# Knock sensor control unit problems?



## pdevinney (Oct 2, 2011)

I am still having the same problem I posted about earlier. I replaced the fuel distributor/DPR with a known good unit. I have checked the fuel pressure both in the driveway and while driving. The fuel volume from both pumps is within limits. I eliminated the pump relay as a possibility also. It still stutters upon accelaration and cuts out under load but when it does fuel pressure doesn't drop. I have swapped in a known good ecu and ignition module.....no change. Has anyone experienced this problem? Could this be related to the KS control unit or sensor? Mitchell ondemand has no info on this.. Any suggestions would be greatly appreciated! Thanks again

89 jetta gli k jetronic cis e 1.8l 16v


----------



## pdevinney (Oct 2, 2011)

*update*

the fuel pressure does drop 5 psi upon acceleration but climbs immediately back up?


----------



## cuppie (May 4, 2005)

That's a problem. I'd start with replacing the fuel filter. If you still have the pressure-dropping issue after that (you probably won't, though), you'll need a fuel pressure regulator.

As to the hesitation, etc. issue:
I doubt that it's the knock control. Typically, they just up and die - no spark, engine doesn't run. Rarely, I've seen (and, had this happen to myself) them suffer an internal failure that allows the engine to start & idle, but go to absolute hell when it's under any load (I think it was a faulty MAP sensor (which is in the control unit.) Very rare, and makes the car pretty much undriveable.
More likely would be:
- intake leak: Been thru the vacuum lines? Replace the injector o-rings?
- intake leak II: Have you removed the intake boots, and carefully inspect them for cracking? Your description just smacks of 'small crack in intake boot' (acceleration rotates the engine rearward, pulling the crack open.)
- Fuelling issue. If it happens only when the enigne is warmed up, O2 sensor is suspect. How old is it?
At any temperature: coolant temp sensor is suspect. Check that yet?
- Faulty knock sensor. Any cracks in the casing, it needs new. Water will get in it, corrode it, and cause it to create all kinds of false signals, playing hell with ignition timing.
- Wiring issues. Make sure your power & ground lines are OK. Clean up the grounds on the back of the intake, and at the B- clamp. Run an additional ground wire from rear of intake to B- clamp. 
Wiggle-test _everything_ in the engine harness, preferably while it's running and/or when you're checking wires.

Go thru all of that, and post back with results. Most of those fixes are low-cost (some near-free); all are far cheaper than a new knock box.


----------



## anlxn (Oct 18, 2009)

pdevinney said:


> I am still having the same problem I posted about earlier. I *replaced the fuel distributor/DPR with a known good unit.* I have checked the fuel pressure both in the driveway and while driving. The fuel volume from both pumps is within limits. I eliminated the pump relay as a possibility also. It still stutters upon accelaration and cuts out under load but when it does fuel pressure doesn't drop. I have swapped in a known good ecu and ignition module.....no change. Has anyone experienced this problem? Could this be related to the KS control unit or sensor? Mitchell ondemand has no info on this.. Any suggestions would be greatly appreciated! Thanks again
> 
> 89 jetta gli k jetronic cis e 1.8l 16v


just make sure that its for a 16v not an 8v they dont interchange trust me I've done it


----------



## WaterWheels (Aug 14, 2005)

Thats not 100% correct. If the two are 8v and 16v CIS-e units, to include the DPR, then they are exactly the same. If the 16v is a 2.0L then there is a difference.


----------



## anlxn (Oct 18, 2009)

WaterWheels said:


> Thats not 100% correct. If the two are 8v and 16v CIS-e units, to include the DPR, then they are exactly the same. If the 16v is a 2.0L then there is a difference.


try it some time :thumbup:I dare you:laugh:.........actually the potentiometer is the difference that is the black switch on the other side from the DPR(the dpr is gray)we just swapped them both to play it safe ....


----------



## WaterWheels (Aug 14, 2005)

Actually I have. I've done more engine swaps/conversions then most people here are years old, plus the numerous work done on both 8 and 16 valve engines for close to 30 years. So making a dare like that is a wasted effort. The potentiometer for both are fixed (sealed from the factory with covering over the screws) and there is not a replacement part. I have removed some and adjusted some and they also look to be the same but I have no way to really be sure. And for the record it is not a switch, hense the name. Things would be so much easier if more people would invest in either an ETKA program or the ETOS one to match parts.
Air flow sensor for CIS-e 8v (like RD) and CIS-e 16v (like PL) is 026 133 471 for both.
Fuel distributor for both is 026 133 481X (exchange, rebuilt as there are no new ones).
Diferential pressure regulator for both is 026 133 482 (light gray, the 2.0L 9A is a dark gray).


----------



## anlxn (Oct 18, 2009)

WaterWheels said:


> Actually I have. I've done more engine swaps/conversions then most people here are years old, plus the numerous work done on both 8 and 16 valve engines for close to 30 years. So making a dare like that is a wasted effort. The potentiometer for both are fixed (sealed from the factory with covering over the screws) and there is not a replacement part. I have removed some and adjusted some and they also look to be the same but I have no way to really be sure. And for the record it is not a switch, hense the name. Things would be so much easier if more people would invest in either an ETKA program or the ETOS one to match parts.
> Air flow sensor for CIS-e 8v (like RD) and CIS-e 16v (like PL) is 026 133 471 for both.
> Fuel distributor for both is 026 133 481X (exchange, rebuilt as there are no new ones).
> Diferential pressure regulator for both is 026 133 482 (light gray, the 2.0L 9A is a dark gray).


so I it was dumb luck that it worked out for me?


----------



## WaterWheels (Aug 14, 2005)

That is something I can't answer. I have no idea of what you had for a problem and what all you did to fix whatever the problem was. All I can say is the parts you indicated as being different for 8 and 16v CIS-e engines are not. Now if you want to expand on the problem and your work done I might be able to then answer the question.


----------



## anlxn (Oct 18, 2009)

WaterWheels said:


> That is something I can't answer. I have no idea of what you had for a problem and what all you did to fix whatever the problem was. All I can say is the parts you indicated as being different for 8 and 16v CIS-e engines are not. Now if you want to expand on the problem and your work done I might be able to then answer the question.


so on my nephews car(88 1.8 16v gti) he said the plunger was leaking fuel on the air filter so i said here is my old one from my 86 gti 8v try this so he swapped them and it idled fine but would not climb thru the rpms under load so he switched the DPR and no go then he switched the poentiometer and bingo it worked . I was thinkinking that the Pot.told the ECU what the engine called for in the rates of air flow how much/how fast etc.then the ECU told the DPR to adjust accordingly I guess I gotta dust off my bently/bosch book now:thumbup:


----------



## WaterWheels (Aug 14, 2005)

The air sensor potentiometer signal is only accepted on CIS-e when the engine is cold to add a touch more enrichment. Once the engine reaches a slight warm state the ECU disregards this signal. CIS Motronic I have read uses this the whole time but I have only read so so articles on it and never really worked much on that system so I can't say for sure. In any case the need to replace or adjust the potentiometer on CIS-e is maybe 1:100,000. I would assume that might be one reason the screws are covered at the factory. The engine will also run good without that even being connected, on a real cold day it might show a very slight bog if you hammer the gas pedal but thats about it.

Just why the engine ran OK when you did what you did is something I can't say for sure from here. I would have to have my own hands on it or at least watch the work being done. Maybe it was a wire that was/is not connected real great and contact was improved? Maybe your nephew or you just happened to touch or correctly fix/install something overlooked before without knowing you did and just believe the potentiometer fixed things? I really don't want to guess as I will never really know what happened anyway being where I am. Just be happy it runs OK now, but don't believe the parts are different between the two engines, at least those parts. That was the intent, not to control your work, just to inform you the parts are the same.


----------



## anlxn (Oct 18, 2009)

WaterWheels said:


> The air sensor potentiometer signal is only accepted on CIS-e when the engine is cold to add a touch more enrichment. Once the engine reaches a slight warm state the ECU disregards this signal. CIS Motronic I have read uses this the whole time but I have only read so so articles on it and never really worked much on that system so I can't say for sure. In any case the need to replace or adjust the potentiometer on CIS-e is maybe 1:100,000. I would assume that might be one reason the screws are covered at the factory. The engine will also run good without that even being connected, on a real cold day it might show a very slight bog if you hammer the gas pedal but thats about it.
> 
> Just why the engine ran OK when you did what you did is something I can't say for sure from here. I would have to have my own hands on it or at least watch the work being done. Maybe it was a wire that was/is not connected real great and contact was improved? Maybe your nephew or you just happened to touch or correctly fix/install something overlooked before without knowing you did and just believe the potentiometer fixed things? I really don't want to guess as I will never really know what happened anyway being where I am. Just be happy it runs OK now, but don't believe the parts are different between the two engines, at least those parts. That was the intent, not to control your work, just to inform you the parts are the same.


well said:thumbup:


----------

