[SOLVED] Misfire/Hesitation under slight load at highway cruising speeds

Bump

 

I’m just going to reiterate the importance of a pro tune or even just getting the base map+1 revision from freektune. Cobb ots maps are dicy. Also I just read back and saw that you are cruising at 2k-3k in 6th. I wouldn’t suggest being that low in the rpms in a higher gear especially when going up a hill

 

Oh okay, so you do you think I should go with another company? My tune is from stratified at the moment.

when I mean hill I mean the tiniest incline from flat that only slightly loads the car. Of course I’m not lugging the car up a big hill in 6th

 

Stratified is good man no need to worry, you've clearly stated that's what you're running Pat must have skimmed over that.

As far as the issue does it happen in you're not in low Rpms in ,5th /6th because heck that's not good for these cars...
Also are you getting any misfire codes that would let you know which cycl it Is? Could be a coil pack going or your injector seals, so you see anything leaking around Mainly under it and down the block after driving

Also if it's the injector seals with your mileage good time to do intake valve cleaning at the same time if it's never been done as your engine will thank you

Edit also if you can get a data log of it happening that may help. I wonder if it's the upstream o2 sensor going out as well sometimes that causes stuttering with AFR readings

 

I did get a data log while it was happening actually, I’ll try and get it uploaded to this forum when I figure out how to do it haha

as for engine codes, I’m not getting anything whatsoever

and it only seems to be happening in 6th on the highway from what I’ve seen. As soon as I let off throttle it goes away instantly, but will come back as soon as I touch the throttle. And then after 5 mins it won’t do it at all. It’s very sporadic

 

Am dealing with this exact issue right now and also posted about it here. Any luck on a diagnosis? For me, it also happens in 4th and 5th while at very low load (barely touching the pedal) and between 2k and 3k rpm, generally. Thinking it was my MAF sensor, I replaced it to no avail. I suspect it's one of the following:

- Primary 02
- Throttle Position Sensor
- Dirty EGR
- Injector seals (I hope not)
- Small vacuum leak (although both LTFT and STFT are bang on for me)

 

I'm curious if either of you guys are seeing drops in hpfp pressure when you're experiencing the chugging.

 

I’m definitely not as far as what the accessory is showing me

 

What RPM range is this occurring in? For example, I had a similar issue, and it was <3000rpm. This would be the case if you were cruising on the highway and tried to accelerate. I had a similar issue resolved here

For me, it was always <3000rpm, and the stuttering/hesitation perfectly matched the car logging low fuel rail pressure (~70psi).

 

Yeah, below 3,000rpm. However, my logged fuel pressure is looking fine. I gave up and took the car to a tech, and we went out to log with a scan tool. The logging data apparently shows an issue with the VTCS system, which make sense as I was getting 'VTCS Stuck Open/Closed" codes earlier this year and actually replaced the VTCS valve, solenoid, and sensor earlier this year. It may be a problem with the internal "flapper" mechanism within the intake manifold itself, and the only fix for that is a new intake manifold or removal of the VTCS assembly in the manifold and blocking the code via a tune.

FWIW I have never had code P0089, like you did. Glad you were able to fix your issue, though!

 

I haven’t driven the car for a while, but from
What I can remember I don’t think the actual fuel pressure was dropping when the symptom started occurring

 

If it vcts you could disconnect the rod from the module and find a way to hold it open. As long as the module is plugged in you will not get a code

 

Hey dude I’ve been having this issues for the longest as well I’ve change out all 4 injectors and changed out spark plugs and the issues is still there. Have you found or heard our any solutions. Ima at a lost

 

Seems like there are various symptoms that can cause this. First thing is look at your fuel pressure when you experience the problem.

I am also experiencing a similar issue, but have found several factors that change the severity of the problem. Aftermarket ignition coils make the problem worse (Even performance aftermarket), Different MAF sensor (Not new, but OEM) seriously reduced the problem for me, but did not eliminate it. This tells me I am compensating for something with all these variables.

 

By any chance would you happen to have a data log of whats going on with your car? I'm noticing that whenever it does misfire my STFT will sometimes compensate supper hard, in one case it corrected 33% during its misfire period. Not sure if this is due to lack of air or fuel but AFR holds steady 14.7-14.21 when it does misfire. Fuel pressure stays the same as well and I've also changed out the MAF sensor a good while ago and it did help a bit but the problem is still there. I've also gone through and redid all my catch can lines/intake piping thinking it could be a possible PCV/vacuum issue going on but no luck. when cleaning out my catch can i did note that there was a heavy fuel smell when draining the catch can I'm not sure if this is normal on these cars or something i should further look into. Also i went to put in some Denso ITV 24 2-step colder plugs and the problem got even worse to the point that misfiring was happening even more consistent, I changed back to the itv 22 plugs that were in it prior to new ones. I did not check on gap on itv 24 plugs but they were fouled from only 2-3 days of use. With all that I'm noticing going on I'm leaning towards a spark issue happening that only seems to occur in that 2k-3k range and goes away when at WOT and ITV 22 plugs seem to aid it a tad bit. I also have some data logs i can post up if interested maybe someone can see something I'm not seeing. Thank you for any and all help in advanced and taking time out the day to help a fellow speed in need .

 

@jesus you don't need colder plugs. They fouled because they are too cold

 

Yup this, spark issue because they're too cold. Put in stock heat range NGK plugs ( NGK LTR6IX-11 (6509): Stock Heat Range) and gap them .026"-.028" and should fix the fouling

 

I just put in some new ITV 22s in about a week ago I'll give them a try and see what happens. Still misfiring just on cylinder 4 i got a log during it misfiring ill post up and see if you guys notice anything I don't see.

 

update to this whole mystery it ended up being a improper seating intake valve. I ended up putting some work into the head getting new oem valves, crower springs & fresh seals since then no more cylinder 4 misfire. even went ahead and slapped on the BNR S4 i had waiting around.