autocomman

So Im sur esome of you have seen my restooo thread on this 86 951 I have. Im stuck with a limp mode boost issue and no blink codes. Ive rebuilt the entire engine harness, thats new injector, TPS, ECT, Knock, IAC wiring, etc etc, new grounds, battery cables, alternator cable, voltage regulator, CV valve, vacuum and intake hoses. Verified the operation of the TPS multiple times, voltage and OHMs, ECT is new, IAC is new, RPM sensors both of them are new, air flow meter ive verified works smoothly without any jumps or dead spots on an OHM meter. Verified these signals at the ECU and KLR respectivly. Knock sensor is new, but it didnt ohm out like the original, this one is in the mega ohm range, and from what ive read thats normal...I just dont know i thats my issue as the original one didnt ohm out that high. The DME and KLR I sent to ECU doctors for this problem exactly, and they of course said they needed repair, bad caps, bad solder joints, I totally get that. Got car back on teh road today, same thing, .2 bar boost.

I disconnected the waste gate (which I shimmed for kicks with 2 washers) and it will boost just fine, no issues, so the cat convertor or muffler being plugged isnt an issue. And since I had the motor out recently i looked into the down pipe and nothing looked collapsed.

What the hell am I missing, CV will click if I rev it quick over 60% throttle. I have verified and rechecked the signals at both DME and KLR. So is the new knock sensor an issue? I would think if the knock was keeping it from boosting Id see a blink code. Or do I potentioally have an issue with the KLR or the chip inside still. I dunno if ECU docs checkes the CV circuit when they do their testing. Someone help steer me in a direction cause im frekin lost and totally over this. I need it fixed so I can put this car to bed already

Mark

Tom M'Guinn

Can you explain what you mean when you say you "disconnected" the wastegate and it boosted fine? Do you mean you clamped the hose going to it, and got tons of boost?

The new knock sensors do have higher resistance, but I've used them with no problems (although I haven't run the factory cycling valve in a long time). Doubt that's the issue. You might call ECU docs and ask if they test the CV controller circuit -- never heard of one going bad, but everything can fail.

autocomman

Disconnect the hose to the wastegate, same as pinching or clamping it, and yeah it will hit 1.8 2 bar no issues modulating the pedal to keep it from over boosting. Plenty of boost and quick boost. So as far as im concerned, that eliminates any intercooler, or exhaust plugged issue. Im gonna contact ECU docs, when I sent them in this is exactly what I told them, no boost, limp mode boost AND the CV does cycle if you snap the throttle above 60% just sitting there. That is what its supposed to do, but i am gonna ask them if the tested it and if so how they tested it. THe driver circutry works otherwise it wouldnt click. Im gonna put a gauge on the ports and try to get my meter on the valve to monitor the duty cycle tomarrow and drive it to try and see if its even trying to command more boost. Then at least I have more of a direction to go in, but im stuck on there is still something wrong with the KLR.

Mark

fwb42

Mark, It sounds to me that you have a wastegate problem. If it boosted fine when disconnected it sounds like everything is doing it's job but the wastegate..

944hal

I have a similar problem, with perhaps a slight difference. Sometimes it will get max boost when I first go out on track. The longer it runs, the less boost I get, until, like you, I have only got a couple of pounds. I've did all you have done. New harness and sensors, Cyclic valve and I even swapped out the waste gate. I also borrowed a different ECU and KLR. Nothing helps. I totally rebuilt the engine and it still does it. So, I just installed a manual boost gauge and it runs perfectly. Great boost from the start, and falls off after 5500 hundred RPM as supposed to (not a Turbo S). I've also tried various air boxes to no avail. I had a similar problem a couple of year ago. Car was going into limp home mode. That turned out to be the stock chip. I had put a 3" exhaust on the car and increased air flow was read as overboost by the ECU. An aftermarket chip fixed that problem. Anyway, if you discover anything, I'd be interested in the solution. I'll do the same,if by some miracle I figure it out.

autocomman

Fixed fixed FIXED!! This has been a super long term issue, but being grandmas car I never bothered to deal with it. 8 yeas ago I tried and failed and gave up. So, long story short, the vent line from the CV to the J-boot is restricted. I pupped the hose off the CV and blasted it around the block. Full .7 BAR. Go figure. Now I swear 8 years ago when I first started to tackle this I checked that line, but either its only partally restricted, or I had other issues such as the failing engine harness, or DME and KLR issues. Either way sometimes going back to basics is what ya need to do, frekin A man.

Jfrahm

Wow, quite a saga. Glad you figured it out! I will try to remember to check/replace lines like this when I have problems. At one point I thought I had belt slipping on my blown 968, after having done some significant work to address that issue, and later found I'd blown the boost/vac line off the BOV and while I had slippage and fixed it I had a new problem that acted the same (hit 5psi and level off rather than boost climbing with RPM). In the meantime I went a whole new direction to deal with the belt slippage.

944hal

I shall take a look at mine. Thanks for the info. If it works for me, I will let you know.

autocomman

Cool man, Im gonna try and figure out where the restriction is this weekend. For now the hose is just off the CV. Man its so much fun to drive again! But yeah, 3 inches of rubber hose to 6 inches of metal pipe to 8 inches of rubber hose with a metal fitting on the end of that. Im guessing its in the metal pipe but ill report back with what I find

Jfrahm

Jetted banjo bolt maybe?

autocomman

I dug into it and I think the pic is pretty self explaintory. Thats the J-boot, it was replaced some time for ever ago way before I was working on this car (over 10 years) and thats where the bleed form the CV goes, works a helluva lot better now that I punched it open