Hi all,

Don't know if im posting in the right place as this may be mechanical setup but here goes anyway.

Just finished a zetec conversion running Suzuki Hayabusa TB's and having loads of trouble getting the car to idle properly.

ECU is Omex and scatter spark idle is off. Ignition values around idle are 10Deg. so should be fine.

The problem is i keep getting iginition in the inlet manifold and a rough idle. When i check the plugs and cylinders you can see it is very rich however a reduction in fuel causes the engine to stall.

Can anyone tell me what could be causing this?

Things i have checked already:
Engine sensors are calibrated and operational
Mechanical engine timing checked and ok
Injectors all working and consistent fuel coming through
Dont think i have an air leak
Have balanced TB's as best i can but rough idle is preventing getting any better (also needles on vacuum gauges fluctating a lot)

I had old single butterfly GSXR TBs on mine till recently with omex ECU. You have a choice of spark scatter or ICV to control idle. Throttle stop isn't enough to control idle by itself and the air bypass screws were closed. Enable spark scatter.
Mine is set to 'idle on' below 1300 with target idle of 950rpm. My graph is a straight line between 20 advance at 325 below target to 10 retard at 300 above target and passing through the zero point (so two straight lines with a kink between. Try it. It can only help!

ignition in the inlet could mean timing?......Have you checked your timing belt in relation to TDC is correct.

Yeah checked the mechanical timing and all is ok - when slots in cams align at top (correct way up due to offset) the key on the crankshaft points vertically up.

Omex told me to turn scatter spark off until i could get a decent idle - then to set that idle slightly high before turing scatterspark on to let it do the ultra fine tuning.

Was having same problem on old engine aswell so it says to me the problem is TB / inlet related?

Other than timing, what else could cause ignition in inlet?

When the butterflies are in idle position how open should they be?

Can you wind the idle stop in a bit and get it to 'fast idle' at about 1500rpm or so? There is a chance one of the butterflies is almost completely shut and it's effectively running on 3.

Have you checked the ignition timing to make sure that you are getting the advance you are expecting?

Will try changing the idle stop to open the butterflies a bit more tomorrow - does sound like it could be that.

Advance is correct - running at 10 degrees of advance for idle zones - Omex said 5-10 should be fine. Did try increasing this before but made it worse - felt like there was too much and it started trying to stall.

I didn't do it that way but the guys at Omex are very helpful. Sounds as if you have balance problems. You can do some by eye. Unscrew the throttle stop on one, the one with the throttle cable till its just closed. Then adjust number two to just open and wind out to just close it. Then number three to just open and then wind out to close and then number four. Do in that order as adjusting two moves three and four, adjusting three moves four etc. Start engine and open up the throttle stop on one till the engine will run even if that is at 2000rpm. Now try to adjust balance with meter or stethoscope style always moving from the throttle cable end, one. Balance two to one, then three to one ,then four to one. As it runs better close the throttle stop on one to drop revs toward 900 or so. I still think having spark scatter enabled helps this process when I am doing it.

Thanks for the help so far guys, i will have another play after work tomorrow and post back with the results - hopefully an improvement!

Well, got some improvement in that got it running by using plenty of throttle!

Still got issues though, rough as hell! Tryed pulling the leads off while it was running and 2 had more effect (although they are all sparking) so it seems like a plug or coilpack problem however it is all brand new and the same issue was ocurring when the setup was on the old engine with other coilpack and leads / plugs. Will be testing with another coilpack and plugs tonight.

Failing finding a fault in the above (which i dont think i will) what else could be causing this?

Could it be th ECU or an earth fault?

Any other thoughts / ideas would be much appreciated.

Backfiring suggests weak mixture, any chance of the manifold flange being distorted and leaking air into one or more cylinders?

Have done further fiddling and testing but still to no avail, simply seems to keep getting worse!

Have got ignition in inlet which i thought pointed to a rich mixture but havent got the wideband hooked up yet. Didnt really want to until i get a decent idle.

Had a long conversation with Omex and as it is doing the same thing on two engines with different ignition components and have tested the new parts to confirm there is nothing wrong there then there could be a fault with the ECU - great

So sent it off today so they can get it on their test rig.

I'll post the results when i get it back - surely this time its gonna work!

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Originally posted by izzywizzy
Have got ignition in inlet which i thought pointed to a rich mixture

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