weird misfire

[scott@8pm]

1990 crx dx w/ D15B6 (HF) MPFI

After I did the swap it would intermittently miss at idle. Not real bad. Injector pulse never dropped out, spark never dropped either.

I had to clean out my EGR ports, and at that time I also put on some spare injectors and rail.

Now the miss at idle is the same, or maybe slightly worse -but it also will miss sometimes on accel and cruise. Just sometimes, but badly.

No CEL and no codes. I had an EGR code but I fixed that.

If I rev it from idle w/ no load it usually revs smooth, but if I hold it around 1500-2000 RPM Cyl #1 and Cyl#2 drop out completely.

While these two cylinders are dropped out, they both still have good spark and good injector pulse. I found them by pulling the ign cables off.

So I ran it for a minute w/o the 1-2 cables on.
I pulled the plugs and they were not wet.
I swapped #1 and #4 injector. Misfire did not follow the injector.
Misfire also did not follow the spark plug I swapped.

So I have this weird 1-2 miss. Compression is great. Spark is strong. Injector pulse is there. Both ign and valve timing were rechecked. Firing order has been triple checked. And it doesn't always miss except where described above.

It's like those two aren't getting any fuel at times, but the injector pulse is fine.

I was hoping maybe someone here has seen this. I haven't checked fuel pressure yet. I was wondering if incorrect pressure could cause just these two cyls on the end of the rail to miss.

Unplugging the regulator has no effect. Pinching the return line just makes it run worse. New filter and pump before the swap.

I also checked for vacuum leaks with a smoke machine.

I still need to check valve lash.

Maybe that rail I put on had some debris? The 2 plugs should have been wet by my reckoning. But why intermittent while driving/idling?

 

[t3t4delsol]

check your coil, and check the solder spots on yout fuel pump relay, problem sounds like a electrical issue

 

[scott@8pm]

OK. Coil checks good. Spark is still strong and consistent. Coil is new as is distributer. Relay is new too- had to replace that when I bought the car.

EGR code came back. Thought I fixed it, but it seems to be the main culprit. While the EGR is activated, #1 and #2 miss.

If I disconnect the EGR the miss goes away

..or rather back to the slight intermittent miss at idle like it was before I cleaned the ports. I'm thinking that I must not have got #3-4 ports cleaned out well, so all the recirculated exhaust hits 1 and 2, smothering them and making them miss. Gotta have EGR to hit my high fuel economy on this pig. (still wondering about the dry plugs though. Maybe all that hot exhaust dried the cylinders?)

I'll have to thoroughly clean the original manifold and stick it back on to (hopefully) fix the major miss before I proceed with finding the minor miss. Thanks. I'll try to post back. It might be a while though.