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Discussion Starter · #1 ·
Hello 3si community. I had recently installed 3sx’s FMIC (btw was the biggest pain in the ass) but turned out good. Problem is- I start the car, let it warm up for 5-10 min, and go out for a drive (today was 84 degrees out.) When i accelerate to 3k RPM or more (usually right at 3k) it will start to stutter, or jolt. You can feel it through out the entire car. I’m not sure exactly what it is- like it jolts, then jolts harder. Then shift to 3rd, same thing. After driving for about, 5-10 min, it goes -away. I figured it was something about temp? I’m not sure and how safe it is for the engine (first time having a turbocharged car) Please give any info on this, thank you.
 

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Initially, what you described sounded like surge. Now it just sounds like a delayed closed-loop with temp probably has fuel trims compensating for vacuum leaks...

(If it did not do it beforehand, then it is obvious what caused the issue)

-sent from my Galaxy Note 9
 

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Discussion Starter · #5 ·
Initially, what you described sounded like surge. Now it just sounds like a delayed closed-loop with temp probably has fuel trims compensating for vacuum leaks...

(If it did not do it beforehand, then it is obvious what caused the issue)

-sent from my Galaxy Note 9
Agreed, didn’t do this before and now it does. Drained rad and new coolant, temp gauge is fine, needle is dead middle. It just really weird, only does it when I guess it’s “not warmed up” but after hittin the throttle after a while it just goes away very weird
 

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1992 3000GT VR4
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Metered air or air flow going thru mass air flow sensor is metered
lower rpm ranges oxygen is metered by your O2 sensors till your reach higher rpms in closed loop this will create Knock or pre detonation which is bad
With O2 sensors seeing this will try to correct the issue and run rich
If you have anyway to data log it this will show in short term fuel trim with it adding or subtracting fuel in open loop in lower rpm ranges
Do you have a way to veiw your fuel trim wideband O2 to give you live feed in a gauge thru - out rpms ranges
If you have a vacuum leak anywhere this is unmetered extra oxygen that your O2s are seeing but your MAF can't see it because it is get sucked in from leak from some wheres else other then where the air is supposed to be coming from

Idle to cruise will suck air in being that the engine is under vacuum
Higher rpms to acceleration the engine will go under pressure pushing air out of the leak
Vacuum leaks make your turbos work over time which is also bad
 

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Agreed, didn’t do this before and now it does. Drained rad and new coolant, temp gauge is fine, needle is dead middle. It just really weird, only does it when I guess it’s “not warmed up” but after hittin the throttle after a while it just goes away very weird
Not weird. It is exactly what I just described above. Open-loop to closed-loop with vacuum leaks.

Air and fuel are whack along with possible random misfire.

-sent from my Galaxy Note 9
 
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Discussion Starter · #8 ·
Metered air or air flow going thru mass air flow sensor is metered
lower rpm ranges oxygen is metered by your O2 sensors till your reach higher rpms in closed loop this will create Knock or pre detonation which is bad
With O2 sensors seeing this will try to correct the issue and run rich
If you have anyway to data log it this will show in short term fuel trim with it adding or subtracting fuel in open loop in lower rpm ranges
Do you have a way to veiw your fuel trim wideband O2 to give you live feed in a gauge thru - out rpms ranges
If you have a vacuum leak anywhere this is unmetered extra oxygen that your O2s are seeing but your MAF can't see it because it is get sucked in from leak from some wheres else other then where the air is supposed to be coming from

Idle to cruise will suck air in being that the engine is under vacuum
Higher rpms to acceleration the engine will go under pressure pushing air out of the leak
Vacuum leaks make your turbos work over time which is also bad
Everything’s stock, besides downpipes, FMIC, and BOV. But i have no way to monitor AF or fuel trim wideband. I’m pretty new to all this, is that what the jolt is- knock? What should I do first? Should I be driving the car? Thank you for the response.
 

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Okay, what is the first thing I should do? Again I apologize for my lack of intelligence, im still learning the car.
Like @bboyalan said, probably has fuel trims compensating for vacuum leaks, so you need to check for vacuum leaks and then drive again to see if issue persists. You can search the forums for different methods of pressure testing the system, or go on 3SX and look at their pressure tester and make a replica or buy what they have. Just our of curiosity, is your BOV now externally blowing off or did you recirculate it?
 

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Discussion Starter · #11 ·
Like @bboyalan said, probably has fuel trims compensating for vacuum leaks, so you need to check for vacuum leaks and then drive again to see if issue persists. You can search the forums for different methods of pressure testing the system, or go on 3SX and look at their pressure tester and make a replica or buy what they have. Just our of curiosity, is your BOV now externally blowing off or did you recirculate it?
Okay, i will def do a test when i get home. I am not 100%, but I think it’s recirculating. Again, not very familiar with BOV, I am not too sure how to tell if it’s to the atmosphere or recirculating. I know a hose goes to on of the inlets/outlets from the top of the intake tube to the BOV, and then another to I think the tubes for the front turbo inlet. So there are 2 hoses on the BOV.
 

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What I would do is some intense research on what you wanna do with the car before putting any aftermarket parts in upgrades to the car
Running stock ECU I would leave everything bone stock unless you do plan on getting better performance and increased horse power
Which consists of a lot of components
Front mount innercooler you could run on your stock turbos shouldn't be an issue just make sure you have all of your vacuum lines checked and everything consisting of leak tested
If your running stock exhaust with upgraded down pipes this isn't helping anything out really
The faster you can move and get rid of air the more performance you can put to the wheels

Running aftermarket BOV that vents to the atmosphere does screw with our cars but its mainly at idle speed some have problems with stalling out running on stock ECU
No way to tune or correct this issue without some sort of piggy back set up or running full stand alone tunable ECU like a jester chrome or AEM would be preferred....
Piggy back set ups seem to cause a lot of issues on constant battles with flashing and stock ECU telling it NO it needs to do this not what the piggy back is telling it to do Battle between the 2 running into conflicts
So if your wanting to get some power to the ground a really nice wideband and aftermarket full catback and a stand alone ECU with tuning capabilities will probably be your next step
 

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I Wouldnt be driving the car till you have means of pressure testing for vacuum leaks
With it running rich running car for a good while or driving it will put some wear and tare on a good bit of things people really don't pay that much attention to

Destroying Cat converters in exhaust - O2 sensors - fuel in oil - washing rings and rod bearings in some worst case scenarios - wear and tare on your turbos - fouling plugs faster - pitting in piston faces from knock / detonation
Just the top things that this issue could cause
 

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Discussion Starter · #14 ·
What I would do is some intense research on what you wanna do with the car before putting any aftermarket parts in upgrades to the car
Running stock ECU I would leave everything bone stock unless you do plan on getting better performance and increased horse power
Which consists of a lot of components
Front mount innercooler you could run on your stock turbos shouldn't be an issue just make sure you have all of your vacuum lines checked and everything consisting of leak tested
If your running stock exhaust with upgraded down pipes this isn't helping anything out really
The faster you can move and get rid of air the more performance you can put to the wheels

Running aftermarket BOV that vents to the atmosphere does screw with our cars but its mainly at idle speed some have problems with stalling out running on stock ECU
No way to tune or correct this issue without some sort of piggy back set up or running full stand alone tunable ECU like a jester chrome or AEM would be preferred....
Piggy back set ups seem to cause a lot of issues on constant battles with flashing and stock ECU telling it NO it needs to do this not what the piggy back is telling it to do Battle between the 2 running into conflicts
So if your wanting to get some power to the ground a really nice wideband and aftermarket full catback and a stand alone ECU with tuning capabilities will probably be your next step
Could any have asked for a better response, props to you. Thanks for helping, it truly opened a few doors for me. I will search deeper into these problems. Ive been wanting a jester chrome for some time just money is a issue (even tho I just dumped it on a fmic lol) Again I truly appreciate your time and effort to help a rookie out.
 

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Discussion Starter · #15 ·
I Wouldnt be driving the car till you have means of pressure testing for vacuum leaks
With it running rich running car for a good while or driving it will put some wear and tare on a good bit of things people really don't pay that much attention to

Destroying Cat converters in exhaust - O2 sensors - fuel in oil - washing rings and rod bearings in some worst case scenarios - wear and tare on your turbos - fouling plugs faster - pitting in piston faces from knock / detonation
Just the top things that this issue could cause
I have on last question. So what does it seem to go away after driving for a little? Like i said, it happens for the first 5-10 min, then just goes away?
 

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Its trying to compensate for air to fuel trim is what's happening
It's not going anywhere it's still there just because sometimes you can feel it and other times you can not doesn't mean it's still not there because it is still there
 
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