360 misfire help

how did you check o2 sensors? how did you check coil packs?

you got the misfire when cold?

 

You possibly have and intake gasket leak. The symptoms you are describing point directly to this. Have the car smoke tested.

 

Fuel air and spark that's the main things for a cylinder to fire other things can cause the ECU to read it wrong. Few things come to mind. Good luck!

• Vacuum or other air leak
• MAS/MAF issue
• Injector issue
• FPR issue
• Coil issue
• TPS possibly
• Crank sensor issue
• Cam sensor issue

 

I replaced everyone of those on my car (except the MAF which I de-corroded and cleaned). All those tend to fail over time so I replaced proactively, they were not that expensive and quite easy to do yourself. Many of those parts cross reference to other cars usually Porsches in my 348 case so you don't have to spend $750 for a part the same Bosch part is $75 usually if you shop with Bosch part numbers not Ferrari part numbers.

Good luck!

 

One word on the coil packs.. they'll "check out" OK, but they won't throw a code but still misfire. Buy 4 and replace that bank if you haven't yet. If not the coils.. That many misfires on different cylinders I'd be seriously suspect of the intake gaskets.

 

Check for oil in the intake plenum as it can and will cause problems with engine running.

 

I had the same problem when I owned my 360. It was the MAFS which I ordered off Ebay (they stated they were Bosch MAFS - and they worked) and shipped to the US from Germany in about 3 days. I had the same multiple cylinder misfire codes. I replaced both MAFS. Also, make sure your battery is fully charged as a weak battery messes with the car's computer and can result in all kinds of CEL codes.

PS - if you do a search about MAF cleaners you will figure out that MAF spray cleaners work as good as snake oil. If a MAF goes bad, most of the time it is due to an electrical problem within the MAF and not that they are dirty. If the car was ever overfilled with oil, it can mess with your MAFS as well then maybe a MAF cleaner spray would help.

 

When the cats in the manifold give up you will find chunks all through the intake system these chunks float around in the valves and cause random misfire, have take the throttle bodies off and have a good look inside the plenum see if any white chunks of cat are in there

 

Humm...interesting, please can you explain how this may be possible?

 

I can only guess how it gets into the plenum, when the cat breaks up the chunks get into the cylinder possibly because too high backpressure and back firing. You will get intermittent random misfires, backfires when cold and yes check the plenum for small chunks of catalyst if you find white dust up there you could also find particles large enough to cause valves to not seat properly. I would guess if the intake sticks open and backfires that could explain how. The air pump is also blowing air into the manifold which is full of dust from catalyst, that may have something to do with it. Im not talking about huge pieces but dust with some larger than sand pieces.

 

Sounds like rubbish.


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Misguided explanation of a known issue. I highly doubt you will see "white chunks of cat" in the intake plenum unless Fluffy got too close to the throttle body during a non-filtered rev. I think the issue you are referencing is the breakdown of the pre-cats in the MY2000+ stock exhaust manifolds which can end up in the combustion chamber, and typically cause much bigger issues than just a misfire. Thank God I have a 99.

 

I don't think it migrates to the intake side of the engine. The broken up pieces of cats will end up in the combustion chamber and cause an expensive problem. However, you will likely get an CEL code way before that happens.

 

That is what I am referencing didnt they guy say that he just gutted the pre-cats because of a missfire issue? Often the issue is repaired before it causes more severe issues but it is a random missfire and shops often can figure out the issue, they clear the codes and it comes back in a week they keep doing this until they find the pre-cats are the cause, after a long time yes the dust from the cats gets into the whole intake system. It causes valve guide issues, sticking valves, burnt valves and even yes you should inspect and clean out the plenum if you find anything in there, I did on one vehicle that actually had valve seating issues. Had to sent the heads out and I did find the material in the plenumn. I would say if you just gutted the cats because of a missfire issue and you STILL have a missfire issue how long does it take to remove the throttle bodies and look to see if the engine is dusted?