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Re: missing under load Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Wed, 13 Dec 2000 14:43:55
In Reply to: missing under load, Chris R 85 900T, Wed, 13 Dec 2000 14:30:51 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Check your spark plug gap. That's a common cause of missing under load, especially at higher RPM.
In neutral, even if you rev the crap out of the engine, there is very little boost, and the pressure in the cylinders is relatively low. Under load, you get higher cylinder compression. The denser charge in the cylinder makes it harder for the spark plug to make a spark. If the gap is too large, you won't get a spark, and the engine will miss. This then pumps the unburned (gas rich) charge into the exhaust, where it will find something hot and burn (backfire).
First thing, check your plugs. Make sure they are the right kind, and that they are gapped to the specification on the decal in the engine compartment. DO NOT (1) go by the gap on the box, and (2) assume they are gapped properly out of the box. As plugs age, the gap usually increases.
There are other possiblities, but the plugs, by far are the both the most common and the easiest and cheapest to fix. What you are seeing is NOT a sign of a bad turbo, which is usually oil burning in the exhaust (bad seals) and sometimes a squeal as it spins up (bad bearings).
If the plugs work out OK, it could be the coil. A weak coil will give a weak spark, which would give the same symptoms as an over-gapped plug. Of course, make sure the timing is set correctly, and that the vacuum retard is working. I don't see the hall effect sensor affected by load, but timing and vacuum retard is.
Good luck!
, Wed, 13 Dec 2000 14:43:55 <-- Viewing This Message
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