3000GT/Stealth International Message Center - View Single Post - Lean Misfires at 2700-2800 rpm

DoctorDex · 04-02-2008, 10:21 PM

Scoped the injectors today and I'm not sure what to make of the findings or if I even found anything at all.

As I'd increase the rpms to the 2600 - 2900 rpm range, the AF would get leaner and the injector pulse widths would gradually increase until the point it would stumble, the rpms would drop, and the injector pulse width would shrink. When I examined a series of pulses I couldn't detect any missed pulses which would explain the sudden drop in rpm. In the end, I was unable to determine whether the injector pulse width was shrinking because of the drop in rpm, or if it was shrinking and causing the drop in rpm.

After running numerous tests, the tech guy I had helping me out thought it must be the ECU cutting fuel. I can't say I'm convinced either way. I guess one way to find out would be to buy a used AEM system and if it doesn't fix the problem, I can always sell it for the price I paid. Now if only I could come up with $1500 for this little experiment...

I think I'm going to try changing the rear lifters first.

Badass: You have an Emanage Ultimate unit right? With that setup can you fully override the stock ECUs injector pulses and can you see the stock ECUs pulses on a log? How are you making out? Have you changed your lifters yet?

04-02-2008, 10:21 PM	#654 (permalink)
DoctorDex Forum Member Join Date: Jul 2005 Location: Edmonton, AB Drives: '91 VR4 - RIP Trader Rating: (16)	Re: Lean Misfires at 2700-2800 rpm Scoped the injectors today and I'm not sure what to make of the findings or if I even found anything at all. As I'd increase the rpms to the 2600 - 2900 rpm range, the AF would get leaner and the injector pulse widths would gradually increase until the point it would stumble, the rpms would drop, and the injector pulse width would shrink. When I examined a series of pulses I couldn't detect any missed pulses which would explain the sudden drop in rpm. In the end, I was unable to determine whether the injector pulse width was shrinking because of the drop in rpm, or if it was shrinking and causing the drop in rpm. After running numerous tests, the tech guy I had helping me out thought it must be the ECU cutting fuel. I can't say I'm convinced either way. I guess one way to find out would be to buy a used AEM system and if it doesn't fix the problem, I can always sell it for the price I paid. Now if only I could come up with $1500 for this little experiment... I think I'm going to try changing the rear lifters first. Badass: You have an Emanage Ultimate unit right? With that setup can you fully override the stock ECUs injector pulses and can you see the stock ECUs pulses on a log? How are you making out? Have you changed your lifters yet? __________________ '91 VR4 - Rebuild in progress: Mods TBA.