What are the symptoms of a failed Knock sensor

andydunn2 · 06-08-11, 01:21 PM

As above can anyone advise what the symptoms are for a failed knock sensor?

I am trying to get this pig of a Cab sorted and it was mentioned that it could be the knock sensor.

Ta
Andy

msh · 06-08-11, 02:05 PM

Engine?
Problems?

andydunn2 · 06-08-11, 03:02 PM

Quote:

Originally Posted by msh

Engine?
Problems?

Yes would help wouldnt it.....

2.3 10V (NG)

Its a running saga but.......

1. Down on power
2. drinks fuel
3. missfire that gets worse when very hot (in town driving etc) at which point car misses backfires stinks of fuel and throws its toys out the pram.
  
  So far its had new dizzy, Lambda sensor & both temp sendors.....

mikes2 · 06-08-11, 03:12 PM

I had a knock sensor fail on my 90 20v.

It would misfire at about 4k and feel like it was holding back the power. Once you got to 4500rpm, it would take off again.

it made overtaking quite entertaining

msh · 06-08-11, 03:13 PM

Sounds more like usual problems with KE-jetronic

Dead knock sensor would mean detonation, especially when driving around town using throttle enough and backfire when turning off engine, maybe some "dead spots" at low rev range, but negligible impact on fuel economy and very small on performance.

Long time ago I had 3A with dead knock sensor, I came to conclusion that that KE-Motronic can't provide proper ignition without it. While driving without it, I had adjusted a bit later ignition, so it didn't detonated while driven on road [as was most of my usual route], but when I got new knock sensor and readjusted ignition, max speed increase was 30 kmph

msh · 06-08-11, 03:17 PM

Are you changing that stuff or someone else for you? I have a couple of recommendations what you could check, but it requires some tools and pair of straight [not curve

] hands

msh · 06-08-11, 03:18 PM

Quote:

Originally Posted by mikes2

I had a knock sensor fail on my 90 20v.

It would misfire at about 4k and feel like it was holding back the power. Once you got to 4500rpm, it would take off again.

it made overtaking quite entertaining

hitachi MPI is a bit different opera than bosch KE-jetronic's

andydunn2 · 06-08-11, 03:30 PM

Quote:

Originally Posted by msh

Are you changing that stuff or someone else for you? I have a couple of recommendations what you could check, but it requires some tools and pair of straight [not curve

] hands

I am doing the work myself.........hmmm maybe thats the problem...

msh · 06-08-11, 05:06 PM

First thing to check, I think, should be cold start injector, because it's the least difficult part of all

Disconnect connector, undo both bolts, remove it, point it away, close that hole in manifold with your finger or something else that won't be sucked in manifold

and ask someone to start engine. If injector is squirting fuel, you have found fault.
But actually before that you can try to disconnect air mass meter potentiometer and pressure regulator - one at once. When everything's fine, disconnected potentiometer should only make strange, fluctuating idle but nothing more, while disconnected pressure regulator should decrease performance, probably some starting issues and it also removes redline

missfire · 06-08-11, 06:12 PM

Quote:

Originally Posted by andydunn2

[*]Down on power[*]drinks fuel[*]missfire that gets worse when very hot (in town driving etc) at which point car misses backfires stinks of fuel and throws its toys out the pram.

mine did that. fault codes said lambda and knock sensor. replaced them. now it doesn't do that..

dunno if its the same cause though. you never know... well, at least i never know...

06-08-11, 03:12 PM	#4
mikes2 4 ring whore! Classic Audi Club Member Join Date: Nov 2007 Location: Polmont Posts: 2,617	I had a knock sensor fail on my 90 20v. It would misfire at about 4k and feel like it was holding back the power. Once you got to 4500rpm, it would take off again. it made overtaking quite entertaining __________________ 1991 90 quattro 20v sport 1991 90 quattro

06-08-11, 02:05 PM	#2
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Engine? Problems?

06-08-11, 03:13 PM	#5
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Sounds more like usual problems with KE-jetronic Dead knock sensor would mean detonation, especially when driving around town using throttle enough and backfire when turning off engine, maybe some "dead spots" at low rev range, but negligible impact on fuel economy and very small on performance. Long time ago I had 3A with dead knock sensor, I came to conclusion that that KE-Motronic can't provide proper ignition without it. While driving without it, I had adjusted a bit later ignition, so it didn't detonated while driven on road [as was most of my usual route], but when I got new knock sensor and readjusted ignition, max speed increase was 30 kmph

06-08-11, 03:17 PM	#6
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Are you changing that stuff or someone else for you? I have a couple of recommendations what you could check, but it requires some tools and pair of straight [not curve ] hands

06-08-11, 05:06 PM	#9
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	First thing to check, I think, should be cold start injector, because it's the least difficult part of all Disconnect connector, undo both bolts, remove it, point it away, close that hole in manifold with your finger or something else that won't be sucked in manifold and ask someone to start engine. If injector is squirting fuel, you have found fault. But actually before that you can try to disconnect air mass meter potentiometer and pressure regulator - one at once. When everything's fine, disconnected potentiometer should only make strange, fluctuating idle but nothing more, while disconnected pressure regulator should decrease performance, probably some starting issues and it also removes redline