Xu9 Dkz - Misfiring Above 3500 Rpm

[Roeland_Vester 5]

Hello all, this is my first topic here, and despite learning a lot from all of you, I can't get my lovely 1992 205 GTI to run properly.

 

It seems to run well below around 3500 rpm. It pulls strong, hot or cold, idles hot or cold, and starts consistently.

However, when I pass 3500 rpm, it flutters and the tach drops a bit. This happens hot or cold, and at part or full throttle. As the tachometer drops a when it flutters it seems the car is misfiring. I've already changed out the ignition amplifier (a proper blue Bosch one) and mounted it properly. The coil, distributor cap, dizzy, ignition wires, and spark plugs are replaced. I've also tested it with a different ECU (same part nr) and that gave the same result. As far as I know, those are all the parts in the ignition. As the problem is rev-dependent and the car drives well below 3500, I figure the wiring harness is okay.

 

So my question is to you, what could be the problem?

[Telf 224 2 Cars]

Have you tried a known good AFM?

[Roeland_Vester 5]

Thanks for your quick reply,

I have not tried a different AFM as the problem seems ignition related. I figured that for a given power (air and fuel flow), the motor should behave the same. However, at 3000 rpm full throttle the motor behaves fine. But at say 3800 rpm part throttle (delivering less power and drawing less air) it isn't in its happy space and starts misfiring.

 

I would also like to add that this problem happens in every gear, even in neutral. I can also get the engine to rev higher but it's sputtering all the way up to 5k (haven't pushed it further).

[2-Pugs 57]

From your description I would concur that it appears to be an ignition problem, though I had a similar problem on my DKZ 1.9 engine that got progressively worse and started off with occasional misfire at motorway cruising speed. Anyway to cut a long story short it was the air flow meter. I happened to have a newly- rebuilt one that I'd bought from someone off here and it cured the problem. Not saying this is your issue too but it's certainly worth a try if you can get your hands on one (which is not necessarily an easy task, granted!)

[welshpug 1,657]

it may well be running lean as the rpm goes up, so certainly worth checking it at the very least.

 

I dont recall which management system the dkz has though, is it a 122 bhp motronic engine?

[Roeland_Vester 5]

It is indeed the 122bhp engine, running motronic 1.3. Thanks for your suggestion

[PhilNW 44]

Check the fuel pressure could be the pump

[Roeland_Vester 5]

Hi Phil, thanks for the suggestion. I had the fuel pressure checked and it was a solid 4 bars, so it should be alright.

 

I was thinking about the crankshaft position. Could that be the source of the issue? So either the sensor,itself or the wiring to it?

[Anthony 1,003]

If that tester is accurate then that fuel pressure is very high - should be 3 bar less manifold vacuum (ie it'll read lower at idle and be around 3 bar at WOT)

[wicked 103 3 Cars]

Did you exchange the crank sensor as well?

[Roeland_Vester 5]

hmm I was told the fuel pressure was correct and now I'm in doubt as to whether it was 3 or 4 bars. Regardless, I've found this clip of a guy with a bmw e30 318is, running motronic 1.7, which is very similar to motronic 1.3. His problems were very similar to what I'm experiencing, including the unrealistically bouncing tach.

search on youtube for 318is 5k rpm hesitation (can't seem to copy-paste the url from mobile device).

In any case, I hope a new crankshaft position sensor will remedy my problem. Those BMW guys have a wealth of,information on Motronic systems.

 

 

 

[Roeland_Vester 5]

This is the clip in question:

 

Where the crankshaft position sensor was identified as the culprit. Which is almost the same unit as used in the Peugeot:

http://www.bogijn.nl/onderdelen/16/bmw/290/3-e30/28/318-is/sensoren-en-schakelaars/30/bosch/0-261-210-057/krukassensor <-- that is the Bosch crank position sensor as used in the BMW M42 engine

https://www.bogijn.nl/onderdelen/artikel/30/bosch/0-261-210-043/toerentalsensor-motormanagement <-- that is the Bosch crank position sensor as used in the Peugeot XU9/JAZ DKZ engine.

 

As you can see, the part number is a bit different, but the units look really similar.

 

I'm really hopeful a new CPS will mean the end of the shenanigans.

[Roeland_Vester 5]

Okay, I've solved the problem, and it turned out /not/ to be the crankshaft position sensor. As a long shot I refitted the old ignition amplifier, and that did the trick. I'm happy the car runs again and I am quite annoyed with the guy I bought the ignition amplifier from.

 

Also, it took a bit longer because a few online parts salespeople did not have the correct crankshaft position sensor. I bought mine from autodoc gmbh (they have several online outlets), and instead of sending me the bosch part, they sent me an imitation 'Mapco' part and tried to give me store credit for the difference. I got the money back, but be warned if you buy there that you won't get screwed over.

 

The mapco part does seem to work though.