hodmandod

Hi Toolmaster

It all depends on the engine load. As you know, if you look at air pressure at the J-boot, by which I presume you mean the rubber boot to the throttle body, that will be a negative pressure at idle. If you floor the accelerator, it will instantly become atmospheric pressure. Then the turbo will spool up, and the air velocity from the AFM to the throttle body will increase substantially, but the tube at the J-boot will remain at negative pressure (?venturi effect). So the pressure there is always negative or atmospheric, and never positive, as it is the wrong side of the turbo. So, the air must generally gomto the J-boot. Or is my thinking wrong. Makes your brain spin, and the turbo. Philip

Oddjob

The KLR supposedly will cut timing by 3 deg, then 6 deg on the knocking cylinder and will then start cutting boost if knock still exists, but in millibar increments. It wont cut all boost and go to limp mode for knock control.

But its actually a pretty dumb system. Even though there are fault codes for bad knock sensors (which should cause limp mode), you can unplug the knock sensor and drive around and the KLR will not generate a fault code or go into limp mode.


As you and others initially mentioned, I would suspect the CV, hose routing from the CV, or the KLR. If you are certain the hoses are right, and odds are that a new CV should be good, may want to try to borrow a known good KLR from someone local to test that (before buying one). I had a bad KLR that did not generate a self fault code.

The CV will be open to the WG/closed to the j-boot when the car is off, this is the fail safe mode. I believe at idle it is the same. And that the KLR does not start signaling the cycling valve to divert air pressure away from the WG diaphram to the j-boot until there are throttle/load inputs. I am not sure what the KLR/cycling valve will do if you blip the throttle.

Toolmaster

My buddy Chris came over for a Chinese food lunch, and an O-Scope drop off today.

I've checked the speed and ref senders, and they are sending more than enough sine waves per the manual. I also tested the other sensors, and all but the knock sensor seem good.

Knock sensor, I get infinite resistance when I probe the pins on the KLR. According to the manual, this means either a bad sensor, or a bad wiring connection, or a bad engine ground. I'm thinking sensor, but I'm going to pull the knock sensor first if I can reach it with the intake on and test it on the bench.

So the theory now is that if the sensor shorts or opens but not quite all the way, then we see a blink code. If the sensor opens all the way, we might not see a blink code, yet the KLR might be erring on the safe side rather than letting boost build. I know a prior poster said that you can unplug this sensor and drive around all day and not set a blink code - but I'm a little unsure if I'd get full blown limp mode out of the car with a totally open sensor.

hodmandod

Toolmaster
Tell me how you probed the pins on the KLR. Do you actually put the pins into the wires or what?

You can get the knock sensor off easily without taking the IM off. Get the cruise control wire out of the way, and the rubber tube to the intake, as well as the spark plug lead. Do it carefully, cause if you drop the bolt ...well. I used a magnetic disc in the socket.
I am interested to see what happens.Philip

special tool

Forgive me if I missed it, but what are the codes?
4-1, etc?

hodmandod

Also I would check all the wire connections from the engine to both computers. I know there are a lot, but they are a weak link, as are any connectors in the engine.

hodmandod

Supa Tooner

http://www.lindseyracing.com/LR/Parts/BLINKCODE.html

special tool

UUUh - do you think I don't know what blink codes are?
I want to know WHICH codes are showing.

We are glad to have new Rennlisters - maybe you should search my previous posts.

hodmandod

Supa Tooner
Whoops!

Toolmaster

Ok.

Blink codes : None. None at all. I remove the TPS and get the correct 4-1 and 3-something (previous post), but turn car off, turn on, make a run for boost, get limp mode, and no codes show at all.

Knock sensor - pins 11 and 13 on the KLR connector should show something like 300k ohms. I get infinite, meaning wire break, bad sensor, or no ground or something. That's my current project to ID. I plan on pulling the thing tonite or tomorrow hopefully to bench test the sensor, and wire harness at the same time.

All suggestions are welcome as always. I do appreciate the queries and suggestions!

Chris White

hmmm...how about a tec3...sure cure!

The blink code system is not very reliable, I have seen many ‘limp mode’ cars that don’t throw any codes. I didn’t read all the posts – did you do the wastegate line clamp test yet? (danger!!unlimited boost!!).
BTW – the same thing (stuck in limp mode) drove me to my first stand alone 944 almost 10 years ago….and Toolmaster was close behind back then!!!

Oddjob

Might try doing some searches on knock sensors - this has come up before. Seems that it is relatively common to get infinite resistance across pin 11 to 13, or directly across the knock sensor pins - even on brand new sensors.

I have done quite a bit of testing and troubleshooting of the knock sensor/system, and the only sensor/car that I have that measures the correct resistance range (270-320? kohms per the factory manual) is the car that I cant get to run right.... go figure.

Toolmaster

Jim - perhaps true - but technically even a piezo (the knock sensor element) should have SOME resistence. I'm thinking engine ground issue on those - assuming my new sensor which arrives in 2 days also has infiniteresistence.

Toolmaster

Knock sensor in hand, I went over to the multimeter.

Interestingly enough, the sensor reads about 5 meg ohms on the bench for internal resistance. A far cry from the 300ishKohms that it should. I'll be testing the new sensor once it arrives in a day or two. The connecter looked fine, and I have continuity to pins 11 and 13 of the KLR from the connector, so the sensor seems to be the culprit. I'll know better once the new ones arrives.