What causes a car to run rich under boost?

[bpu699]

Lots of threads on cars being to lean... Few on too rich...

My car used to go silly rich at idle... Now that's gone...

Idle is 14.4... Cruise is 13.5... Boost quickly falls below AFR of 10...

Previous owner had a 1 bar spring... I went back to stock... Not sure if he modified the fuel head for the increased boost?

Odd thing was, ran fine last year before winter...

Runs fine, isn't missing, but doesn't feel as powerful as it was on boost...

Vacuum line issue? Distributor? Timing? Bad plugs? Can a malfunctioning WUR run to rich at peak boost??? Most every thread I see is about cars being to lean under boost, not to rich...

[RarlyL8]

A lazy WUR can cause overly rich midrange, but other things can as well such as fouled spark plugs or a weak ignition. Check the plugs first and gather AFR data.

[bpu699]

Can a WUR cause issues only on max boost? Midrange is fine...

The AFR starts at 14.5, stomp on the gas, turbos kick in, afr starts falling hits 10 by 5000 rpm and stays there...

The afr meter doesn't read below 10... Doesn't misfire, or bog down...

Msd ignition is new, plugs are bosch w3dpo...

Started a separate thread on the plugs... Just want to make sure platinum is ok with the msd...

Appreciate the input...

[Ronnie's.930]

Is the fuel head a Lambda assist one (aluminum) and if so, is the Lambda system hooked up and functioning? I ask, because your cruise AFRs are too rich - Lambda corrects it to high 14s/low15s during cruise . . . high 14s is about perfect for that (no rough running and as good as you can get for fuel economy with these cars).

10 AFR boost enrichment is just on the verge of full throttle misfiring - mid 9s and lower would do it. If you've ruled out air leaks, which can cause a rich condition during boost enrichment (the air metering arm travels down farther than it really needs to due to air leakage under boost), then the full throttle enrichment control pressure is too low. If you have an adjustable WUR, you can push the large disk on the bottom inwards about 2mm with a c-clamp (thus raising the control pressure and leaning the mixture) and then your enrichment control pressure will be about perfect.

[bpu699]

Correction, it's at 14.7 at cruise while at 3000 rpm and under lamba. Cruising at 5000 rpm is 13.5 or so off boost...

That all seems correct, I think...

Under boost, it drops to an afr of 10 pretty fast. If it's misfiring, I can't tell...

I thought air leaks make it run lean? I will double check, as I did have the intercooler off several times...

Stupid question... Would putting in the 1 bar spring cure this? Did de tuning to 0.8 effect this? Thought it would be safer...

Odd thing is, I didn't have this problem in the fall.... Nothing with the wur changed...

[kenikh]

.8 BAR, less air, same fuel = rich

[Norm K]

Originally Posted by bpu699

Cruising at 5000 rpm...

_

[Ronnie's.930]

Originally Posted by bpu699

I thought air leaks make it run lean?

Not with K-jetronic/CIS when there is any positive manifold pressure (like under boost) or if the air leak is prior to the throttle plate (due to the air metering arm phenomenon that I described)

Originally Posted by bpu699

Odd thing is, I didn't have this problem in the fall.... Nothing with the wur changed...

That makes me think air leak(s). Be sure to check if the manifold/injector block nuts (different than Norm's wee nutz ) are tight (the opposite of Kenik's bungholio ) .

[bpu699]

Ronnie, are you still around ?

Still chasing this issue, posted in another thread about checking timing as someone suggested it...

Changed from bosch platinums to NGK gapped at 0.04 with the msd and now it seems to "fart" at hig RPM ander boost over 5000 rpm...

Is that what you were reffering to when you said it usually misfires at an AFR<10??? Oddly, didn't happen with the bosch platinums, but MSD says not to use them...

Thoughts?

If I accellerate slowly under boost (IE. Dont mash the throttle, it doesnt happen...)