2G Misfire/subi sound

[JuGs]

Ok doing this frommy phone. But I'll try and be as detailed as I can. So when I start my car for the first time in the day it will start and run fine. Only issue I have is sputtering under more than a few lbs of boost. I know I have no boost leaks tested it 5 times now. But that isn't my issue I need help with but could be part if my main issue. So my biggest issue is after a period of driving my car will start to misfire and sound like a subi. It will not accelerate at all. Now once that happens if i shut the car off for 2 seconds and start it, it will be fine again except for sputtering under a few lbs of boost.

What will or is causing it to misfire and sound like a subi after a period of driving but not upon start up? Im thinking possible cam sensor or maf/map sensor

 

[lasershark]

I would suspect an ignition related problem. As load increases so does the demand placed on the ignition system. I had this problem a while back and did plugs=no change, wires=no change, replaced coils= problem solved.
Sounds similar to my problem when it was only exacerbated by boost...

 

[JuGs]

I haven't tried changing coil packs yet. But just put in new plugs and wires yesterday. I have a spare coil pack I'll check that and see what happens.

 

[lasershark]

I have a spare coil pack I'll check that and see what happens.

I had a spare too so it was easy to check out... hopefully it's that simple...

 

[JuGs]

I have a feeling it isn't. Sadly. Cuz it runs great and drives great. But the subi sound and massive misfire and complete loss of power once i been driving for over 45 mins yeah...doesn't make since to me.

 

[lasershark]

So after the problems starts (~45min in) does it still subie out under all conditions or just under boost? Make any changes to the car? or did the issue come out of no where?

 

[JuGs]

Thats when the subie sound starts is after a while of driving. But it goes away if I shut down the car and restart it seconds after. But does come back after 20 mins. Its like it only does it when hot. The sputtering under boost is always there. Its just the severe misfire subie sound and no power what so ever after i been driving for 45 plus minutes

 

[lasershark]

ya probably not the coil then, mine would do it hot/cold (all times) whenever in boost...
You do any mods/changes to the car?

 

[JuGs]

Cars practically stock. Hard ic piping and 16g turbo. This issue is fairly new. I swapped motorsback around Thanksgiving and it never had issues with long drives (drove to Michigan and back) 8 hour trip.

The only issue thats same as before I swapped motors is the sputtering under boost. I do have a cel for iac and o2 sensor but dont think that would cause any of that.

Thats why I was thinking map/mas or cam sensor (cam sensor is not the one from motor I had pulled) so thats why I was thinking possible cam sensor

 

[ThunderChild]

Maybe the PTU is crapping out, or has a poor ground that's being over-saturated, then once you key cycle the car it resets essentially.

 

[brads]

Do you have a way to datalog the car? Maybe you can see if you have either a MAF signal dropping? Looking at your oxygen sensor output might tell if you are going lean before the misfire, if it were a fuel issue.

 

[JuGs]

Sadly no wayto data log. And not sure if any local people will have what i would need. I do have the black box ecu..but nothing for requirementsfor logging anything

 

[JuGs]

Maybe the PTU is crapping out, or has a poor ground that's being over-saturated, then once you key cycle the car it resets essentially.

I can swap my ptu with one of the spares i have and see if the problem persists or not. Will be a few days or more before I can get a full test on it.

 

[JuGs]

Update...well ptu wasnt the issue. Swapped it before work...and still after about 45 minutes of running it starts to misfire and sound like a subi. Would a bad ics or iac whichever you prefer to call it cause this?

 

[ThunderChild]

My next guess would be coils or poor grounds somewhere.

 

[jstory352]

Just out of curiosity have you tried seafaring the intake? I just had an issue with a misfire that wasn't even throwing a code but mine was constant until I took it out got into the boost. I'm guessing something in my valve seat for some reason just wasn't sealing up. I'm stumped but you don't by chance have a spare ecu to swap in and try do you? To me this seems to be either resistance related to a component that my begin to fail under certain environments or maybe like my situation something possibly valve related and a simple fix. Hope you figure it out soon, I know it sucks not having your dsm to drive.

 

[JuGs]

Its driveable. But cant get on it. No i haven't seafoamed this motor. Not sure if previous owner has with this motor.

I still need to swap coils but will soon. Not sure if this is relivant or not...but theres no change if I unplug he map/mpd sensor. Just tested that once it started to misfire while idling at work (roughly 45 mins of straight running)

 

[lasershark]

but theres no change if I unplug he map/mpd sensor

This is strictly emission related so it wouldn't really have an effect on anything crucial...
It works in conjunction with the egr system...

 

[brads]

Would a bad ics or iac whichever you prefer to call it cause this?

How expensive is it to get something to datalog your ECU? Is it more or less than an IAC? A functional method of checking the stuff on your car will save you some money in random parts swapping. You could use it to check your coolant temps, make sure your TPS and MAF appear to be reading right, look at your injector DC, fuel trims etc.

 

[JuGs]

How expensive is it to get something to datalog your ECU? Is it more or less than an IAC? A functional method of checking the stuff on your car will save you some money in random parts swapping. You could use it to check your coolant temps, make sure your TPS and MAF appear to be reading right, look at your injector DC, fuel trims etc.

The data port cable to use evo scan is roughly 300 bucks. I wish I had one...it would save me alot of headaches .

 

[doubleclutch]

I had the same problem. I tried coil pack, plugs, wires, ptu, and ecu. Never could really figure it out. It hasn't happened in a long time, but i drive the car a lot less. My only thought is it could have been the injectors. I went larger and haven't had the issue since. It can't be mechanical otherwise it would be constant. Electrical could be possible, I had the same response with a restart. Mine definitely wasn't load related because it could happen on the highway or idling at a light.

 

[boostdawd]

If it goes away after you turn the ignition off and back on I would suspect a bad ecu. Just me speculation though as no way of data logging or checking the sensors like brads suggested.

 

[JuGs]

I have a spare ecu...but its from a 95/96 and not even sure its good. Plus the ecu in the car is better than my spare(non eprom) and i have the black box.

It is possible I damaged the ecu when i replaced my core support. Engine and trans was out but never unplugged the ecu while welding the support in. And this main issue I'm having started after swapping motors and putting the core support in.

 

[doubleclutch]

ECU only takes 10 mins to swap. Give it a shot.

 

[JuGs]

ECU only takes 10 mins to swap. Give it a shot.

Yes i know..but the 95/96 ecu will take a bit extra to swap. If i remember right its easiest if link is installed but otherwise i believe i have to swap injector pins around and firing order around...or maybe its just firing order...cant remember 100%