'87 325 w/ '89 m20b25 motor MISFIRE AT IDLE, rough

[mbonanni]

I cannot answer that, but I am pretty sure multiple people use the m50 injectors as a stock upgrade.

Also, the car holds and idle just finex it is just rough because it is running on four cylinders. Hopefully today I will get the chance to see if those two cylinders are getting spark and fuel, and check if they have compression. If all checks out I will readjustment the valves.

Then post back with my finidngs.

If anyone has any other tips please chime in.

[mbonanni]

Well, I ended up only having enough battery life for a compression test, and I hardly had enough. It came up something like
1-115 2-125 3-130 4-130 5-130 6-130

I didn't have full battery when doing the last few, but I still was able to get four full cranks with throttle wide open.

I am kind of bummed with the result... But my main problem (misfire) is still abroad, because cylinder 2 and 3 are fine.

Can a needed valve adjustment effect cylinders misfiring and low compression numbers?

EDIT: just read the motor should be warm... The motor was cold, had not been started in a few days.

[Ginsterman98]

1 is no good and thats why it might be missing at idle. try it again with a good battery and then repet with a shot of oil in each piston. If the numbers go up a bunch the rings are the source of lost compression. If they don't change much you might have a burnt/ bent valve. A leak down test will tell you for sure if the misfire is related to the mechanics of the engine.

Try swapping in known good set of wires and swap the plugs because they might be fouled by now.

[mbonanni]

I will give it a try with a good battery and get some oil handy next time. I am reeaaalllyyy hoping it is not the rings.

I am confused as to why 1 would be the misfire? While I was running the car it was rough, when I removed spark plug wire one it got rougher, but when I did 2 and 3 it stayed the same, which is why I was saying it is cylinder 2 and 3. Is there any way that cylinder 1 can cause 2 and 3 to misfire?

I think the plugs are fouled now also, I was stupid and bought the "upgraded" plugs from blunt, and turns out they actually foul more often is what I read.

Thank you for your help.

[mbonanni]

I wanted to know exactly what oil does when you squirt it in the cylinders? Does it create a seal, which prettymuch gives better compression?

Is it possible that because I have ran my motor less than a minute combined since the swap that the oil hasn't really moved around and what not? Or am I just making stuff up?

Is it okay to let the car sit in the driveway and run to warm up to do a compression test even though I have a misfire??

EDIT: Also, can having the valve cover off affect anything? I was going to adjust the valves, but opted for a compression test first, and the valve cover was off.

Thank you

[Ginsterman98]

I wanted to know exactly what oil does when you squirt it in the cylinders? Does it create a seal, which prettymuch gives better compression?

Is it possible that because I have ran my motor less than a minute combined since the swap that the oil hasn't really moved around and what not? Or am I just making stuff up?

Is it okay to let the car sit in the driveway and run to warm up to do a compression test even though I have a misfire??

EDIT: Also, can having the valve cover off affect anything? I was going to adjust the valves, but opted for a compression test first, and the valve cover was off.

Thank you

Valve cover being off wont effect any thing. I would let it run for a few minutes and give it a few good hard revs and see if its just a sticky valve. After that, redo the test. How long has the motor sat before the swap? Having it run with the misfire wont hurt anything, just don't drive it around like that or you could wash the rings out with fuel. A shot of oil will seal bad rings, helps diagnosis if they are the culprit.

I missed the part about cyl 2 & 3, low CR on 1 wont cause a misfire anywhere else except 1. And now that you have said it has not run much don't worry to much until its gone through a heat cycle.

Side not is make sure you take all the plugs out and leave them out until your done. It is possible to have a compression leak between cylinders and this can be masked if you just pull one plug at a time. Are you sure those injectors are good?

[mbonanni]

Okay, I think I will put it all all back and let it run how you said. The motor sat like a month in the car i pulled it from, then about 5 months during the swap process/refresh.

All the plugs were out and throttle was open when test taken, but engine was dead cold.

I bought the injectors from a member on here. They are rebuilt and flow tested, so unless he lied to me and sent me bad injectors, but I don't think this is the case. If you are referring to the fact if i can use m50 injectors, then I also believe I can. I read multiple thread saying m50 injectors are good for stock.

Thank you

[mbonanni]

Was not able to do anything to the car today, but I did talk to my dad. He does not want to run the car with the misfire, so I guess I will have to double check spark and fuel with working wires and plugs.

I do have a new question. A friend brought this up today.

Do I have to prime the oil etc?

Thanks

[Ginsterman98]

Let it idle and it will prime its self. Or disconnect the round connector under the intake manifold, pull the coil lead and remove the plugs. Then crank it for like a minute, that will prime the oil system.

[mbonanni]

Okay, it idled for about 20 seconds, is that enough?

[Ginsterman98]

Honestly I would just run it for a few minutes without your dad around and see if it clears up.

[mbonanni]

Yeah, I think I am going to have to. He is so busy as is work hardly gets done.

I will do it this weekend cause he will be gone.

Friday we are supposed to be checking for spark and fuel to those cylinders..

[Ginsterman98]

Well good luck and keep us in the loop on what you find.

[mbonanni]

Just ran car up to about the half way point on temp gauge. It still has the misfire.

I pull all the plugs and eveyrone is a brownish black except cylinder 1 and 2. They are still new looking, no signs of fuel stain or wetness, but then again none of the plugs seemed wet.

I am about to do the compression test.

[mbonanni]

So compression numbers

1-135 2-140 3-140 4-140 5-140 6-140

I then checked for spark, and cylinder 2 and 3 both have spark.

So what is next, fuel? The injectors are rebuilt m50 ones, maybe there is no signal going to cyl 2 and 3 so they arent firing? I think I will have to go rent a noid light set again and double check.

Any other suggestion on how to check fuel?