No CEL random misfire at idle
 

2001 d2 with 118k miles on it, well maintained. About a month ago I developed a random misfire at idle while at a stop light or when parked. No check engine light. I was due for plugs and wires so those were changed, as well as coil packs and top end gaskets to cure the leaky valve covers. I haven't noticed any difference in fuel economy. Under load the disco runs fine as it's intended to do. I don't have any mixing of fluids and I have not lost any coolant or oil. Completely leak free. I have not done a compression test yet. Around 200 miles ago I heard a rattle on the on ramp under good acceleration and was thinking it may be the cat? Tapping on either cat doesn't reveal any noises and I only head it one time. Engine doesn't tick or over heat whatsoever so I'm aggregated by this obviously. Any ideas please chime in.

no one has an idea?

No CEL really throws things off. Without a troublecode anything is just guessing, which can be expensive.

IACV, MAF, CmPS could all have issues, but would normally throw a code if there is a problem with them.

You could also try looking for any vacuum leaks?

no vacuum leaks, maf was replaced at 89k. Yesterday I did a seafoam induction treatment and fresh fill up with seafoam in the tank. 100 miles later and no luck yet. I appreciate the response. Hopefully going to be able to get some live data in the next few days to see what's going on. Last tank was roughly 30 miles under normal distance so there is now a drop in economy.

I know you replaced the coil packs but I would start there. Check all connections. I had issue similar to yours and did not get CEL. Replaced the packs and it was gone.

the issue was prior to me servicing the coil packs, plugs and wires, and top end gaskets. Tomorrow I have some time and I'm going compression check. I'll post results. Thanks for the help so far.

Make sure your idle air control cage is plugged in. If it is, clean it out really well. I used brake cleaner, but throttle body cleaner is probably more recommended.

You say you're not getting any CEL on dash, but did you check for codes? If you bought it used, the dash light may be disabled or covered.

Brian.