please help missfire on my highly tuned pinto

[drifter69]

Hi guys I have a 2l pinto that's now 2.1+ and I have developed a missfire iv changed the coil/plugs/leads has brand new dizzy and electronic ignition any other ideas please share

[Pumaracing]

Compression test!

[Doctor Volt]

Bad fuel?

[anonymous-user]

If only my Crystal Ball wasn't still broken!


(it broke a couple of weeks back, after i overloaded it by asking it to remotely diagnose an intermittent minor wiring fault with a 1992 Toyota Corolla owned by a guy in Huddersfield, but that isn't important right now).........

[andyiley]

Is the missfire constant/intermittent/when under load/when idling/when accellerating et. etc. etc.

The more information the better chance our crystal balls will have.

[drifter69]

Hahaha I know it's the old can u find a problem over the Internet but I'm just after any common things or tricks to sort this it does it under load and Its quite intermittent but starts off up high in the revs then when warm all over the revs

[andyiley]

Is it regular like it is all firings on 1 cylinder affected, or random every few minutes etc.

Also define highly tuned?

Edited by andyiley on Tuesday 10th February 20:24

[drifter69]

When power it put down it pulls but as it's building up the revs it it sort of feels like it misses a spark and then catches again and so on
I have had head skimmed
Big valves
Ported
Valve spring seats dropped
Bronze guides
Fr33 kent km
Kent alloy pulley
Bronze spray bar

Block dropped 96.4 bore
2.9 forge pistons
Forge rods
New crank
Basically the whole inside of the engine was brand new built by lowman race engines

[stevieturbo]

And the ignition system consists of ?

[Doctor Volt]

It doesnt matter what you put inside your block and cylinder head for diagnosing this problem, unless you have a problem with a bad build
The fact of the matter is - The engine was working well and it developed a fault

If you are convinced that the fuel system is ok, why not hook the thing up to a diagnostic machine and get the spark plug voltages looked at

There is a chance that the vehicle is suffering from a volt drop on the ignition supply to the engine circuits. Perhaps it is best that you check voltages before going any further

[andyiley]

Another similar possibility I have come across 2 x before is the coil insulation breaking down when warm.

Try a spare/second hand/cheap coil, pretty much any coil will do for a test, just change the terminals to yours if they differ.

[Kinkell]

I ditched an Omex rev limiter due to a misfire. Bosch distributors are prone to problems with modern internals.