Flippin misfire on classic - help?
 

Hey Guys

I have a 97 UK turbo with 157K on the clock now.

A number of mods but for this problem I only think the Apexi ECU is relevant.

Changed plugs about 4000 miles ago and gapped to 0.75 simply as they'd only been changed once before and at the same time I put on some after market 8mm plug leads a friend had donated to me.

Coil pack is about 70K miles - 7 years old as changed that soon after I first bought the car.

I commute up & down the M1 to work through 50mph road works 35miles each way and in the past few weeks I've turned down my boost setting on the Apexi from 1.3bar to 0.6bar for my commute to help save fuel, and it works I've been getting over 30mpg (but its dull!)

Anyway last week I noticed a misfire. It seems to happens at any throttle position / engine load. Its not a single mis fire, I'm loosing power for a fraction of a second then it comes back. Sometimes its quite jerky sometimes its not happening at all.

I've seem quite a few people here recommend 0.65 plug gaps and I'm afraid I have no idea about the quality of the plug leads but I reduced my plug gaps this evening and it made the situation much worse.

Obviously I'm going to change them back tomorrow and see if the situation improves but any advice or experience with something similar?

Cheers

It could well be a plug lead or coil pack issue given they have done quite a few miles,once disturbed the plugs/leads or coil pack can make misfire's worse so i'd be looking at changing the above or getting it booked it some where that can tie the problem down for you mate.

What plugs are fitted to it? Reason i ask is because i had Iridiums, gapped them and it ran like a total dog. Its common during gapping for the Iridium tips to break off. But i would deffo get a new set of leads and plugs.

Plugs are new NGK PFR7Bs and leads are new too

As musso says check the gapping again

Thanks Guys but more info.

Plug gaps were 0.8 (as the Subaru book says) and problems as reported. I reduced the gap to 0.65 and it became MUCH worse. Last night I opened them up to 0.9 and the problem is much reduced but still there.

I think the plug gaps are a red herring (Where does that phrase come from?)

Anyway, engine is very sooty - ie running very rich so I'm looking into sensors, Apexi PFC sensor readings when car is cold:

AF-1 0.24v
THRO 0.46v
BST1 2.32v
BST2 0.00v
WTRT 2.20v
AIRT 4.88v
o2-1 0.00v
EXTM 5.10v

I've checked the lambda sensor, on tick over it cycles from 0v to 0.74v and back again. Under boost conditions it reads 0.8 or a bit higher so seems to be working fine.

BST2 always reads 0v dont know what this is

I think all the others change except can the AIRT? On a 97 UK Classic I dont think there is an Inlet Air Temp sensor. Will check in the morning.


Love my car to bits - blood sweat and tears invested but I have to confess I'm thinking my next toy out to have carbuettors and a distributor