2001 350 mag mpi slight misfire

I've just had the engine out to replace the gimble pin, while it was out it was serviced very badly, since I got it back its had a misfire,cut a long story short the agents were usless so I fitted new dist cap, rotor arm which needed it, and still have the problem? Anyone had this happen because of the risers only the service agent is saying its not possible? Wondering if they could have messed up the reinsall of the risers, Any ideas? all welcome many thanks Geoff, oh its fresh water only. one idea I have is never use that agent again.

Re: 2001 350 mag mpi slight misfire

If it's regular (the miss), then look for a cracked plug. With the engine idling pull a plug lead off and note how much the engine speed drops. Re-plug the lead, move to the next one.... That will help you identify the cylinder causing the miss... Go from there.

Very unlikely to be caused by an exhaust elbow (I assume you mean elbow when you say 'riser') to cause this sort of problem.

Chris..............

Re: 2001 350 mag mpi slight misfire

have you checked the firing order??

1-8-4-3-6-5-7-2

Re: 2001 350 mag mpi slight misfire

Sorry wasn't very clear, the misfire is irregular, you don't hear or feel it when just reving out of gear. Once underway its not a regular or a complete die out, more of a hesitance, a few times a minute. Unfortuantly I can not say if its there under full load as I'm on a river with a very low speed limit, but it does rev freely and smoothly out of gear, and it there up to 2000 under load.

Just took the IAC out and cleaned it, wouldn't say it was bad, a small amount of carbon on the end and the rest was good, had to remove the throttle body as one of the screew broke removing the IAC, luckily it left enought to thread to get grips on. All cleaned waiting for new throttle body gaskets to arrive.

The 350 mpi has a riser block between the EX mainfold and the elbow, probably 6" hight, so there are 2 sq 4" or so gaskets one at the bottom EX mani to Riser and one at the Top, Riser to Elbow. They took the lot apart and checked the flap vavles at the bottom and then re assembled.

I've double checked the leads and plugs and all look good.

I'll see if the IAC clean does anything, just strange that for Ten years its been faultless and as soon and I let someone else play with it and starts playing up :-(

Anyone know how to test the 4 wire IAC while its out?


Thanks again will keep you posted.

Geoff.

Re: 2001 350 mag mpi slight misfire

Bad plug wire will do that. Did you check the resistence on all of them?

Re: 2001 350 mag mpi slight misfire

Thanks Good Point

Will put a meter on the leads to be sure

Geoff.

Re: 2001 350 mag mpi slight misfire

forget the IAC, all it does is control idle air, once you advance the throttle the IAC is no longer an issue

have you run any diagnostics (DDT/CDS)??

Re: 2001 350 mag mpi slight misfire

Hi,

Yes its was checked by the agent before returning it and no fault codes.

I'm hoping to climb over it today and check they connected every thing up when they put it back in.

Thanks