1998 Ford Crown Victoria Police Interceptor rattle with sli

LARRYKING

MEMBER
1998 FORD CROWN VICTORIA
V8
2WD
AUTOMATIC
162,000 MILES

When I accelerate slightly, I here a noise that sounds like valves rattling. The check engine light is not on and it only happens when the engine is at normal operating temperature. When I accelerate hard, the noise goes away or is significantly reduced. I have replaced the spark plugs and replaced the timing chain and gears. There was no change.

I have noticed that when the outside temperature is cool, it does not happen as much. I have been told it could in the EGR system or something to do with ignition timing. From what I understand, the ignition timing is controlled by the ECM and cannot be adjusted. Is this correct? Can someone give me some guidance on what I can try next?

6 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

Hi
Check EGR function need a vacuum pump or find a hose on intake with vacuum at idle. Engine idling apply vacuum to EGR it will stall or RPMS drop 100 or more when vacuum is released engine will idle normally.
Let me know
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Thursday, September 2nd, 2010 AT 2:55 PM

LARRYKING

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4 POSTS

I took a vacuum hose that had a vacuum at idle and attached it to the EGR. I would say the RPMS dropped about 100 RPM and the engine started idling rough. I was able to hear the EGR operate when the vacuum was attached. When the vacuum was removed from the EGR, the engine idled normally.

Does this mean that the EGR is operating normally? Is this noise I am hearing detonation knock caused by ignition timing? What do you think I should try next?

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Thursday, September 2nd, 2010 AT 5:34 PM

DOCFIXIT

MECHANIC
18,828 POSTS

EGR is operating I do suspect a detonation problem try some SEAFOAM maybe carbon on valves and top of piston detonation fuel before plug fires. Fact that is does it at OP. Temp

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Friday, September 3rd, 2010 AT 11:11 AM

LARRYKING

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4 POSTS

I will try this and post back.

Thanks

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Tuesday, September 7th, 2010 AT 3:11 PM

LARRYKING

MEMBER
4 POSTS

I tried the Seafoam as per manufacturer's instructions. The noise is still there. One thing I noticed was when I started the engine after it set for 5 to 10 minutes, the noise I am hearing was constant until the smoke started to clear.