Would the wrong temp spark plugs do it?

Exhaust leaks and fuel pressure I know are two.

Advanced Timing?

I'm talking just at idle.

Thanks.

 

How about a faulty O2 sensor?

BTW, if you raise the RPM does it clear up?

If so do you have a heated O2 sensor?

Jumper ALDL pins A&B and start up the engine. Watch the SES flashes after a minute or so. Normally the On duration should equal the Off duration and the flash rate be 1Hz; if it drops out of closed loop at idle you will may see it in the flash rate/duration.

 

O2 sensor new and heated. After I drive a little it goes away, pulling away from a light.

I'm going to drop the timing back to 6* and see if it clears up.

Can't do it until tomorrow.

 

Watching this thread, as I have the same condition....I can get every BLM cell @ 126-130 BLM's except for cell zero, which is serious lean. I've increased the MAF table 1 to the point it is almost at 22.8 all the way to the top, and still the same. I can track it with my WBO2, and it's at 18.0 at idle, and as soon as I give it some gas, it goes to 14.7....so I'll be interested to see what people say....Good Luck with yours....

Cheers,
Michael

 

I'm going to roll back the timing and try that, I'll let you know.....

 

From the chip's perspective:

Target AFR too high in open loop (open loop vs coolant or load tables too negative)
Injector constant too large.
Maf calibration too low for actual airflow.
Injector low pulse offset too low for actual injector.
Injector voltage offset too low for actual injector.

With non-standard injectors, I'd guess that the low pulse width and voltage offsets are incorrect.

 

Patrick, I know you are somewhat familiar with my car, as we have conversed before. You really helped me narrow down some of my problems, so I know you know what you are talking about. I've looked at everything you mentioned above, but for the life of me, I can't get my idle cell to budge off of 18.0 - 17.5. I've tweaked everything in the above, and nothing seems to budge the AFR. Just as soon as I give it any throttle, it jumps right into the 14.6-14.7 range, all the way to WOT, where it'll go in the 12.6 range. I'm really stumped. as is jsup on this, so if you have any more words of wisdom, I'm sure both of us could use the help....BTW, how's that MAF project comin'? sounds interesting....

Cheers,
Michael

 

FWIW, I put the timing back to 6*. Haven't had a chance to drive it today, if no rain I'll try tomorrow.

 

Michael,

When its idling lean, what is your injector pw? Injector size and fuel pressure would also be helpful to know if they have been modified.

Around 1.5-1.6 ms or so at idle is what I'd expect to see for 23-24 lb. injectors. With my 42 lb. injectors at 46-47psi, I typically see around 0.7-0.8 ms in an 800 rpm idle.

If your injector pws are in line, then I have to think there is extra air being introduced into the exhaust via a misfiring cylinder, air or vacuum leaks, camshaft overlap, or the injectors aren't responding.

There is also potential for measurement error. I don't have any experience with a WBO2 or HEGO sensor so I can't comment on the measurement accuracy at idle. My car idles in open loop, so I just tune it to run smooth at standstill and while rolling in 2nd gear.

If its really lean at idle it should stumble with any applied load like idling in gear or with the a/c on or when opening the throttle to drive off. If its idling smooth and you can drive off without issue, I'd question the measurement accuracy.

If all else fails you can tweak the 02 tables vs airflow to shift the rich/lean threshold, etc. to help bring the blms in line at very low flow levels. The injector low pulse width offset can also be used to add extra enrichement for small pws say under 2 ms or so to compensate for lazy injector response.

My MAF conversion project is working out very well. Thanks for asking.

After a recent crank pulley swap, I'm finally pegging the 05 Ford MAF (6 volts at the sensor) above 5300 rpm (39,000 impeller rpm) on 7-8 lbs. of boost. With my present calibration this is roughly 460-470 gm/sec of airflow. O2 is showing 920 mv in 3rd at about 90% duty cycle on the 42s. It meets all of my airflow/fueling needs at this level.

 

Patrick, glad to hear you have made some progress on your Maf project...it will be interesting to see if anyone else picks up on it, maybe we can get away from these outrageous Bosch mafs...but back to jsup's and my problem. My injector constant matches my injectors @ 24#, and the pw's appear to be in the area you describe, but it's been a while since I've been able to datalog. Had some surgery, and haven't been able to get back to the car. I'm thinking, like you, I've got some extra air, but I can't find anywhere it can come from. Done a smoke test on the car to find any possible leaks, but none were found. I'm beginning to think I might have a bad cam lobe, from discussions on the board, but it seems to run too good for that. I do get the dreaded "off-idle" stumble, and lean pop when I hit the throttle, but then it seems to run pretty well for a stock, 25 year old motor...I'll keep lookin' and tweakin'....I'll run it down sooner or later (or maybe I'll just carb it....)

Cheers,
Michael