Knock Sensor Question ...

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Aug 10, 2004 | 11:40 PM

NightFlight

Thread Starter

Burning Brakes

Joined: Jul 2004

Posts: 956

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From: Mesquite Nevada

Knock Sensor Question ...

As previously posted, I had my car in the shop to have the starter replaced and a hose replace. While they were doing it, they found the connection portion of the knock sensor broke so they replaced it. After a couple of other problems related to replacing the starter, I got my car back today. However, I noticed a slight surge at idle that wasn't there before. Also, after stopping for gas, the check engine light came on when I started the car and the surge was a little worse. When I got home, I turned the car off and then, about a minute later restarted it. No check engine light and the surge was very mild again -- but still there.

Now for my question, if the shop routed the wire going to the knock sensor too close to the starter, like right over it, could the vibrations from the starter be causing false signals to the ECM?

I know this may seem a little far fetched, but nothing was done to the engine while it was in the shop and I can't figure out why it would start running this way all of a sudden ... any ideas would great be appreciated.

Aug 10, 2004 | 11:53 PM

chriswtx

Le Mans Master

Joined: Feb 2002

Posts: 5,970

Likes: 19

From: San Marcos Texas

sounds like a vacuum leak. Which hose did they replace? I would look around the intake for a loose hose. Knock sensor wouldnt do this.

Aug 10, 2004 | 11:59 PM

NightFlight

Thread Starter

Burning Brakes

Joined: Jul 2004

Posts: 956

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From: Mesquite Nevada

The hose they replaced was a coolant hose to a turbo; so that shouldn't be causing me any problems. I'll look for a vacuum leak tomorrow -- thanks

Aug 11, 2004 | 12:25 AM

chriswtx

Le Mans Master

Joined: Feb 2002

Posts: 5,970

Likes: 19

From: San Marcos Texas

ahh, Turbooo. Yepee. Ok, I bet something is loose on the pressure side of a turbo or something to that effect. Or they left something off. Check all your hoses etc. Also check all the clamps to the intercoolers. Anything they had to move out of the way to get to the coolant hose or knock sensor would be suspect. Loose wire connectors and hoses, damn those mechanics

Oh wait, I'm a mechanic

oh well, I've left hoses loose before also, it happens.

Aug 11, 2004 | 07:56 AM

NightFlight

Thread Starter

Burning Brakes

Joined: Jul 2004

Posts: 956

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From: Mesquite Nevada

chriswtx: When I get home tonight I plan on checking every hose & wire conncetion from top to bottom to see if they either forgot to connect something back up or knocked something loose when the ran the new hose. I've done that myself a couple of times, it happens and I hope that's all it is -- thanks.

Aug 11, 2004 | 08:22 AM

vettefast

Drifting

Joined: Sep 2003

Posts: 1,652

Likes: 2

From: 1990 383 Stroker Baltimore Maryland

If there were a problem with your knock sensor the results would be your timing would begin to retard from time to time.
I have had this problem before. It feels like you lost all your power no matter how hard you hit the gas.

Aug 11, 2004 | 09:46 AM

brian pinner

Instructor

Joined: Jul 2004

Posts: 118

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From: Smithfield Va.

Hey guys. I seem to be having this problem. Seems like the timing retards, the engine starts rattling under acceleration and then my engine light comes on. The "knock sensor" code showed up on the diagnostic. Where is the knock sensor and connections anyway? I'd like to take a look at it or replace it if I can.

Aug 11, 2004 | 10:06 AM

vettefast

Drifting

Joined: Sep 2003

Posts: 1,652

Likes: 2

From: 1990 383 Stroker Baltimore Maryland

As I remember you can get to it from underneath on the passenger side of the engine. The sensor is about $40 and it just screws in. I could be wrong about location. Check you haynes or service manual. It's a easy install once you find the location.

Last edited by vettefast; Aug 11, 2004 at 10:10 AM.