Lean Misfires at 2700-2800 rpm - Page 2 - 3000GT/Stealth International Message Center

AudioPmp23 · 09-25-2006, 12:49 PM

Just a thought.... did you still retain the high/low voltage switching relay for the fuel pump when you did your hotwire?

AudioPmp23 · 09-25-2006, 05:54 PM

Yeah, that looks right. Did you cut the wire going to the FP (capping off stock relay output and using aftermarket relay output) and disconnect the resistor from the circuit?

Come to think of it, if the stock switching is still connected, the voltage spike might tweak out the system for a second.

DoctorDex · 09-26-2006, 06:57 AM

Quote:

Originally Posted by AudioPmp23

Yeah, that looks right. Did you cut the wire going to the FP (capping off stock relay output and using aftermarket relay output) and disconnect the resistor from the circuit?

I tapped into the line after the relay and/or resistor so as to run the line in parallel to the stock circuit. I figured since I have stock wiring running to the back, why not take advantage of it and it use it also.

The stock switching/relay system is still more or less connected. However, I disconnected the input (5) to the stock relay, which results in the relay being bypassed at all times. The relay can still switch back and forth, but when it does, it doesn't do anything because there is no input power source. This also has the effect of eliminating/bypassing the the resistor.

Declan

DoctorDex · 09-26-2006, 06:22 PM

Quote:

Originally Posted by keithmac

Declan, could you post picks of your blow through setup please, interested in having a go at this myself.

Here are the pics you requested. I apologize for the somewhat ghetto looking engine bay.

If you're wondering why I have a breather filter on the HKS SSQV, its because at one point in time, I tapped a line in to the bottom of the SSQV and I was using it as a "turbo bypass" in order to help with compressor surge. This didn't work so well with the MAF only a few inches away as it created a load of turbulence and it would really screw with my AFRs. I have since done away with the "bypass" but I just haven't gotten around to removing the filter.

Declan

keithmac · 10-01-2006, 04:30 PM

Cheers for the pics!

DoctorDex · 10-01-2006, 04:52 PM

I tried disconnecting my EGR to see if this would help and it did not help. I'm still of the opinion that I have an exhaust leak on the front bank. I'm going to put some combustion chamber cleaner in tonight to see if I can see a leak.

Declan

TurboBob · 10-01-2006, 08:14 PM

Take the BOV off and cap the fitting as a test. There may be air sneaking in at part throttle and messing with the MAF....

Bob

DoctorDex · 10-01-2006, 09:05 PM

Thanks for the suggestion, but I did away with the fitting when I switched to blow through (a number of months ago) because of the problem you describe. Air was sneaking in at idle/part throttle which was causing turbulence.

You'd think that turbulent air would cause the MAF to see more air than there really is, but for some reason, it did the opposite. The turbulencec made me run really lean (the MAF saw less air than there was). I no idea why it works this way, does anybody else know why this would be?

Declan

DoctorDex · 10-07-2006, 05:10 PM

Initially, I thought this problem was due to an exhaust leak on the front bank, because when I pulled the DP a few weeks back, I noticed that my rear exhaust manifold was white (lean) and my front was black (rich). However, I'm starting to wonder if its something else.

Today, I drove home to visit the parents and while doing some short WOT pulls, I noticed that I was getting, what looks like, heavy spark blow out on my rear bank. My rear O2 voltages were dipping as low as 0.60V, @WOT, in between 4600 - 6000 rpm and then it would start to knock.

At WOT, despite the voltages being as low as they were, I couldn't feel/hear any spark blow out and the voltages weren't bouncing around like they do with spark blow out.

In addition to the above mentioned issue, I still have the lean misfires anywhere below 3000rpm, but it is definitely worse between 2700-2800rpm. Contrary to what I thought before, it doesn't seem to make much difference, if I'm in closed loop or open loop, so long as I'm under 3000rpm it wants to miss.

Does this sound like spark blow out? Or it could it be an exhaust leak? Could it be bad wires, or does it sound like something else?

At the moment, I'm running ngk iridiums gapped to .028, new stock coils, NGK resistor wires, @ 17.5 psi of boost.

I'm almost at my wits end with this problem and _any_ help would be greatly appreciated.

Thanks.

Declan

badass3000 · 10-08-2006, 09:50 AM

I think i just started getting this too.
dont know why, it just started one day. Backfire/loss of power ~2700 rpm.
in for help too..

09-25-2006, 12:49 PM	#11 (permalink)
AudioPmp23 Getrag Wrestler Join Date: Aug 2003 Location: Lakewood CO Drives: Pearl White 93 VR-4 Trader Rating: (3)	Re: Lean Misfires at 2700-2800 rpm Just a thought.... did you still retain the high/low voltage switching relay for the fuel pump when you did your hotwire? __________________ Hi my name's Nate and I've been addicted to boost for four years now...

09-25-2006, 05:54 PM	#12 (permalink)
AudioPmp23 Getrag Wrestler Join Date: Aug 2003 Location: Lakewood CO Drives: Pearl White 93 VR-4 Trader Rating: (3)	Re: Lean Misfires at 2700-2800 rpm Yeah, that looks right. Did you cut the wire going to the FP (capping off stock relay output and using aftermarket relay output) and disconnect the resistor from the circuit? Come to think of it, if the stock switching is still connected, the voltage spike might tweak out the system for a second. Last edited by AudioPmp23 : 09-25-2006 at 06:04 PM.

10-01-2006, 04:30 PM	#15 (permalink)
keithmac Forum Member Join Date: Sep 2006 Location: YORK / UK Trader Rating: (1)	Re: Lean Misfires at 2700-2800 rpm Cheers for the pics!

10-01-2006, 04:52 PM	#16 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Saskatoon, SK Drives: '91 VR4 Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm I tried disconnecting my EGR to see if this would help and it did not help. I'm still of the opinion that I have an exhaust leak on the front bank. I'm going to put some combustion chamber cleaner in tonight to see if I can see a leak. Declan

10-01-2006, 08:14 PM	#17 (permalink)
TurboBob Resident mad scientist Join Date: Jan 2003 Location: Near Detroit Drives: 86 GN 91 RT/TT Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm Take the BOV off and cap the fitting as a test. There may be air sneaking in at part throttle and messing with the MAF.... Bob __________________ Need a datalogger? Check out the Scanmaster 3 PM me about ECU mods for 8000+ RPM rev limits !!!!!!!! Stock = 7300 RPM Stage 1 = 8060 RPM Stage 2 = 8200 RPM Stage 3 = 8400 RPM Stage 4 = 8800 RPM (By request only) 1991 Stealth RT/TT, Grooms Shortblock, 13G's, Translator Pro, www.maftpro.com

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10-01-2006, 09:05 PM	#18 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Saskatoon, SK Drives: '91 VR4 Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm Thanks for the suggestion, but I did away with the fitting when I switched to blow through (a number of months ago) because of the problem you describe. Air was sneaking in at idle/part throttle which was causing turbulence. You'd think that turbulent air would cause the MAF to see more air than there really is, but for some reason, it did the opposite. The turbulencec made me run really lean (the MAF saw less air than there was). I no idea why it works this way, does anybody else know why this would be? Declan

10-07-2006, 05:10 PM	#19 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Saskatoon, SK Drives: '91 VR4 Trader Rating: (13)	Re: Lean Misfires at 2700-2800 rpm Initially, I thought this problem was due to an exhaust leak on the front bank, because when I pulled the DP a few weeks back, I noticed that my rear exhaust manifold was white (lean) and my front was black (rich). However, I'm starting to wonder if its something else. Today, I drove home to visit the parents and while doing some short WOT pulls, I noticed that I was getting, what looks like, heavy spark blow out on my rear bank. My rear O2 voltages were dipping as low as 0.60V, @WOT, in between 4600 - 6000 rpm and then it would start to knock. At WOT, despite the voltages being as low as they were, I couldn't feel/hear any spark blow out and the voltages weren't bouncing around like they do with spark blow out. In addition to the above mentioned issue, I still have the lean misfires anywhere below 3000rpm, but it is definitely worse between 2700-2800rpm. Contrary to what I thought before, it doesn't seem to make much difference, if I'm in closed loop or open loop, so long as I'm under 3000rpm it wants to miss. Does this sound like spark blow out? Or it could it be an exhaust leak? Could it be bad wires, or does it sound like something else? At the moment, I'm running ngk iridiums gapped to .028, new stock coils, NGK resistor wires, @ 17.5 psi of boost. I'm almost at my wits end with this problem and _any_ help would be greatly appreciated. Thanks. Declan

10-08-2006, 09:50 AM	#20 (permalink)
badass3000 Wanted: Traction Problems Join Date: Nov 2002 Location: Jacksonville, Fl Drives: one "badass" VR4 Trader Rating: (18)	Re: Lean Misfires at 2700-2800 rpm I think i just started getting this too. dont know why, it just started one day. Backfire/loss of power ~2700 rpm. in for help too.. __________________ ++++++++++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