miss after wot

mexicanzero · Post by **mexicanzero** » Wed Sep 30, 2009 1:30 am

so usually i only really go wot when racing a stupid kid in his riced out honda or daddy's mazda 3 off a set of lights so only up to 50-60km/h.
and all is well, lots of power i always win very linear and a nice kick in the back when full boost hits.

but lately i've been using the highway more and the ramp i get on from is right after a light so i'll basically be going from 20 or so to 100km/h without letting off and all the way to 100 or wtvr i go to its smooth and pulls real hard. but once i let off i have a very obvious missfire and total lack of power. but right after this miss shows up it goes away within 15 seconds or so of letting off the gas. so if i stop the car and stick in it park by the time i'm opening the door it clears up and goes away, and the engine resumes its silky smooth idle. so i have no way of figuring out which cylinder it is cuz i dont have the time to go unplug an injector before clearing up.

it kinda feels like a flooded cylinder. i only have a narrowband o2 gauge but at wot it reads rich but not too rich only 2or so of the green lights which according to its calibration is right on with where it should be so i dont think i'm running overly rich. so i've been thinking maybe one of the injectors isnt closing fast enough so even though i've let off the gas its still dumping fuel in for a split second causing a flooded cylinder.

what do you guys think? i'll be pulling the plugs to check for any abnormalities tomorrow and if i have time i'll do a motovac to clean out the injectors and maybe a power balance test alhtough i dont see what good that would do.

normally with the eng warmed up my idle is fairly smooth with almost 20 inhg (which tells me the engine mechanicals are all in good condition) whereas when this miss is happening it goes to 15 or so.

other than a motorvac what do you guys recommend to do to clean out the injectors? what should the ohm reading be for yellowtop 480cc sti injectors? and do you guys think a power balance test could be of any use?

thanks
-Alex

ericem · Post by **ericem** » Wed Sep 30, 2009 2:55 am

Hmm, my car has a miss too, but its like if I jump on the pedal from a stand still and the power light comes on, then I gun it, and it goes pop pop pop, takes off.

mexicanzero · Post by **mexicanzero** » Wed Sep 30, 2009 3:40 am

yeah that is nothing like my miss... buut

kinda sounds like maybe its leaning out. i've seen dirty maf sensors do weird things including causing poping sounds cause of leaning out or maybe running too rich cant remember

clean your maf! cheap place to start. wen was your last tune up?

ericem · Post by **ericem** » Wed Sep 30, 2009 4:12 am

Did plugs and wires and seafoam within the last few thousand km all NGK ad gapped at .40 I think. Running 94 octane. Not sure if that matters? I think shell 91 might have run better going to switch next fill up. I think your right about the MAF sensor. I dropped mine accidentally and I wonder how it will affect it. I have my revtronix chip stage 2 , jecs MAF's, 440cc injectors, but I plan on just installing the IC and turbo and seeing how it runs, then Ill put in the chip and injectors and MAF.

mexicanzero · Post by **mexicanzero** » Thu Oct 01, 2009 3:20 am

did a motovac and put some new plugs in. car idles smoother and overall drive is smoother (i think due to the motovac more than the plugs).
its nice having the coolest people in the world as bosses. i did my plugs and motovac on my lunch hour and they charged me a grand total of 0$! they didnt even charge me cost on the plugs or detergent.

one of the plugs was a bit wet but i think its due to a mix of oil carb cleaner gas and dirt on the outside that just got on the threads and electrodes as i was pulling it out. spilt some gas on the dirty block/valve covers when doing the motovac. either way my car is burning no oil whatsoever and it didnt really smell of gas which it would have if it were fouled/cylinder running rich.

havent had a chance to do a good high speed run but i should be able to tomorrow so i'll post back then.

-Alex

mexicanzero · Post by **mexicanzero** » Thu Oct 01, 2009 11:39 pm

did 2 fairly aggressive and long accelerations today and no issues whatsoever

hopefully its for good!

-Alex

mexicanzero · Post by **mexicanzero** » Thu Oct 08, 2009 1:57 am

nope nevermind i guess i just hadnt had a good enough run.

still same thing wot for an extended period of time (e.g. from 20 to 90km/h) and it feels great the whole way no miss no roughness lots of power and a great pull. then once i let off the throttle for a few seconds and then stop or accelerate the car misses, and once i pull over it clears up and goes away within 10 or so seconds.

plugs are new coil is new (msd) wires are of unknown age but in good shape probably about 2 years old, injectors are off an engine that sat for who knows how long but they were motovac'ed and the car idles silky smooth at 650-700rpm with a vacuum of about 19 inhg.

what should the resistance through the wires be roughly? and my plugs are currently gapped at 35thou, they were at 28thou (as per what had been said in the chip forum) before i changed them and still had the problem so i tried the bigger gap to see if it would help.

any ideas? i'm all out...
-Alex

BSOD2600 · Post by **BSOD2600** » Thu Oct 08, 2009 2:01 am

You have the stage 2 v2 chip right? The stage 2 v1 chip had a bug where it fuel cut too fast after throttle let off... your car always had this problem or just started?

mexicanzero · Post by **mexicanzero** » Thu Oct 08, 2009 2:55 am

yeah i have the v2 chip and its no fuel cut, i know what that feels like.
if it were fuel cut then on let off the car would miss once and then regain itself, as this is what it did with the v1 chip.

with me on let off there is no abnormalities but if i stop at a light right away or give it gas right after i let off it misses (makes that gross smell out the exhaust too) and then clears up

it feels a lot like when i used to have a leaky injector when i had the stock injectors in, it would leak into the cylinder so after sitting i would go start the car and the cylinder full of gas would miss until the gas went out the exhaust or burn off then it would clear up and resume normal operation.

-Alex

mexicanzero · Post by **mexicanzero** » Thu Oct 15, 2009 1:36 am

so by going wot from near zero to 100-120ish and then lettign it coast to 80 and holding it with part throttle i can get the missfire to stay around long enough to unplug stuff so by unplugging injectors i determined drivers front (closest to rad) cylinder is the one missing. swapped that injector with one from the other side and no difference, still same cylinder. put in a new coil (old one was cracked) new fuel filter and new plug wires still no change.

so basically i've determined the injectors are fine, my plugs, plug wires, coil, fuel pump and fuel filter are brand new. so wtf could it be!? when it comes to spark the igniter, cam, and crank sensors are as far as i know original. could any of these cause a wacky issue like this?

-Alex

log1call · Post by **log1call** » Thu Oct 15, 2009 3:05 am

The ignition is wasted spark right? So it would miss two sparks if it was missing one. That tends to suggest it won't be spark, but how about fitting a timing light and checking for spark, or pull the lead and listen. Perhaps one spark is shorting, perhaps inside the coil even.

Just to be quite clear too... your drivers side is the left as you are driving right? So it's number two that's missing?

mexicanzero · Post by **mexicanzero** » Thu Oct 15, 2009 4:02 am

no way its the coil i changed it after the issue started happening with no change and same with the plugs and plug wires.

but you are right it is a wasted spark system so anything spark related would hit 2 cyls... hmmm i'm stuck! its not the worst issue possible i mean in city driving even driving aggressively its all perfect. but once i accelerate onto the highway the fun ends.

and yeah drivers side front so left if youre sitting in the drivers seat and closest to the rad.

i'm starting to think maybe computer related? for some reason the ecu is telling that injector to stay open longer?

argh... thanks!
-Alex

log1call · Post by **log1call** » Thu Oct 15, 2009 10:23 pm

Hmm. Here's a cut and paste I find myself posting quite often.....

If you are getting elusive, varying, intermittent codes, or no codes at all, and the car is a few years old....
Pull the ecu and have a look inside. Look for blown transistors(they can explode a piece out of the side of them), burnt resistors, cracked circuit boards, dry solder joints, leaking capacitors, water damage.
Use a magniying glass and inspect every component, circuit and joint.
It only takes a matter of minutes and given the number of things that can happen inside there, and the number of checks you could have to do to track it to there, it's best to do it earlier than later in the diagnostic process.

I'm a mechanic and I have spent hours in the past checking everything only to finally find a leaking capacitor etc. Ten cent part and a bit of solder and varnish and it's all fixed. Having said that, I'm not sure I have ever found a subaru ecu faulty. They are in a pretty dry place and they seem damn reliable.

mexicanzero · Post by **mexicanzero** » Thu Oct 15, 2009 10:57 pm

i had the computer out not long ago when i was diagnosing another issue and taking the revtronix chip out and then putting it back in.
and evrything looked in order, didnt look with a magnifying glass though. so maybe i'll pull it back out just in case.

-Alex

log1call · Post by **log1call** » Fri Oct 16, 2009 2:47 am

You only really need the glass to look at the circuit board's circuits for breaks and for dry solder joints. The other things are normally obvious.

I was just thinking though(while standing in the hot sun breaking a tractor in half), could it be the bumps on the back of the cam sprocket are damaged or too far from the sensor and it's getting a weak signal from one bump, perhaps made worse at speed, then flooding or some such thing? That could give a miss on one plug. Even though it's wasted spark you wouldn't be missing the other spark, just the one from the one bump which fires that particular bump.

Don't ask me how to test that though unless you have an osciloscope.

Actually... you can ask me... There is a cheap and simple way to use your laptop for an osciloscope.... Get a dataq voltage to serial port adaptor. I have one of those DI-194RS and it's quite handy for checking waveforms. Other than that get a shop to connect it up to a scope or go see an electronics repair dude.

mexicanzero · Post by **mexicanzero** » Fri Oct 16, 2009 2:52 am

yeah i highly doubt theres anything wrong in there as i did look around a bit to easy my curiosity and nothing stood out as unusual.

i'm going to try to get compression and leakdown tests done. although i would expect internal issues to show up at other times and not allow the car to run as great as it does, who knows...

thanks for the ideas
-Alex

log1call · Post by **log1call** » Fri Oct 16, 2009 3:11 am

Yeah, compression problems nearly always show up at idle.

mexicanzero · Post by **mexicanzero** » Fri Oct 16, 2009 3:15 am

what do you think about a valve not sealing properly at high temperature? this is what a few people have been saying but then there should be loss of power at wot if i hold it long enough not after letting off. with me power and smoothness is fine untill i let off. only thing fuel related i havent looked at has been the fuel rails although the motovac flushed them out too...

-ALex

mexicanzero · Post by **mexicanzero** » Fri Oct 16, 2009 3:18 am

hmm what you mentioned about the cam sproket bumps is a plausible idea... its a piece of cake to remove the timing cover on the end too so maybe i'll have a look tomorrow...

-Alex

log1call · Post by **log1call** » Sun Oct 18, 2009 10:38 pm

There are some good articles here.... http://endwrench.com/main.php?smPID=PHP ... ticles.php

There are a couple about the cam signals. Can't remember if they are in emmissions or engine mechanlcal

ericem · Post by **ericem** » Sun Oct 18, 2009 11:07 pm

mexicanzero wrote:hmm what you mentioned about the cam sproket bumps is a plausible idea... its a piece of cake to remove the timing cover on the end too so maybe i'll have a look tomorrow...

-Alex

Don't even have to remove the cover. Just remove the connector and 1 10mm bolt. And it comes right off. I found mine to be really dirty so I cleaned it.

mexicanzero · Post by **mexicanzero** » Mon Oct 19, 2009 1:42 am

well i'll remove the cover anyways to check the cam gear but i'll do that too.

and thanks for that site, lots of good info

-Alex

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miss after wot

miss after wot