Lean Misfires at 2700-2800 rpm - Page 64 - 3000GT/Stealth International Message Center

ProwlerGT · 03-10-2008, 12:42 PM

Quote:

Originally Posted by DoctorDex

I can't help but think that my pressure pulsing problem, in the 2600 rpm - 2900 rpm range is somehow related to this issue. It just seems like too much of a coincidence to have 2 completely different issues that affect the same rpm range. ? Reasonant frequencies perhaps?

"this issue" as in wrong plugs? or what? Man ya lost me there. lol - resonant frequencies? huh? I wanted to take physics in school, but I didn't. lol

DoctorDex · 03-10-2008, 03:11 PM

Quote:

Originally Posted by ProwlerGT

"this issue" as in wrong plugs? or what? Man ya lost me there. lol - resonant frequencies? huh? I wanted to take physics in school, but I didn't. lol

Sorry, what I meant was the pressure pulsing seems as though it must be related to the missing problem. Seems like too much of a coincidence that they both happen in exactly the same rpm range.

DoctorDex · 03-15-2008, 02:15 PM

Its going to be a little while before I can get the scope on my car. My car is temporarily out of commission while I wait for tranny parts.

badass3000 · 03-15-2008, 03:47 PM

what do you need?
I have my OEM tranny on the bench without any plans for it.

with our problem, I just found something that might be the cause of our lifter tick and might have a chance at being the real problem here.
I noticed two of my lifters are soft, while the rest seem super firm.
Ive only tested the few in the general area of where my ticking is coming from.
in the short video below (once it uploads), I first push on a firm lifter (that seems to be normal)
then I push on the other two softer ones.

Im not sure, but I think if a lifter where able to move like this then the valves would not open as much, the 2mm that the lifter gives up could get magnafied by the rocker enough to keep the valve from opening.

DoctorDex · 03-15-2008, 04:20 PM

Excellent work. Looks like I'm checking my lifters next.

PM Sent re: the tranny parts.

ProwlerGT · 03-15-2008, 04:41 PM

Quote:

Originally Posted by DoctorDex

Its going to be a little while before I can get the scope on my car. My car is temporarily out of commission while I wait for tranny parts.

It seems like this is all I am ever saying myself except not just about the tranny, but every other part imagineable.

Dammit I was really excited about the scope results! lol - Guess we'll have to wait.

badass3000 · 03-15-2008, 06:20 PM

heres the video

badass3000 · 03-15-2008, 06:38 PM

Ive got a good feeling about this.
The more I think about it.
The way I see it, lifters arent supposed to move (they will slowly adjust to the proper height but thats it) hense 'solid aftermarket lifters'.
So If these two are broke (collapsed) then when the cam pushes on the rocker, the rocker pushes the lifter down and uses the valve as the pivot point but does not open the valve.
a stuck valve will definatly cause a loss of power.
I cant quite link this to 2800rpm, but maybe thats just a critical speed for the lifter.

ProwlerGT · 03-15-2008, 07:04 PM

This find stands to be the most incredible I've seen yet for this problem and because for 1 it is a "new" find (at least to me) and for 2 it is not something most people would know to look for or ever find because lets face it.... the engine being apart isn't something that happens that often.

I just hope this turns out to be "IT" and I wish that I would've been the one to find it. lol....... me or Dex. lol - but whats important is that if this is "IT" that it was found.

DoctorDex · 03-15-2008, 07:42 PM

So in your video, the two lifters (that are at the same position, ie. same cylinder) have different compressabilities? I've never seen a bad lifter, but that can't be how they are supposed to be.

If I didn't have 3 other separate projects going, I'd run out and check my lifters right now. I guess they'll have to wait until next weekend, but I think I'm going to order at least 6 lifters in advance just in case.

03-15-2008, 02:15 PM	#633 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Edmonton, AB Drives: '91 VR4 - RIP Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm Its going to be a little while before I can get the scope on my car. My car is temporarily out of commission while I wait for tranny parts.

03-15-2008, 03:47 PM	#634 (permalink)
badass3000 Wanted: Traction Problems Join Date: Nov 2002 Location: Jacksonville, Fl Drives: 18 Y.O. "badass" VR4 Trader Rating: (19)	Re: Lean Misfires at 2700-2800 rpm what do you need? I have my OEM tranny on the bench without any plans for it. with our problem, I just found something that might be the cause of our lifter tick and might have a chance at being the real problem here. I noticed two of my lifters are soft, while the rest seem super firm. Ive only tested the few in the general area of where my ticking is coming from. in the short video below (once it uploads), I first push on a firm lifter (that seems to be normal) then I push on the other two softer ones. Im not sure, but I think if a lifter where able to move like this then the valves would not open as much, the 2mm that the lifter gives up could get magnafied by the rocker enough to keep the valve from opening. __________________ ++++++++++JUNE 2007 RIDE OF THE MONTH+++++++++++ Slideshow1..........Slideshow2..........My Photobucket..........My ImageStation.........MOD LIST Questions about the silver car?.....Rear message board info.....Turbo oil cap info.....nicest ass

03-15-2008, 04:20 PM	#635 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Edmonton, AB Drives: '91 VR4 - RIP Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm Excellent work. Looks like I'm checking my lifters next. PM Sent re: the tranny parts. Last edited by DoctorDex : 03-15-2008 at 04:50 PM.

03-15-2008, 06:20 PM	#637 (permalink)
badass3000 Wanted: Traction Problems Join Date: Nov 2002 Location: Jacksonville, Fl Drives: 18 Y.O. "badass" VR4 Trader Rating: (19)	Re: Lean Misfires at 2700-2800 rpm heres the video

03-15-2008, 06:38 PM	#638 (permalink)
badass3000 Wanted: Traction Problems Join Date: Nov 2002 Location: Jacksonville, Fl Drives: 18 Y.O. "badass" VR4 Trader Rating: (19)	Re: Lean Misfires at 2700-2800 rpm Ive got a good feeling about this. The more I think about it. The way I see it, lifters arent supposed to move (they will slowly adjust to the proper height but thats it) hense 'solid aftermarket lifters'. So If these two are broke (collapsed) then when the cam pushes on the rocker, the rocker pushes the lifter down and uses the valve as the pivot point but does not open the valve. a stuck valve will definatly cause a loss of power. I cant quite link this to 2800rpm, but maybe thats just a critical speed for the lifter.

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03-15-2008, 07:04 PM	#639 (permalink)
ProwlerGT King Detail Join Date: Oct 2003 Location: New Orleans area Drives: 95 3000GT Base DOHC Trader Rating: (11)	Re: Lean Misfires at 2700-2800 rpm This find stands to be the most incredible I've seen yet for this problem and because for 1 it is a "new" find (at least to me) and for 2 it is not something most people would know to look for or ever find because lets face it.... the engine being apart isn't something that happens that often. I just hope this turns out to be "IT" and I wish that I would've been the one to find it. lol....... me or Dex. lol - but whats important is that if this is "IT" that it was found.

03-15-2008, 07:42 PM	#640 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Edmonton, AB Drives: '91 VR4 - RIP Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm So in your video, the two lifters (that are at the same position, ie. same cylinder) have different compressabilities? I've never seen a bad lifter, but that can't be how they are supposed to be. If I didn't have 3 other separate projects going, I'd run out and check my lifters right now. I guess they'll have to wait until next weekend, but I think I'm going to order at least 6 lifters in advance just in case.