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AAV delete... now having fuel issues???

All,

I have a stock '88 930 that was running great except for a high idle on occasion. After doing a little investigation, I decided to delete the AAV (part #930 606 102 00) to see if it solved the high idle issue. At the same time, I deleted the stock air box (added K&N filter on top of the metering plate), replaced intercooler O rings, and deleted the decel valve entirely. I had previously removed the vacuum hose from the decel valve, but decided to get rid of it and clean up the engine bay.

With all this work completed, the car cranked right up and idled well once I richened up the idle a bit. It seemed my problem was solved...

After the car sat for a week, I tried to start it. It would crank and catch for about a second, and then die. After many attempts, I started troubleshooting. I pulled a spark plug and verified spark, I reinstalled the AAV to see if that solved it, checked the fuel pumps to make sure they were working. Everything seemed okay. I pulled off the air filter and depressed the metering plate slightly while my wife cranked the car. The car cranked up! Seems that I have an issue with the cold control pressure. My next step is to get a set of fuel gauges and check all pressures.

So, is this fuel issue related to the deletion of the AAV? I don't know what else it could be other than a complete coincidence? As I mentioned, the car was running great before I started tinkering. Anyone have any thoughts?

Thanks in advance for your comments...

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Kirk
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1988 930 Daily Driver
1997 Land Cruiser
Old 05-30-2012, 11:31 AM
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Maybe coincidence. Is your fuel pump fuse ( 6th in from windshield) secured properly? Are your two fuel pump relays (closest two to windshield) secured properly?
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Old 05-30-2012, 04:21 PM
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Sounds to me like your idle mixture is too lean due to un-metered air entering from one of your deleted component orifices. Turn the mixture screw a click clockwise before you try anything else. If that works then find the air leak(s).
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Paul B.
'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb

Last edited by 911nut; 05-30-2012 at 05:18 PM..
Old 05-30-2012, 05:15 PM
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Oilonly: The fuel pump fuse is good, and I have checked the relays. Strangely, my fuse panel decal does not identify the fuel pump relays.






Also, I unplugged the green metering plate switch, turned the key on, and can hear both pumps working.

911nut: I will try your idea and see if anything changes. I have plugged all openings, but will double check them. If there is un-metered air getting in, it seems odd that the car ran fine a week ago.

When I push the metering plate down to keep the car running, it takes a fair amount of force to depress the plate. Does this indicate a high cold fuel pressure?

Thanks for your replies!
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Old 05-31-2012, 03:57 AM
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With all the stuff you did, air leaks is the first fault candidate.
Also, check the metering plunger for free movement; with time they tend to gum out.
And after, if the symptom continues, I'd check the WUR - you mentioned a high idle issue also...
May be coincidence but s**t happens.
Old 05-31-2012, 06:09 AM
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Sounds like the cold fuel pressure is too high. You can remove all the air handling CIS stuff and the engine will still fire fine normally as long as the cold pressure is in range. The idle will of course be low until the engine is warm.
Strap a set of gages on and see what you have.
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Old 05-31-2012, 08:00 AM
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I will order a set of gauges and see what the pressures are. If they are out of spec, the only fix is a rebuilt / adjustable WUR, correct? If so, I'll be giving you a call, Brian...

While I am awaiting the arrival of the gauges, I will look for possible air leaks as others have mentioned.

Thank you all!
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Old 05-31-2012, 08:21 AM
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No you can press the plug on top and watch the pressure change without going to an adjustable WUR. Don't go too far though or it has to be taken apart to push back.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 05-31-2012, 12:26 PM
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Just to verify... pushing the plug in reduces the cold pressure?
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Old 05-31-2012, 12:59 PM
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Found the answer... plug in reduces pressure, plug out increases pressure.

I have pressure gauges on the way...
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Old 06-01-2012, 07:20 AM
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Quote:
Originally Posted by 1-6-2-4-3-5 View Post
Found the answer... plug in reduces pressure, plug out increases pressure.

I have pressure gauges on the way...
Hold on a moment.
Why would you cold CP suddenly change? It's a fact that you removed stuff in the intake tract prior to your start issue. If you have un-metered air entering the engine, pushing on that plug would compensate for the extra air. In reality, you have yet to find the source of your issue. Not following a methodical approach to troubleshooting could end up costing you a lot of money over the life of your Turbo ownership.
It's good to have gauges but while you wait for their arrival, look for air leaks.
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'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb

Last edited by 911nut; 06-01-2012 at 07:28 AM..
Old 06-01-2012, 07:25 AM
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As I mentioned above, I plan to look over everything this weekend as I await the gauges. I agree that something must have changed between a couple weeks ago (car running fine) and now. I'm still baffled that the car ran well once after I made the changes, and now won't start. Maybe one of the plugs I installed came loose?
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Old 06-01-2012, 07:33 AM
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Well...well...well....

After snooping around the engine this afternoon looking for air leaks, I ran my hand along the bottom of the rubber elbow from the metering plate to the recirc valve. Sure enough, there was a tear along the bottom! As a quick test, I took my trusty duct tape and patched it. She fired right up!

Just ordered a new elbow from Wayne. Should be here next week and then I'm good as new!

I'm still wondering how this tear happened in the week the car sat dormant. I must have torn it when I was reassembling, but it didn't open up until I tried to start it a week later.

Thanks to everyone for pointing out the need to look for air leaks. Pelican rocks!
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Old 06-01-2012, 01:48 PM
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Outstanding! Take the $1k you just saved by troubleshooting it yourself and buy some go-fast parts (unfortunately it'll take more than $1k to buy the first part).
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Paul B.
'91 964 3.3 Turbo
Port matched, SC cams, K27/K29 turbo, Roush Performance custom headers w/Tial MV-S dual wastegates, Rarlyl8 muffler, LWFW, GT2 clutch & PP, BL wur, factory RS shifter, RS mounts, FVD timing mod, Big Reds, H&R Coilovers, ESB spring plates- 210 lb
Old 06-01-2012, 05:41 PM
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If in doubt check relays/fuses, air leaks and check your pressures!! Solves most CIS problems.

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Old 06-02-2012, 02:20 AM
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