Extremely rich

RobH · Post by **RobH** » Thu Jul 17, 2008 8:44 pm

Hi all,

I've been somewhat delayed with my project by a stuck open injector which had to be replaced. Anyway, I now have 6 injectors again and all seem to be working. Car is a Z32 VG30DETT, 550cc injectors, hybrid tubs, FMIC, AVC-r and a few other bits that won't have a big effect on the way it runs.

Problem is it's running extremely rich, to get it to idle and make it run marginally better than awful I have to drop the K constant right down to 70 (!) where it should be around 193 according to the resize function. Black smoke and black plugs. (all plugs are black so I don't believe this to be an injector problem). Could the latency have such a major effect? I've tried tweaking this to no avail.

Engine has been out and I've junked a few bits and pieces (EGR, AIVs carbon can, cats, standard recircs, air con, stock boost solenoids).

I'm of the opinion that an air leak would cause it to run lean rather than rich although I s'pose if it was leaking under boost then it would be running rich (hmm....)

Does anyone have any suggestions as to why it might be running so obscenely rich? I don't think that such a major problem with AFR is down to the ECU map (which should be approximately correct).

I should perhaps mention that I'm using Venom injectors which I know are not highly regarded by most, anyone know what the latency of these is - no tech info was supplied with them...

Any advice appreciated.

Cheers

RobH

RobH · Post by **RobH** » Fri Jul 18, 2008 4:00 am

Further to earlier post, I've dropped a fresh JDM DE30TT image into the ECU and modified only K constant and related TP values. Dropping the latency down below 1 millisecond seems to help a bit but the idle is still very 'up and down' when warm. It's not erratic, it's a steady low revs (300) and then high revs (1200) to compensate , revs drop, revs go up, cycling about once every 5 seconds.

I also tried disconnecting the MAF sensor, this gave me a much better idle but obviously wouldn't rev. Does this sound like a potentially knak'd MAS?

Cheers

RobH

Matt · Post by **Matt** » Fri Jul 18, 2008 4:22 pm

If you disconnect the MAF then it uses 'limp MAF' values for base idle injection upto 2000rpm

It is a good test to see if the engine runs okay otherwise

I suspect vacuum leaks if running too lean (more air sucked in than can be measured) and dodgy MAF if its running too rich. Sounds like K constant just worknig around it

I would suggest cleaning your hotwire inside the MAF and see if that helps somewhat

RobH · Post by **RobH** » Fri Jul 18, 2008 8:07 pm

Thanks Matt. I did some checks on the MAF last night, showing <0.5V engine not running, 1.8V at idle - these figures appear to be out of tolerances. I'll give it a clean and see if that helps.

Also, my MAF has only 4 pins (A is missing, NA version?) whilst the connector has 5 wires. It has run ok in the past

It's definately rich, fuel pressure has not been tested yet so I guess that's where I should have started...

Cheers

H

Matt · Post by **Matt** » Sat Jul 19, 2008 11:25 am

Same as the Z32 MAF and adaptor I have here. It doesnt seem to be used on any of them

I suspect the extra wire is for the calibration pot in case it was installed on the AFM... but without tracing that wire back through the diagrams/loom I cannot confirm for sure

RobH · Post by **RobH** » Sat Jul 19, 2008 8:52 pm

Thanks Matt. I still think the readings are a little out of tolerance so will try a swap.

I thought I'd found the problem for sure - being the dunce I am, I'd plumbed the fuel pressure regulator in upside down - it was working in reverse. I put it right but was very disappointed that it made no difference. I guess I could have damaged it, a fuel pressure check is in order...just need to get my hands on a gauge...

Have a good weekend.

RobH