1991 Ej22 with a spark issue. The front 2 cyl's get spark, the back two do not. Any ideas on why are appreciated. We have checked the teeth on the cam pulley and crank gear and they seem fine.

depending on the orientation of the coil pack, one cylinder could be affecting the other. i dunno if its left right or front back.

 

obviously the basics, check plugs, wires for resistance. worst case swap out a coil if you have a spare.

Hi Shawn,

 

I think the rear cylinders are #'s 3 and 4 unless they are different from other models. There have been other theads with this same kind of problem and it appears that the ECU is at fault. You may want to try opening it up and inspect it for a bad connection problem. Here is one thread that refered to the same type of problem:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=42239&page=1&pp=10

I have a spare ECU and coil pack, if you would like to borrow them for troubleshooting lemme know.

I keep seeing alot of PO30X codes popping up lately. My personal experience = bad plugs or wires. I'd pull one of the plugs that is NOT sparking, and one that IS. When I got the PO301,302 codes, I pulled the Bosch Plat +4's and 3 were white while one was fouled. However, I noticed that the inner connector at the plug end had become disconnected and could be pulled to the end of the boot. Either way, I put in NGK's and replaced the Napa wires with the OEM. No codes in 3k+ miles. The other prob with this, (which I found out yesterday) is that the end result is, or can be, a ruined front o2 sensor. To lean = Too hot = ruined sensor. Will be white like a lean plug. Since yesterday, I've driven about 40 miles, and the needle on the gas gauge has barely moved. I still plan on replacing the rear 4-wire in the near future, but $$$.

 

The problem is this (In theory):

 

With the limited, or non-existent, spark to the plug from the wire, the ECU compensates. For one reason or another in my case, it dumped ALOT more fuel into one cylinder than the others. Therefor, 3 lean and 1 fouled.

 

There are just certain maintenance items that need to be done/replaced after so long in order to keep the vehicle running properly. When I bought my car, I looked at big ticket items when bartering. Tires, leaks, body... Wish I had looked closer and added Plugs, Wires, Fuel filter, o2 sensors, CRANK PULLEY!!! Oh well, live and learn. I'll know for my next subie purchase:grin:.

 

You are about 20 Miles from me, so we are experiencing the same climate. Don't know if that makes a difference or not, but interesting nonetheless. Should look at altitudes of others who experience the PO30X codes.

 

At any rate, I'd recommend that you throw a meter on the wires and measure resistance. According to Subaru, anything measuring above 4,000 Ohms per foot, or 20,000 Ohms per wire, needs to be replaced. Hope this helps. Let me know what you find.

Coug is right 1 & 3 are the right side and 2 & 4 are the left side, so the front two would be 1 & 2 and the rears would be 3 & 4. It could be a back coil pack, if you replace that and you still have the problem, pull the belt covers and see if something is wrong with the sensor pick ups on the crank and left cam pulley. If that is the case, you have to replace those parts. I'm betting on a bad coil pack.

Thanks for the verification about the cylinder numbers Dr. RX. I agree, swapping the coils would be the first thing to try and checking the sensors is next if that doesn't help. Problems with the ECU aren't common but there have been some trouble reports with them according to some posters here that cause this problem.

We have tried 4 different coil packs and a different ECU and ignitor.

What about the CAS and CPS sensors? I assume you have also checked the wiring to the coil pack from the ECU.

We have tried 4 different coil packs and a different ECU and ignitor.

Well it sounds like it's time to dig into the engine. There must be something wrong with the way the engine is picking up the singles from the two sensor (crank and cam angle). On the crank, there is an odd shaped gear looking piece that looks like some of the teeth are missing, this is the trigger for the crank sensor. One of the triggers may have broken off somehow. Anyway this would be the first one I would check. The cam angle sensor triggers are part of the left cam pulley, I don't know of a single time when one of these were damaged. If you have access to a 91 Legacy FSM, check out section 2-7 page 10 and 11.

 

This is kind of out there, but before you get digging into the engine, see if changing out the sensors (crank and cam angle) does anything. You are getting spark in the front cylinders, so they seem to be working, but they are part of the system, and shouldn't be over looked.

So there is no spark at all on the back two cylinders?

 

Does the car start? Does it idle high? Have you driven it, does the engine ever "click" in?

 

I've been chasing a problem that has shown up a bad wire, a bad plug, a cracked knock sensor and a bad air control valve or a bad purge solenoid.

 

Going to switch out the purge solenoid and go from there.

 

The difference is I get spark but no combustion.

 

Almost seems like you have to think outside of the box. Is the car getting a good charge from the alternator? Or a bad wire between the igniter and the coil pack? Sorry keep trying.

 

Good luck anyways.

Maybe some kinda fuel starvation? Could the fuel pressure be low?