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Why am I misfiring?

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lil corb

15+ Year Contributor
758
7
Sep 7, 2005
Woodbridge, Virginia
So I have this choppy MafRaw/ misfiring issue going on and I narrowed it down to (Boost leaks, Misfiring, wastegate actuator)

I replaced my Bov with forge piece, fixed ALL my boost leaks, checked and cleaned maf and filter. Turbo is a 1500 mile evo3 16g which was bought brand new. Still having this issue...

Replaced plugs and wires and gapped the bpr7 to .028...and I'm still having this issue!! I installed plugs by using and extension until it was seated then gave it a little more than a quarter turn with the ratchet.

Any idea why this is going on? Should I try a different gap?

Running 19psi and it only starts to miss around 3000-4500 rpm and on link it's causing and erratic Maf raw. This is all started after installing my ets street kit so I don't know if more air being introduced caused the problem?

Any ideas?

Log attached of a 2nd gear pull (happens mostly in 2nd and 3rd so far, haven't tried 4th)
 

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Did you recirculate your new BOV?

Yes recirculated, after more research it seems that maybe a smaller gap with a more accurate gapper ( using a ramp style gapper) might fix the issue. What I may have thought was .028 could of been .032 apparently. Going to re do gap next and I'll advise of results.
 
I would suspect there is still a boost leak based on the RPM of the misfire or you somehow contaminated your MAF resistor, take a q-tip and some rubbing alcohol and wipe it off and see if there was any dirt on there, other than that bring the plugs down a little bit and see if that helps.
 
I would suspect there is still a boost leak based on the RPM of the misfire or you somehow contaminated your MAF resistor, take a q-tip and some rubbing alcohol and wipe it off and see if there was any dirt on there, other than that bring the plugs down a little bit and see if that helps.

Hmm, still boost leaks? I did a very thorough test right before putting it back together up to 25psi. I guess I can do another test and see but I'm hoping fixing the gap is the issue because what I'm feeling between those rpms is hesistation and the sound of it missing. Where as before with a boost leak I was just running leaner or richer depending if it was a pre or post turbo boost leak. Which is why I'm leaning towards more plugs than boost leaks but I'll double check.

Thanks
 
.028 is pretty big. I would drop down to .020. I have not opened your log, but that stands out. Mine did that when gapped too big
 
Ok, here is a update on some the things that's going on including photos and a new log.

So I re gapped my plugs to .026 to see if it fix the issue and I noticed it was a little better in terms of less stuttering but not fully cured and at idle it did not miss at all like it would before with bigger gap. I then re gapped it to .023 and even worse now. It seems to start missing really bad around 4000rpms and stay there for about 1.5 seconds then it pulls incredibility hard all the way up top. But idle miss is gone still.

I took pictures showing everything that I could think would be a problem and to see if maybe anyone can help me fix this issue.

It always happens around 3000 to 45000 rpms and mostly in 3rd. I do notice a little in 2nd and 4th.

This is a example of what I feel doing a 3rd gear pull from about 2000rpms:

WOT at 2000rpms= starting to hear turbo spool

2000-3000rpms= a little slight hesistation probably due to bad a/f ration because of still calibrating air flow

3000-4500rpms= turbo is hitting full spool around 3500 when it starts to buck/ hesitates/ it hits 4000rpms and massive misfiring is going with no knock on link to about 4200rpms but tach just hovers at 4000rpms for a second or two.

4500-7200rpms= pulls like a crazy animal all the way to fuel cut of 7000 ish( and feels like it wants to keep pulling until 8000rpms (probably due to fp2 cams)

Now on the log, it's hard for me to determine if it's the choppy maf raw causing this sputtering/ misfiring feeling or if it's the mis firing causing the choppy maf raw.

A couple of things I want to add for possible culprit.

1. A boost leak test which I can not find or hear up to 25psi: i dont think this is likely as i have done numerous BLT and no one has heard or felt any leaks. New Forge BOV (fixed the gasket sealing issue during a BLT) and ETS 7: street kit.

2. My CAS is going out: For some odd reason, with my Mechanical timing being dead on (pics will follow) the furthest I can get my non adjustable timing light and the mark on my fludampr (I am assuming the marks are right because my crank sprocket marks line up) is TDC with the grounding pin checked on link. I found that strange because the CAS is adjusted all the way forward! After unchecking the grounding pin and re checking the timing mark, it overs around the 5-8 btdc* mark. Which I hear is what you want to shoot for without timing pin grounded. CAS was installed with cylinder one being TDC with the 180* marks being together (notch on CAS) and plus this issue would of happened even before ets kit.

3. Someone how my evo 8 MAF is going bad or the filter elements is so dirty which is causing air flow issues: I checked the MAF and any preturbo potential leaks and I guess I can see the filter being dirty enough to cause this but wow if it is that :confused:

4. The intake is causing compressor surge because of the 2.75 to 2.25 coupler neckdown and since my motor is built is causing surge on my evo 16g: I highly think not.


Other points to make is this just started happening after I installed my ETS 7" street kit. The car runs great all the time except the 3000-4500rpms WOT missing issue. Other than that beautiful! perfect a/f ratio during closed loop and cars pulls hard other than issue during the process of calibrating my maf but this is making it difficult to do so.

The pics following show the new gap of the new plug and there is also a pic of my old plug with the bigger gap. Pics of my crank timing being dead on along with cams, intake with evo 8 maf with filter, CAS and my compressor inlet with boost leak tester on it. I usually have 2 clamps on it.

Also attached is a log from 2000rpms to redline in 3rd gear.

Maybe a wisemen might be able to point me in the right direction (Calan etc..) Is this even misfiring as well? Could this be a mechanical issue? Bent valve? I had my engine builder do a leak down test in front of me a couple months ago and it was three with 4% one cylinder was 6%. Only thing changed since then is I replaced my OEM timing belt due to a weird blemish from the factory with a gates one but no issues other than. I thought maybe a possible bent valve because I had to try and set timing marks couple of times with a wrench but motor was never turned on, all done by hand. but from a I recall a bent valve would cause more issues than just certain rpms???

Any other info needed to help me solve this issue please do not hesitate to ask.
 

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I'll be honest I just scanned over everything that was said and just took a look at the last log... .

But,
Holly rich... Pull some fuel out and target something besides like the stock maps 9.3:1... . Dropping the gap like you did. But, with a more desirable AFR should help.
 
I'll be honest I just scanned over everything that was said and just took a look at the last log... .

But,
Holly rich... Pull some fuel out and target something besides like the stock maps 9.3:1... . Dropping the gap like you did. But, with a more desirable AFR should help.

Thanks my1G. I know you are a knowledgable when it comes to tuning and I'm hoping its something as simple as that. Any other ideas? The more the better!

Thanks
 
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