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Discussion Starter · #1 ·
It is easier to list the components i have not replaced when it comes to fixing this issue.

1993 Vr-4, It had immense electrical issues when i got it 4 years ago. It had this issue before the engine blew and i rebuilt it. I have searched for so long trying to find a solution to this problem.

It revs out to redline in nuetral with no issues, however in gear the car will pull hard until it hits 5000ish rpm then fall on its face, then pull again, fall on its face, pull again then redline. It is a violent bucking.

So new parts/ what i have already done to try and solve the issue.

3SX went through and fixed my wiring, i got a chrome ECU, the entire ignition system- plugs, wires, coils, PTU. Supra fuel pump-was factory wiring but i hotwired it, that help minimally. TPS, Boost leak checked- with the 3SX kit, vacuum delete- done by 3SX, HKS boost controller set up properly, also happens with no boost controller. MAF is new. Injectors are 370cc brand new. also happened with 550s installed. I had all the cats gutted too.

Where im at now is that it could be a faulty blow off valve, crank angle sensor, or replace my fuel pump.- which i strongly dont think it is, looks new and seems to work fine.

My AFRs look fine when it happens, 11.5 ish under boost. The car has been tuned twice recently.

This car is so close to being a monster, i just am at my wits end with this godforsaken issue.

I appreciate any and all input, i am sure i have left things/information out. I am active on here and will answer any questions to the best of my ability.
 

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Which exact plugs were used and at what gap? It could very easily and simply be spark blowout.

It could also be fuel cut/load limiter. A datalog would easily verify that. The reasons behind this vary, and I can only assume that you are BPU with stock 9b turbos despite the flashable ECU. Boost leaks are the usual cause though, and you have not really elaborated on how thoroughly the test was performed.

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Discussion Starter · #3 ·
Which exact plugs were used and at what gap? It could very easily and simply be spark blowout.

It could also be fuel cut/load limiter. A datalog would easily verify that. The reasons behind this vary, and I can only assume that you are BPU with stock 9b turbos despite the flashable ECU. Boost leaks are the usual cause though, and you have not really elaborated on how thoroughly the test was performed.

-sent from my Galaxy Note 9
I have changed plugs probably 6 different times throughout the issue. I have ran iriduims, platinums, but most often and currently running copper plugs. All NGK and gapped to .32 or .40. Currently .40 changed them all last night with valve cover gaskets.
As for fuel, the tuner was adiment that it was NOT a tuning or fuel issue. I had the car converted to OBD2 and i use the 3SX custom scan tool, pretty awesome piece of kit. I can see all the onboard computers and systems with it.
As for the boost leak hypothesis i have checked and re checked the system, fixing minor issues. But keep in mind the same issue is prevalent before and after an entire engine rebuild.
That is why i suggested that my HKS blow off valve may be faulty, i dont know much about them though.
 

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I mean my first reaction was to say it was fuel related, specifically the fuel pump resistor, but you've hotwired it so that shouldn't be an issue. But that "fall on it's face, pull hard, fall on it's face, pull hard" cycle would indicate fuel from my experience.
 

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weird, i also would've said spark blowout/arcing or a bad PTU, but all that stuff is new in your case.

does it always happen around 5000 RPM regardless of the gear you are in?
 

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When my CAS was coming partially unplugged i would get that bucking. Long shot but worth checking.

It could also be that you are hitting fuel cut due to load as Alan mentioned. Something to check with datalogging/monitoring.

Your spark plug gap also seems huge. I had to go down to 0.026'' with coppers to fix my blowout issue with anything over ~9psi. But my coils have 300,000 miles on them. A healthy ignition system might be able to support a larger gap.

Are you able to go past 5000rpm at partial throttle/lower boost?
 
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When my CAS was coming partially unplugged i would get that bucking. Long shot but worth checking.
His being a ’93 it wouldn’t have a CAS unit, just separate crank and cam sensors on timing belt side. Guessing you knew that and just over looked his being a ’93, unless your were thinking maybe one of those sensors coming partially unplugged.
 

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His being a ’93 it wouldn’t have a CAS unit, just separate crank and cam sensors on timing belt side. Guessing you knew that and just over looked his being a ’93, unless your were thinking maybe one of those sensors coming partially unplugged.
Ah yeah missed his year in his OP. But i think the same concept would hold true, if he had an issue with the sensor, plug, or wiring, especially given the history of electrical issues. The only time i ever experienced violent bucking was when that happened to me. I had spark blowout issues on and off for years but it wasn't exactly violent. And in his OP it sounds like he was running WG boost (no boost controller), and it would be surprising to get blowout on low boost.
 
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Discussion Starter · #10 ·
Ah yeah missed his year in his OP. But i think the same concept would hold true, if he had an issue with the sensor, plug, or wiring, especially given the history of electrical issues. The only time i ever experienced violent bucking was when that happened to me. I had spark blowout issues on and off for years but it wasn't exactly violent. And in his OP it sounds like he was running WG boost (no boost controller), and it would be surprising to get blowout on low boost.
So you guys are on board with thinking it may be the crank angle sensor? That was an idea from a post in 2002, didnt know if it was worth the $120 and the trouble to replace. Mine looked fine when putting it back on, but i did not run any tests on it.
I am leaning heavily toward the Crank sensor being at fault.
 

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Discussion Starter · #11 ·
His being a ’93 it wouldn’t have a CAS unit, just separate crank and cam sensors on timing belt side. Guessing you knew that and just over looked his being a ’93, unless your were thinking maybe one of those sensors coming partially unplugged.
I dont think the sensor would be unplugged, since i put it on myself and 2 shops went over most everything. Maybe just a bad or faulty sensor.
 

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I dont think the sensor would be unplugged, since i put it on myself and 2 shops went over most everything. Maybe just a bad or faulty sensor.
I didn’t mean to imply your sensors were loosely plugged, just trying to let jrhorne know that he may have overlooked your car being a ’93 and it wouldn’t have a CAS unit like his car has.

I also don’t think a bad sensor would cause your problem solely at 5000 rpms, either a bad crank or cam sensor I suspect would cause problems even at an idle or with starting. I’d think spark blowout is more likely as bboyalan and jrhorne suggested, especially if plugs are gapped at .040 as you indicated. I’d think jrhorne’s suggestion of .026 is closer to correct for a good performing turbo engine. I've had to run .025 gapped plugs on a blown alcohol burning engine with a 44 amp mag to keep from getting spark blowout.
 

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Discussion Starter · #13 ·
I didn’t mean to imply your sensors were loosely plugged, just trying to let jrhorne know that he may have overlooked your car being a ’93 and it wouldn’t have a CAS unit like his car has.

I also don’t think a bad sensor would cause your problem solely at 5000 rpms, either a bad crank or cam sensor I suspect would cause problems even at an idle or with starting. I’d think spark blowout is more likely as bboyalan and jrhorne suggested, especially if plugs are gapped at .040 as you indicated. I’d think jrhorne’s suggestion of .026 is closer to correct for a good performing turbo engine. I've had to run .025 gapped plugs on a blown alcohol burning engine with a 44 amp mag to keep from getting spark blowout.
No offense taken here, just want to eliminate variables. The issue occurs at other rpms also, just mainly around 5k. Sometimes it is 6k. The car does sometimes sound not right when it fires up, like it stumbles for a second. Others it just fires perfectly right when i turn the key, that happens less often. New starter, old flywheel. (Looked fine)
I can gap the plugs smaller, but with only running 10lbs of boost or wastegate pressure i dont think that would blow out the plugs. Along with the entire system being brand new, i would hope the spark is strong. I believe the manual calls for .44 gap. Could easily be wrong though.
 

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New does not guarantee good. You can try measuring voltage drop at the coils compared to battery/alt.

-sent from my Galaxy Note 9
 

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Yes in any gear, does not matter if i am WOT or ease into it.
But by ease into it, do you mean you are still in boost once you get into the upper RPM?

In other words, what if you accelerately gently, with no boost, up to redline? Can you do that without the issue? If you can NOT, then that would suggest its not spark blowout. If you can rev up to redline without boost, but get the issue when you get into boost (even if you ease into it), that would suggest it might be spark blowout, or could be something else load/boost related.
 
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Discussion Starter · #16 ·
But by ease into it, do you mean you are still in boost once you get into the upper RPM?

In other words, what if you accelerately gently, with no boost, up to redline? Can you do that without the issue? If you can NOT, then that would suggest its not spark blowout. If you can rev up to redline without boost, but get the issue when you get into boost (even if you ease into it), that would suggest it might be spark blowout, or could be something else load/boost related.
It revs happily and perfectly to redline in nuetral, to the best of my knowledge boost amount isnt a factor with the issue. I have a top speed dictated by rpm now because i dont like the bucking, it is very violent.
Say im in 4th gear, no boost. I can climb to 5ish k or a bit more. All in vacuum, no boost. And the issue occurs, so i am limited to 130-140 ish in 4th. Due to rpm limit. Also i did a Vehicle Speed sensor/ capacitor change on my rpm guage and had to reset the needles. I got the rpm one within 50 rpm
 

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Discussion Starter · #17 ·
It revs happily and perfectly to redline in nuetral, to the best of my knowledge boost amount isnt a factor with the issue. I have a top speed dictated by rpm now because i dont like the bucking, it is very violent.
Say im in 4th gear, no boost. I can climb to 5ish k or a bit more. All in vacuum, no boost. And the issue occurs, so i am limited to 130-140 ish in 4th. Due to rpm limit. Also i did a Vehicle Speed sensor/ capacitor change on my rpm guage and had to reset the needles. I got the rpm one within 50 rpm
I wasnt finished typing when i sent that last one, my bad.
The speedo is off by a larger margine than my rpm guage. Says i am going faster than i am (dont tell my passengers) 😆
 

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No, there is not. Search this forum for "coilpack hotwire" if you need a better explanation and illustrations.

-sent from my Galaxy Note 9
 
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It revs happily and perfectly to redline in nuetral, to the best of my knowledge boost amount isnt a factor with the issue. I have a top speed dictated by rpm now because i dont like the bucking, it is very violent.
Say im in 4th gear, no boost. I can climb to 5ish k or a bit more. All in vacuum, no boost. And the issue occurs, so i am limited to 130-140 ish in 4th. Due to rpm limit. Also i did a Vehicle Speed sensor/ capacitor change on my rpm guage and had to reset the needles. I got the rpm one within 50 rpm
Can you datalog?
 
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