PDA

View Full Version : Misfiring when load increases - Randomness



jickel240
01-27-2006, 12:17 PM
My SR just randomly decided to start misfiring under increased load. I was driving on the highway, I got on it a couple of times (pulled great), and then after a steady 10 minute cruise, I noticed my car misfiring under boost and increased load.

1st gear, it misses horribly (it's got the WRX sound to it), but I noticed that in gears 2-5, it doesn't miss as badly until I get closer to positive boost. So basically, the car runs on all 4 cylinders cruising on the highway, but as soon as I add a little more throttle and boost, it starts missing.

The car idles fine though, and doesn't miss..it didn't so much when I used the other AEM, but that ECU had a slightly different tune.

The weird thing is, if I let the car sit for a few hours, the car will run great, and it'll let me boost it through the gears once. After that, it starts missing again.

So far I've swapped coil packs with another SR, swapped ignitor chips, and even swapped my AEM with another to diagnose the problem. I have not checked my plugs yet. I figure if one was bad, it'd be bad under boost all of the time, and it wouldn't give me that one pull after letting the car sit for a while. But I could be wrong.

I've tried seaching through past threads, but my symptoms are kind of unique, and I'm not sure why all of the sudden the motor would start doing this. Anybody else have similar issues?


I have an AEM ECU amd stock coil packs.

Water
01-27-2006, 12:28 PM
What kind of plugs are you using?

jickel240
01-27-2006, 12:43 PM
What kind of plugs are you using?



NGK 3330s gapped at .026 when I put them in last month. :-/

killjoy
01-27-2006, 12:59 PM
You will need an ignition amplifeier of sorts. I had this exact same thing happen only under boost and after I went to the msd it was fine. You can use the XS or B&M amplifier which are the cheapest or the C2DI if you are a aem fan. Bet money that will fix it though. I changed everything out and as soon as I swapped in more spark it was perfect.

RyanZ06
01-27-2006, 01:20 PM
Um no kelly. Installing an ignition amp will only band-aid the problem. A fix is out there. If he needed an ignition amplifier, it would have been aparent about a year ago when he put the motor together.

RyanZ06
01-27-2006, 01:20 PM
and change the plugs you lazy son of a *****. http://forums.freshalloy.com/images/graemlins/rolleyes1.gif

Water
01-27-2006, 01:25 PM
I dunno, myself and others have had problems with copper plugs. An ignition amplifier would be a good idea too.

RyanZ06
01-27-2006, 01:29 PM
Why?? Why is that? Explain to me how a car can "all of the sudden" need an ignition amp? That is not the problem!

That's like saying you need more boost pressure for your motor, to make up for the lack of power because your rings are shot in 2 of your cyl.

RyanZ06
01-27-2006, 01:29 PM
Why?? Why is that? Explain to me how a car can "all of the sudden" need an ignition amp? That is not the problem!

That's like saying you need more boost pressure for your motor, to make up for the lack of power because your rings are shot in 2 of your cyl.

jickel240
01-27-2006, 01:36 PM
Nice double post you bastard. I'm going to change the plugs, you know this, I'm looking for ideas on what else it could be in the meantime.

Come by and pick up your Pistons and Rods

jickel240
01-27-2006, 01:38 PM
You will need an ignition amplifeier of sorts. I had this exact same thing happen only under boost and after I went to the msd it was fine. You can use the XS or B&M amplifier which are the cheapest or the C2DI if you are a aem fan. Bet money that will fix it though. I changed everything out and as soon as I swapped in more spark it was perfect.



Yeah, it's possible..but I want to fix the problem instead of compensating for it http://forums.freshalloy.com/images/graemlins/wink.gif

_Def_
01-27-2006, 01:53 PM
My car was misfiring at higher boost(17 psi on a GT28R). It was entirely random, and my AFR was around 11.8-12.0:1 so it wasn't too rich for pump gas(93 octane).

I had some NGK BKR7E's that had about 4-5k miles on them and they looked fine, changed them out for some new BKR7E's and the misfire went away entirely.


I think iridium plugs are a really good idea when approaching higher cylinder pressures, as it should take less voltage to get a spark given the same conditions with the smaller electrodes.

killjoy
01-27-2006, 03:39 PM
Why?? Why is that? Explain to me how a car can "all of the sudden" need an ignition amp? That is not the problem!

That's like saying you need more boost pressure for your motor, to make up for the lack of power because your rings are shot in 2 of your cyl.



I wish I knew. My car was fine and all of the sudden one day it started missing. So i dicked around and tried everything else and then finally added an aftermarket ignition and it fixed it like that. I have always run bkr7eix-11 plugs since forever. i don't see why it is to hard to understand. Coils get weaker and even replacing them does nothing. I don't see why its so hard to figure out. You are using an ignition meant for 8 psi and a small turbo. When you updgrade turbos you need more fuel so you get bigger injectors. So it can't be the same with spark?

Ryan has had an sr for about 8 months though so i am sure he is right. Personally I think he likes to contradict everything I say no matter how right or wrong.

If I told him he was straight, he would probably tell me he's gay.

Band-aid, schmand-aid.

Everybody else making 450+ has an upgraded ignition. Must just be coincidence....

a2low240
01-27-2006, 09:19 PM
Sounds like an injector is sticking open. What size are your injectors?

jickel240
01-27-2006, 09:57 PM
Sounds like an injector is sticking open. What size are your injectors?




They're Blitz/Sard/FD 850cc injectors...but wouldn't they (or it) be stuck open all of the time if it was sticking?

a2low240
01-28-2006, 02:02 AM
If your running over 85% - 90% duty cycle on them the side feed injectors have a problem getting stuck open for a second flooding out the engine. At 850cc you should'nt be having a problem with injectors running too high duty cycle unless there is a high bump in your fuel map.

klattr1
01-28-2006, 03:35 AM
Jickel, pressure test your system.

also, do u have any major exhaust leaks near the turbo/manifold? blown turbo-to-manifold gasket, etc?

RyanZ06
01-29-2006, 11:11 AM
Jickel, pressure test your system.

also, do u have any major exhaust leaks near the turbo/manifold? blown turbo-to-manifold gasket, etc?



The car runs on MAP, so a boost leak is not the problem.

The car does have an exhaust leak on the manifold, but that still doesnt explain anything.

RyanZ06
01-29-2006, 11:11 AM
Jickel, pressure test your system.

also, do u have any major exhaust leaks near the turbo/manifold? blown turbo-to-manifold gasket, etc?



The car runs on MAP, so a boost leak is not the problem.

The car does have an exhaust leak on the manifold, but that still doesnt explain anything.

klattr1
01-29-2006, 03:42 PM
The car runs on MAP, so a boost leak is not the problem.

The car does have an exhaust leak on the manifold, but that still doesnt explain anything.


i forgot he had a standalone.

but yea a major exhaust leak between turbo and manifold can cause issues like that. not sayin thats his problem, but its something to check. ive experienced that for myself (when the metal fire ring T3 gasket between turbo and manifold blew out).

Jickel, what are your afrs/timing like when you start to misfire or just right before into that transition? did you try gappin your plugs any lower? did you get new ones as well?

and RyanZ06, are you like his defense attorney or something? hehe

RyanZ06
01-29-2006, 06:15 PM
I'm his dad.

killjoy
01-29-2006, 07:00 PM
BWwwwahhahhhhahahahhahahaaa

jickel240
01-30-2006, 09:29 AM
Yes, thanks RyanZ06/Dad http://forums.freshalloy.com/images/graemlins/blush.gif

I pulled the plugs last night, and found that the gaps have actually closed up some (to around .021ish). Cylinders 1 and 3 look fine (a little on the lean side, but I'm not sure if it's lead deposits from some c16 race gas I had in the car not too long ago), cylinder 2 looks very dark like I've been running overly rich, which is proabably the cylinder missing, and cylinder 4 is an "in between" of the others.

I'll take pictures of them asap.

jickel240
01-30-2006, 03:19 PM
Here are pictures of the plugs clylinders 1-4 (starting from the left). Is it possible that cylinders 2 and 4 are combusting properly, and that 1 and 3 are not?

http://i1.tinypic.com/mv6whw.jpg

killjoy
01-30-2006, 03:20 PM
Don't look as bad as I had pictured...

jickel240
02-04-2006, 10:16 AM
Well I finally got to drive the car today after my spark plug and fuel filter change out...the car still is missing under load only after I get on it once. I'm at a loss here. Any other recommendations? http://forums.freshalloy.com/images/graemlins/mad.gif

Colorado_S14
02-04-2006, 11:33 AM
It almost looks like cyl 1&3 are running a bit leaner than the others.

jickel240
02-08-2006, 06:52 PM
yeah, I've since swapped Map sensors, fuel fiters, and I've checked everything in the AEM, and all the sensors, injectors, etc. are seemingly fine.

I'm still having the problem! My A/Fs are fine as well. Dubbya Tee Eff

ItzGenX
02-08-2006, 07:29 PM
I'm with killjoy on this one. My first SR had the same problem until I added the splitfire coils into the mix, and it went away. Before getting the splitfires though, I noticed a lot of odd things of when the missing happens. It is just like yours, can run it as long as the engine is cold or cooled off a little (not such a good idea), but when it is warmed up to operating temp, it does it again. Another thing I have found is it happens more often in cold weather (with stock ecu), because of course, more dense air will lead to more fuel, leading to higher cylinder pressures (harder to jump a spark). I tested the theory by advancing the ignition to 18 degrees. Firing the spark earlier when the cylinder is under less pressure let the spark jump the gap easier. When I advanced the timing, it let me take it up to a higher boost pressure before it began to miss again. If you do not want to get an amp or more coils, try regrounding everything involved in the ignition system. Use larger guage wire where you can. Ground the head with a large strap, and try different grounding locations. I say to try playing with the grounds because my cousin's car missed terribly and random until I regrounded everything. The SR20DET ignition system has notorious small grounds to begin with.

jickel240
02-09-2006, 04:07 PM
I'm with killjoy on this one. My first SR had the same problem until I added the splitfire coils into the mix, and it went away. Before getting the splitfires though, I noticed a lot of odd things of when the missing happens. It is just like yours, can run it as long as the engine is cold or cooled off a little (not such a good idea), but when it is warmed up to operating temp, it does it again. Another thing I have found is it happens more often in cold weather (with stock ecu), because of course, more dense air will lead to more fuel, leading to higher cylinder pressures (harder to jump a spark). I tested the theory by advancing the ignition to 18 degrees. Firing the spark earlier when the cylinder is under less pressure let the spark jump the gap easier. When I advanced the timing, it let me take it up to a higher boost pressure before it began to miss again. If you do not want to get an amp or more coils, try regrounding everything involved in the ignition system. Use larger guage wire where you can. Ground the head with a large strap, and try different grounding locations. I say to try playing with the grounds because my cousin's car missed terribly and random until I regrounded everything. The SR20DET ignition system has notorious small grounds to begin with.



Thanks for the tip. I'll just start adding a poop load of grounds to the motor and see if that helps. http://forums.freshalloy.com/images/graemlins/grin.gif This sucks.

RyanZ06
02-09-2006, 05:27 PM
you said poop.

240Shorty
05-16-2006, 12:11 AM
Ever figure out what your problem was?!

dbrass14point5
05-16-2006, 03:48 PM
chances are . . . . that if your car is sounding like a wrx - you might not be runnin on all 4 cylinders all the time . . . i had an ignitor chip go bad, but somehow still managed to fire the engine around town, just sounded like butt, when i got into boost it would spit and spudder til the boost really got in there and it "acted" like it was on all 4 . . . i had the car cranked one day while it was acting up, pulled the number one coilpack out and the motor's sound didnt change at all - thought it was the coil, but ended up being ignitor chip. just a suggestion - a bunch of my buddies own wrx's and i know EXACTLY what those [censored] motors sound like . . . not a good thing and only one thing sounds the same as a boxer motor - an sr on 3 cylinders (they both pull about the same too, hehehe)

Td5turbo
09-14-2006, 08:23 PM
Ever figure out what it was?

S14_James
09-15-2006, 09:54 PM
First step would be fix the exhaust leak
If the plugs are in order get a fresh set and switch around your coilpacks and see if the miss changes cylinders. How does all your fluids look? Oil look good no problems with coolant right, if you lose some cylinder pressure during compression you can create a "miss" as well so ensure the it is not escaping. Brown is what my one plug looked like when it was pushing compression out through a headgasket.
If you find that the cylinders issues change place with the coil packs, get some new ones, if not check with a good ignitor and go from there.
-James

harlock_ssx
09-17-2006, 08:57 PM
SR coilpacks are notortious for going bad, as the stock cover plate holds all the heat in & kills them over time. Two other things you need to consider (one's already been mentioned) is good grounding (I also run an additional ground from the engine to battery & engine to chassis) and your factory injector harness or coil pack harness. Think about it...heat kills electrical components over time...if the coil packs are going bad over time, what do you think is happening to their connector harmess? I had a similar problem from a bad soldering job on my injector harness, after switching to Sards & having to replace the injector connectors...

jickel240
09-19-2006, 10:52 AM
Wow I didn't expect to see this bumped again! I found that one of my heater hose clamps was digging into my coil pack subharness behind the motor. I simply moved the subharness around and turned the hose clamp where the hose clamp band end wasn't rubbing anymore. The ends of a hose clamp band can be sharp as you all have probably cut yourself a few times from them.

This solved the problem!