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Inconsistent idle surge

The surge has a range from 800-1200 rpm. Perhaps this is a clue: I can get the surge to stop if I give it small amounts of revving, maybe to around 1500 rpm and then let off slowly. It will then have a solid idle at around 800+- 50, and the AFR is at 13.6 to 14.2. When it surges, obviously the AFR goes up and down. Also, the surge usually doesnt occur until fully warmed up. All fuel pressures spec out. If I try to adjust the CO screw and or the idle screw to tune to surge away, it will work, but its only temporary, as the surge resurfaces everytime!! The only thing I havent done is presurize the intake tract...I will be doing it as soon as i can find a proper size adapter (anyone got tips for that?). I keep thinking it must be a vacuum leak but Ive triple checked everything vacuum related and have come up emtpy handed. I also keep hearing about a rich condition causing a surge? Ive also tried playing with the timing at idle. Latest thing Ive done was remove the fuel head and its plunger for inspection, thinking it may be sticking, but all was good and it had no effect. Valves just adjusted and leak down performed (5-8% across the board).


Background: Decel valve was removed years ago and lines were capped. AAR still installed and functions correctly. About 6 months ago, injector blocks were changed along with their gaskets, recirc valve resealed, new plug wires/plugs/cap/rotor, diassembled dizzy and relubed all components, WUR rebuilt by Leask, all new O rings throughout, a few injectors replaced due to questionable spray pattern, all new vac lines, timing is spot on (26@4k rpm), new filters blah blah blah and the car ran rather great! The K27HFS that was installed at the time failed so the car was down for a bit. A stock 3LDZ was reinstalled and the surge was noticed immediately. Triple checked all connections and found nothing wrong. I suspected the compressor side of the turbo was leaking (due to oil seepage at the bottom of the compressor to center housing mating) so I didnt worry about it as the 3LDZ was temporary. I then installed a GT35R and the problem still exists.

On a positive note, the car kicks butt with the GT35 and with the .8 spring in the wastegate, I see 7.5-.8 bar on the Andial gauge. Ive only taken the car up to about 5k rpm and not 100% full throttle thus far. Here's a pic for the hell of it:

Last edited by DailyDriven'88; 10-19-2009 at 08:10 PM..
Old 10-19-2009, 08:02 PM
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Same problem here what helped was removal of the aav .you should read my posts had the same exact problem .one of my posts showthe tool needed to presurize the intake.
Good luck
Old 10-20-2009, 04:27 AM
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I think I may have come across your thread already. Is the AAV the same as the 'decel valve'? I realize there are multiple names for the same part.

The AAR is still installed but it looks to be functioning correctly (fully closed when warmed up) and even so, pinching the hose while the car is warm and idling makes no difference. What really gets me is I can get the surging to stop every single time if I play with the gas pedal a little bit.
Old 10-20-2009, 09:16 AM
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same excat problem I had.the AAV is the gold disc on the left when you look at the engine from the back under the I/C . from your pic it looks like it is blocked.
Old 10-20-2009, 10:00 AM
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With all the confusion and multiple names for the deceleration valve, AAV, and AAR I just call them golden saucer valves now.
The early 930's had 2 golden saucer valves, one has a small vacuum line that opens it during times of high intake manifold vacuum and that one is the deceleration valve or vacuum limiter valve.

The other saucer valve doesn't have a small vacuum line that operates it and only the 2 larger hoses that bypass the throttle body. That one is called the AAV most of the time and the late eightee's 930's do not have one of those, thankfully.

The last throttle body bypass valve is the AAR that is cast aluminum and looks nothing like a golden saucer valve. This one bypasses air around the TB when the engine is cold so the idle is raised. I call that one the aux. airslide valve to try and make it less confusing.

Your engine is running a little rich when idle oscillates while warmed up. There are alot of things that could cause that and the simplist thing may be the air sensor plate pivot bearing is just a little stiff or gummed up and not raising back up to where it should at idle.
Could be a vacuum leak(s) and could be your control pressure regulator being inconsistant too.

Next time you have the rear tin off you might want to take the time to strip off all the rust with phosphoric acid, sand or bead blasting, or wire brushes on a die grinder... whatever works for you. Then paint it with 1500 degree header paint or barbecue paint.
It'll stink when the paint burns off right above the turbine housing at first but will make the tin last longer and look alot better down the road.
They are getting very expensive for a piece of stamped out and spot welded sheet metal and not easy to find when they rust away.
Old 10-20-2009, 10:15 AM
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JFairman said: "Your engine is running a little rich when idle oscillates while warmed up. There are alot of things that could cause that and the simplist thing may be the air sensor plate pivot bearing is just a little stiff or gummed up and not raising back up to where it should at idle."

Q: How could I go about "unstiffening" or "ungumming" the pivot bearing? Thanks
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Old 10-20-2009, 03:57 PM
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googd question would not mind cleaning this as well . where and how is this done?
Thanks
Old 10-20-2009, 04:51 PM
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ertech: Car only has the aux air slide valve, NO gold discs. Your issue may have been the same but the cause here is different.

Jfairman: Air sensor pivot has been de-gummed with carb cleaner. I did that when I removed the entire unit and separated the fuel dist. from the housing. There was some varnish around the pivot, but operation was still very smooth. I completely flushed that area out and the pivot moves just as freely as before, NO change in surge was noted.

Vacuum leaks to me would indicate a lean condition at idle? Correct or not? If so, how does that conicide with a rich condition surge?

Inconsistent control pressure regulator? You mean faulty WUR? Been rebuilt by Leask less than a year ago, and it ran fine after the install. I guess it could go bad, but pretty unlikely. Obviously though, I wont rule anything out.

What REALLY gets me is I can stop the surge if I play with the gas pedal a little bit. A slight rev to around 1500rpm and let off a little slowly it will idle ROCK SOLID like a normal car.
Old 10-20-2009, 04:56 PM
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Quote:
Originally Posted by DailyDriven'88 View Post
ertech: Car only has the aux air slide valve, NO gold discs. Your issue may have been the same but the cause here is different.

Jfairman: Air sensor pivot has been de-gummed with carb cleaner. I did that when I removed the entire unit and separated the fuel dist. from the housing. There was some varnish around the pivot, but operation was still very smooth. I completely flushed that area out and the pivot moves just as freely as before, NO change in surge was noted.

Vacuum leaks to me would indicate a lean condition at idle? Correct or not? If so, how does that conicide with a rich condition surge?

Inconsistent control pressure regulator? You mean faulty WUR? Been rebuilt by Leask less than a year ago, and it ran fine after the install. I guess it could go bad, but pretty unlikely. Obviously though, I wont rule anything out.

What REALLY gets me is I can stop the surge if I play with the gas pedal a little bit. A slight rev to around 1500rpm and let off a little slowly it will idle ROCK SOLID like a normal car.
Hmmmm.....mysterious, especially since you can get it to stop that nasty symptom by revving a bit and SLOWLY letting off the throttle. Sounds like something in the throttle body itself, maybe gummed up and not letting the throttle valve close completely, or an obstruction in one of the vacuum or bypass air ports in the TB. Try pulling off the two vacuum hoses from the TB, as well as the idle adjustment screw...and shooting some carb cleaner in there. Just a long shot idea, I admit.....

Oh...when's the last time you ran any fuel injection cleaner (Techron) through a tank of gas?
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Old 10-20-2009, 06:59 PM
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It sounds like everything is in good working order from what you say.
I also have a BL WUR. I would try raising the steady cruise control pressure a little.
Not seeing your car or experiencing the problem and going from your description I'd try turning the allen head screw in the center of the large steel disc on the botton colckwise 1/4 turn. That will raise steady cruise and idle CP and lean it just a little.
If that doesn't help you can experiment more or put it back where it was and try something else.

Other people asked how i meant to clean the air flow meter housing and internal hardware. Remove it and clean it in parts cleaner and re lube the pivot bearings and contact points under the fuel head if things are dirty or gooey from age.

The height of the sensor plate at rest is also adjustable. It could be off a little.
Old 10-20-2009, 07:24 PM
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Mark: Funny you mention those 2 tips. I knew I forgot some stuff the background section of my first post because I have done so much to get rid of this issue! I have completely removed the throttle body and sprayed out all passages, including removing the idle screw for cleaning. Nothing serious noticed and no change after reassembly. It has also occurred to me that if the throttle was being hung open for any reason, wouldnt that just give me a high idle and not a surge? Regardless though, I have also checked all linkages and verified the throttle plate does return to its rest position against its linkage stop, even while it surges. All return springs are tight and in place as well.

Ive also ran numerous bottles of chevron techron fuel injector and fuel system cleaner (not at the same time) as well as the tried and true "top engine cleaner" from GM. That stuff comes in a little bottle that you add to a bigger bottle of techron, then add to the fuel tank along with a fresh fill. It works great at mostly cleaning carbon buildup out of the combustion chambers, but does clen other areas/components as well. I have verified results with a 5 gas analyzer before (on other cars) and I swear by the stuff. As I type this, yet another bottle of techron fuel injector cleaner is mixed with the gas thats in the car from my last fill up.
Old 10-20-2009, 07:33 PM
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J: I have tried warm cp's from 3.4 to 3.7 with no change. It runs best at 3.4 (albeit a little rich at cruise) due to it giving me the ideal afr just prior to the rpm delay at 4k rpm. If I raise it, the afr is just a bit on the lean side (IMO) prior to 4K...so 3.4 is where it looks best. Does the warm cp have an effect on idle (obviously to a certain extent)? I can adjust the afr at idle independently with the CO screw. If im misunderstanding this, please fill me in.

Height of the sensor plate is possible, but its never been touched and this surge did not occur with the old K27HFS, or the old 3LDZ prior to that. Very strange, but it could have fallen out of its adjustment. Again, I doubt, but its possible.

And yes Mark, its VERY strange how I can get it to stop every time I play with the pedal. Sometimes I have to play with the pedal a few times, and sometimes just once, but I can get it to stop fairly quickly. Let me tell you, Ive gotten good at it too! Its annoying as hell sitting at a light and having it surge! haha. I thought for sure that would tip someone off as to what it is. I guess not..

Last edited by DailyDriven'88; 10-20-2009 at 07:42 PM..
Old 10-20-2009, 07:39 PM
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Yes, the 4mm allen head for warm CP adjustment on the bottom does affect idle and steady cruise AFR to a real small degree if you turn it only 1/4 turn at a time.
Brian had mine set at 4bar for steady cruise.
If you have the instruction manual he gives you with it I'm talking about figures 2A and 2B.
If you want to lower boost CP to get more fuel on boost after doing that then use the tool he gives you to draw out the steel disc on the bottom in figure 3A.

After doing all that you may have to do a fine adjustemnt on the cold start CP on the top of the WUR.

I have a flowtech IA modified fuel head that flows +20% under boost so my CP's are tuned around that fuel head and will be different than a stock fuel head.
I have CIS gauges and very rarely use them on my car. I adjusted the WUR and system pressure on the fuel head by experimenting alot, road testing, and a wideband AFR gauge.
Old 10-20-2009, 07:58 PM
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4 bar would really help my cruise afr out a lot! But, a third gear pull at WOT would most definitely show a lean condition prior to the 4k rpm enrichment switch. Brian had mine preset at 3.8 when he knew I was running the HFS. I forwarded him a few dyno pulls with afr readings and he recommended lowering warm cp until I reached a safe level. 3.4-3.5 is where that ended up being with the HFS. I have it at 3.4 with the GT35.

The boost cp is fine. It dips nicely at 4k and does not lean out on its way to 6800 rpm (has aftermarket rod bolts), or at least it didnt with the HFS. My boost level has not changed so I have a feeling it will look very similar if and when I retest all the way to redline.

I also tune with an LM2 when its not on a dyno.

Last edited by DailyDriven'88; 10-20-2009 at 08:16 PM..
Old 10-20-2009, 08:08 PM
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I have an rpm switch set at 5000rpm and boost line solenoid for the WUR and was using an HFS at 1 bar with the IA fuel head.
I never checked to see what the CP's are other than cold start.
I adjust and go by the way it runs and an AFR gauge till I like it.

7006 on the car now.
Old 10-20-2009, 08:26 PM
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A little OT but what kind of cruise afr's are you seeing? Idle afr?

I'd like to see how they compare with mine, even though I know our set-ups are quite different.
Old 10-20-2009, 09:21 PM
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Quote:
Originally Posted by JFairman View Post
Yes, the 4mm allen head for warm CP adjustment on the bottom does affect idle and steady cruise AFR to a real small degree if you turn it only 1/4 turn at a time.
Dont think you answered my exact question so let me try and be a bit clearer.

I totally understand that it will have a direct effect on the idle afr IF you dont touch the CO screw. However, I make adjustments with the CO screw after each warm CP adjustment. So, for example, what does it matter if the warm CP is set at 4 bar or 3 bar (nevermind cruise)? Does warm CP have an effect on idle recovery or something? I kind of perceived it to have little to no effect on idle (unless of course its something like 0 bar) when you can tune the idle afr to whatever you want.
Old 10-20-2009, 11:07 PM
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I'm only suggesting you try what I said and see if it helps. I don't know if it will or not but there's a chance it might.

Adjusting the idle AFR by the CO screw has no direct effect on idle or cruise control pressure it is just reindexing the location or height of the control plunger in relation to the metering slits in the fuel head in relation to the position or height of the air flow meter sensor plate.
So adjusting the CO screw will have absolutely no effect on how hard control pressure pushes the sensor plate upwards against the force of air pushing down on it.

Adjusting the 4mm allen head on the bottom of the B.L. WUR for higher control pressure will affect control pressure at idle by pushing the control plunger downwards and the sensor plate upwards, higher than it was at idle and steady cruise so while it is for adjusting steady cruise warm AFR's it also affects the idle AFR.
Your car is running rich at idle so I would try a 1/4 turn clockwise on the 4mm allen head in the middle of the stainless steel disc on the bottom of the WUR. That will raise CP a little bit and push the airflow metering plate up with more pressure, raising it a hair higher.
You said if you let off the gas slowly your idle is steady and that makes me think the metering plate is settleing to higher position at idle when you do that. Raising control pressure will also make it raise to a higher position at idle so thats why I suggest adjusting it.

I have adjusted my WUR to have these AFR's with the IA modified fuel head when warmed up:
Around 14.5:1 at a steady 30-40mph cruise for decent gas mileage.
Around 13.9-14.1 at idle. Idle is smoothest around 13.5:1-14:1 in my car.

I can adjust it leaner easily with the CO screw but then idle lowers and becomes less smooth. Idle at 14.7:1 is not as smooth as 13.7:1 with 964 cams.

Boost AFR's depend on what rpm and what gear your in. They are far from perfect but CIS never will be and I'm not into spending/wasting any more money on frequency valves and controllers to try and make it better or flatter.

The modified flowtech IA fuel head and B.L. adjustable WUR were almost $1000 together and that plus the AFR gauge and rpm switch/vacuum solenoid and time spent adjusting things over and over are enough time and money spent on the AFR subject for me.

I don't know if that answers your questions but you can try raising warm steady cruise and idle control pressure a little at a time like 1/4 turn clockwise to start and if it doesn't work you can very easily return the adjustment to where it was in a few minutes if you have a small air cleaner on the car during the adjustable WUR tuning process so you don't have to remove the intercooler and factory air cleaner to get at the WUR every time.

When I was adjusting my WUR daily I didn't replace the 2 - 10mm nuts that hold it down everytime, I just slid it off the 2 studs without even removing the 2 fuel lines and tipped it sideways to fit a 4mm allen wrench in there to adjust warm steady cruise control pressure or AFR.

You have to remove it to tap in the stainless steel disc on the bottom with a brass drift and small hammer for lowering boost control pressure to get richer acceleration AFR's.
Old 10-21-2009, 09:05 AM
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Ok, well as I said Ive tried warm cp's 3.4 to 3.7 with zero effect. I do appreciate the tip though, but Im not sure if the adjustments Ive made have proven it not to help? Perhaps, i should go above 3.7bar and see. Of course this means I wont be able to any hard accelerating due to the lean condition it will cause prior to the 4k rpm enrichment switchover.

I see you keep saying my idle is rich, which Im going to assume you think its a rich surge. Ok, but once I get the idle to settle, its 13.6 to 14.1:1, which to me, looks very good. If I lean it out (which Ive tried) to get rid of the surge, once I get it to settle, the idle is quite a bit leaner, sometimes in the high 16's:1! To me, thats not right, and not to mention the damn surge continues on the next drive cycle!! It does change the intensity and speed of the surge though. One thing is certain, so far it always returns no matter what adjustments are made, its truly makes very little sense. Due to the fact that nothing Ive touched thus far has seemed to cure it, Im thinking Im poking around in the wrong area(s) entirely (duh!), and the problem would have to be internal (such as fuel distributor) or god knows what else.

I appreciate your help so far as well as your afr details. My cruise afr is around the 13.5 or a tick lower. Its not the greatest for gas mileage thats for sure, but anything leaner and im not in a safe range under full load/WOT. For me, it looks like a trade off, and Id rather see cruise mpg's go down versus a $costly$ lean condition.

I will slowly raise warm cp again and maybe something different will happen, who knows.
Old 10-21-2009, 11:03 AM
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[QUOTE=JFairman;4964824]

I have adjusted my WUR to have these AFR's with the IA modified fuel head when warmed up:
Around 14.5:1 at a steady 30-40mph cruise for decent gas mileage.
Around 13.9-14.1 at idle. Just about exactly where I have mine set. 14.2 steady cruise, 13.8 to 14.0 at idle. And I still have the stock fuel head and cams.

The modified flowtech IA fuel head and B.L. adjustable WUR were almost $1000 together and that plus the AFR gauge and rpm switch/vacuum solenoid and time spent adjusting things over and over are enough time and money spent on the AFR subject for me.QUOTE] Well said Jim! Before I started adding all the CIS "bandaids" and on-board AFR gauges, I felt better. Now, I've got too much information, forcing me to always seek the perfection that CIS will never deliver. Sometimes too much information is too much.
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Old 10-21-2009, 02:27 PM
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