CIS pros help

[MD540iT]

I posted in the regular forum, was suggest to post here since im dealing with a turbo.
This is really starting to drive me nuts, ive probably driven around my neighbor hood 100 times, constantly getting out, adjust, drive; park; adjust, rinse, repeat.

Right now, the main issue is that when accelerating (not hard, just normal) the A/F will go to 10, so it will be low on power. once I get to speed and back off the throttle, A/F is ok while cruising.

So in the garage, if I push on the gas pedal, just cracking the throttle its ok, but as I start to give it some gas it will quickly drop to 10 A/F, then slowly come back up.

It didnt do this before.

(also have the typical too rich on full boost, but thats always been there)
I can set the A/F and pressures between the WUR and the Mixture on the CIS, everything seems fine, but no matter how I set it, It STILL gives the too rich spike on acceleration!!


So i have a double adjustble WUR, and I have adjusted it everywhich way, tried many combos, also have an inline pressure gauge.

heres a short list of what been done, related to fueling:

CIS diaphragm replaced
Injectors cleaned and
new fuel filter and pre fuel pump filter
all new silcone vac lines, and intake hoses.
new O2 sensor
new fuel pump.
Rebuilt and modified WUR



thanks so much, this is drivng me nuts, just when I thought I was getting pretty good at CIS!

[356911930]

One more item to check would be the piston in the fuel distributor might need to be very gently cleaned.

I’ve read many posts where the op has stated completed testing … only to find out days later that when the actual test results are posted the numbers were out of spec. I sure you have not done this but specific test results might just help our local experts.

Rahl

[MD540iT]

Originally Posted by 356911930

One more item to check would be the piston in the fuel distributor might need to be very gently cleaned.

I’ve read many posts where the op has stated completed testing … only to find out days later that when the actual test results are posted the numbers were out of spec. I sure you have not done this but specific test results might just help our local experts.

Rahl

When I had the CIS meter apart to replace the diaphragm, everything looked good an clean, no reside or anything , and moved quite freely, and that was about 200mi ago.

the system was surprisingly clean. I expected the gas tank to be dark and ugly with crud all over, But it was clean as the day it left the factory.


im wondering if something such as the decel valve or something else went out?

[MD540iT]

also I found this interesting:
so after warm, with the engine running, I decided to adjust the Control pressure with the allen on the bottom of the WUR, i raised it all the way to 80psi, and it didnt raise the A/F (at idle) stayed at about 15-/+
the A/F control (after warm) really seems to come from the mixture on the Meter.

[MD540iT]

Originally Posted by 356911930

One more item to check would be the piston in the fuel distributor might need to be very gently cleaned.

I’ve read many posts where the op has stated completed testing … only to find out days later that when the actual test results are posted the numbers were out of spec. I sure you have not done this but specific test results might just help our local experts.

Rahl

also, I did do a spray test, while Ive been working on it over the winter, I didn't check the Volume, however, just checked the spray pattern.

[Matt at Pelican Parts]

Hi MD540iT,

I don't have any personal advice here but i tried to do some searching on the subject. I found a pretty good thread here where members make recommendations to check on a similar condition
https://forums.pelicanparts.com/porsche-911-technical-forum/913685-cis-running-rich.html

And searching through our DIY article i came across a few regarding CIS. Although it covers 911 as a whole it still could be of use to you for troubleshooting. Hope this helps!
https://www.pelicanparts.com/techarticles/101_Projects_Porsche_911/31-CIS_Fuel_Injection/31-CIS_Fuel_Injection.htm

-Matt

[356911930]

Sometimes a fuel pump that is getting lazy can cause an over rich condition ( low pressure) there is attest in the workshop manual that can determine if front or rear pump is out of spec.

Rahl

[Alan L]

Air leak on boost?
Alan

[MD540iT]

Originally Posted by Alan L

Air leak on boost?
Alan

no boost at that point, even does it parked.

[MD540iT]

I just read this, as i was considering the FV
"The throttle switch causes the system to goes open loop after 35% throttle to provide the richer mixture for best power." Could this, or related be a possibility??

and can I unlug the FV and see if it still spikes?

[gsxrken]

Might help if you can post more specifics.
What year is your turbo? Is it the stock WUR but modified to be adjustable?
Do you have your lambda O2 disconnected (if 86-89)
Do you hear the frequency valve buzzing?
What is your system pressure?
What is your cold control pressure?
What is your warm pressure? And how long does it take to reach your warm control pressure from stone cold?
Does pulling each fuel pump relay significantly change how the engine runs?

It’s confusing that raising your WCP didn’t lean out the AFRs.
Don’t go nuts with the idle mixture screw. It has very little to do with off idle tune.

[T77911S]

air leak on pressure side.
when the air leaks out of the pressure side the turbo "asks" for more air in. so that means more air through the AFM which puts more fuel in there but that extra air is pushed out on the pressure side.

check Orings and make sure the IC is bolted down.

[MD540iT]

Originally Posted by T77911S

air leak on pressure side.
when the air leaks out of the pressure side the turbo "asks" for more air in. so that means more air through the AFM which puts more fuel in there but that extra air is pushed out on the pressure side.

check Orings and make sure the IC is bolted down.

yeah, new Oring, silcone hoses. I can't spot a leak. I tried using a propane torch to see if I could find anything.

But this is while still on vacuum, just moving off the line.

[Alan L]

Can you monitor WP while simulating that - blip throttle in garage and watch WP. It has to be dropping - simulating boost, at a guess. If it is stable, need to look elsewhere.
Alan

[mark houghton]

Originally Posted by MD540iT

I just read this, as i was considering the FV
"The throttle switch causes the system to goes open loop after 35% throttle to provide the richer mixture for best power." Could this, or related be a possibility??

and can I unlug the FV and see if it still spikes?

If you unplug your lambda frequency valve, things will go leaner than $hit and you can't "easily" tune around it. The fuel distributor is made to work in concert with the FV.

[MD540iT]

Originally Posted by Alan L

Can you monitor WP while simulating that - blip throttle in garage and watch WP. It has to be dropping - simulating boost, at a guess. If it is stable, need to look elsewhere.
Alan

A few days prior I did try that, I didnt really rev too much, but just maybe to 1500 rpm (obviously couldn't see the tach) the Pressure gauge showed a slight dip, maybe 5psi?? figured it was normal??

what gets me is that it seems like the fuel curve is out of sync. because it eventually comes back to normal.


Perhaps this could be some kind of clue: I have 3 WUR's. The one i was running, didn't seem to adjust correctly, with the Warm adjustment,(It did in the past) so I put in the second one I had. (which is the one im currently having the issue with, not that is causing the issue, but maybe.)

Im thinking about putting back in the 1st one (which doesn't have the 2 bi-metallic elements, just the single) and see if it does the initial "too rich" thing, Or put in the 3rd one (which is stock, non adjustable, 2 bi-metallic elements)

[Alan L]

The boost dump drop is around 0.5 bar. Which makes most cars pig rich temporarily, - on boost. AFRs in the 10s often.
If you are getting 5 psi - around 0.3 bar drop in WP just by blipping throttle, this is an issue.
You have a vac /boost gauge I am taking it. And it shows a drop in vac when you do this.
This would suggest the WUR is plumbed up wrongly somehow, or maybe not the right WUR. The only pressure port to the WUR should be fed from the TB and it should be above the WUR diaphragm.
Alan

[MD540iT]

Ok, So got a chance to mess with it some more.
I swapped out the adjustable WUR for a stock one.
and it still does the same thing. initial A/F around 15 (Didn't mess with the Meter Setting yet) and giving it some gas, same: Initial gas, gradual increase in A/F then around 3k is drops to 10-11.


So This time I paid attention to the Pressure gauge when opening the throttle, and it didnt drop.(I didnt pay that much attention previously)
But I didnt watch the vac/boost gauge, (going by memory it seems to stay around -20hg, untill boost builds)

(HOWEVER: the cold pressure on this WUR was 80psi, it went up to about 85, as it warmed up. But that didnt seem to affect the A/F.)

SO right now, I almost want to rule it out.

[MD540iT]

Originally Posted by T77911S

air leak on pressure side.
when the air leaks out of the pressure side the turbo "asks" for more air in. so that means more air through the AFM which puts more fuel in there but that extra air is pushed out on the pressure side.

check Orings and make sure the IC is bolted down.

Hrmmm, Im trying to think this out. I understand what you are saying and it makes sense, but I can't see where it would happen. Plus its not making boost, especially when parked.

One thought I did have was what if the Waste Gate was leaking on the diaphragm side? (but I doubt it)

[Alan L]

WG has nothing to do with it You are not on boost. It is a bleed valve for excess pressure.
Cold Pressure should be around 30 psi +/- on temp.
You have WUR issues.
Alan