Traditional causes for dieseling are:
-Engine running to hot, cooling problems, wrong thermostat
-wrong stationary mixture leading to carbon build up in cilinder head
-low octane fuel
-hot spark plugs
-cilinder head not properly finished after a rebuild, leaving sharp
edges that can glow
-to high compression after shaving the cilinder head, thus needing
higher octane fuel
Kees Oudesluijs
NL
allen c miller jr wrote:
> I am helping a friend who just bought a 100 sort out a few issues with SEVERE
> dieseling and a sticking throttle. Her car is a BN1 converted to BN2 4-speed,
> and the prior owner mounted a 100-6 top-pedal box to accomodate a hydraulic
> clutch (presumably a BN4 bellhousing).
>
> the throttle linkage was sticking rather severely because the rear brass ball
> joint casing was hanging up on the original asbestos shielding (the pedal
> pivot is at the top, and obviously displaces the horizontal linkage a little
> downward). we've cut away enough of the shielding to eliminate this
> obstruction, and can set the idle down to 700-800. i had hoped this would kill
> off the dieseling, but does not. nor does lifting up on the pedal with your
> toes to assure the throttle is fully back.
>
> the dieseling is really bad. you have to engage in 4th and the car wants to
> drive forward, even when not engine temp is not very high. I have read past
> threads, and noted several 'usual suspects'...
>
> 1. idle speed (not a problem here)
> 2. choke cable adjustment
> 3. leaking throttle plate shafts
> 4. timing
> 5. too high compression
> 6. carbon buildup
>
> is there an order in which i should check these to rule out contributing
> factors? are there any other causes of dieseling you've encountered.
>
> the engine runs vigorously and has great throttle response. by history from
> the seller, there was an engine build in the 1970's by his P.O., but we don't
> know if the head was shaved more than appropriate. if it is a compression
> issue, would using a tank of CAM2 prove/disprove compression as contributing
> to the dieseling? if it is, can the problem be solved with having a steel shim
> made to the shape of a head gasket? are the Dennis Welch steel gaskets thicker
> so we could lower compression should that be the issue? there is no leakage
> out the side by the motor number plate, so I don't see a need for one
> otherwise.
>
> allen miller
> bn2/m
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