knocking problem under acceleration

99 Lesabre.. 150K knocking problem under load - upon acceleration but not necessarliy from a stop? and its only intermitent. I run the bronze unleaded fule and havent tried a higher octane.. plugs are pretty new and she runs well. Any sugegstions?

Make sure your egr system is operating, number one cause of pinging on accel in these cars.

thanks .. now... I'm pretty mechanically inclined and know what an EGR system is but i'm a liitle sheepish on the best way for me is to go about testing/cleaning or otherwise replacing a component as reg maintenance. I dont belive this system has ever been addressed or looked at.

Only other piece of info is... sounds like when it she does the old 'pingaroo' it's coming from under the hood psgnr side... Again- this issues is intermitentaly as in... slowing down to about double idele speed and then accelerating from there- that's where the problem is..

thnks

Tough to say what exactly you are hearing, a tech should reasly listen to this or you could go off on a tangent. If the egr passages are carboned up/blocked and /or the egr is inop this usually sets a cel code. The noise could be some rattle from the exhaust or such also, someone on site should listen to this for you.

i'm asuming this is a 3.8 or 3800? i'd check harmonic balancer as these are bad on them..

good luck.....

well the pinging /knocking is definately an engine as opposed to something loose. I had it itn the shop and no error codes. Could I still have a bad EGR with no Error codes?
thanks

well the pinging /knocking is definately an engine as opposed to something loose. I had it itn the shop and no error codes. Could I still have a bad EGR with no Error codes?
thanks

Absolutely. If one of the egr tubes is partially/completely clogged and the egr valve is still functioning properly, you will not get a code. How is the computer supposed to know a pipe is clogged? Pull the valve off and check the tubing and valve for excess carbon build up. Clean the valve and tubing with carb cleaner, and then reinstall the valve with a new gasket. A can of carb cleaner and a new gasket shouldn't cost more than $15 and the whole job should take 1/2 an hour. Not a hard job.:icon16:

ok thanks - will do.... I have another problem if you're interested... major violent front end shaking clunking - like the engine is coming apart upon left hand turn from a stop upon hard acceleratioon- usally happens when the light is changing from a amber to red on a left hand tunr in an intersection. It'll do every time. wont do it on a right hand or stariaght out of the gate.If I take it easy - no issue The dealer said it is likely the tranny and was thinking it muight be due to the oil pick up when the fluid shifts.. Persoanlly I think thats BS as the tanny shift beaut and is 130K. Its like something is brioke in there- alos I'd say something sounds loose when I dive over a man hole cover with the left tires... Only other thing I;d mention is the car took a very hard hit on the right side a couple years ago which resulted in the lower and upper arm being replaced... suggestions?

Absolutely. If one of the egr tubes is partially/completely clogged and the egr valve is still functioning properly, you will not get a code. How is the computer supposed to know a pipe is clogged? Pull the valve off and check the tubing and valve for excess carbon build up. Clean the valve and tubing with carb cleaner, and then reinstall the valve with a new gasket. A can of carb cleaner and a new gasket shouldn't cost more than $15 and the whole job should take 1/2 an hour. Not a hard job.:icon16:
Actually the pcm does know if the egr is not able to function, as the exhaust enters the combustion chamber o2 readings change and a code can be set, plus the map drops slightly for the same throttle and load.

ok thanks - will do.... I have another problem if you're interested... major violent front end shaking clunking - like the engine is coming apart upon left hand turn from a stop upon hard acceleratioon- usally happens when the light is changing from a amber to red on a left hand tunr in an intersection. It'll do every time. wont do it on a right hand or stariaght out of the gate.If I take it easy - no issue The dealer said it is likely the tranny and was thinking it muight be due to the oil pick up when the fluid shifts.. Persoanlly I think thats BS as the tanny shift beaut and is 130K. Its like something is brioke in there- alos I'd say something sounds loose when I dive over a man hole cover with the left tires... Only other thing I;d mention is the car took a very hard hit on the right side a couple years ago which resulted in the lower and upper arm being replaced... suggestions?

It sounds like your CV joint on the left side. Have that diagnosed at a garage. If it was simply fluid shifting, why wouldn't all LeSabres do this? Wouldn't the fluid shift the same in all cars?

Another possibility is one or more of your motor/transmission mounts are bad. Look at them and look for signs of failure (rubber coming apart, etc).

I asked about the VC and the shop forman said the boot was intact and no obvious signs fo any problems there... I thougt bad CVs click aorund tghe conrners.. this my man is a likfe there's a guy under the hood with a sledge wailing away when I accelerate.... bang bang bang bang

So if he drives it he says this is a fluid change issue, find another shop. All the recommndations here are on target, you must now follow up on them however you see fit.

good advise and I agree... Tires are due to be rotated and I deal witha good shop for front end rubber so will ask them to have a look..

can I go back top the other issue.. I took off the Linear EGR... looked ok but blewe er out with carb cleaner and did the same on the tubes.. didnt see anything obvious - in fact all looked really normal.. some carbon but I;d expect that.. re-installed with a new gasket and .... same pining at 50-60 and then acceleration... I belive it only does it in second gear actually...It sounds just like the timing is out but I understand this is all governed by the overhad cranfshaft and MAF.... not the sort of thing you get out the timing light for and I guess I'd have a hard time finding the distributer.:banghead:

so... can you point me to something else... my gut tells me if I ran the expense gas... or the MORE expense gas that would fix it...

what about the MAF - is there something there a pretty handy guy can clean or have a look at...

thanks my man- Im appreciate it

Greg from Langley BC Canada...

MAF is easy to clean. Remove the 4 screws holding it in the throttle body and inspect the little wires that make up the sensor for dirt, contamination, etc. I've used a little spray of carb cleaner to remove gunk from the wires. Then just reinstall. :runaround:

Just out of curiosity, does the car use oil?

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

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

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.:uhoh:

:popcorn:

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.:uhoh:

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.

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?:banghead:

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

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

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

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