Lean Misfires at 2700-2800 rpm - Page 12 - 3000GT/Stealth International Message Center

DoctorDex · 12-20-2006, 03:10 PM

Quote:

Originally Posted by badass3000

i think diode is CR, ad D might be a potentiometer

I'm pretty sure D is for diode. In Wikipedia (I know this isn't a reliable source), they have pictures of diodes and they are identical to the ones on the board.

badass3000 · 12-20-2006, 03:37 PM

Quote:

Originally Posted by DoctorDex

I'm pretty sure D is for diode. In Wikipedia (I know this isn't a reliable source), they have pictures of diodes and they are identical to the ones on the board.

we're both right.
proof of CR=diode

91STT · 12-21-2006, 07:27 AM

Quote:

Originally Posted by badass3000

we're both right.
proof of CR=diode

CR=crystal rectifier=diode, but D is more commonly used

DoctorDex · 01-02-2007, 03:49 PM

Well, I got my ECU back today and they couldn't find anything wrong with it, except for the fact it was missing a large proportion of the "humi-seal" coating.

As a prophylactic measure, I had the caps changed and a new "humi-seal" coating applied. However, I have serious doubts that either of this two things is causing my problem.

I'll post again, once I have a chance to test the refurbished ECU (many months from now). In the meantime, if anyone has any other ideas they'd be greatly appreciated.

Are there faulty caps in other components that could be causing the misfiring? One component of I've heard of that can cause misfiring is a bad ECS computer. I have no idea how/why the ECS could be related to ignition system, but according to some board users this helped with their hesitation/stumbling. I tried unplugging the ECS and it made no difference... any other ideas?

jwetzler · 01-02-2007, 07:34 PM

Quote:

Originally Posted by tokaygecko

The reason the ECS computer can cause hesitation is that is shares an input with the TPS on the ECU. A fried ECS computer will cause strange things to happen but as FirestormTT mentioned, it is usually a horrible hesitation that results in the car not being very driveable.

Unhooking it worked for me, but from some of my searches, it seems like it's a 50/50 chance on it working.

I got that from the following thread:
long term/knowledeable members...NEED INPUT..car on death bed!

davidm5287 · 01-03-2007, 08:27 AM

Yes, I was told by the mechanics at ESP that when the ECS caps go, the wire that is shared between it, the TPS and the ECU is at first a 5v, but once they go that signal wire now puts out a full 12v which ends up damaging the ECU. Some people have this problem, but I tried it as well without any luck. The guys at ESP and myself are still working out this problem with my 92, so I will let you know the results on the return of my car.

keithmac · 01-03-2007, 11:17 AM

Sounds about right, I suppose one way to protect the ECU would be to fit a diode in the tps line to the ECS unit (just before the connector) that would allow the TPS voltage to be passed to the ECU but would stop a faulty ECS frying the ECU via the tps line?.

May do that to mine for a bit of insurance..

iceman8446 · 01-05-2007, 05:47 PM

Now this may be totally wrong but my friend was having a kinda similar problem with his car and he found out that one of his spark plug wires had a break in it. It was resting on the header and got burned. When he went to pick it up it broke apart in his hands. I'm gonna check out my spark plugs tommarow because I've been wanting too anyway and its supposed to be close to 70 degrees.

davidm5287 · 01-10-2007, 07:56 PM

Well I recieved my car back from ESP a few days ago with no luck finding the problem. I decided yesterday that I would try and tinker around with things, check some connections and small stuff like that. I figured I would try unplugging my O2 sensors and taking it for a drive. As soon as I drove the car without the sensors plugged in the problem is gone. Now the front 02 sensor is brand new, and the back one seemed to be working fine. Either the back one isn't working the best it should be, causing this hesitation or having the car in open loop the entire time is masking this problem. If that is the case it leads me to believe I am coming close to figuring out this problem.

The things that I have done so far are:

-Unplug ECS
-Bypass Fuel pump relay
-Tested and adjusted TPS
-Replaced ISC
-Replaced and rebuilt ECU
-Changed plugs and wires
-no boost/vacuum leaks
-fuel pressure is in check
-I tried advancing the timing to 7.5 without success
-coil packs are fine
-ptu is fine
-replaced PCV valve
-replaced MAS

I am sure there are other things I have tested, but my question is, what other sensors operate as a switch telling the ECU to go from closed loop to open loop. I haven't changed the coolant temp sensor, but I was wondering if this may have any correlation to the problem. Any other input is greatly appreciated.

01-02-2007, 03:49 PM	#115 (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, I got my ECU back today and they couldn't find anything wrong with it, except for the fact it was missing a large proportion of the "humi-seal" coating. As a prophylactic measure, I had the caps changed and a new "humi-seal" coating applied. However, I have serious doubts that either of this two things is causing my problem. I'll post again, once I have a chance to test the refurbished ECU (many months from now). In the meantime, if anyone has any other ideas they'd be greatly appreciated. Are there faulty caps in other components that could be causing the misfiring? One component of I've heard of that can cause misfiring is a bad ECS computer. I have no idea how/why the ECS could be related to ignition system, but according to some board users this helped with their hesitation/stumbling. I tried unplugging the ECS and it made no difference... any other ideas?

01-03-2007, 08:27 AM	#117 (permalink)
davidm5287 Forum Member Join Date: May 2005 Location: Massachusetts Drives: 92 Stealth TT Trader Rating: (4)	Re: Lean Misfires at 2700-2800 rpm Yes, I was told by the mechanics at ESP that when the ECS caps go, the wire that is shared between it, the TPS and the ECU is at first a 5v, but once they go that signal wire now puts out a full 12v which ends up damaging the ECU. Some people have this problem, but I tried it as well without any luck. The guys at ESP and myself are still working out this problem with my 92, so I will let you know the results on the return of my car.

01-03-2007, 11:17 AM	#118 (permalink)
keithmac Forum Member Join Date: Sep 2006 Location: YORK / UK Trader Rating: (1)	Re: Lean Misfires at 2700-2800 rpm Sounds about right, I suppose one way to protect the ECU would be to fit a diode in the tps line to the ECS unit (just before the connector) that would allow the TPS voltage to be passed to the ECU but would stop a faulty ECS frying the ECU via the tps line?. May do that to mine for a bit of insurance.. __________________ JDM GTO TT, Emanage Blue - 450`s Hotwired Walbro - Gutted MAS - K&N Blitz SSBC - Aquamist Water Injection

01-05-2007, 05:47 PM	#119 (permalink)
iceman8446 RWARRR!!! Join Date: Feb 2005 Location: Chadds Ford, Pa Drives: 92 vr4 Trader Rating: (1)	Re: Lean Misfires at 2700-2800 rpm Now this may be totally wrong but my friend was having a kinda similar problem with his car and he found out that one of his spark plug wires had a break in it. It was resting on the header and got burned. When he went to pick it up it broke apart in his hands. I'm gonna check out my spark plugs tommarow because I've been wanting too anyway and its supposed to be close to 70 degrees.

01-10-2007, 07:56 PM	#120 (permalink)
davidm5287 Forum Member Join Date: May 2005 Location: Massachusetts Drives: 92 Stealth TT Trader Rating: (4)	Re: Lean Misfires at 2700-2800 rpm Well I recieved my car back from ESP a few days ago with no luck finding the problem. I decided yesterday that I would try and tinker around with things, check some connections and small stuff like that. I figured I would try unplugging my O2 sensors and taking it for a drive. As soon as I drove the car without the sensors plugged in the problem is gone. Now the front 02 sensor is brand new, and the back one seemed to be working fine. Either the back one isn't working the best it should be, causing this hesitation or having the car in open loop the entire time is masking this problem. If that is the case it leads me to believe I am coming close to figuring out this problem. The things that I have done so far are: -Unplug ECS -Bypass Fuel pump relay -Tested and adjusted TPS -Replaced ISC -Replaced and rebuilt ECU -Changed plugs and wires -no boost/vacuum leaks -fuel pressure is in check -I tried advancing the timing to 7.5 without success -coil packs are fine -ptu is fine -replaced PCV valve -replaced MAS I am sure there are other things I have tested, but my question is, what other sensors operate as a switch telling the ECU to go from closed loop to open loop. I haven't changed the coolant temp sensor, but I was wondering if this may have any correlation to the problem. Any other input is greatly appreciated.