new member from cali

whats up everyone i'm a new member but not new to this and previous forums like this one. thought id post my truck and some of the problems that are driving me crazy.

i have a 1991 MM single cab, 2.4L 4g64 in y59 San Marino Yellow. here's some pics from over the years.

Attachment 19060Attachment 19061
last year my camshaft sheared in half between cylinder 2 and 3 driving home on the freeway. Since then ive installed a new camshaft but the truck continues to misfire and run shitty. good compression, spark, timing (checked a million times) but i did notice a wet exhaust valve on cylinder one when i removed the manifold and when i disconnect the fuel injector plug for cyl #1 i dont hear the engine get worse. replaced the injector but problem persists?!?!? id like to check ground pulse from ecu or maybe this is a common problem among 2g fuel injected trucks?
Attachment 19062thanks for the help and thanks for having me!

Welcome to the forum, Mits187.

I'm not sure what to suggest- if compression is good, then a warped or bent valve doesn't seem to be the problem. I'm thinking surely SOMETHING got hurt when the cam shaft sheered, but your report indicates everything's fine.

So, I just wanted to put out the welcome mat for you. Someone who has brain cells will come along and make a sane suggestion, I'm sure :)

Thank you royster. Ive told myself the same thing, either something got hurt when the cam sheered or something caused the cam to sheer or a combination of both is causing me problems. I havent been able to do a leak down i need to fix my compressor (thanks to my k9's) and buy a kit. If i have to ill start a seperate thread and start over with my diagnostics in the appropriate area. Thanks for the warm welcome royster!

Hi and welcome to mightyram. Considering the damage done when the cam froze I would have a tendency to look at the valve train from where the cam broke (#3 and #4 cylinders) as they were not timed when the cam failed. Also for the cam to break like that takes a lot of stress. I would have a good look at the head (yeah, it'll have to be removed...) to see what damage was done to the cam journals from oil deprivation. This will also give you a chance to look at the tops of the pistons for damage. Where there any other issues as the cam failed (overheating, oil pressure drop etc)? It will give you a few clues to what went down.

Welcome to the forum :)

Thanks geezer101 I was really trying to avoid pulling the head (again!) but your right i need to pull it and check the head valves valve seats pistons etc. The cam snapped randomly doing about 70mph not gassing it, running cool, not sure about the oil pressure at the time however. Time for me to suck it up and buy some head bolts. Thanks for the advice geezer101.

Thanks! @ BradMph

If the running didn't change with the #1 injector disconnected, there may be ECM issues as well. Pull the ECM from the kick panel on the passenger's side and look for leaking capacitors. There may be other damage from the sheared cam, such as bent jet valves, that could be working against you causing poor performance.

A 4G64 wouldn't have jet valves. But I think Mits187 is in for taking off the head and scrutinizing things anyway. The ECU check might be the best place to start.

thanks for the replies! Before i do remove the head is there a special way to get into the computer (is it sealed, etc) to check capacitors or is it straight forward?

Phillips screws...

It should be behind the passenger kick plate...sort of a bitch to get to. Removing the glove box will be helpful...it pops out pretty easy (the glove box). Also, there is a place in Florida that rebuilds the ECU for around $150.00. The address is somewhere on the forum, do a search and you should find it.

Best of luck, Mits187!!