War on Misfires
TReK
Joined: Sep 2010
Posts: 2,073
Likes: 6
From: Ketchikan, Alaska, USA
Lie to your ECU by simulating the presence of the cats.
Perhaps try removing the post cat sensors and zip tie them out of the way. You should be able to find something to plug the holes with at a hardware store, short bolt or something. It may be as simple as the ECU being super sensitive to the sensor readings.
This will at least eliminate or confirm that the issue is caused by the sensors.
I'm not sure a shop can help you, pretty sure it is illegal for them to work on a vehicle that has had the smog stuff gutted out.I doubt they would be willing to commit a felony for whatever they would make on the repairs.
Perhaps try removing the post cat sensors and zip tie them out of the way. You should be able to find something to plug the holes with at a hardware store, short bolt or something. It may be as simple as the ECU being super sensitive to the sensor readings.
This will at least eliminate or confirm that the issue is caused by the sensors.
I'm not sure a shop can help you, pretty sure it is illegal for them to work on a vehicle that has had the smog stuff gutted out.I doubt they would be willing to commit a felony for whatever they would make on the repairs.
Two, any shop can work on a vehicle with the emissions removed by the vehicle owner without breaking any laws. Problem lies in that they may want to install a new cat prior to doing any toubleshooting to bring the vehicle back to stock configuration. If you get a good shop, they can work around that issue IF they know what they are doing.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
How about knock sensors? The ECU tries to compensate for their inputs as well, and can actually have a different timing advance for each cylinder all at the same time. They're on the block, the block (like Elvis) left the building, maybe they are not hooked up? Or mounting has loosened up?
Rock Crawling
Joined: Feb 2012
Posts: 267
Likes: 4
From: Southwest CT
If the post cat 02's have no effect then why does the ECU have post cat trouble codes programmed into it? Because the ECU reads both pre and post cat sensors.
If you can find a shop that is willing to work on the truck with a gutted emissions system then good for you.
If you can find a shop that is willing to work on the truck with a gutted emissions system then good for you.
Baja
Joined: Mar 2010
Posts: 5,584
Likes: 7
From: Pittsburgh PA suburbs.
guess you could also wedge something in the throttle body stop to idle it up and know that your foot was not moving the throttle.
If you want to run it up to a steady rpm and hold it there, you can use the adjustment on the throttle cable to do so.
If you want to run it up to a steady rpm and hold it there, you can use the adjustment on the throttle cable to do so.
Baja
Joined: Mar 2010
Posts: 5,584
Likes: 7
From: Pittsburgh PA suburbs.
Eric you said you repaired the insulation on the wiring, maybe that is a contributor to your problem.
Higgs, Do you need any potentiometers or test jacks? Like I said I have surplus electrical panels that have several of them mounted and could send you some components if you want them.
When I spoke of using a breakout box, I also was thinking if someone had a problematic sensor, they could possibly overide that input with a potentionmeter that they could use to "dial-in" a desired value.
Higgs, Do you need any potentiometers or test jacks? Like I said I have surplus electrical panels that have several of them mounted and could send you some components if you want them.
When I spoke of using a breakout box, I also was thinking if someone had a problematic sensor, they could possibly overide that input with a potentionmeter that they could use to "dial-in" a desired value.
TReK
Joined: Sep 2010
Posts: 2,073
Likes: 6
From: Ketchikan, Alaska, USA
If the post cat 02's have no effect then why does the ECU have post cat trouble codes programmed into it? Because the ECU reads both pre and post cat sensors.
If you can find a shop that is willing to work on the truck with a gutted emissions system then good for you.
If you can find a shop that is willing to work on the truck with a gutted emissions system then good for you.
Thread Starter
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Pro Wrench
Joined: Sep 2011
Posts: 1,526
Likes: 18
From: Oregon
Thanks I tried revving to a constant RPM and it held it rock solid with no variation.
When I replaced the old O2 sensors with new ones I only did the front since I figured the rear were useless anyways, but maybe the rears are used for detecting misfires? Maybe they're bad and causing false alarms? I'll unplug them like HB said. It's an easy test.
When I replaced the old O2 sensors with new ones I only did the front since I figured the rear were useless anyways, but maybe the rears are used for detecting misfires? Maybe they're bad and causing false alarms? I'll unplug them like HB said. It's an easy test.
Last edited by EricTyrrell; Feb 22, 2012 at 04:43 PM.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
ET- attached is Rover manual on the GEMS, has detailed explanation of the misfire monitoring. Read thru it if you have not seen it before. IMHO you may want to revisit the crank position sensor mounting, perhaps even consider another one if easily available. That is the device that is the primary input for timing info to the ECU.
Also covers CAT monitoring.
Also covers CAT monitoring.
Thread Starter
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Pro Wrench
Joined: Sep 2011
Posts: 1,526
Likes: 18
From: Oregon
That document really does point to the CKP as being the only important sensor for misfire monitoring. It also says it takes 15% of ignitions to be considered a catalyst damaging level misfire event. You'd think if my engine were actually misfiring at least 15% of the time I'd feel it right? I'll try to find a good sensor around here to swap and see.