Miss At Idle

[tacker]

Have a strange problem with the old car.

It has a miss on #5 cylinder at and idle but appears to run fine when engine is loaded up.

Any ideas?

[PHA71L]

plugs?

[tacker]

Hmm i have changed them and had injectors cleaned, even compression test across all pots etc etc.

car pulls well on dyno just has a miss at idle think it might be a wiring issue

[MBS206]

What was the readings on the compression test?

[tacker]

between 150 and 153 off the top of my head, and the engine builder said the #5 cylinder was one of the higher readings.

I cant think of any reason could it be weak spark? think i will check the connection on the ECU

[J'z-R33]

coil pack, mines doing the same thing...

[GeeTR]

Assuming you've tested fuel and spark through normal means... could be a gasket leak (yes, im scared from my experiences..)

[tacker]

Yep fuel pressure seems ok have a fuel pressure gauge on the car and it seems to work fine have 40 psi at idle and 58 psi at 1.1 bar boost and AFR is 11.4 at WOT. also have wide band.

I checked spark by removing coils, earthing them and installing another set of plugs into the coils and turn the engine over. So it has spark of some sort. Have another set of coils off and old engine i brought and it seems to make no difference.

Sprayed heaps of brake cleaner on the intake side looking for a vacum leak but after a half a can it didnt make any difference at all.

very strange.

[tacker]

seems i do have a wiring problem a few wiggles of the loom near ecu and it running again grrrr