Lean Misfires at 2700-2800 rpm - Page 80 - 3000GT/Stealth International Message Center

DoctorDex · 05-20-2008, 09:01 PM

Not sure why they cost so much. Maybe markup?

markoverclock · 05-22-2008, 08:21 PM

i had the exact same problem with mine. i tried to tune around it. but i had to make it pig rich to not misfire. like in the 10's when cold and low 11's when warm. i could feel it loose power during the 2500-3000 rpm band now only thing replaced is the aem. i have it in the 16-17's afr and no misfires (no load of course normal cruising). and now im gettting 19mpg with mosly city driveing(ruffed in tune). i had also replaced my ecu with a reman prior to that i replaced the ecu caps. also tested my emanage ultimate with a known good one. only thing fixed it was replacing it with a stand alone. both tunes were in speed density. i didnt even change the plugs or oil witch is overdue.

i dont know what exactly was going on but its completely gone now.

markoverclock · 05-22-2008, 08:22 PM

Quote:

Originally Posted by DoctorDex

The earliest I might be able to scrounge up enough cash for an AEM will be ~ July/August. Any chance the group buy will still be going on then?

for you ill hook ya at the time when you are ready just pm me.

DoctorDex · 06-12-2008, 07:03 PM

Put some race gas in the tank to see if the knock counts I'm seeing in the suspect rpm range are phantom knock (vs. true knock). The knocking during cruise/revving in neutral was unaffected by the race gas and I continued to see 1-2 counts of knock while revving in neutral, and 1-2 sustained counts of knock (total sum ~ 10 - 12). Therefore, the knock is almost definitely phantom knock.

Anybody have any ideas with regards to the cause? Could the knock sensor be somehow "hearing" the miss? Or maybe its just my noisy valvetrain?

Mike1992 · 06-12-2008, 08:14 PM

I had alot of phantom knock in my old dsm. New set of lifters cured it

badass3000 · 06-15-2008, 07:12 PM

I am going to put my stock heads back on when I get home from the NG.
12 hrs there and 12 hrs back should give me plenty of time to run some tests to see if I notice anything else.

badass3000 · 06-22-2008, 09:56 PM

alright, try to keep this short.
I discussed my problem with some 3S vets at the NG, gave some a quick ride but came up short.
then I gave a ride to Gray Haze (Grayson), for some reason the car acted fine so I couldnt show him the problem but he suggested that I throw more fuel at it.
so on the way home thats what I did.
Now I am at 14:1 most of cruzzing (20in/hg of vac),
then it dips to 13:1 around 10in/hg/-5psi
about 12:1 around 0psi,
11:1 at any boost.
and the car drives like a dream!! Damn near perfect.

the only thing is, in the situation where the car would have hesitated before,
now my knock sensor goes crazy. only in the 2500-3K zone and only with a least a little bit of load, 10in/hg or more boost.
I saw counts as high as 20 with a 13:1 AF, with 10in/hg, theres just no reason for that.

so here is what I think is going on.
I think we are dealing with only a few or one cylinders.
I think somehow its not getting enough fuel.
before the extra fuel I think a cylinder would have been way too lean to even ignite but now with the extra fuel that cylinder is now still lean, but rich enough to ignite with a hot lean combustion that results in lots of knock.

I am going to check my plugs here in a min and hopefully one looks totaly different than the others.
if not, then I might need to record individual PW or put WB sensors in each runner.

badass3000 · 06-23-2008, 10:46 AM

anyone see anything?

the gap on #3 in that last pic looks small. but there all the same, its just the angle.

DoctorDex · 07-12-2008, 04:25 PM

Well looks like I'm going to have to put off getting the AEM. My car has much bigger problems: Catastrophic engine failure, suspect pre-ignition (Pics to follow)

Not sure whether to part it out and give up or hold on to it until I can get it back together.

DoctorDex · 07-23-2008, 05:42 PM

I just got my oil analysis results back from blackstone. These results were sent away ~ 2 weeks before I destroyed my motor.

It appears the high levels of iron in my oil essentially fixed itself, therefore, this was not related to the missing. The only difference between then and now is that I recently switched to Amsoil 20W50 full synthetic racing oil. Interestingly, enough wear characteristics were improved across the board for all indicators (Amsoil 20W50 > Royal Purple 20W50 > Mobil1 10W30). The only negative in my report was that I had 2.3% fuel dilution in my oil, which effectively made the 20W50 into 10W40. I attribute this to the recent development of an extremely rich idle condition that occurs only when the car is _hot_. I have been unable to come up with an explanation of why it has been occurring and I am unsure as to whether or not it is related to the misfire problem, or if it is just another red herring. Hopefully I'll be able to come up with the cash for an AEM by spring, along with the money for a shortblock, heads and transaxle rebuild. Talk about a money pit.

05-20-2008, 09:01 PM	#791 (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 Not sure why they cost so much. Maybe markup? __________________ '91 VR4 - Modlist: DR650R turbos, Snow stage 2D alky kit, DSM SMICs, blowthrough ported LT1 MAS, Dejon Tool intakes & y-pipe, Blitz DSBC Spec R, HKS SSQV BOV, PTE 580cc injectors, Dual feed fuel system with Aeromotive FPR & filter, Hotwired Supra pump, HKS DLI, MSD Wires, Apex'i S-AFC II, MAFTranslator, Turbobob ECU, Scanmaster III, LC-1 WBO2, ESP downpipe, Vac/EGR delete, Gutted precats and test pipe, Maximal solid mounts, 300m 18 spline output shaft, Centerforce Dual Friction clutch, RPS flywheel, GC coilover conversions with helper springs, Powerslot slotted rotors, Goodridge SS brake lines, Hawk pads (front), Stillen metal matrix pads (rear)

05-22-2008, 08:21 PM	#792 (permalink)
markoverclock Forum Member Join Date: Sep 2005 Location: Tomball,Tx Drives: 92 RT-TT Trader Rating: (43)	Re: Lean Misfires at 2700-2800 rpm i had the exact same problem with mine. i tried to tune around it. but i had to make it pig rich to not misfire. like in the 10's when cold and low 11's when warm. i could feel it loose power during the 2500-3000 rpm band now only thing replaced is the aem. i have it in the 16-17's afr and no misfires (no load of course normal cruising). and now im gettting 19mpg with mosly city driveing(ruffed in tune). i had also replaced my ecu with a reman prior to that i replaced the ecu caps. also tested my emanage ultimate with a known good one. only thing fixed it was replacing it with a stand alone. both tunes were in speed density. i didnt even change the plugs or oil witch is overdue. i dont know what exactly was going on but its completely gone now.

06-12-2008, 07:03 PM	#794 (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 Put some race gas in the tank to see if the knock counts I'm seeing in the suspect rpm range are phantom knock (vs. true knock). The knocking during cruise/revving in neutral was unaffected by the race gas and I continued to see 1-2 counts of knock while revving in neutral, and 1-2 sustained counts of knock (total sum ~ 10 - 12). Therefore, the knock is almost definitely phantom knock. Anybody have any ideas with regards to the cause? Could the knock sensor be somehow "hearing" the miss? Or maybe its just my noisy valvetrain?

06-12-2008, 08:14 PM	#795 (permalink)
Mike1992 DSM GURU Join Date: Apr 2007 Location: Springfield, Mo Drives: 91 Stealth RT/TT Trader Rating: (25)	Re: Lean Misfires at 2700-2800 rpm I had alot of phantom knock in my old dsm. New set of lifters cured it __________________ 1992 Mitsubishi 3000GT VR-4 RIP 3/06 1990 Eagle Talon TSI AWD - 11.29@126 - SOLD 1991 Dodge Stealth RT/TT - Traded 1992 Eagle Talon TSI AWD - Where fast really is cheap

06-15-2008, 07:12 PM	#796 (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 I am going to put my stock heads back on when I get home from the NG. 12 hrs there and 12 hrs back should give me plenty of time to run some tests to see if I notice anything else.

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06-22-2008, 09:56 PM	#797 (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 alright, try to keep this short. I discussed my problem with some 3S vets at the NG, gave some a quick ride but came up short. then I gave a ride to Gray Haze (Grayson), for some reason the car acted fine so I couldnt show him the problem but he suggested that I throw more fuel at it. so on the way home thats what I did. Now I am at 14:1 most of cruzzing (20in/hg of vac), then it dips to 13:1 around 10in/hg/-5psi about 12:1 around 0psi, 11:1 at any boost. and the car drives like a dream!! Damn near perfect. the only thing is, in the situation where the car would have hesitated before, now my knock sensor goes crazy. only in the 2500-3K zone and only with a least a little bit of load, 10in/hg or more boost. I saw counts as high as 20 with a 13:1 AF, with 10in/hg, theres just no reason for that. so here is what I think is going on. I think we are dealing with only a few or one cylinders. I think somehow its not getting enough fuel. before the extra fuel I think a cylinder would have been way too lean to even ignite but now with the extra fuel that cylinder is now still lean, but rich enough to ignite with a hot lean combustion that results in lots of knock. I am going to check my plugs here in a min and hopefully one looks totaly different than the others. if not, then I might need to record individual PW or put WB sensors in each runner. __________________ ++++++++++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 Last edited by badass3000 : 06-23-2008 at 09:59 AM.

06-23-2008, 10:46 AM	#798 (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 anyone see anything? the gap on #3 in that last pic looks small. but there all the same, its just the angle.

07-12-2008, 04:25 PM	#799 (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 Well looks like I'm going to have to put off getting the AEM. My car has much bigger problems: Catastrophic engine failure, suspect pre-ignition (Pics to follow) Not sure whether to part it out and give up or hold on to it until I can get it back together.

07-23-2008, 05:42 PM	#800 (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 I just got my oil analysis results back from blackstone. These results were sent away ~ 2 weeks before I destroyed my motor. It appears the high levels of iron in my oil essentially fixed itself, therefore, this was not related to the missing. The only difference between then and now is that I recently switched to Amsoil 20W50 full synthetic racing oil. Interestingly, enough wear characteristics were improved across the board for all indicators (Amsoil 20W50 > Royal Purple 20W50 > Mobil1 10W30). The only negative in my report was that I had 2.3% fuel dilution in my oil, which effectively made the 20W50 into 10W40. I attribute this to the recent development of an extremely rich idle condition that occurs only when the car is _hot_. I have been unable to come up with an explanation of why it has been occurring and I am unsure as to whether or not it is related to the misfire problem, or if it is just another red herring. Hopefully I'll be able to come up with the cash for an AEM by spring, along with the money for a shortblock, heads and transaxle rebuild. Talk about a money pit.