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Old 08-14-2003, 03:31 PM
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Join Date: Jun 2002
Location: Monrovia, CA
Posts: 490
86 300E - Knocks on Acceleration

My 300E with 120k miles pings noticeably on moderate to hard acceleration. Sounds like somebody's under the hood shaking a coffee can full of rocks! I've never put anything other than premium fuel in it (91 octane So. Cal. gas). I replaced the plugs, rotor, cap and complete ignition wire set recently, and when the plugs were out, they all had a nice medium tan color. None of them appeared to have any significant carbon buildup on them. I looked into a couple of the plug holes with a small penlight and there was just a normal light buildup of carbon on the piston crowns, so I'm at a loss. I do know that the valve guide seals were replaced about 30k mi. ago.

Is there any kind of knock sensor in this system that should adjust the timing when it pings?

Is there any manual timing adjustment that needs to be done?

As the cam chain wears, does the distributor timing advance or retard? As far as I know, the cam chain has never been replaced.

Can a worn out O2 sensor cause this? (btw, what triggers the o2 sensor light on the dash? Mine hasn't come on yet, but I'm just curious)

An old trick we used to use to remove carbon deposits involved introducing a fine mist of water into the intake tract. The sudden heating and expansion of the water into steam in the combustion chamber would blow off any excess carbon buildup. Could these carbon particle cause any problem with the catalytic converter?

Thanks for any help

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Old 08-15-2003, 12:20 PM
Registered User
Join Date: Apr 2001
Location: Hawaii
Posts: 147
Hi Gary:

I had the same symptoms you described with a 87 260E. I did all the different brands of octane booster, had my timing checked. I hope you don't have the same problem I did which is worn cam lobes. The last two lobes for cylinder six were badly worn.

The car made loud knocking noises only on like you said moderate to hard acceleration. When I would baby it, no knocking at all or it was really soft I couldn't hear it over the radio. It also felt like I didn't quite have full power and the engine was lagging just a little. After changing the cam, everything went back to normal and I haven't had a problem since.

I hope this helps.

1987 260E Charcoal Grey 157,000 Miles
1987 260E Forest Green 120,000 Miles
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