Slight Miss on 2 cylinders

[Ybnorml]

My car has been missing a little. I changed plugs and wires. It still misses, but not a dead miss. I bought a spark tester to make sure the coil was getting spark to the plugs. On the first two narrow settings it fired equally across all 4 cylinders. When I went to the third step it looked like #2 and #4 were losing spark compared to the others.

So I'm thinking this is a no-brainer. I went to the junkyard and bought a coil to see if the problem went away. Sadly enough it didn't. I know it was a junkyard part but the new one is $191 from Oreilly and I don't see that happening right now.

Is there a chance I just picked up another coil or is there somewhere else I can look for answers? I sprayed all the plugs and contacts, but still have no idea where to go with the troubleshooting next.

Any help would be appreciated.

 

[Ybnorml]

I can't imagine people not knowing what to reply with. Surely there are a few people on here who are knowledgible enough to be able to point me in the right direction or offer some constructive input!

Could the ECU be making this happen? If it's missing on the plug wire would it be ignition only or could it be something else?

 

[Old Mitsu Tech]

Well, first of all. I'm not even sure what year and engine of a vehicle you have as there is no profile on your car.

Secondly, you could be correct in your diagnostic, or you could have something else contributing to your "problem" I would check and listen to all the injectors.

Do a compression test just to humor me if for no other reason. I need to see and know that part is ok.

I"m going to call O'Reilly's in the morning to confirm this price. I do business with them every day. It seems very high to me. Not to say you are incorrect, but for my own curiosity. You could have a weak igniter, but usually they just die and a no fire situation exists. Check wiring and connections. Exchange coils and see if the problem follows. If the same 2 cylinders are misfiring, you can at least rule out the coils. What I mean is rotate them in the housing and retest.

Give us some more to go on.

Good Luck

 

[Ybnorml]

Oookay, sorry. I thought I had my profile updated.

91 GS-T 140,000 on the short block and about 100 after I had the head rebuilt and put on. I replaced everything on the front of the engine, vatted the intake, cleaned the inside of the exhaust manifold, installed ARP head studs, used a OEM replacement head gasket and made sure everything was right, to the best of my ability.

There are no mods on the car, only the cat converter off. I had to do the head and have valves, seats, and seals replaced because the belt slipped and I bent 8 valves.

It cranked and ran fine to not be tuned or anything. There is no boost controller, so I'm still about 7 pounds with my B&M boost gauge. I was doing logging and it was fine. I let out and noticed the miss. I turned off the #4 injector and this made almost no difference. I checked plugs and they were good, gapped at .032. I changed the wires. So I'm thinking the injector needs to be replaced. I did that to no avail. That's when I started to test firing from each wire. As the gap widened, the spark decreased on 2 cylinders, 2 and 4.

So, I replaced the coil and that made no difference. The car runs good to be missing like that, but could be better if it weren't. I didn't know there was an ignitor either.

I have a compression gauge and thought about checking that. I guess anything is possible, but I don't know why that would make the spark weak on 2 cylinders from the coil.

Also, before the belt slipped, there was no CEL. When I put it back together it started okay but after about 1 minute I had a CEL. I checked it and it was throwing 3 codes, something like a 28, 31, and 32 I believe. All 3 were related to the CAS and another sensor. I still haven't figured that one out yet. The guy who put the front back together has done that several times, so I don't know if there's anything that could have been done wrong. The belt is on right, I know that much.

Any help would be appreciated.

Thanks,
Greg

 

[Old Mitsu Tech]

Swap the coils and see what you get. I'm curious to see if it follows. These things are rather difficult to diagnose if you don't have proper equipment. If the other coil is known good as it fires good, I would like to see what happens when it is on the weak fire cylinders. If the problem follows the coil, you know the answer. If it doesn't at least that part is eliminated. Then we can look elsewhere.

Good Luck

 

[Ybnorml]

I may try a third coil. If it isn't that I'm not too sure what it'll be. I didn't even know they had an ignitor. But someone said the auto places can check a coil, I just don't know how they would on this car even if it were off if they can't get power through it.

What are you thinking it is if the second coil is doing the same thing?

 

[Mike Marnik]

If you are going to the junkyard again get transistor pack. its the big plug looking thing. its located to the right of the ignition coil they cause some ignition problems sometimes. it fixed the problem of my coil cutting out sometimes. i still have a miss every so often though that i havent nailed down so i will be interested to find out what solves your problem.
oh and old mitsu tech new ignition coils are that expensive. i believe advanced auto was a bit cheaper though i was to say 181 maybe 151 i cant quite remember.

 

[Ybnorml]

I will have to wait to go back out there next weekend. But yeah I guess something had to plug into the coil. I'll give that a shot, run a compression check and see what else I can come up with.

Thanks!

 

[Mike Marnik]

oh ya i also forgot you mentiond somethign about a cel for the cam angle sensor. the cam angle sensor is what sends the signal out as for when the cylinders need to fire. it may be off or not working properly i would look into that also good luck.

 

[Ybnorml]

Thanks for the replies, guys. I've got a few things to do this weekend, but will definitely update this post once I get a few things changed out to see if anything helps.