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boost related problem

Hello everybody, I han an stock 87 951 with 190 000Km. The only aftermaket thing on it it's the blowoff valve witch it's an adjustable atmospheric tipe from sytec motorsport. My problem: when I reach ~5000 rpm the boost presure drops below 1 bar mark on the stock boost gauge. This problem happens in all the gears from 1st to 5th gear. If I put the car on 5th gear on highway it pulls from 3k to 5k with no problems ( boost gauge indicator stays betwen 3th and secont withe mark, from right to left).Once it reaches 5k boost cut's out and no mater how mutch more I keep the throttle stik to the floor engine won't revi higher then 5k rpm.
What I did befor I post this topic it's:
Checked wastegate and removed shims.(no change)
Checked all the hoses and vacum tested, also venturi delete.(no change)
Clamped wastegate line.( 2 BAR on boost gauge still dies at 5k, tested just once)
Replaced and gaped speed and referance sensors.
Blink code tester shows no errors. Removed TPS plug show 4-1 and 3-3. ( Some time about 2 months ago before I changed AFM when boost presure was cuted it blinked only one time, now it doesn't do that).
Repalced CV with new.(with old CV boost presure droped at first whtie line after 1BAR when reach 5K, with new one boost pressure drops below 1)
Replaced AFM with two other used ones.
Replaced spark plugs, rotor and distribuitor also checkd spark plug wires.(slight improvment).
Cleaned most of the grounds in engine bay area.
Checked knock sensor position and retorqued.
Replaced 2 lifters.( still no change)
Changed all filters 2000 Km ago. ( no change)
Checked timing and it's ok. Also did a test run with timing set 1 tooth on camshaft gear after mark and the car runs a bit difrent but still the same problem. (when I bought the car from the previous owner this it's how the timing was set).
I checked turbocharger - it doesn't have any shaft play.
The problem it's that I don't have any 951 owners nearby who could give me an DME and KLR to have a go with them and see if there lies my problem.
Can anybody tellme what to do next or what to check. I have almost 2 year since I have this problem and still no result. So if anybody can helpme with this I would be very gratefull .
Old 10-15-2008, 12:20 PM
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it sounds suspiciously like it might be an electrical ground problem. have you checked the two main ground wires from the battery?

have you tested the AFM connector and wires to make sure they are not shorted? how about the TSP connector and wires? speed/reference sensor connectors and wires, etc.

a local friend had a similar problem at higher rpm's and it turned out to be some suspicious/bad wires and/or connectors.
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Old 10-15-2008, 04:38 PM
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Cleaned the gto AFM TPS and speed sensor, also replaced speed sensors and checked gap and still the same problem. Here it's what I did today. I removed the vaccum hose witch goes to KLR.I have to say that the car pulled all the way to redline hiting the revlimiter. It feel like the power was limited. I think the KLR it is the source of my problem . I'll check that tomorow.
Thank you for your replay.
Old 10-16-2008, 12:04 PM
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sometimes, oil can get in that vacuum line from the intake manifold to the KLR. make sure that line is clean.
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Old 10-16-2008, 05:32 PM
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Checked - it's white and dry.
Today I changed the fuel hose withch goes to fuel pressure damper. The one I had on tha car wasn;t the original hose and the inside diameter of the hose was 8mm witch it's smaler than orig line (9mm).I installed a 9,5 mm hose, unfortunately the garage where my car it's located very busy area and I could not go faster then 1st and 2nd gear.Tomorow morning I'll make a test run and post the result.
Old 10-17-2008, 10:18 AM
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Did the test run - no improvement. I think thet KLR it's the problem. I opened it in this weekend, it lookd dry, no rust and it wasn't opened before. I think the pressure sensor inside the KLR it's bad or out . The reason I think this it's that when I buyed the car from the ex owner the hose from the IC pipe to CV had an Open/close swich installed on it witch was close at that moment and the car overboosted frequently... Today I buyed a boost gauge and tomorow I will install it to see if there are diferences betwen the real boost and what KLR reads.
Old 10-22-2008, 12:59 PM
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3bar (43.5psi) gauge! woohoo, party time !
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Old 10-22-2008, 01:54 PM
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Alex,
When your car reaches 5k does it stay there or does it seem like the ignition is turning on and off? The reason I ask is I had a problem simaliar to yours several years ago.
LeeC
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Old 10-25-2008, 03:01 PM
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Quote:
Originally Posted by carsonmx114 View Post
Alex,
When your car reaches 5k does it stay there or does it seem like the ignition is turning on and off? The reason I ask is I had a problem similar to yours several years ago.
LeeC
It's stable but it won't revs wont go up and the boost gage indicates below Bar.
Old 10-29-2008, 07:04 AM
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Today I installed the boost gage and did a few test runs.
ST run - .75~.80 bar
ND run - .75 bar
3rd run ( WG line clamped) - .65 ~ .70 bar ( it jumped once to Bar)
On all runs the boost was cut at around 5k rpm. The values indicated on stock boost gage installed on the dash are similar to the values indicated on the aftermarket boost gage. Next thing I want to recheck it's the AFM. It's anyone who had a similar problem? There it's any way to check if the KLR it's sending wrong signals to dme? cold be AFM related or a DME problem.
Old 10-29-2008, 07:18 AM
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if boost only goes to .65bar with the wg line clamped, it shows you have a boost leak somewhere.
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Old 10-29-2008, 08:03 AM
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Don't know what to think. I already checked the intake for leaks. Last time when I checked I pressurized the intake from the first pressure pipe ( the one that links the turbocharger to intercooler) using a compressor with tha car in gear. At around 2~2.2 Bar the car moved froward and no leaks. On the next days I plan to check the exhaust. Last winter I've somme stones hit the CAT and bent the aluminum shield. I will also recheck the intake this days.
Old 10-29-2008, 11:08 AM
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how do you know your wastegate is good?
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Old 10-29-2008, 12:14 PM
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I don't know if it's good. All I know it's that the diaphragm holds vacuum, and the WG valve it's opening and closing.I check that 3 or 4 weeks ago when I removed the shims. I also did the test specified in workshop manual, and the WG discharge pipe stais cool when the car idles.I don't 100% ok or how much boost will hold and I also taught that this could be a part of the problem. Do you know how can I test to see if this it's the problem. I also have to tell you that I don't have a spare unit . Thanks for help
Old 10-29-2008, 01:50 PM
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if you clamp the wg control line, the car should overboost to the point where the engine could blow up. since you said it doesn't boost past .65bar even with the wg line clamped, it shows there is a boost leak somewhere. the leak could be on the intake side, or the exhaust side. you'll have to do the legwork to find the leak.
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Old 10-29-2008, 02:36 PM
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I think you are very right about this. The the joint between the WG and exhaust ( manifold side) it's very loose. Tomorrow I'll make a few pics to see how lose it was. Today I removed the exhaust and and I had a little surprise.As I was looking at the end of the downpipe where the CAT ends to see the condition of the CAT ( I taught maybe it's clogged or something) I've seen that the cat internals has been removed but only the main CAT, the small cat located after the WG it's still in place. The pipe looks ok no sign of collapsing.
Old 10-30-2008, 11:44 AM
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I fixed the joint from the WG today. But boost pressure it's just a little bit up, and the 4500 ~ 5000 rpm problem it's still there. Obviously I'm missing something but I can't figure it out what.
Thank you for replays and nice weekend everybody.
Old 10-31-2008, 02:20 PM
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Alex,
Is it possible that you have an exhaust restriction? Why not try driving the car without the cat on it at all? I think your problem is different than mine, but I know how you feel right now. That's how I found this forum several years ago. My car had a burned trace in the dme unit. It would run great and do everything fine except under boost it would die hard and jerk on and off. Also what about an intake restriction? Maybe the air flow sensor? I have a good stock one if you need it let me know.
Lc
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Old 10-31-2008, 03:41 PM
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I haven't open the DME ( yet), only the KLR. I'm trying to find someone with an 87 951 to swap some parts. Can you send the AFM to Europe - Romania and what it's the price ?
Old 10-31-2008, 10:17 PM
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