Hi everyone,
I have a 1995 Discovery 3.9L V8 MFI, left hand drive, with 97,000 miles that I've had for about 3 years. There are no modifications and I keep it on the roads.
About 6 months ago I started getting the check engine indicator and fault code 48 for the stepper motor / idle control valve. I reset the fault and it would come back every week or two. Since then it has progressed to rougher starts and twice has not started at all, the fault code comes every day or two now. When the engine is cool, or is restarted almost immediately (less than time to fill the gas tank) it starts up perfectly. When the rough starts occur it is always after the engine is at operating temps and the car has been parked for between 5 and 30 minutes. During these rough starts the engine fires and the RPMs go to 1500 and then as it settles down to idle it begins to faulter and sound like the pistons are going to go through the hood when the RPMs start to drop below 500 and would die if I didn't give it the acellerator to keep the RPMs up around 1000. After a minute or two of keeping the RPMs at 1000 I'll let it go back to normal idle, then I can drive away and it runs perfectly like nothing ever happened. On the two occassions that it didn't start at all, the engine would crank and turn over but would not fire - waited a half hour and then it started right up and ran fine.
Here is what I have done to the car while trying to fix this problem, in order
None of these seemed to improve or worsen the condition.
replaced pcv restrictor and hoses
replaced all the vacuum hoses
replaced O ring on stepper motor
replaced spark plugs (Bosch), plug wires (BWD), distributor cap and rotor button (BWD I think)
replaced stepper motor
air intakes look pretty clean
replaced fuel filter (Fram)
replaced coolant temperature sensor and washer
replaced fuel temperature sensor (Lucas)
A couple seemingly unrelated repairs during this time:
replaced bleed hose from coolant tank to radiator
replaced fuel tank filler breather hose
repaired rear window ECU by replacing solder joint on ECU
replaced A/C hose and refill.
I'm starting to go a bit crazy trying to fix this but I can't afford to keep throwing money at it.
These are some things I'm considering and could really use some help in what I should do.
1. I just noticed the under side of the throttle position sensor has two copper wires exposed - could this cause the problem. Can I use electrical tape to cover or is the heat too much?
2. After filling gas tank, I usually get a rough start as described above, could the release of pressure in gas tank contribute to that? fuel pressure regulator?
3. grounding problem? I cleaned off one near the battery, but where are other locations
4. spark. Is there a problem with distributor or ignition coil. I was going to use a spare spark plug to check for spark. I also just got a test light to check on coil too. Probably this weekend.
5. The main relay and fuel pump relay? I thought I read somewhere heat can be a problem for them sometimes.
6. When I replaced the fuel temp sensor last night, I pulled off the pcv hoses for access and there was a little oil inside the hoses...is that normal?
7. am I right in thinking this disco is not OBD II compliant? it only has the fault code output under the passanger seat, right?
Sorry for being so long, I wanted to give as complete of a picture as I could. This is my first post, but this forum has been a great resource for me and my wallet. Thank you all very much.
Eric
I have a 1995 Discovery 3.9L V8 MFI, left hand drive, with 97,000 miles that I've had for about 3 years. There are no modifications and I keep it on the roads.
About 6 months ago I started getting the check engine indicator and fault code 48 for the stepper motor / idle control valve. I reset the fault and it would come back every week or two. Since then it has progressed to rougher starts and twice has not started at all, the fault code comes every day or two now. When the engine is cool, or is restarted almost immediately (less than time to fill the gas tank) it starts up perfectly. When the rough starts occur it is always after the engine is at operating temps and the car has been parked for between 5 and 30 minutes. During these rough starts the engine fires and the RPMs go to 1500 and then as it settles down to idle it begins to faulter and sound like the pistons are going to go through the hood when the RPMs start to drop below 500 and would die if I didn't give it the acellerator to keep the RPMs up around 1000. After a minute or two of keeping the RPMs at 1000 I'll let it go back to normal idle, then I can drive away and it runs perfectly like nothing ever happened. On the two occassions that it didn't start at all, the engine would crank and turn over but would not fire - waited a half hour and then it started right up and ran fine.
Here is what I have done to the car while trying to fix this problem, in order
None of these seemed to improve or worsen the condition.
replaced pcv restrictor and hoses
replaced all the vacuum hoses
replaced O ring on stepper motor
replaced spark plugs (Bosch), plug wires (BWD), distributor cap and rotor button (BWD I think)
replaced stepper motor
air intakes look pretty clean
replaced fuel filter (Fram)
replaced coolant temperature sensor and washer
replaced fuel temperature sensor (Lucas)
A couple seemingly unrelated repairs during this time:
replaced bleed hose from coolant tank to radiator
replaced fuel tank filler breather hose
repaired rear window ECU by replacing solder joint on ECU
replaced A/C hose and refill.
I'm starting to go a bit crazy trying to fix this but I can't afford to keep throwing money at it.
These are some things I'm considering and could really use some help in what I should do.
1. I just noticed the under side of the throttle position sensor has two copper wires exposed - could this cause the problem. Can I use electrical tape to cover or is the heat too much?
2. After filling gas tank, I usually get a rough start as described above, could the release of pressure in gas tank contribute to that? fuel pressure regulator?
3. grounding problem? I cleaned off one near the battery, but where are other locations
4. spark. Is there a problem with distributor or ignition coil. I was going to use a spare spark plug to check for spark. I also just got a test light to check on coil too. Probably this weekend.
5. The main relay and fuel pump relay? I thought I read somewhere heat can be a problem for them sometimes.
6. When I replaced the fuel temp sensor last night, I pulled off the pcv hoses for access and there was a little oil inside the hoses...is that normal?
7. am I right in thinking this disco is not OBD II compliant? it only has the fault code output under the passanger seat, right?
Sorry for being so long, I wanted to give as complete of a picture as I could. This is my first post, but this forum has been a great resource for me and my wallet. Thank you all very much.
Eric
