Cyls 3 and 4 not firing

[thanatos2k]

I have a 1991 Prelude SI with that pinche B21A1 motor, I know this forum is for accords but you guys have helped me out in the past with techie probs that I couldn't figure out and I can't find any prelude specific (or even general honda) tech forums (any links/ideas welcome!).

Anyway, cyls 3 and 4 are not firing, so it is running super rough. The honda shop manual said to test the injectors, which I did, they all have resistance within tolerance, they all have battery voltage in the 2P connector, and they all have connection to the ECU. I even swapped them with the 1 and 2 cyl injectors and the problem stayed with 3 and 4.

I also made sure the plugs were solid, and verified that they are getting spark.

At this point the shop manual says to replace ECU with known good and retest. Before I go get one on Ebay or at the junkyard I wanted to see if any of you had ideas on what else to check.

I should add that the check engine light is not on at this point. This is the wife's car and she is one of those people that will drive it as long as it physically moves in the forward direction regardless of status lights or strange sounds emenating from under the hood. ;-)



Thanks in advance for any ideas.

[AccordEpicenter]

compression check this beeeoootch

[shepherd79]

check the ignitor and check the compression in the pistons. you probably blew the headgasket between cylinders 3 and 4.