Cylinder #4 not firing

[Avyar]

A few weeks ago I bought a 1990 240sx with a sr20det blacktop from a s13. I was told it was swapped beginning of 2014 and it was done pretty ghetto. The sr is completly stock. Most the time I solve any of the problems my car has by searching the forums but this time I cant.

The car was running fine besides a bad wastegate actuator so it overboosts to 18psi but other then that it ran fine. Now the problem I'm having is cylinder #4 is not firing I have changed the spark plugs and switched around the coil packs and it's getting spark. I also switched around injectors to see if it was bad but also checked out fine. The compression is a little low at 130psi in that cylinder other were a little higher around 150 psi. I need some help if anyone has any ideas.

[that1guywithans13]

Is it constant or is it something that comes and disappears then reappears?

[Avyar]

It's constant for about a week now

[cbeuglas]

I had a coil pack harness go bad. It did the same thing.

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[Avyar]

Harness seems to be working any other ideas?

It's also something that happened all of a sudden was driving then just changed to crappie sound and idle.

[cbeuglas]

Possibly igniter. I used my timing light on my #4 to verify signal pulse. That is how I found out it was the harness. Maby bad cas.

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[Avyar]

Pulled codes from ecu told me nothing not even misfire. Think I might buy a new harness instead of this cut up one and see if that solves anything

[Avyar]

Update now cylinder 2 and 4 both not firing so either wiring, cas or need to rebuild engine.

[Shiftkickslide]

Test out a new igniter and ecu if you can get your hands on a loaner. I had the same problem with mine and it was the ecu and I checked literally everything from ecu to plug

[Avyar]

Yea I thought of that so I bought a new isis/isr ignitor was going to buy cas too but figured to do one step at a time but I didn't think about ecu probably try to find one

[Shiftkickslide]

So when you got it, it ran fine or did 4 not fire from the beginning?

[Dboyizmlg]

Low compression cylinder might be piston rings.
If you are getting 150psi on three cylinders, and the fourth is 130psi then more than likely will be piston ring.
Time for rebuild.
Good luck

[Avyar]

When I first got it, it ran on all 4 cylinders ran a little rich and I could only half throttle it most of the time cause of bad wastegate actuator so any more the 10psi it would start bogging the one day while driving it backfired and the idle turned rough

[Dboyizmlg]

When I first got it, it ran on all 4 cylinders ran a little rich and I could only half throttle it most of the time cause of bad wastegate actuator so any more the 10psi it would start bogging the one day while driving it backfired and the idle turned rough

Bad rings in #4 cylinder.
You are going to have to tear her down, and fix issue.

sorry man

[Avyar]

Bad rings in #4 cylinder.
You are going to have to tear her down, and fix issue.

sorry man

Cylinder 2 also is having the same problem though and it hast 150 compression before it went out. Haven't tested its compression yet due to breaking my compression tester. If it checks out fine im going to assume the problem is some where else.
Also when the car was running fine when I would run the car pretty hard for any longer then 5-10 min it would start bogging at low rpms and die at stops or have under 500 rpm at idle until the car had a 30min cool off. Oil and car Temps would stayou fine

[nismo240sxdrifter]

Not to thread jack but this is the problem I am having.

So I just bought a car for the sr swap that was in it. It was running ruff when I looked at it so I got the car for a great deal. That's the history of me with the car.

So I've figured why the car is running so rough. #4 is not getting any spark. -Compression is healthy across all 4 cylinders (around 143-148 for all four).
-All injectors are firing, I swapped them around to be sure.
-I have swapped coil packs around to see if that is the issue, it is not.
-I checked power to all four coil packs with a test light and they all light up. --When I take #4 coil out and put an old spark plug in it to ground and test for spark I get nothing. All three of the others spark fine.
-I have checked all connectors and they're secure.
-I also checked the ECU pins and everything seems good.

FYI the car has a #62 Blitz ecu.

What are some other ideas you guys have?
Thanks.
Michael

[Shiftkickslide]

Open the ecu case and look for burns on the databoard

[Avyar]

Okay I have narrowed my problem down to the injectors not firing using the long flathead against injector to ear method. So what controls the injectors ecu and cas anything else?

[brndck]

ok. back to basics
130 compression is not enough that i would tear down an engine

have you swapped injectors to other cylinders to see if the misfire follows the injector?

if cyls 2 and 4 are misfiring, swap injectors from 1-2, and 3-4. then see if 2 and 4 are still missing or if 1 and 3 are now missing.

get a noid light kit. learn how to use it. theyre EXTREMELY simple and easy to use, and will tell you if your wiring, ecu, etc are working properly, and they're on sale at walmart right now.

http://www.walmart.com/ip/47906405?wmlspartner=wlpa&adid=22222222227035249203&wl0=&wl1=g&wl2=c&wl3=75768324874&wl4=&wl5=pla&wl6=176019827314&veh=sem

report back later.

[Avyar]

I have swapped around the injectors the problem does not follow the injectors.

[Dboyizmlg]

I have swapped around the injectors the problem does not follow the injectors.

You should take into consideration what I told you.

[cotbu]

Wow!

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[Avyar]

You should take into consideration what I told you.

If it needs rebuild im probably gonna sell the motor but that is my last resort. This morning I checked compression on cylinder 2 and it was 148psi so I'm pretty sure there is a problem lies somewhere else

[cotbu]

Why do people believe a compression test can tell you if an engine is healthy? Forum folklore! 1 a wet cylinder should yield higher compression results, regardless of the fluid. 2 timing being correct, spark, compression, air are present the cylinder should fire.
If one of those is missing or timing is off the cylinder will not fire or not fire correctly.
Contaminates usually cause a misfire, too much will cause a cylinder not to fire.
If the cylinder or plugs are wet try drying them, then pull the fuel pump fuse, once the engine fires install the fuse. Let it idle check verify the timing. Shut it down, pull the plugs examine.

Some of that info can be use for another thread I was reading too. A no start thread. It just kinda got merged into a supertech thought!

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[Avyar]

Okay so I did the noid light test and all injectors are getting pulse. Then i noticed injector 1 was leaking so I pulled it and the o ring was cut up from not being seated correctly. I did not notice that before I don't know if I did it when I switched around injectors (the injector in cylinder 1 was originally in the problem cylinder 4) or if it was originally cut up when I first took it out.

[Avyar]

http://i1318.photobucket.com/albums/t648/Aj_Gann/Mobile%20Uploads/20151207_140140_zpsvd3fy8lk.jpg (http://s1318.photobucket.com/user/Aj_Gann/media/Mobile%20Uploads/20151207_140140_zpsvd3fy8lk.jpg.html)

So I found the problem

[Shiftkickslide]

That's no Bueno

[Avyar]

Are rocker arms easy to replace my self and do I have to replace all of them or can I just replace one?

[Dboyizmlg]

Are rocker arms easy to replace my self and do I have to replace all of them or can I just replace one?

By the looks of the head, looks like oil wasn't changed every 3k miles.
Yes, you can replace one rocker arm only, but if I where you I would inspect it and verify what caused it to happen i.e. shims.

Also it's not difficult task to do, you just have to have some good understanding of how valve train works, and how to properly tq cam caps.

GL

[cotbu]

Lol that's no air and timing for sure! Did you mention any noise during cranking, idk but that's an easy fix. Hope you're at tdc now?
And are the guides and shims still around?

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[Avyar]

Guides ands shims are still in place rocker arm was clean break didn't look like it caused any other problems

[Avyar]

All problems solved. Cylinder #4 problem was due to broken rocker on exhaust side. Cylinder #2 not firing due to loose igniter connection. Very coincidental but all is good and runing now