Misfire when warm, can't go over 2000 RPMs
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2nd Gear
Joined: Nov 2011
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Misfire when warm, can't go over 2000 RPMs
I just picked up a 97 Discovery. It has a problem after it warms up for a couple minutes. I can't get it to go over 2000RPMs and after driving for about 2 minutes it hesitates bad and cut out. Flashing CE light. Backfire if I rev past 2K while under a load. Does ok while idling in park. I do have a ton of codes for O2 sensors, cylinder 8 misfire, catalytic converter. I thought the cats could be clogged so I cut them out and put straight through pipes in their place. Changed all the plugs and wires. I do have a coolant leak blowing out of the rear drivers side of the block. No mix of oil and water even though I pretty sure that gasket is trashed. Any ideas? I thought about testing the O2 sensors and the ignition coil but I can't find the test procedures for either of these even though I read through the rave.
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Joined: Jan 2011
Posts: 16,322
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From: Savannah Georgia
Throttle position sensor can cause that "can't get over 1750 rpm". Flashing light is "turn off the truck dude" indicator.
This note from RAVE engine management about the TPS:
the ECM will initiate overrun fuel cut off.
If you have a code scanner that can read live data, you can watch your TPS % and see if it changes smoothly.
You could also have problems with fuel pressure, there is tire valve on the pasenger side fuel rail, shold be in the 32-34 PSI range. Fuel filter cold be plugged up, under passenger rear wheel well.
Your head gasket leak is a big problem for some of the codes if it is also leaking inside. Obviously coolant loss and overheating will kill the engine. You can see from the pix that gasket does not have much meat in that area, so an external leak does not have far to go to become an internal one.
This note from RAVE engine management about the TPS:
As there is no default strategy,
failure of the sensor will result in poor idle and lack of
throttle response. If failure occurs in the closed
position the engine will only reach 1750 rev/min when
failure of the sensor will result in poor idle and lack of
throttle response. If failure occurs in the closed
position the engine will only reach 1750 rev/min when
the ECM will initiate overrun fuel cut off.
If you have a code scanner that can read live data, you can watch your TPS % and see if it changes smoothly.
You could also have problems with fuel pressure, there is tire valve on the pasenger side fuel rail, shold be in the 32-34 PSI range. Fuel filter cold be plugged up, under passenger rear wheel well.
Your head gasket leak is a big problem for some of the codes if it is also leaking inside. Obviously coolant loss and overheating will kill the engine. You can see from the pix that gasket does not have much meat in that area, so an external leak does not have far to go to become an internal one.
Last edited by Savannah Buzz; Feb 21, 2012 at 04:21 AM.
Thread Starter
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2nd Gear
Joined: Nov 2011
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Thanks. Wow, that head gasket is so narrow. Those things must crap out all the time. Do you have test procedures for the TPS or MAF? Just need to figure out what pins to put on the meter and what voltage/ohms I should be seeing.
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