Misfire under WOT

[Kyle97-clipse]

Ok So I dont know what happened but anymore if I give my car WOT it will miss in the upper rpms at like arond 5k on up. Everytime else the car will run nice and smooth, you can drive it fine its just when you get on the gas in the upper rpms it will miss with the CEL flashing. Funny thing is it used to show code 43 which is the misfire code but I keydanced it today and code 43 isn't there anymore even though its still misfiring. Any help would be appreciated, thanks

 

[inferno617]

I had this same issue last year and it wound up being one of the spark plug wires. The motor had a miss after i rebuilt and i though i screwed up the cylinder. I tore the head back off and drove myself completely nuts. Check your compression in all of you cylinders and make sure they are the same. I suggest you also check your plugs, wires and power pack.

 

[Kyle97-clipse]

Update

I puled all the wires off today (msd 8.5 super conductor) they all looked fine. I tested the coil and got 13,600 on 1 and 4, and 13,900 ohms across 2 and 3. Still misfiring, I really need some help on this guys

 

[My1GLaser]

Did you ohm the wires? What are your plugs gapped to? How much boost are you running?

Run a set of NGK wires if the MSD test out bad. (I don't know the ohms you should get)

I run 28 psi and I have my 7es plugs gapped to .025 on stock coils with NGK wires.

 

[Kyle97-clipse]

Did you ohm the wires?

No, how do you do that?

What are your plugs gapped to?

.050

How much boost are you running?

None its a nonturbo

 

[Bluefire16]

I thought the gap should be around .045? Idk thats just what i thought i might be wrong. But i was misfirng (although im boosted) and i forgot to gap my last set and i was at a .033 and boy did it help when i gapped them correctly to a .028 Well i went a little smaller tho like .026/7 ### im running higher boost...

 

[Kyle97-clipse]

Yeah pretty sure gap has nothing to do with my problem though because it never used to miss till last week, and those plugs have been in there for 3,000 miles with the same gap. I rechecked the gap and it was still the same, so i dont know

 

[Fotowntalon]

he;s gonna want a bigger gap than that on a N/T. Also resistance of wires will change due to the kind you have. I was thinking the higher quality of wire the less resistance, but could be wrong. You might want to check your fuel pressure, the higher the rpms the more fuel you are demanding, so if you are misfirng more up there it could very well be a fuel problem, more than likly not enough, indicating a bad fuel filter or pump and possibly fuel line leakage.

 

[Kyle97-clipse]

Yes Fotowntalon is right they will have much less resistance then stock, I have no clue how to test them or what they should be though

 

[Jeff99GS]

Yes Fotowntalon is right they will have much less resistance then stock, I have no clue how to test them or what they should be though

My old Accel wires had about 200 ohms for the short wires and 400 for the longer ones.

If your check engine light was FLASHING then you have a MAJOR misfire. PULL OVER... the coil pack is BAD 100%

Go get that MSD one for the 420a's. its like 70 or 80 bucks. Make sure you check the plug tho cause they came with 2 different types. The flat pins or Round pins in the plug I believe.

 

[Kyle97-clipse]

I already have the MSD one. But I heard that there known to go bad, owell I guess I'm going to have to buy another one. Are you sure that it was the coil pack because of the flashing, I don't want to waste money

 

[cabbageman97]

If the ignition can be ruled out, start with the fuel filter

 

[Jeff99GS]

The only time my old 420a check engine light flashed in the 9 years I owned it was when that coil pack went bad.

Unless you have a grounded out wire or something I dont see any other reason for that major misfire. Those MSD's do go bad often I heard, but mine lasted me a long time!

 

[Kyle97-clipse]

Yeah this one has probably been on there for about 2 and a half years. I didnt own the car that long, but I know the previous owner I'm pretty sure thats when he installed it.

 

[My1GLaser]

I have no clue how to test them or what they should be though

Use a multimeter set to ohms. Put on lead on one end of the wire and one lead on the other end and read the resistance. The longer wires will have more resistance, but you will be looking for anything way out of whack. Like if number 4 (the longest) ohmed out at 400 and number 1 (the shortest) ohmed out at 1000. (random numbers used)

You can check your plugs and see if one of them is slightly darker than the rest or looks fouled out. That would be your problem cylinder, and pay special attention to that wire when testing.

You can reduce the gap to help a weak ignition even if the gap itself isn't the problem. I have a friend with a high mileage 96 civic and his ignition module went out. I replaced it and he got a misfire. I regapped his plugs, which were about .010 to high and it went away. It never misfired before replacing the module, which uncovered or caused a problem.

 

[LD25Delta9]

woah... It sounds like it could be alot of problems, if it's only happening at WOT at high RPM it could be any number of sensors. OP: if you have proper readings from your coil and wires, check the resistance going at your fuel pump. I'd also check your MAP sensor. The cutting out at 5K under WOT is a symptom of fuel pump failure due to not getting enough current at high RPM. I'd have a freind check the pressure at the rail while in neutral at WOT, same with fuel pump resistence.

 

[Fotowntalon]

hey thats what i said!! Also misfire is not 100% of the time a coilpack, i am still getting a blinking misfire and i put in a brand new coil and didnt do anything.

 

[Kyle97-clipse]

Ok thanks everyone for the input so far. I'm going to test some things tommorow like map sensor, fuel pressure, and also going to hook up a vacuum gauge and read that.

Also if this helps it seems like anymore when I start it up it revs to high and then falls back down to idle. It will go over 2k when I first start it up, and it never use to do this, so this problem is also related I think.

 

[Jeff99GS]

I didn't see that you said it was only at WOT above 5000 rpm. it could be a bad injector.

Do an ohms test across the coils of each injector. They should all read the SAME resistance If one read different then its BAD.

 

[Kyle97-clipse]

Ok will try reading ohms on the injectors then also. I used a mechanics stethescope and listened to each injector already and they are all ticking fine. However so you think at the higher rpms the injector could stop working?

 

[RoninEclipse2G]

However so you think at the higher rpms the injector could stop working?

Yes. You're more likely to see injector issues at higher RPMS

 

[Fotowntalon]

maybe wont stop working completly, but not working as effectivly supplying as much fuel as you would need as quickly as you would need. Reall depends a lot on what is wrong with the injector, if it is even the injector at all.

 

[Kyle97-clipse]

UPDATE

Did a vacuum test today to check for leaks, there is none which is good. Vaccum gauge held at a steady 17 in HG. Also reset the ecu and cleared some codes, still missing though, next step is going to change injectors, when I get time

 

[Fotowntalon]

check your fuel pressure before you change injectors, to save you some work.

 

[Jeff99GS]

See what I find strange is that The Engine light was flashing. I have had an Injector go bad while driving my old 420a The ENGINE light came ON but did NOT flash... I have also had the ignition coil go bad while driving my old 420a as well. The engine light DID flash when the coil went bad.

I would double and triple check that ignition coil before you go spend $300 dollars on injectors.

Also check the things everyone else is saying too, before buying injectors.