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Interestingly enough, I may have uncovered the issue today, but need some confirmation that it connects to the issues I'm having. After reinstalling my intake manifold, I started the car once and it went through the usual cycle, however, the second time starting it, I jumped the DME pins for the ISV. The car then seemed to be running normal.
My question would be - how does this pertain to the boost issue? What would cause the KLR to dump boost if there is an issue with the ISV? The sequence of events for the two problems seems to show a connection. 1. After replacing my turbocharger, due to FOD, at my indy, the car comes back idling around 1100RPM. They could not confirm if one of the techs had adjusted it higher so I took it with a grain of salt. 2. Car was driving down the road and boosting fine for 2 or so weeks, then 45 minutes or so into a drive, the car violently dumps boost sporadically depending on gear. 3. The next day, the car appears to run richer and misfires at idle. Now it take 5 minutes of horrendous idling for it to clear up, and once warmed up, it hits an idle mixture of 12.5:1-ish. It still seems to struggle returning to idle (lean surge sensation.)
Could the ISV be the culprit?
Extra notes to add - my idle vacuum is around 12 at cold and maybe 15 when warm.
I need some resolution as it is getting nicer out, and I've put maybe 1500 miles on my car since I bought it.
Do You mean you shorted the two pins for the ISV? I hope not, there are many members that have fried their DME because of shorted ISV wires on the harness, or accidentally shorting the two wires.
Do You mean you shorted the two pins for the ISV? I hope not, there are many members that have fried their DME because of shorted ISV wires on the harness, or accidentally shorting the two wires.
Negative. I jumped the pins on the diagnostic port (factory-recommended process to adjust idle speed.)
I had Issues with cold warm up and warm restart where my afr would randomly go lean like up to 18-20 and buck and stumble, unplugging o2 sensor didnt do anything, but if I did the same thing, jumping diagnostic port, car would run good. When you jump the diagnostic port, the DME goes into open loop, basically running on preset maps. The problem resolved itself when I purchased my 3rd DME, So im assuming there was something failing in the DME. If you feel brave you can crack your dme open and reflow all the solder points, they are prone to growing cracks in older motronic DMEs. Not saying your DME is bad, but it could be. So try and find a good used on you can borrow and try.
I had Issues with cold warm up and warm restart where my afr would randomly go lean like up to 18-20 and buck and stumble, unplugging o2 sensor didnt do anything, but if I did the same thing, jumping diagnostic port, car would run good. When you jump the diagnostic port, the DME goes into open loop, basically running on preset maps. The problem resolved itself when I purchased my 3rd DME, So im assuming there was something failing in the DME. If you feel brave you can crack your dme open and reflow all the solder points, they are prone to growing cracks in older motronic DMEs. Not saying your DME is bad, but it could be. So try and find a good used on you can borrow and try.
Interesting... unfortunately I don’t have access to a 944 Turbo DME to swap it with at the moment, and it’s too inconclusive of a fix to throw $$$ at. I did open up the DME to check the type of chips installed and there wasn’t much to note visually wrong, though that can be deceiving. I haven’t tried starting with the ISV unplugged to see what that yields.
To my understanding, the ISV is a bypass valve that provide metered, pre-throttle body air to assist when starting cold. It is notable that when I have a rough cold start, the car misses when idling and under load. I don’t see the connection here since the ISV is out of the picture under boost. But then again, little seems logical with this car.
Get a multimeter, and take about an hour of your time. pull your carpet and dme, and the dme connector.
start working through some diagnostic checks.
Voltage supply to dme: ignition: on pin 18 to ground and pin 35 to ground should be about 12 volts
Grounds: ignition off: check continuity, 5 to ground, 10 to ground, 16 to ground, 17 to ground, 19 to ground
full throttle switch: 3 to ground continuity, should read no continuity if throttle closed or partially open
same test, throttle open full, should have continuity
tps idle: 2 to ground continuity, throttle closed, no continuity, open partially or fully, should have continuity
air temperature sensor: ignition off: ohms between pin 6 and 22 , 20 degrees C 2000-3000 ohms, 80 deg C 250-400 ohms
idle speed control valve: pins 34 and 33 with ignition off, should read 40 ohms
o2 sensor: pin 28 and ground with ignition off, should read continuity
There are lots of other tests you can do, but I would work through those and it will help eliminate wiring or sensor problems. If you find any abnormalities post it.
FYI - tested these points with my multimeter today. All measured within spec, with the exception of the TPS, which was off the car with the intake manifold. It tested fine yesterday at the KLR.
FYI - tested these points with my multimeter today. All measured within spec, with the exception of the TPS, which was off the car with the intake manifold. It tested fine yesterday at the KLR.
Alot of people have bad DME problems. And bad solder joints cannot really be visually identified. You have hundreds of solder connections on the board. If you feel like reimbursing me for shipping, i can send you my DME that was known good, if you want to see if that works.
I had Issues with cold warm up and warm restart where my afr would randomly go lean like up to 18-20 and buck and stumble, unplugging o2 sensor didnt do anything, but if I did the same thing, jumping diagnostic port, car would run good. When you jump the diagnostic port, the DME goes into open loop, basically running on preset maps. The problem resolved itself when I purchased my 3rd DME, So im assuming there was something failing in the DME. If you feel brave you can crack your dme open and reflow all the solder points, they are prone to growing cracks in older motronic DMEs. Not saying your DME is bad, but it could be. So try and find a good used on you can borrow and try.
First of all, I'm not trying to pick on you, but I just want to point out a few mistakes in the above statement, which hopefully will help other understand the system as well. All that happens when the diagnostic port pins B and C are jumped is the automatic idle speed control via the idle control valve is disabled, and you get your "base idle" as set by the adjustable bypass screw on the throttle body. It does not change anything with the DME maps, nor does it affect anything above the idle speed range. I think you are confusing this with when the O2 sensor is unplugged, the DME enters "open loop" and operates solely via the basic maps without feedback from the O2 sensor. Even with the O2 sensor connected and working normally, the DME also enters open loop at above about 2/3 throttle, as determined via the full load signal from the KLR----the potentiometer of the throttle position sensor is only fed to the KLR, and not the the DME. The DME is only connected to the idle contact inside the TPS, which signals the idle control valve to activate, unless pins B and C of the diagnostic port are jumped.
Which leads us to our next topic: based on Tyler's updated and more detailed description of the sequence of events, I would be very suspicious of the TPS and/or its wiring, or the sensor itself might be loose or misadjusted. The TPS is a direct input to the KLR, and if there are any issues, the boost control will not work properly and the KLR may enter the low-boost "limp-home" mode. I would check this next.
Replaced my TPS with a known good unit due to some flakiness when tested on and off the car.
The car appears to be running slightly better, but still rich and misfiring when cold. The car leans out and the idle increases to about 1100-1300 after a short while, however, I am still in KLR limp mode. I am still suspect of a vacuum related issue - I see 12-13 in/Hg at idle according to my boost gauge.
On examining the vacuum lines to the damper and FPR, I made some changes to match the Lindsey Racing diagram instead of the Pelican Parts diagram and the car seems to maybe run better(?) but it is hard to say because it is not stone cold.
Regardless, I am still hitting this nasty, violent, boost cutoff at varying PSIs/gears/engine speed.
I'm beginning to see this as fuel related and am going to test pressure at the rail, regardless of what the indy told me because I have a constant whine from the passenger side, and removing the vac lines from the damper or regulator does not seem to have an impact on the car's mixture. Additionally, after test driving it following my vacuum line updates, the car stalled at idle at a red light.
Alot of people have bad DME problems. And bad solder joints cannot really be visually identified. You have hundreds of solder connections on the board. If you feel like reimbursing me for shipping, i can send you my DME that was known good, if you want to see if that works.
I really appreciate the gesture, however it doesn't seem necessary at the moment. Stay safe and healthy!
Take the test DME offer! It would be very valuable to confirm that yours is indeed good. Your car ran fine then without any changes it started acting up, correct? And despite much time diagnosing including serviced by a pro, you're still far from the cause. Here's what was killing my car for a few weeks:
I hope you test fuel pressure and find the problem (PS the hard part is finding that rail end-fitting; some just clamp a hose on there briefly but you didn't hear it from me). But if it tests fine?
Trying another DME --even if your car is running fine-- can offer a lot info re: chip, general behaviour, etc. One time, after lots of work, my car wouldn't start. A super nice guy saw my posts and brought his DME over. No change. It was a major help. If I was nearby, I'd bring mine over. Moalaska is offering the next best thing
My reasoning for attributing it to a vacuum leak (and please correct me if I'm wrong) is the fact that the car is misfiring, so my wideband sensor is detecting the excessive fuel in the exhaust.
Ok, since you asked i'll correct that!
The O2 sensors measure O2 and not fuel. So it you have a misfire you will not burn the O2 during the misfire and it will show up at a lean AFR reading. If fact a misfire usually makes the ECU try to add fuel because it believes it lean when it really isn't.
my best guess is that you have a wiring issue in the harness. Getting more and more common as our cars age. Kt sounds like you have been working on the engine (removing fuel rail / intake manifold etc.) - that means you have been bending the harness and that can crack the brittle insulation.
My usual solution is to recommend the possibility of stand alone system and completely replace the stock wiring. Yes, its a little extreme but from experience I can tell you that I have had customers spend more $ chasing bad wiring than the cost of a stand alone.
Measured the fuel pressure at the rail and and it appeared within spec during the first 15 seconds, however, when it begins to misfire, the fuel pressure jumps to 100+ psi. At this point, I'd say its safe to assume that Rennwerke did not test the fuel pressure, as there is clear evidence of an issue.
However, the 15 second delay as well as the fact that the fuel pressure drops off almost immediately after turning off the car indicates that this may not be a FPR-related issue, but a check valve, damper, or clogged return.
I've attached a video so any input is much appreciated.
04-16-2020, 09:21 PM
