Diagnosing a misfire

[Tannhauser]

Apologies in advance for longish post.

 

I've already had some suggestions on this issue from various helpful people, but I'm opening this up a bit in the hope of getting more ideas before I start testing/replacing bits.

 

OK, I've recently had the following combination installed:

 

T61

E manage and E01

Dual walbros and 850 injectors, custom fuel rail

 

Other mods:

 

CW race plugs

oldish apexi intercooler

 

The car now stumbles under anything near heavy acceleration. It's a violent lurching motion together with a break in engine 'rhythm' and loss of momentum. I'm assuming it's a misfire from some other people's interpretation, though TBH I wouldn't know a misfire from a rice pudding. The car runs well under other circumstances - sometimes needs a touch of gas pedal to start now, but other than that, fine. However, it does feel very gutless.

 

The boost pressure this misfire occurs at is very variable, but sometimes quite low e.g. 0.6 bar. It usually occurs at 4000rpm in Auto 3rd. I can sometimes get all the way to the redline in auto 2nd without problems. Gradual acceleration in other gears will occasionally allow higher revs.

 

When the emanage was mapped, the afr s were datalogged and these appear to be fine.

 

Here's my list of things to get checked/try:

 

1. Check plugs as car ran quite a long distance before mapping and may have been overfuelling like mad - could this foul them permanently?

2. Check coil packs, which might be on the way out and unable to cope with increased airflow. Someone on the BBS has been good enough to lend me his.

3. Get injectors flow tested and cleaned - they were sitting around quite a while before fitting - could this gunge them up?

4. Fit afr sensor/gauge to check that ratios are as OK as I am assuming.

5. Retard timing on e-manage - this was never touched. I don't really understand how this might cause a misfire, but it's a suggestion that's been made.

 

Any comments ( preferably at suitably Noddy level) on:

 

a) the plausibilty of any of these?

b) any additional suggestions?

 

Thanks.

 

Cliff

[dude]

When you change the coil packs throw some BCPR7ES's in the car , i dont think this will take too much finding dude .

 

Dude:flame Dev

[Tannhauser]

Originally posted by dude

throw some BCPR7ES's in the car

 

What, literally? Front seat or back?

 

pm'ed.

[Nic]

When you change the coil packs also check the condition of the plastic electrical connectors to the the coil packs, these go very brittle with the heat and break easily. I had an intermitent miss-fire which was a result of knackered connectors, fitted new ones and it was cured.

[Tannhauser]

OK I'll check these. Cheers, Nic.

[matt]

Make sure the correct jumper settings have been used in the emanage