Backfire, 1990 3.0 MTX

[Bruce M]

1990; 3.0; 100k on drive train; all 60K stuff done 5K back. Body near mint.

Recently on start up thge engine will backfire until it warms up. The backfire is very erratic – no discernable frequency. If you shut the engine down and start it right back up the backfiring goes away. These are not loud backfires just a shallow thud type. I’m thinking cam position sensor as I recall pulling codes a while back on this unit and there was a failure to ID a cylinder.

Just fishing for input, I will do a complete exam tomorrow when I get my computer back. Could a cam position sensor do this? This problem never accrues after warm up. There are no vacuum leaks in this system.

 

[SHO-NUF93]

I would guess more along the lines of a bad plug wire or incorrectly gapped, or fouled plug.

 

[Bruce M]

Thanks, never thought about (wires and plug) that given that the wire and plugs have about 5K on them, could easily put in a bad wire or mis gapped plug