Low boost 951 and a possible fix
08-19-2017, 12:43 AM
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Low boost 951 and a possible fix
So Ive posted here a few times, been a few years though. With grandmas 1986 951. Car has hardly been driven at all, 3 blocks a few times a week. Anyway I picked up the car to service it and fix a fuel smell issue and decided its time to fix this low boost issue once and for all. I dunno if grandma will be driving it anymore, shes really gettin up there, but it needs to be sorted.
After a few days in the car its got issues. The idle valve is sticking, temp gauge is wacky, midpipe between the cat and muffler was swiss cheese and the boost sits at 1.2 bar, and thats it. Ive been down this road before with the car and found a plugged muffler causing power issues. After that fix the car revved much more freely and ran much better but still seemed as if it was in limp mode. No codes, new cycling valve...so anyway here is where its at.
It dawned on my (frekin derp) the knock sensor could be causing this and not setting a code. So among other things figured id yank the intake, do the IAC, the knock sensor the gauge and DME temp sensor, its cheep so why not. And while im in there check the engine wiring harness. And well its not good. The knock sensor plug wired and boot are split open, which I expected and the wires are green inside. The harness is broken open elsewhere but I dont see anymore bare wires, however I bet if I start to move stuff and strip it back it will all fall apart. The battery cables also are toast. So looks like I have to rewire the engine pretty much completely. Since thats what I do for a living its no biggie.
Im on the fence bout pulling the turbo and checking the double wall pipe that supposed to collapse. Pinching the wastegate hose it will boost, and it doesnt run like the exhuast is plugged. So I may not. Car has 96k miles on it and hasnt been abused really. Im pretty confident the harness will fix the boost issues. Also gotta order up a bunch of the hoses and whatnot. Is Lindsey the only one who has a replacement harness? even though its sections and not a complete harness...
Nice as the car is to drive, man working on this pig can be a pain haha
by https://www.flickr.com/photos/103785479@N08/, on Flickr
by https://www.flickr.com/photos/103785479@N08/, on Flickr
by https://www.flickr.com/photos/103785479@N08/, on Flickr
by https://www.flickr.com/photos/103785479@N08/, on Flickr
After a few days in the car its got issues. The idle valve is sticking, temp gauge is wacky, midpipe between the cat and muffler was swiss cheese and the boost sits at 1.2 bar, and thats it. Ive been down this road before with the car and found a plugged muffler causing power issues. After that fix the car revved much more freely and ran much better but still seemed as if it was in limp mode. No codes, new cycling valve...so anyway here is where its at.
It dawned on my (frekin derp) the knock sensor could be causing this and not setting a code. So among other things figured id yank the intake, do the IAC, the knock sensor the gauge and DME temp sensor, its cheep so why not. And while im in there check the engine wiring harness. And well its not good. The knock sensor plug wired and boot are split open, which I expected and the wires are green inside. The harness is broken open elsewhere but I dont see anymore bare wires, however I bet if I start to move stuff and strip it back it will all fall apart. The battery cables also are toast. So looks like I have to rewire the engine pretty much completely. Since thats what I do for a living its no biggie.
Im on the fence bout pulling the turbo and checking the double wall pipe that supposed to collapse. Pinching the wastegate hose it will boost, and it doesnt run like the exhuast is plugged. So I may not. Car has 96k miles on it and hasnt been abused really. Im pretty confident the harness will fix the boost issues. Also gotta order up a bunch of the hoses and whatnot. Is Lindsey the only one who has a replacement harness? even though its sections and not a complete harness...
Nice as the car is to drive, man working on this pig can be a pain haha
08-19-2017, 11:54 AM
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Yeah, already got a list go in including the air boots and what not. I don't wanna get too crazy as we are probably going to be selling the car at some point, and I really don't think it's gonna be driven much more. Otherwise I'd do engine mounts and some other stuff. It's so easy to rack up 2gs in parts as aftermarket avaiablility of quality stuff is limited now. Most of what I'm seeing in terms of parts is crap uro, or genuine. And genuine is $$$. 500$ for 2 oil filled engine mounts, really? Haha. I need to inspect deeper in to see where the oil is seeping from too. It's either the balance shafts or the oil separator. Either of which is a nightmares worth of labor. And if it's a little seepage I'm not gonna be doing it. Looking at the guides for just the turbo removal so you can get the heat shield out cause I'm not a fan of cutting things....holy crap man. I've wrenched for years but only done timing belts and normal service on this beast. We just dumped 6k in to their E 500 benz, that was just parts, and it was to go through the airmatic suspension and other safety things. Normally this deep into the motor it wouldn't be a question. Reseal, prevent and repair it all. But gotta keep budget in mind right now as it may not see the road with our family much anymore. And since the guys that buy these cars tend to upgrade and change stuff if rather not go too crazy haha.
08-27-2017, 03:23 PM
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So I ordered every harness I could get at lindsey. Im impressed with the quality. Labels printed on wires, loomed nicely, etc etc, and I do auto wiring for a living. Also got factory battery cables, an alternator harness, silicone hose kit for the intake tubes. I could have made new cables but right now it made more sense to just use factory parts for ease and quickness, and they are factory parts, cant go wrong.
Yanked the harness yesterday and when i pulled the vacuum line off the KLR fuel came out. I did not expect that, ever. Then thought about how the FPR is attached to the intake manifold and then thought, stupid frekin Porsche. It was a great idea to stack vacuum lines with a banjo bolt and to have the KLR vacuum line shared with an FPR line. So when the FPR inevitably fails it will the ecu with fuel. Oiy
So Ive got some thoughts. The boost gauge was working though last 2 times i drove, but when I started the car it wasnt working so well, it was lazy, and read much lower than it should. Im thinking when the car sat the fuel settled in the line in the pressure sensor and was causing issues. Then after the motor has been running for a bit the fuel is pulled out of the sensor. Im gonna try and leave the KLR and see what happens. Hopefully there is no permanent damage. If there is I gotta either find a new sensor and replace it on the board inside the KLR, find someone who repairs them, or find a good used one.
Oh and I have to do the timing belts. Less than 10k on em, but 7 or 8 years old, and I dont like how they look. Super awesome
by https://www.flickr.com/photos/103785479@N08/, on Flickr
Yanked the harness yesterday and when i pulled the vacuum line off the KLR fuel came out. I did not expect that, ever. Then thought about how the FPR is attached to the intake manifold and then thought, stupid frekin Porsche. It was a great idea to stack vacuum lines with a banjo bolt and to have the KLR vacuum line shared with an FPR line. So when the FPR inevitably fails it will the ecu with fuel. Oiy
So Ive got some thoughts. The boost gauge was working though last 2 times i drove, but when I started the car it wasnt working so well, it was lazy, and read much lower than it should. Im thinking when the car sat the fuel settled in the line in the pressure sensor and was causing issues. Then after the motor has been running for a bit the fuel is pulled out of the sensor. Im gonna try and leave the KLR and see what happens. Hopefully there is no permanent damage. If there is I gotta either find a new sensor and replace it on the board inside the KLR, find someone who repairs them, or find a good used one.
Oh and I have to do the timing belts. Less than 10k on em, but 7 or 8 years old, and I dont like how they look. Super awesome
