/bad flywheel can result in a misfire and subsequent check engine light a couple seconds after startup.

Ken911 · 11-04-2009, 10:43 AM

Hey all, thanks for the reply, the misfire takes up to 5-7 minutes to occur and the CEL light flashes and eventually stays on. I will investigate all these ideas and post again, thanks Ken911

11-03-2009, 05:55 PM	#1
Ken911 Addict Rennlist Member Join Date: Mar 2005 Posts: 3	2002 996 misfire Has anyone been able to diagnose misfires on cyl 1 and 2 ? we've tried coils, lifters, plugs, and air/oil separator....to no avail . thanks for helping.

11-03-2009, 06:22 PM	#2
peavynation Addict Rennlist Member Join Date: Aug 2009 Location: San Diego, CA Posts: 272	It's the IMS letting go and the RMS leaking. Lol!! Sorry Ken911. And welcome! __________________ '01 C4 Coup, Ylw/Blk 6sp Areo '67 Mustang Fastback, 390FE S-code 4sp (now with TCI C6) Video '70 Mustang Mach1, 351C 4V M-code 4sp (now w/ worked 2V's & T5) '95 Toyota T-100 Pickup, V6, mild lift '05 Suzuki SV650S, Yosh exhaust (just sold; sniff sniff) '03 Honda CRV '89 Nissan Stanza (yellow bumper as paint came off!! Awesome) '84 Toyota SR5 Pickup '78 Chevy Stepside 4x4 w/ 1ton trans/T-case/axles '75 IH Scout, Orange

11-04-2009, 12:38 AM	#4
garrett376 C4 Specialist Rennlist Member Join Date: Oct 2003 Location: La Jolla, CA Posts: 4,166	When does the misfire and CEL happen? Right at startup? A worn/bad flywheel can result in a misfire and subsequent check engine light a couple seconds after startup.

11-04-2009, 10:43 AM	#5
Ken911 Addict Rennlist Member Join Date: Mar 2005 Posts: 3	Hey all, thanks for the reply, the misfire takes up to 5-7 minutes to occur and the CEL light flashes and eventually stays on. I will investigate all these ideas and post again, thanks Ken911