![]() |
|
|
|
|
![]() |
|
LinkBack | Thread Tools | Rate Thread |
Junior Member
Join Date: Jun 2003
Location: Groveport, Ohio
Posts: 5
|
![]()
__________________
~~'O=^-o> |
||
![]() |
|
Registered User
Join Date: Feb 2000
Location: Kingsport, TN
Posts: 2,925
|
The first place I would look is the vacuum system. Those little tubes that go all over your engine top age and crack especially at tees. There are at least two tees where three vacuum lines come together. One is by the fuel damper, another between #3 and #4 intake runners. If they are cracked, the boost will not work properly. There may be another tee near the back of the engine. If the tees are cracked, the engine won't run properly.
Another area that I would check is the circular valve that is next to your coolant reservoir. Its purpose to let compressed air back into the intake of the compressor so you don't lose turbo rpms if you let up on the gas. The valve is spring loaded and MUST remain closed unless a vacuum is applied to the nipple at the top of the valve. If it opens, your engine immediately bogs down. To check the valve, remove it and try to blow through one of the large holes. No air should pass. Apply vacuum to the nipple at the valve top. The valve should open. There should be absolutely no leakage of vacuum into the part of the valve where the positive pressure exits. None, nada, zip! Another possibility is a crack in the big hose coming off the compressor part of the turbo. The elbow shaped hose hardens with age and might work until just enough boost is present to suddenly open the crack. Also check the rubber unions between boost tubes and intercooler and boost tube and throttle body. Also check for cracks in the short hoses where the circular valve attaches to the boost tube and line going to turbo intake. This is valve I was talking about above. I actually had my valve get loose. It would work ok for low boost but would let air escape at high boost bogging engine. Lastly, the recycling valve between #3 and #4 intake has three plastic nipples on it. Feel around in there to see if the nipples are still there with the hoses attached.
__________________
Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i Last edited by Lawrence Coppari; 06-19-2003 at 04:00 AM.. |
||
![]() |
|
Registered User
|
First...I would be afraid your funning too lean...does this not sound lean to anyone else? I mean lean as in not enough fuel pressure. This can be VERY bad! Ahhh! It is chipped? Perhaps your fuel pump is on its way out? perhaps fuel regulator not working? perhaps you need a 3 bar reg. At anyrate...don't burn your motor! Figure out what it is!
__________________
If you don't live life on the edge, you take up too much space. |
||
![]() |
|
Registered User
Join Date: Jun 2000
Location: Northern VA
Posts: 636
|
Quote:
|
||
![]() |
|
Junior Member
Join Date: Jun 2003
Location: Groveport, Ohio
Posts: 5
|
Excellent tips, Gents. I obviously came to the right place. I am currently checking the vacuum lines, the recycling valve, and the circular valve next to the coolant res. I will also take a look at the plugs to see if I am too lean. Is there any better way to check if the motor is running too lean?
Thanks a bunch!!!
__________________
~~'O=^-o> |
||
![]() |
|
Junior Member
Join Date: Jun 2003
Location: Groveport, Ohio
Posts: 5
|
At first inspection, all the vacuum lines appear ok and so do the T's. I removed the circular vavle by the coolant res and I think it is bad. I can not blow through the bottom of the valve but if I apply vacuum I get leakage on the side that goes into the intake. Is this what you where saying indicated a faulty valve?
__________________
~~'O=^-o> |
||
![]() |
|
Registered User
Join Date: Feb 2000
Location: Kingsport, TN
Posts: 2,925
|
Yes, the valve is bad. There is a leak in its diaphragm. The nipple should not connect to anything. All it does is open the valve against a spring. It is letting air into your vacuum system which controls a number of things.
__________________
Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
||
![]() |
|
Registered User
Join Date: Nov 2001
Location: Melbourne, Florida
Posts: 431
|
Quote:
The second possibility, detonation, could be caused by running lean, a faulty or weak injector, or carbon buildup. Quote:
Quote:
Rob
__________________
1986 951 Last edited by robm-951; 06-22-2003 at 08:28 PM.. |
|||
![]() |
|
Registered User
Join Date: Feb 2000
Location: Kingsport, TN
Posts: 2,925
|
There must be NO leakage at the nipple. It connects to a diaphragm. If you apply a vacuum, the vacuum should remain. If you apply pressure, the pressure should remain. It does not directly connect to any other portion of the valve. If you apply a vacuum to it, and the vacuum goes away, then you have a leak probably in the diaphragm. If it does not hold vacuum or positive pressure, get a new one.
This is the point I was making.
__________________
Lawrence 1986 951 2002 SLK32 AMG 1987 328GTS 2011 528i |
||
![]() |
|
Junior Member
Join Date: Jun 2003
Location: Groveport, Ohio
Posts: 5
|
Thanks Guys! As per Lawrence's last few posts, I have established that the diaphragm on the valve by the coolant is definitely defective. I have a new one on order and will test as soon as I get it installed. Call me dippy, but I can't find the cycling valve. Is it hidden under the intake manifold or am I missing the obvious? I know the chips came from Autothority but I can't remember if there were one or two. I am currently looking for the old parts as a comparison.
__________________
~~'O=^-o> |
||
![]() |
|
Registered User
Join Date: Nov 2001
Location: Melbourne, Florida
Posts: 431
|
Quote:
Quote:
Rob ![]()
__________________
1986 951 |
||
![]() |
|
Registered User
Join Date: Nov 2001
Location: Melbourne, Florida
Posts: 431
|
Quote:
You can check out the 2 kits at the Autothority website Rob
__________________
1986 951 |
||
![]() |
|
Registered User
Join Date: Oct 2002
Location: Dubai
Posts: 388
|
It can all so be your over boost protection. Check the line that goes from the cv to the waste gate.
I have just replaced my Air circulation valve and I'm still losing boost pressure.
__________________
coupe http://www.p-caronline.com/directory/coupe Porsche 944 Turbo, 1986 Fiat Coupe 20v Turbo, 1997 |
||
![]() |
|
Registered User
Join Date: Feb 2003
Location: East Bay
Posts: 1,481
|
Uhh.. the Stage-1 APE upgrade is the single-chip DME-only upgrade. It is not meant to be used with increased boost !!! That means the boost-gauge should only go up to 1.8bar and no more. Above this level, the stock KLR chip will activate the overboost-protection.
Most likely the culprit is a leak someplace in the cycling-valve hoses. This would cause insufficient pressure to make it to the wastegate to regulate boost, thus higher-than-stock boost. |
||
![]() |
|
Registered User
Join Date: Feb 2003
Location: East Bay
Posts: 1,481
|
Or... if you have the Stage-2 APE chip upgrade, then overboost-protection shouldn't be an issue. In which case, this clue: " It is sometimes quite violent." would seem to indicate a leak big enough to severely mess up air-fuel ratios. Such as if enouigh air leaked out that the mixture was so rich it causes the stumbling. The only places that can leak this much air is the turob-outlet hose and the intercooler-pipe hose-connections... Good luck!
|
||
![]() |
|
Junior Member
Join Date: Jun 2003
Location: Groveport, Ohio
Posts: 5
|
![]()
It is a stage two kit and the problem seems to be solved! I replaced the valve that keeps the turbo spooled up (by the coolant res) and the boost was a lot smoother but it still had signs of the problem. I then put a new set of wires on. While replacing the wires I noticed that there was a bunch of slop in the dist. cap. I reseated the cap and the problem is GONE. I would never have pegged this as an ignition problem. This is really screwy as I don't understand why the motor dist. cap would only cause the problem when the turbo spooled up. Maybe it was throwing the advance off??? This problem still has me confused but at least it hasn't come back yet!
__________________
~~'O=^-o> |
||
![]() |
|
Registered User
Join Date: Feb 2003
Location: East Bay
Posts: 1,481
|
yeah, strange too. It would appear a loose distributor cap would cause you problems regardless of boost. Perhaps it was RPM-related and you only had high-RPM with high-boost? I've pulled one of these off a car that was performing perfectly (the one on the right):
![]() We actually only discovered that disttributor rotor a month after running this dyno chart. |
||
![]() |
|
![]() |
Thread Tools | |
Rate This Thread | |
|