More misfiring

Hi guys

I have just been out in my GTA. Initially the car ran ok, but progressively got worse. It started misfiring under load at about 2500 rpm, I didn't want to push it too much, but it didn't seem to clear if I accelerated. On a lighter throttle it ran ok with just an occasional misfire.

However when I got home & let it idle. it was very lumpy & popping through the exhaust.

I have replaced just about everything over the last year or so.

any suggestions ?

Thanks, Paul

water ingress?
Is it kept wet outdoors or dry indoors.
While the car is idling, pull off 1 HT lead at a time. As each one is pulled the idle should drop and get worse. If this is not the case for 1 cylinder.....that will be the most likely cylinder. check there is no water around the top of that plug.

Hi Simon

The car is kept in a dry garage. I replaced the plugs & leads about a year ago. Ill check them like you suggest

thanks, Paul

What have you replaced Paul? List it and we'll play spot the ball.

Dizzy cap and rotor arm.

They corrode so easily even if not in use.

certainly worth checking the condition of.

Okay, here goes. Over the last year, I have replaced:

Spark plugs & leads, Coil. Dizzy cap & rotor arm. TDC sensor. Rear fuel pump & filter. The injectors have been refurbished & I have replaced some of the vacuum hoses.

Paul

Does it smell like it's running rich? What colour are the spark plug tips?

Could be fuel pressure regulator. Are you running the standard one?

[BIG_MVS]

Are both fuel pumps running?

Check the front is running all the time.

Darren, Mine is an early car with the single FPR under the plenum. I will have a good look at it. Maybe it needs changing / updating. Is there a simple swap for something better, or are they a serviceable item ?

Martin. The rear pump is a brand new Walbro so should be fine, new filter fitted also. The front one is as far as i know original, so that is definitely worth checking out. I have fitted a new front filter.

Thanks, Paul

I have seen on a few occasions now an Italian brand distributor cap getting a type of conductive ooze on the inside causing a miss whenever the boost came on. These caps failed inside a year. I recommend you only use Bosch caps and buttons. The GTA Turbo has the same cap and button as a mid 80's BMW 635 and many other BMWs.

I had tried cleaning out this siliconey ooze but it returned. Kerosine and thinners hardly touched it, with only Acetone making much of a dent in it.

Check your plugs aren't fouling,running rich and yes check for a damp dizzy.Sounds like fouled plugs .

Thanks for all the replies & suggestions.

I took the left hand plenum off to have a look at the FPR. The small bore vacuum hose that goes into the top of the regulator was a loose fit. It had a clip on it, but could be easily pulled off. I fitted a new clip, the hose seemed fine, it wasn't fouling anything so i checked all the other hoses & put it back together.

I took it out for a run & its much better. It does still cut out if full throttle is applied when under load in a high gear. I have decided that I will fit a new front fuel pump (any suggestions or recommendations please ?) & i will pull the dizzy cap & plugs to check them, They are both newish (supplied by Lee about a year ago) so i think they will be ok.

Moving in the right direction

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