2-3k rpm misfire
Car threw a P0170 on the way home. It ran fine today, albeit a little rough idle. No symptoms.
Ltft Lo is 0.19
Ltft mid is -9.375
I thought the trim had to be past 12 to throw the code. I'm really confused. Front O2 has less than 200mi on it. Trims are what they've pretty much always been.
MAP sensor shows life, and moves around when logging. TPS is sitting at 12% at idle.
Ltft Lo is 0.19
Ltft mid is -9.375
I thought the trim had to be past 12 to throw the code. I'm really confused. Front O2 has less than 200mi on it. Trims are what they've pretty much always been.
MAP sensor shows life, and moves around when logging. TPS is sitting at 12% at idle.
When it does it, it will do it on a free rev. So I should be able to just hit it at the throttle body and watch my FP gauge on the regulator.
That pump pre-dates me owning the car. So it's an easy 10Y old. I'd love for it to be the pump. $100 and 20 minute fix. Although I guess it could be the relay as well? Isn't there one on the firewall that regulates pump voltage at idle etc?
The last time I looked in that direction those all looked a good bit like ****.
That pump pre-dates me owning the car. So it's an easy 10Y old. I'd love for it to be the pump. $100 and 20 minute fix. Although I guess it could be the relay as well? Isn't there one on the firewall that regulates pump voltage at idle etc?
The last time I looked in that direction those all looked a good bit like ****.
I watched FP this morning after starting it. It did not stutter at all, and FP appeared "normal". Mine as stated, is high. And the AFPR is set to mimic the overrun the car was tuned at a million years ago. The code did not return. The last two days were a lot cooler than the last week. Not sure if that's playing a role.
Newbie
Joined: Feb 2016
Posts: 47
Likes: 1
From: TX
I watched FP this morning after starting it. It did not stutter at all, and FP appeared "normal". Mine as stated, is high. And the AFPR is set to mimic the overrun the car was tuned at a million years ago. The code did not return. The last two days were a lot cooler than the last week. Not sure if that's playing a role.
Not sure if you guys ever found a fix, but I'm gonna revive this old thread quick. I'm really happy I found this thread this morning, because I have been having similar symptoms for MONTHS and it took me forever to figure out what was wrong. I have had all of the symptoms everyone has listed, hanging idle, sputtering at idle and driving at light throttle (both of which showing almost like a lean misfire on wideband), and between 3-4k rpms the car would backfire like a ****. After putting an oscilloscope on all the sensors (crank,cam,TPS, MAP, etc.), doing a compression test, checking for burnt valves, changing fuel pumps, MAP sensors multiple times, and more, I decided to change my IACV and that helped some of the symptoms slightly. My idle did drop a little, and the bouncing idle went away with the exception of when I was rolling to a stop. I plugged my laptop in and parked the IACV and adjusted the BISS screw to drop the idle to where it's set in Evoscan and my sputtering went away, and that backfiring almost completely went away. I need to fine tune it more to get it dialed in where Evoscan has my idle set exactly, but I can tell you it got way better by doing this, so it may be worth a shot if you haven't already figured it out. I figure the previous owner adjusted the BISS screw improperly as the IACV was crapping out which screwed up my idle and the calibration for the IACV. Just a thought I figured i'd share. Best of luck!
Mine just, went away shortly after. Until, recently. Now it's back, and it's worse than ever. It will LITERALLY stall the car pulling out, complete with jerking at most low throttle cruise situations. The car warms up and it goes mostly away. I just built a coil on plug. Swapped plugs and changed the IAT (I use for SD). It is literally shutting off fuel. It will put your head into the windshield. It also does it over bumps at part throttle. There's a little jerk, but the car is at speed so it doesn't do anything.
I thought that too. So I unplugged it. Car stuttered for maybe a half second and it made no real difference. Didn't stall. It was the map sensor, or rather, the tap from the original MDP sensor harness feeding the MAP signal to the translator in the glove box. It must have just vibrated to the point where it occasionally did stupid stuff. I flicked the connector and nada. Started tugging on it though, and voila... Idle change. So I kept fooling with it and that was it. I drove it home with no issues after squishing it back together tight.
I cut the connectors off today and installed a new one. But I'm going to peel the harness back to where I originally jumped in on the harness and triple check it. (I put a disconnect in so you could peel the harness back normally.) Pretty sure I soldered that tap in. It's been 10 years though, and the harness feeding back into the car. WB, MAP, IAT etc is on the firewall, while the MAP is on the motor. So it probably just played tug of war for a decade.
The fluctuations were happening so fast it wasn't showing up on logs. Split second stuff. Really annoying. It's been coming and going for years. But I found it. Finally.
I cut the connectors off today and installed a new one. But I'm going to peel the harness back to where I originally jumped in on the harness and triple check it. (I put a disconnect in so you could peel the harness back normally.) Pretty sure I soldered that tap in. It's been 10 years though, and the harness feeding back into the car. WB, MAP, IAT etc is on the firewall, while the MAP is on the motor. So it probably just played tug of war for a decade.
The fluctuations were happening so fast it wasn't showing up on logs. Split second stuff. Really annoying. It's been coming and going for years. But I found it. Finally.
Newbie
Joined: Jul 2016
Posts: 14
Likes: 2
From: Eastern Europe
Hey guys ! Gona have to revive this thread. My car just started doing this recently at 3k rpm in third gear. Did any of guys get a real solution to this problem ? Mine feels like a fuel cut, there also is a pretty noticeable power loss. Im thinking maybe injectors but then injectors would cause a bad drivability at all time and in all gears. Changed plugs, no change. Running COP(less then two years installed). MAF delete. Fresh fuel pumps.
Last edited by 1nf3rn0; Sep 13, 2019 at 01:51 PM.
Evolving Member
Joined: Mar 2021
Posts: 108
Likes: 7
From: South Africa
Anyone with more info on this after the years?
My car was running fine, then suddenly at about 5krpm it had a bad missfire.
all the work was done before this started and it was recently tuned and everything was in check.
it has new BPR double pumper with lines, ID2000, new AEM FPR, AN6 lines feed and return.
I changed plugs and COP and it's still the same.
No boost or vacuum leaks.
car starts and idles like normal. All logs don't show anything wrong and there's no codes
What chances that it's the IACV ? I don't want to spend the crazy amount on 1 as im going DBW in 2 months, just getting all the parts together.
My car was running fine, then suddenly at about 5krpm it had a bad missfire.
all the work was done before this started and it was recently tuned and everything was in check.
it has new BPR double pumper with lines, ID2000, new AEM FPR, AN6 lines feed and return.
I changed plugs and COP and it's still the same.
No boost or vacuum leaks.
car starts and idles like normal. All logs don't show anything wrong and there's no codes
What chances that it's the IACV ? I don't want to spend the crazy amount on 1 as im going DBW in 2 months, just getting all the parts together.
Newbie
Joined: Jul 2022
Posts: 5
Likes: 1
From: Minnesota
Compression or spark
It feels like fuel cut...
I haven't done anything but drive the car and change fluids on it in almost 8Y. I'm approaching 82K. Mods are in sig.
Already changed plugs. Already changed IAT sensor. (I change them every year because the meth sprays right onto them and kills them). I've changed it 10x. Every time I have this problem that's exactly what it is. I've changed it, then when it didn't fix my issue I changed it again just to be sure I didn't get a bad one.
I changed the front O2 and the car is a lot less sputtery everywhere else. So that definitely needed done.
The misfire is only on a cold'ish car, typically between 2-3k rpm. But it's not a stutter, it's fuel cut - head in the windshield bucking, embarrassing, can't safely pull into traffic without fear of death.
Car is on an 8Y old flash before speed density. (Ecu controlled boost, alt maps etc) I had everything about set to swap out of the maft-pro and to factory ecu speed density and then just didn't. It hasn't been touched, and the car ran every day without issue for years and years. There just wasn't a reason to fool with it.
I dug all my old stuff off of dead laptops and fired up evoscan to try to see what was going on. IPW falls flat when it does this. If idle is 1.5ms and I free rev it, it will dip to 1 or 1.2 or 0 for a split second. It is very much pulling fuel.
My fuel trims we're about 0 LO, -10 MID. Cars on 850's, and a 255HP. I replaced the feed line with 6AN line and installed a fuel lab FPR last year because my hard line rotted out. I am running a couple extra #'s of fuel pressure to match the overrun of the factory FPR with the 255HP. (Where the car was tuned at)
Car runs 29#'s of boost on the 30R and has for almost a decade.
I thought maybe ignition coils but it doesn't feel like blow out/break up. The wideband goes full lean when it stutters. Which matches what I saw with the injector pulse width nose diving. (I wasn't sold at first, thinking maybe it was swinging lean to compensate for the unburnt fuel).
The maft-pro no longer displays anything on the screen, it hasn't for years. So desoldered that one, and I put a new screen in it. Nada. I know it's working because there's no MAF in my car. But perhaps it's starting to puke.
The JDM map sensor is still logging and showing boost vacuum. I thought maybe it was cutting out.
It feels like I blew a hose off for a second. (On SD it just goes blaaaaah and your head goes straight into the windshield). But it makes no sense because on a hot car. It runs and drives without any issues. So after eyeballing all my hoses and verifying there are indeed still connected...
I haven't an effing clue.
Cam sensor? Crank sensor? Coolant temp sensor perhaps? Doesn't that (if not present/reading) stop the car? Mayve it's sluggish... Can't remember?
I'm getting TPS steady through the bucking as far as I can tell. I thought maybe TPS.
Can the IACV puking cause it to pull fuel? I'm able to log steps and such. But?
All emission components and systems are disabled...
What system/ sensor kills fuel when it goes bad? I'm really rusty because I have had almost zero problems with this car for almost a decade. Need some fresh eyes.
I haven't done anything but drive the car and change fluids on it in almost 8Y. I'm approaching 82K. Mods are in sig.
Already changed plugs. Already changed IAT sensor. (I change them every year because the meth sprays right onto them and kills them). I've changed it 10x. Every time I have this problem that's exactly what it is. I've changed it, then when it didn't fix my issue I changed it again just to be sure I didn't get a bad one.
I changed the front O2 and the car is a lot less sputtery everywhere else. So that definitely needed done.
The misfire is only on a cold'ish car, typically between 2-3k rpm. But it's not a stutter, it's fuel cut - head in the windshield bucking, embarrassing, can't safely pull into traffic without fear of death.
Car is on an 8Y old flash before speed density. (Ecu controlled boost, alt maps etc) I had everything about set to swap out of the maft-pro and to factory ecu speed density and then just didn't. It hasn't been touched, and the car ran every day without issue for years and years. There just wasn't a reason to fool with it.
I dug all my old stuff off of dead laptops and fired up evoscan to try to see what was going on. IPW falls flat when it does this. If idle is 1.5ms and I free rev it, it will dip to 1 or 1.2 or 0 for a split second. It is very much pulling fuel.
My fuel trims we're about 0 LO, -10 MID. Cars on 850's, and a 255HP. I replaced the feed line with 6AN line and installed a fuel lab FPR last year because my hard line rotted out. I am running a couple extra #'s of fuel pressure to match the overrun of the factory FPR with the 255HP. (Where the car was tuned at)
Car runs 29#'s of boost on the 30R and has for almost a decade.
I thought maybe ignition coils but it doesn't feel like blow out/break up. The wideband goes full lean when it stutters. Which matches what I saw with the injector pulse width nose diving. (I wasn't sold at first, thinking maybe it was swinging lean to compensate for the unburnt fuel).
The maft-pro no longer displays anything on the screen, it hasn't for years. So desoldered that one, and I put a new screen in it. Nada. I know it's working because there's no MAF in my car. But perhaps it's starting to puke.
The JDM map sensor is still logging and showing boost vacuum. I thought maybe it was cutting out.
It feels like I blew a hose off for a second. (On SD it just goes blaaaaah and your head goes straight into the windshield). But it makes no sense because on a hot car. It runs and drives without any issues. So after eyeballing all my hoses and verifying there are indeed still connected...
I haven't an effing clue.
Cam sensor? Crank sensor? Coolant temp sensor perhaps? Doesn't that (if not present/reading) stop the car? Mayve it's sluggish... Can't remember?
I'm getting TPS steady through the bucking as far as I can tell. I thought maybe TPS.
Can the IACV puking cause it to pull fuel? I'm able to log steps and such. But?
All emission components and systems are disabled...
What system/ sensor kills fuel when it goes bad? I'm really rusty because I have had almost zero problems with this car for almost a decade. Need some fresh eyes.
Evolving Member
Joined: Mar 2021
Posts: 108
Likes: 7
From: South Africa
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