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

[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]

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

[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.

[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]

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.

[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.

[Quinthirty]

Here are the values of the injectors from what I gathered from "witchunter"

Stock: 0280150715
cc / min: 152.4 or lbs / hr: 14.5
PSI: 43
Bar: 3

M50: 0280150415
cc/ min: 178.5 or lbs / hr: 17 (likely at 3.5bar as w/ the M50 engine); or 166 cc/ min or 15.8 lbs (likely at 3bar)
PSI: 43
Bar: 3

Nonetheless, if there is more volume of gas coming in, but the ECU is programmed for stock injectors, isn't it likely that there is flooding even at 3bar? If it is flooding, then is it likely that the unburnt fuel is causing the misfire / backfire?

[mbonanni]

Thank you, I will check those.

I will have to run the car again and check back on the plugs if they are wet. M50 injectors are okay to use with the stock ecu if they are the 17lbs ones. The 19 lbs ones need a chip. There is definitely a smell while the car is running, but I also do not have the exhaust on after th cat, if that makes a difference.

[Quinthirty]

IIRC, this is what the Bentley manual says: Backfire caused by unburnt fuel, incomplete / no spark, stuck valve

1. Check coil
2. Check each spark of plug
3. Check connections of injectors
4. Check impedance of injectors
5. Reset ECU
6. Turn crank and see if a valve gets stuck

Misfiring
1. Check grounds: ECU, main C101
2. AFM flap
3. Distributor cap

I suppose it does not hold an idle either. Is there smoke? If you unplug the spark plugs, are they wet?

I also read that you're running on a 173? I don't think its recommended to run M50 #17 injectors on a stock ECU. You need a chip. I got one when I made the switch, or you'll run rich. I did this swap last week, and had this exact trouble. I ended up replacing the coil because the guy who did the job was too excited and didn't remove the negative terminal before replacing the injectors. Car was perfectly fine before the swap.

[mbonanni]

Okay guys, so the car starts with little to no effort, BUT I have a problem.

Cylinder 2 and 3 are misfiring at idle. The car shakes and runs rough. I have not taking it on a drive yet because I want eveyrhting fixed beforehand.

What are some things I should check?

I have
-New Cap
-New Rotor
-Refurbished m50 injectors (#17)
-New spark plugs

What should I check?

Thank you

[mbonanni]

Okay so the nous light blinked when we were using it earlier.

I just hooked up a seperate set of injectors and rail that I have, to see if it sprays, and I get nothing....

[mbonanni]

Just checked the fuel pressure. It was 45 while cranking, then when I let off it dropped down to 30. Took about 30 seconds. I checked the line that goes into the rail.

Man I am stumped.

[mbonanni]

Bump.

I am stumped. I will be renting a gauge and checking fuel pressure in the rail tomorrow. Any tips on how too.

Other ideas?

[mbonanni]

Okay,

I got a noid light. I hooked it up, and each injector wire made the light blink. I am going to recheck spark.

What is my next step? It has to be a fuel related problem in the rail/injectors.

[mbonanni]

You need to have pin 36 and pin 2 bridged at the same time you bridge 16 and ground together, when 16 touches ground you should hear a click of the injectors (1, 3, 5). That is how I understand it.

I bridged pin 36 and 2 with a fuse. When I touch the pin 36 and 2 I hear the white five pin relay click. I then connected pin 16 and touched it to 2, but the slightest touch creates a spark, and I do not hear a click (I am sitting inside the cabin with the door open)

This is what happens