I have a 1991 EF Hatch with the 1.5l. I was driving down the highway one day and it was running fine. Then just out of nowhere it starred running really bad. Its like it has a misfire. It will still Start and run just really rough. I can pull the wire of the distributor for the #4 cylinder and it doesn't change the run quality, but pulling off any other wire it does changeI thought the timing jumped but from what I can tell on the timing marks it's about right, but I haven't ruled it out. My ecu is throwing a tps code but it just doesn't seem like that would cause as big of an issue as I'm having. I feel like the timing could have jumped. could it be out of time far enough to where the #4 cylinder is firing so far off that it seems like a dead cylinder? I'm at a loss. It's got new plugs and wires. I'm waiting on a new cap and rotor. I have a new timing belt. Should have a new tps today.

 

Pull the spark plugs - how does #4 look compared to the others? Do a compression test - how does #4 compare to the others?

 

all the plugs looked about the same. Haven't got to compression test it yet. But that's my next step.

 

I had a similar issue on a D15B2 in the past. All of a sudden one day it started running rough and when I checked I had zero compression on cylinder 4. Pulled the head and one of the exhaust valves was missing about half of the valve head. No damage to the piston or cylinder wall...I guess it broke off and just blew out the exhaust.

 

good lord I hope this isn't the problem.. will compression check thus weekend

 

Try change the spark plug wire on #4. I know yours are new but so were mine. I had a wire arcing out the side into the tube that caused a bad misfire. Same symptoms, easy fix.

 

its got new plugs and wires. i was busy this weekend so i didn't get to mess with it. thinking about an injector. i can unplug the top injector while its running and it doesn't change the run quality. idk, i will get it figured out. hopefully its not a valve. will update when i try some more.

 

By saying top injector, I'm guessing your engine is DPFI. One of the injectors (can't remember if it's top or bottom, but guessing it's top) is a secondary injector and doesn't turn on until the engine needs additional fuel, so unplugging it at idle wouldn't change the run quality.

 

Just because they're new doesn't mean they're good. Try swapping plugs and wires, ie the plug in 4 to 3, recheck, then the swap the #4 wire for the old one and recheck. If the parts store happened to drop the box of plugs you got then it's possible that there is a very minor crack in the porcelain that you can't see causing it to arc internally. After that compression test it.