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Kirk911SC's Avatar
 
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Angry Pig rich under boost

Okay, help me out. What's going on here?

My car is now blowing brown/black smoke under boost and hesitating/stuttering at the upper end of the boost cycle (as the wastegate opens).

I had the boost set for 0.9 bar and backed it down to 0.8.....seemed to lessen the smoke a bit, but the stuttering/hesitation is still there.

I've checked for leaks after the turbo, figuring there's a boost leak. Can't find anything wrong. I tried spraying starter fluid around all the o-rings and hoses while the car was running.....no effect. WUR?

Car idles smoothly and drives fine.

The only other thing to mention is that I recently installed a K&N cone filter in place of the air cleaner assembly.


- '87 930
- Garrett T-04 60-1 hybrid turbo
- SC cams
- B&B stainless exhaust and muffler
- Andial fuel enrichment
- Adjustable boost controller (0.9 bar)
- MSD 6AL ignition
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Old 06-16-2012, 05:16 PM
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nope,, classic vacuum leak... did you try checking all of the nuts that hold the intake down ?
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Old 06-16-2012, 05:22 PM
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The actual manifold? Nope.

I'll check them tomorrow. Why would it loosen up now?
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- '00 Dodge Viper GTS - Steel Grey - Yep...a domestic.
- '87 930 - Guards Red - Sold
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Old 06-16-2012, 05:24 PM
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The insulator blocks take a set and sometimes crack , When checking the nuts on the manifold lubricate them first then back them at least 1/2 turn, be carefull not to overtorque them for the reason mentioned earlier,
But... Try disconecting the manifold press switch for the Andial fuel enrichment, secure the wires and test the car, If this improves the situation under boost then you need diagnose the enrichment unit by measuring the control press drop when the unit activates,

Hope this helps,, Lou
Old 06-16-2012, 06:08 PM
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Boosted air leak (as in turbo plumbing pipes/hoses and/or o'rings). Let air escape, and the ratio of fuel already delivered against the lost air will cause a pig rich condition. Even though you've done the starter-fluid-around -the-o'rings test, it is possible that things are sealing just fine until you pressurize them. You may not see any leaks when cruising non-boosted (such as at idle). Pull the IC, visually check the rings, inspect all vacuum and turbo hoses for splits or cracks. That's painless, free, and easy....put that to bed first, then move on to other possibilities.
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Old 06-16-2012, 06:25 PM
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Insulator blocks are about a year old. I replaced them along with a bunch of gaskets, hoses, etc. the last time I had the engine out.

I've pulled the IC and checked all the seals and hoses.
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Old 06-16-2012, 06:41 PM
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Wrap the IC joints with duct tape, if the symptoms go away, you have your answer re the o rings.
Mine did the exact same thing. Even after I replaced the o rings, I still wrapped a thin black strip of duct tape around each joint just to be on the safe side, belt n suspenders.
Old 06-16-2012, 07:15 PM
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Wrapped the IC joints in duct tape; checked that manifold nuts were tight; disconnected fuel enrichment; and paid closer attention to what's happening.

- Hesitation/stuttering worse as gears go up (i.e. almost non-existent in 1st, but VERY noticeable in 3rd). Car pulls pretty hard in 1st, but gets progressively worse in higher gears. I tried a full throttle pull in 3rd on the highway and once the boost started to come up it felt like the car was going to stall - coinciding with brown smoke

- Worst of smoke is when letting off the gas under boost, but the smoke starts at about 0.7 bar along with the hesitation.

- No apparent leaks from IC joints or hoses

- Car seemed to run worse with the enrichment off, especially as boost came on
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- '00 Dodge Viper GTS - Steel Grey - Yep...a domestic.
- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile

Last edited by Kirk911SC; 06-17-2012 at 07:21 AM..
Old 06-17-2012, 07:11 AM
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I wonder if one of the two fuel pumps is not working (therefore, not enough fuel pressure) - could be a cause of the high rpm/high load rough running but I guess that wouldn't explain the black smoke, however. Maybe you shoud try fiddling with the realays for ****s and giggles anyway?
Old 06-17-2012, 07:15 AM
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Hmm....I can check that. Front fuel pump is about 3 months old. Rear...who knows?
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- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile
Old 06-17-2012, 07:23 AM
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Do you still have your oxy sensor hooked up?
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Old 06-17-2012, 07:43 AM
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No O2 sensor, and no cat.
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- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile
Old 06-17-2012, 07:44 AM
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I agree,, first thing you need to do is get ahold of your fuel pressures..
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Old 06-17-2012, 07:46 AM
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Bit of an update.

This morning I booked an appointment with a Porsche specialist for tomorrow.

Tonight I decided to switch the cone air filter back to the stock assembly.

Took the car for a drive and it's much better.

Ambient temperature is somewhat cooler than the last few times I've driven it, but no more than 10C difference.

Smoke and hesitation is there, but reduced. Cone filter seems to be affecting the metering plate??? Weird.

Still going to take it in tomorrow and see what he has to say.
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- '00 Dodge Viper GTS - Steel Grey - Yep...a domestic.
- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile
Old 06-18-2012, 05:37 PM
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Try disconecting the manifold press switch for the Andial fuel enrichment
Old 06-18-2012, 06:12 PM
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Quote:
Originally Posted by StiltnerCor View Post
Try disconecting the manifold press switch for the Andial fuel enrichment
Try to not be so obvious when you copy and paste someone else's words in an attempt to slip-in a link to some bull**** website!
Old 06-18-2012, 06:36 PM
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Without a calibrated onboard wideband AFR gauge to see how rich it is at different rpms and boost levels you can't really diagnose it.

A CIS fuel pressure gauge kit and mighty vac for checking the boost CPR and the distributor advance/retard pots while using a timing light are good to have.

If everything else checks out you may just need to install an rpm switch and vacuum solenoid in the boost pressure hose going to the bottom of the CPR so it doesn't lower control pressure making it run richer until around 4600 rpms or maybe higher like up around 5200 rpm or so in your car.

An adjustable WUR/CPR from Brian Leask with the seperate cold start, cruise, boost, and boost threshold adjustments may help too.
Old 06-19-2012, 09:13 AM
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Thanks for the ideas.

It'll be interesting to see what the tech comes up with today. He was going to start with the fuel pressures. Supposedly he has many years experience with 930s and he has an excellent reputation amongst other owners in this area.
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- '00 Dodge Viper GTS - Steel Grey - Yep...a domestic.
- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile
Old 06-19-2012, 09:41 AM
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Have you checked to make sure the K&N isn't interfering with the mixture adjustment screw? I did the same install and had to cut quite a good size notch in the base of the K&N so it wouldn't interfere. If the problem began after installing the K&N and improved when you took it off, I'd bet a cold one that the K&N was pushing down on the mixture screw.
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Old 06-19-2012, 10:12 AM
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Just got off the phone with the mechanic. He's taken the car for a short drive.

He said it doesn't seem to be a fuel issue, but a boost leak somewhere. Said it's way down on power.

For starters he thinks the wastegate (stock) is opening too soon or leaking. He'll be focusing on the car tomorrow. I've been eyeing a Tial anyway.

Wastegate issue doesn't explain the smoke though??

With regards to the mixture screw - yes the filter was pushing on the screw when it was installed. Sort of pushing sideways on it, not down. I thought the allen screw (spring-loaded) had to be depressed fully to have any effect on the mixture?

I'll update as I know more.
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- '00 Dodge Viper GTS - Steel Grey - Yep...a domestic.
- '87 930 - Guards Red - Sold
- '82 911SC - Grand Prix White - Gone
- '78 928 - Silver - Long gone
- '97 BMW 540i - The daily-grind-mobile

Last edited by Kirk911SC; 06-19-2012 at 11:16 AM..
Old 06-19-2012, 11:14 AM
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Old 06-19-2012, 11:14 AM
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