Engine problem, need help!
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4wd Low
Joined: Oct 2008
Posts: 12
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Engine problem, need help!
I just picked up a disco 1, 155k miles but had $2.5k worth of top-end rebuild 5k miles ago. However, right after you crank it it sputters a bit and does not run very smooth also when you rev it up and let off the gas it makes a little popping noise kinda like a soft backfire. The guy I got it from said he thinks the Mass Air Flow sensor is gunked up or something, the air filter is pretty nasty so that could be true. It also does not idle too smoothe[/align]Well here is a more detailed version of what it is doing. Right after it cranks with the key it kinda hesitates/sputters then idles decent. If you rev it up and let off the gas when the rpm's drop it goes down to 750rpm, sounds like its gonna die and then jumps back up to 1000rpm. Any ideas?I know if you disconnect the TPS it should make the Stepper motor step up the rpm's to 2300. I disconnected it and it went to 1700rpm and over the next 30seconds it dwindled slowly to about 1400rpm and I finallyy killed it. I pulled out the stepper motor and cleaned it up a ton. It was nasty, the head no longer looked like a point it looked more like a circle of crap. Anyways, after cleaning it well I put it back in and then removed the TPS again. This time it went to a little over 1000rpm and sat there for a little bit then started jumping down a little and coming back.So from all of that it's pretty obvious that my IACV Stepper motor is bad right, maybe PCV valve? Thanks,Spencer[/align][/align]
TReK
Joined: Apr 2005
Posts: 2,111
Likes: 2
From: Dallas TX
RE: Engine problem, need help!
ORIGINAL: rsm688
I just picked up a disco 1, 155k miles but had $2.5k worth of top-end rebuild 5k miles ago. However, right after you crank it it sputters a bit and does not run very smooth also when you rev it up and let off the gas it makes a little popping noise kinda like a soft backfire. The guy I got it from said he thinks the Mass Air Flow sensor is gunked up or something, the air filter is pretty nasty so that could be true. It also does not idle too smoothe[/align]Well here is a more detailed version of what it is doing. Right after it cranks with the key it kinda hesitates/sputters then idles decent. If you rev it up and let off the gas when the rpm's drop it goes down to 750rpm, sounds like its gonna die and then jumps back up to 1000rpm. Any ideas?I know if you disconnect the TPS it should make the Stepper motor step up the rpm's to 2300. I disconnected it and it went to 1700rpm and over the next 30seconds it dwindled slowly to about 1400rpm and I finallyy killed it. I pulled out the stepper motor and cleaned it up a ton. It was nasty, the head no longer looked like a point it looked more like a circle of crap. Anyways, after cleaning it well I put it back in and then removed the TPS again. This time it went to a little over 1000rpm and sat there for a little bit then started jumping down a little and coming back.So from all of that it's pretty obvious that my IACV Stepper motor is bad right, maybe PCV valve? Thanks,Spencer[/align][/align]
I think you are on the right track.
I just picked up a disco 1, 155k miles but had $2.5k worth of top-end rebuild 5k miles ago. However, right after you crank it it sputters a bit and does not run very smooth also when you rev it up and let off the gas it makes a little popping noise kinda like a soft backfire. The guy I got it from said he thinks the Mass Air Flow sensor is gunked up or something, the air filter is pretty nasty so that could be true. It also does not idle too smoothe[/align]Well here is a more detailed version of what it is doing. Right after it cranks with the key it kinda hesitates/sputters then idles decent. If you rev it up and let off the gas when the rpm's drop it goes down to 750rpm, sounds like its gonna die and then jumps back up to 1000rpm. Any ideas?I know if you disconnect the TPS it should make the Stepper motor step up the rpm's to 2300. I disconnected it and it went to 1700rpm and over the next 30seconds it dwindled slowly to about 1400rpm and I finallyy killed it. I pulled out the stepper motor and cleaned it up a ton. It was nasty, the head no longer looked like a point it looked more like a circle of crap. Anyways, after cleaning it well I put it back in and then removed the TPS again. This time it went to a little over 1000rpm and sat there for a little bit then started jumping down a little and coming back.So from all of that it's pretty obvious that my IACV Stepper motor is bad right, maybe PCV valve? Thanks,Spencer[/align][/align]
I think you are on the right track.
Rock Crawling
Joined: Sep 2008
Posts: 311
Likes: 1
From:
RE: Engine problem, need help!
You might need to have your base idle reset. I would also check forvacuum leaks. Definitely perform tune-up related services such as plugs and wires. A simple way to check for moderate to heavy vacuum leaks is to take a can of throttle body cleaner and, while running, spray around the intake system one area at a time(intake gasket, ports, injectors, anything after the MAF sensor). If you do this and the engine idles up, that means the air has enriched due to the cleaner and there is a vacuum leak at that point. Resolve these issues first, tune-up, then have the base idle set.
Thread Starter
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4wd Low
Joined: Oct 2008
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Likes: 0
RE: Engine problem, need help!
The plugs and the wires were replaced 5k miles ago when the heads were rebuilt. How do you set the base idle? I will check for vaccuum leaks and I am going to replace the PCV valve as well since its cheap.
any other ideas?
Thanks,
Spencer
any other ideas?
Thanks,
Spencer
RE: Engine problem, need help!
There is nothing to replace on the PVC system, just to clean. Pull out the oil seperator and clean it good, also spary carb cleaner into the PCV hose so that you clean any blockage.
But a clogged PCV wont cause these problems.
And remember that the base idle on a DI is 500-750 RPM. If the stepper motor is bad the idle will drop below 500 and the engine will stall.
And just because the plugs and wires were replaced 5,000 miles ago doesnt mean squat. Cheap wires and they will fail in no time flat. Bad wires means weak spark which means fouled plugs.
But a clogged PCV wont cause these problems.
And remember that the base idle on a DI is 500-750 RPM. If the stepper motor is bad the idle will drop below 500 and the engine will stall.
And just because the plugs and wires were replaced 5,000 miles ago doesnt mean squat. Cheap wires and they will fail in no time flat. Bad wires means weak spark which means fouled plugs.
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