#3 and 4 cylinders not firing

[specialtywoodsjames]

I have a friend who's car I've been working on for a week or two. It is a 1993 legacy wagon, 5spd 2.2.

First, he called me from the gas station and said his car wouldn't run and he was stuck in the parking lot. I had him tow the car to my house and determined that the fuel pump was kaput. I replaced it and life was good, briefly. A week or so later he called to tell me the car had no power and, well, he had a lot of panicky and not pertinent things to say and I'd rather not divulge the sort of abuse he may have heaped on his poor car in order to get it home. Anyway, I went over to his place and tested the fuel pressure again and I noted that it was a pretty constant 40 PSI and in the manual it says it should be regulated to 26. I replaced the fuel pressure regulator today though I didn't have the fuel pressure gauge with me so I don't know if the fuel pressure is now at 26 PSI. Anyway, the car smokes blue on startup and still runs like it's running on only two cylinders because...wait for it... it's only running on two cylinders. When I pull the plug wires from #3 or #4, nothing changes. The old coil tested OK for the secondaries, but was a bit high for both of the primaries. Thinking that I have encountered coils in the past that test fine but aren't, I put a new coil on to no avail. I am thinking of getting another ignitor from the pull-a-part tomorrow and swapping that in. Also, I need to pull codes, but the CEL is not on, which kind of makes me suspect that it has been disabled.

 

It seems like this can't be a unique problem, but after at least an hour spent searching the interwebs in general and this site in particular, I have not come up with any more ideas.

 

Any thoughts? 

[Gloyale]

Test the signal wires at the coil for pulse.

 

Yellow is constant power, the other 2 are the signal.

 

If no pulse check wiring continuity back to the igniter.  If good, replace igniter.  If no change suspect ECU or wiring back to the ECU.

 

Check for CEL with Key on/Eng off.  Sould prove on before startup.

[specialtywoodsjames]

Can you give me more details about checking for pulse? I had assumed that the primary coils would be energized with the key in the run position, but they are not. I checked for voltage in the same pairs as I used for testing the resistance, but I am no longer at the car and I can't recall which terminal is yellow. I assume that should be term 2 from your description, unless I am completely confused.

[Gloyale]

Middle wire in the connector is yellow wire/ ig. switched 12v.

 

When a test light is bridged across this yellow wire and eitehr of the other 2 wires at the coil  (red or blue) teh light should Pulse quickly......or at least glow dimmer/flickering.  If not pulse isn't happening to cause the spark to jump from the primary to the secondary windings and on out to the plugs.

 

Might be simpler to swap transistors just to check.  that would eb my next real guess barring damage to the wiring.

[DavidPeab]

The KISS test: Swap the plugs - does the misfire change places? Swap the wires - does the misfire change places? It could be bad plugs or wires or a combination of both. I did not see where you tried popping some new NGK plugs or wires in before you replaced the coil. I start with two criteria before I replace parts - is it likely that part (testing helps) and is it the cheaper of two parts that it might be.

 

Too bad you're not getting a P030? DTC. Of course that would help track it down.

[Fairtax4me]

No p0 codes on a 93, its Obd1. And no misfire codes. Just sensor codes and some various trans codes.

 

Pulling spark plugs doesn't rule out fuel injectors, or compression as the cause of a misfire.

[Gloyale]

Just to clarify

 

cylinders=

 

3  4

1  2

 

 

If it's 3 and 4, it's unlikely to be compresion, or timing.......as they are on seperate banks.  1,2 and 3,4 fire togther at the coil though, so if the problem is a pair of front or back cylinders.....it's ussually spark/coil related.

 

If in fact this misfire in question is 2 and 4,  or 1 and 3  i.e.  both on one side not firing, then I would almost garauntee it's a T-belt skipped a tooth or other cam problem.

[specialtywoodsjames]

Thanks, Gloyale, I do have the cyl numbers right and it is the reason I immediately suspected the coil and then the ignitor. Unfortunately, the manual I have is for the wrong year and was copied and compiled badly. It's missing pertinent sections and I've had to go a little by the seat of my pants. I did ponder a lot of unlikely scenarios that involved the #3 and 4 going out independently but simultaneously, but I thought I would pursue the likely first. It also occurred to me that one of those cyls has been out for while and my friend didn't notice, but it hasn't been that long since I drove the car myself so I'm not sure I rate that scenario very much higher than unlikely.

 

DavidPeab, I considered the plug/wire fault possibility as well, but the wires are new and I have rarely encountered a plug that does not fire at all and I have encountered some pretty trashed plugs. Two such plugs in such a suspicious configuration I also ruled out as unlikely. Still, inspecting plugs and testing wires is on the list of fall back options...

Also, what is a P030?DTC? Is that some kind of government assistance program for Subaru owners? ;-)

 

I think I will test continuity of the connections between the coil and ignitor, as suggested and then swap in a different ignitor. Then if I have failed, I will move and change my phone number.

[Cougar]

As Gloyale  stated, the CEL light should turn on with the ignition switch along with the warning lights. You might try replacing the plugs on the bad side since it is a pretty easy thing to do. One of them might be bad. It isn't a common issue but it does happen at times.