Got a lil' prob here:

Car's turbo, tuned on EMS.

Lately (tune untouched) idle's been getting leaner and leaner, worse and worse.

Wideband shows idle in 19s and even 20s AFR!

Car likes to stall.

Hot compression test #: 203 200 189 203 psi (average of 3 runs)


I have AEM 3bar MAP, also, a Cometic 2mm headgasket. Fuel pressure over 40 psi at idle, like it should be.



Recently checked valve clearances, #3 was a bit on the loose side on intake. Tightened them up.


Any ideas, feedback? Please help.

Should I pull the head?

 

FI forum where da pro's live.Ran a SC but never a turbo.When was the last time u had it tuned on a dyno? Not an expert but that's what I'd do before even considering pulling the head.

 

Ran it on the dyno during tuning, about 2.5-3K miles ago.

This weird lean condition is the main reason I'm shying away from the high load of a dyno.



Moderator: If deemed necessary, it's ok to move this thread to FI.

 

IIRC some of my dragster buddy's could adjust their air fuel mixture with a laptop and the right program.Also,thought lean usually=injectors?

 

Could be heat soak combined with an bad air temp sensor callibration.

 

^ Yeah, that's what my tuner said, but why did it start doing it without me touching anything or the weather changing?

 

You didnt state how the vehicle runs Is the vehichle running pretty well? With a idle at 19-20 its barely going to run if at all. Would most likely need to keep giving it gas to keep it running. Thats VERY lean. Reason i ask how its running is because if it seems to run somewhat normal then it could be just a bad sensor. They are pretty common to go bad.

Compression looks good.

If engine runs rough then do a balance test. Start pulling coils to find out if a cylinder is dead. What is the vacuum gauge reading at idle?

 

Ok, these are real good points! Thanks.

Vacuum is lower than normal. It used to idle at about -11. It shows -12 under engine braking (full vacuum, I guess). Now it idles at about -8, -9. I did check the silicone couplings on the intercooler and piping.


What sensor are we talking about? IAT perhaps?

It does run a bit lean, but I don't know if it was tuned that way or got to be that way recently.

When I'm getting on it, as it is just entering boost, AFRs are like 14s. Then as boost goes up, it goes to 13s and high 12s. Cruising is about high 14s-low 16s. I don't really like it, I can change it in a jiffy with a laptop (I have AEM EMS), but what I'd love to know is what causing it.


At idle engine runs kinda ok, not purrrrfect, though, occasional and random stumbles can be heard. Maybe a knock at random, too. Sounds very faint, metallic (like in the head or under valve cover).

I'll pull coils one by one, see if does anything, will keep updating...


^ Hey Rob!, I'm getting your FPR!

 

Yeah i know its on its way to you. Let me know when you receive it.

The sensor i was referring to is the wideband sensor. They often go bad and give false readings. Vacuum seems to be off a bit as it should be around 18 give or take. If your car is really idling at 19-20:1 I would be very suprised because as i said that is super lean. If i were you i would replace the wideband o2 sensor to start before you go crazy especially if it is old. I go through about 1-2 a year but i put quite a bit of miles on my car.

 

Wideband has about 2.5k miles on it. I don't think it's broken. Every once in a while (especially after a brief ride), idle will settle right around 14.7, and the car idles perfect.

I will do a fresh-air calibration on it, though. It's an Innovate LC-1 kit. Should be good.