M20 - "2.7i" Bad Misfire - 2002

[kid325e]

Hey guys,

I finally got my 76 2002 running. It's got a 2.7i M20 that I had built and running in my previous E30. Long story short, I built the engine, had it in my E30 - Aquired the 2002 and swapped over the drivetrain to the 2002.

The M20 sounds like it's running on one cylinder. Literally sounds like a harley that i'm trying to kick over in my garage. It will stay chugging along for a bit and I can keep it firing if I give it throttle. I pulled the plugs and they were not covered in fuel or anything. I replaced them with brand new Bosch Plugs and torqued them to spec.

The fuel system is using a brand new M42 fuel pump to a M20 fuel filter to the M20 fuel rail. Most guys that are running an M20 in their 2002's are using the M42 fuel pump. I'm also running M50 fuel injectors. This whole set up ran amazing in the E30. The engine has less then 500 miles on it since being built and has been sitting for about 2 years until a week or so ago when I was able to crank it in the 2002.

I don't expect anyone to have all the answers, was just curious if anyone has ever heard or seen an M20 sound like it's running on one cylinder. Usually when they miss they at least have 2-3 cylinders going. I'm mentally and physically exhausted, just looking for opinions.

[Tonybeemer]

Check fuel pressure don't guess, make sure you don't have the feed and return line mixed up.. im running a 255 fuel pump in my m20 02 ..

[dpmit94]

Did you end up figuring this out? I’ve been reading the little bits you post over in the PNW chat thread. Hope you’ve got it! Don’t know why I didn’t consider an M20 back when I had my ‘02

[ahlem]

AFM unplugged? What's the spark tester telling you at the coil and at each plug? I'd also guess you cracked your distributor cap on the way in or a CPS type issue.

[kid325e]

Check fuel pressure don't guess, make sure you don't have the feed and return line mixed up.. im running a 255 fuel pump in my m20 02 ..

Fuel Feed and Return are definitely not mixed up. I havn't gotten to check fuel pressure yet, I have the tools to do it, just dealing with verifying spark first..

After some testing I found that only my #2 spark plug was firing. I checked my injector wiring with a noid light set and all six should be firing off as expected.

Did you end up figuring this out? I’ve been reading the little bits you post over in the PNW chat thread. Hope you’ve got it! Don’t know why I didn’t consider an M20 back when I had my ‘02

I havn't got it quite figured out yet. Although I did find that my Crank Position Sensor is out of spec as far as resistance goes. It's supposed to show 540ish and it's showing me 900. I checked the good one in my iX and it's showing 540 so that's kind of a red flag for me. I ordered a new one and it's sitting on my desk until I get home and check it out.

Just super odd to me that cylinder 2 is the only one firing. The bay smells of raw fuel, I'll have more info tonight..

AFM unplugged? What's the spark tester telling you at the coil and at each plug? I'd also guess you cracked your distributor cap on the way in or a CPS type issue.

I've tried with the AFM plugged in and unplugged, nothing seems different. Distributor looks unscathed, i'm getting spark at #2 which tells me my coil is still good. Hoping I throw this new CPS in and it runs just like it used to in the old E30. Just to clarify the car is firing off on cylinder 2, it's combusting like it's supposed to, just nothing on the other cylinders. Engine is fitted with Motronic 1.3 and M50 Injectors - this same combo was running beautifully before. Just wanted to state that it's got those injectors..

Bentley states that a bad CPS could cause a car to not start at all or if it does run with a continous misfure..

Thanks for the inpute guys, I will keep you posted.

[ahlem]

Maybe get some fine sandpaper and clean the oxidation off the rotor and cap contactors.
Don't forget the center point on the rotor and cap. Had the same problem on my M30 and this was the fix, the last time was the CPS.

[kid325e]

Thanks for the input buddy, I will let you guys know what I find tonight. Hopefully the reply has a video of it running in it. haha.

[kid325e]

Just an update - New CPS is installed - car is behaving exactly the same. I'm starting to think the injectors aren't firing like they're supposed to. Not touching the car 'till this weekend. Exhausted with this thing.

[kid325e]

Update

Fuel Pressure is verified at 44psi - bypassed the fuel relay.
Fuel Injectors getting signal and power tested good with a noid light set.
I'm getting spark, I pulled the plugs and also cleaned up the distributor and rotor.

Here's my cliffhanger for the night. I pulled the M50 injectors cause i'm planning on swapping them out. Most of the injectors did not have the pintle caps on upon removal. Literally only injector 2 and 4 still had the pintle caps on. I went to go pull them out of the intake manifold, and they arent' there! They were on when I installed them!

Where could they have gone? Could this be the issue i'm having? I have a spare set of M20 injectors i'm planning on throwing in. Looks like the intake has to come off... ugh.

[kid325e]

Update

Fuel Pressure is verified at 44psi - bypassed the fuel relay.
Fuel Injectors getting signal and power tested good with a noid light set.
I'm getting spark, I pulled the plugs and also cleaned up the distributor and rotor.

Here's my cliffhanger for the night. I pulled the M50 injectors cause i'm planning on swapping them out. Most of the injectors did not have the pintle caps on upon removal. Literally only injector 2 and 4 still had the pintle caps on. I went to go pull them out of the intake manifold, and they arent' there! They were on when I installed them!

Where could they have gone? Could this be the issue i'm having? I have a spare set of M20 injectors i'm planning on throwing in. Looks like the intake has to come off... ugh.

[Hooffenstein HD]

Where could they have gone?

They're only plastic, I wouldn't worry too much. They could have been missing for a long time and be melted into your cat by now. Try using a bore scope to see if they're still around.

[kid325e]

You think it's worth taking the intake off to take a quick look or just swap in some good M20 injectors with the mani on and go?

I wasn't that worried but more or less like, where the hell are they going to end up? I'm baffled, never heard or seen anything like this.

[Hooffenstein HD]

When I swapped my M50 injectors to Mustang 19lb, one pintle cap was gone. I used a bore scope and it was down by the valve. I couldn't get it out and didn't want to remove intake manifold because the car was my daily at the time and I didn't have any gaskets. Just cranked the car over and watched it get sucked in the bore and quickly disappear. Haven't noticed any problems since.

I did post up on the R3V FB and numerous people said they have had the same thing happen and never noticed any issues.

It is possible it could score a valve seat or do some minor damage on its way through though.

[deutschman]

Throw those other injectors in and see what happens.
I wonder if a few of the injectors were stuck closed. I had that happen on my m20 after the injectors sat for a while with out running.

Only other issue I can think of at this point is an electrical one. Some wiring issue or a sensor issue. Bad crank sensor? Or the DME is stuck in limp mode?

[kid325e]

When I swapped my M50 injectors to Mustang 19lb, one pintle cap was gone. I used a bore scope and it was down by the valve. I couldn't get it out and didn't want to remove intake manifold because the car was my daily at the time and I didn't have any gaskets. Just cranked the car over and watched it get sucked in the bore and quickly disappear. Haven't noticed any problems since.

I did post up on the R3V FB and numerous people said they have had the same thing happen and never noticed any issues.

It is possible it could score a valve seat or do some minor damage on its way through though.

Interesting, going to wrap my head around my options.. Prolly won't touch the car till Wednesday/Thursday. Curious if this is something common with injectors, like I said, i've never heard or seen this. I work at an indy euro repair shop.

Throw those other injectors in and see what happens.
I wonder if a few of the injectors were stuck closed. I had that happen on my m20 after the injectors sat for a while with out running.

Only other issue I can think of at this point is an electrical one. Some wiring issue or a sensor issue. Bad crank sensor? Or the DME is stuck in limp mode?

I'm pretty sure the DME is good, I can swap them back and forth between my daily iX and the 02 and I only have misfire issues on the 2002. CPS is new, and I replaced it before I pulled the engine, but still... installed a new one.

What kind of symptoms did you witness when yours were stuck closed? It's missing HARD, and to be honest i'd expect the injectors/plugs to smell more raw fuel ish. The engine was rebuilt and only ran for about 250 miles before the E30 was parked, engine pulled, and installed in my 2002. That period of time was maybe a year or two? Either way, i'm thinking the injectors are a big part of my problem.

Thanks for talking to me guys, My mind is going nuts thinking about the potentials in my head. :loco: