1998 Lincoln Town Car Engine knock/clatter under light/mild

SCOTTCHEP

MEMBER
1998 LINCOLN TOWN CAR
V8
2WD
AUTOMATIC
72,500 MILES

It does so whether cold or warmed up. It doesn't do so while in neutral or park or idle in drive. It will make this noise on the highway too, but again, only under mild acceleration. Hills and climbs don't seem to influence the cause. They do, however, seem to make the sound louder. Give it more gas in any situation and the sound is gone. Give it none or almost no gas and the sound is gone. The engine runs smoothly all the time. It does not lose power or behave oddly while clattering. Higher octane gas does seem to help keep the noise to a minimum. Lower octane gas does not alter the range of power where the noise is made, but it does alter the volume/severity. Until the last few months I hadn't noticed any changes. Now it seems to be getting louder and I am concerned. I'll be glad to provide any additional information I can.

Saturday, January 10th, 2009 AT 11:57 PM

3 Replies

SERVICE WRITER

MECHANIC
9,123 POSTS

Would you describe it as marbles in a tin can kind of noise?

You should be using 91 octane in this car.

4.6 motor? What is the 8th digit of the VIN?

Sounds like you are having a "pinging" situation going on. It is also called pre-detonation. There are a variety of reasons for it to happen and can cause more problems.

The detonation in the cylinders are happening before the full compression is reached.

Have you ever had any carbon removal procedures done?

There may be no codes in the computer, but would be good to check.

Disconnect the MAF sensor and drive it. IF the symptoms are gone then, I would clean the MAF sensor with electrical cleaner. There is a TSB on this.

IF not then the next area I would check is the egr passageways. Remove the egr valve and check for a build up of carbon. Using a good intake cleaner, clean both the egr valve pintle and the passageways. If there is a heavy build up you may need to get in there with more than just intake cleaner. Small brush etc. You can buy a new gasket that has a screen on it, to prevent contamination of the valve in the future.

IF this is still a problem after this, I would suggest have the PCM calibrated to the latest software version as there is also a TSB on this as well.

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Sunday, January 11th, 2009 AT 7:00 AM

SCOTTCHEP

MEMBER
2 POSTS

I would describe it as marbles in a tin can. It's not really a metallic sound. More like something knocking around.

The 8th digit is a 'W'

The car was purchased in Jan 2006 with 34K miles (old car, never driven, it's also the std limo version, the kind you might catch a ride from the airport in, it's even marked 'Presidential'). It was running roughly and I took it in at 41K. My mechanic cleaned the MAF and replacing the EGR valve and it has been running fantastic, except for this knock. It wasn't until it was running smoothly that I recall even noticing the sound. The MAF was cleaned again at 60K along with the throttle body. But the knock was unresolved and the mechanic was out of ideas. I recently put a new battery in and since then the sound seems a little louder.

I'll ask my mechanic to calibrate the PCM but he may have already done so while trying to resolve this. If he did he didn't charge me or record it on my invoice.

I do use 91 octane and am going try adding an octane booster to see if anything changes.

I'll be taking the car in to the shop in about two weeks. Thank you so much for your advice, it is greatly appreciated.

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Sunday, January 11th, 2009 AT 2:00 PM

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