knocking problem under acceleration

[LeSabre97mint]

Hello

I use 87 octane in my 97 and don't get any pinging. I would think your engine maybe carboned up causing higher conpresion. I would run a conpression test to check this out.

Regards

Dan

[coogs]

Chem Man.. I appreciate your assistance thus far.. haven't cleaned my MAF but will do so this w/e if you think its worth a try.. Knocking is worse now... only does it accelerating say from 25Miles or under load up a hill. Doesnt doit from a stop. I;d say uit's when the tranny is in 2nd gear going to third- does that make sense?

Do you have a diagram or somethibg that could lead me to the MAF?
any assitance would be appreciaetd. Also, is there something else I should look at -

thanks again
Greg

[ChemMan]

Originally Posted by coogs

Knocking is worse now... only does it accelerating say from 25Miles or under load up a hill. Doesnt doit from a stop. I;d say uit's when the tranny is in 2nd gear going to third- does that make sense?

A couple things here:

Has the weather changed at all at the same time as the knocking has gotten worse? That could effect how bad the knocking is.

Are you saying that the knocking only occurs as the car is shifting? That would really indicate a trans problem to me.

It would be most helpful to have a scanner on the car while driving and see if you are getting any knock retard. It could be detonation, piston slap, or trans problems causing the noise, and I think any of those could trigger the knock sensor and cause the pcm to retard the timing. But that should also leave a trouble code in the computer.

I really don't think cleaning the MAP sensor would be helpful, so don't worry about it for now.

The reason I asked if the engine used oil, is that oil burning in the combustion chambers will leave a lot of carbon behind and definitely cause knocking/pinging.

I hope others keep chiming in.

opcorn:

[coogs]

My response below in CAPS











Has the weather changed at all at the same time as the knocking has gotten worse? That could effect how bad the knocking is. NOPE

Are you saying that the knocking only occurs as the car is shifting? That would really indicate a trans problem to me. I MAY NOT HAVE EXPLAINED IT CORRECTLY..THE CONDITION OCCURS UPON FIRM BUT GRADUAL ACCELERATION INTERMITTENTLY... I'M DRIVING ALONG... SLOWING DOWN FOR A RED LIGHT.. DON'T QUITE COME TIO A STOP.. LIGHT GREEN.. I ACCELRATE AND "THERE IT IS"... I'M DRIVING ALONG APPROACHING A HILL.. SAY ABOUT 45 MILES P/HR... AS I START TO GO UP THE CAR NATUARLY SLOWS DOWN AND RPM GOES DOWN.. I GIVE IT SOME GRADUAL ACCELERATION AND "THERE IT IS"...

It would be most helpful to have a scanner on the car while driving and see if you are getting any knock retard. It could be detonation, piston slap, or trans problems causing the noise, and I think any of those could trigger the knock sensor and cause the pcm to retard the timing. But that should also leave a trouble code in the computer. I TAKE IT A SCANNER IS NOT A DIY SORT OF IDEA... DOES MY CAR HAVE A KNOCK SENSOR AND WHAT IS IT DESIGNED TO DO?

I really don't think cleaning the MAP sensor would be helpful, so don't worry about it for now. 10-4

The reason I asked if the engine used oil, is that oil burning in the combustion chambers will leave a lot of carbon behind and definitely cause knocking/pinging. NO- DEFIANTELY NOT USING OIL... ENGINE IS IN GREAT RUNNING CONDITION EXCEPT THE AFOREMENTIONED.


I hope others keep chiming in.

[spinne1]

I would do a compression test to gauge the general condition of the engine. That might give you further clues as to what the problem is.

[ChemMan]

Originally Posted by coogs

DOES MY CAR HAVE A KNOCK SENSOR AND WHAT IS IT DESIGNED TO DO?

Yes, it screws into the engine block and is designed to detect knocking/pinging and signal the computer so that the computer can retard the timing and stop it. UGH, sounds like mild knocking to me. It also seems that either the computer is not retarding the timing at all, or it is retarding the timing as far as it can and there is still some residual knocking. Does the car lose power when the knocking begins?

If you're game, fill your tank with the super premium stuff and see what happens.

[jackfoxx]

I have this same problem with my 94 Le Sabre and no one can figure it out. I just found a leak in the incoming fuel line which I had replaced and it doesnt seem to happen as much, I need to check the pressure at the rail though.

Mine started about a year ago and it only happens once the car is warmed up and the outside temperature is on the warm side. I first noticed that while accelerating, the car would stumble and the RPM's would top out around 2000-2500. I then noticed a clunk sometimes when you were cruising on the freeway and wanted to accelerate a bit. I started watching the tach quite a bit and I noticed that on the freeway cruising at 75 mph the rpm would drop to about 1200 rpm's. If I lifted off the gas, the rpm's would go back up to 2000 and then I could accelerate with a little stumble.

I have a new ECM and tried a new Ignition module (didnt help). I have often thought it could be the knock sensor. I did have some sucess by using 92 octane gas, it still had some hiccups but not nearly as much. If you get it figured out let me know.

Jack

[coogs]

Hi... been out of the loop here for several onths but confirming I still have the problem intermitently??? havent done anythingw iht he MAF as of yet.. Car would use 3/4 of a litre every 5000 KM.... so yes.. a bit if oil consumption there...

greg

[HotZ28]

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