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Discussion Starter #1
Ok,
I have a 3.9 EFI installed with ZF auto in my 1988. Since the conversion we have had a problem with the engine progressively running worse over time. Unplugging the battery to reset the system results in better operation for a short bit and the cycle continues. We thought the primary issue was that we did not have a transducer installed resulting in too rich a mixture. Added a transducer and it does appear to be better but still having some issues. When starting the truck cold it seems to stumble and search for idle. It eventually evens out but once I put it in gear and apply a little pressure to the accelerator it wants to stall. It acts starved or flooded, hard to tell. More pressure applied gets it going relatively smoothly but if I quickly take my foot of the accelerator or come to a stop it tries to stall. It appears to get better as the truck warms up. I have only driven it about 50 miles since the transducer install so it could still be the same problem as before. Will drive more today to see if it evens out, stays the same or continues to progress in the evil cycle. Any ideas?

Also, the fuel gauge is not functioning properly. It goes to empty when the car is off but seems to read 3/4 full regardless of fuel level when on. I know the mechanic had a fit getting the gauge to read at all but not sure this is any better. prior to the engine and transmission replacement the gauge worked fine - a quick search shows that it is likely a grounding issue. my question here is how many of you have fuel gauge issues? Seems that many of us defender owners just use our miles trip counter?
 

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I use the trip odometer even though my gauge works,as I have had grounding issues in the past and when I figure out the gauge is inop, I will be out of fuel.

As for the motor stalling, my guess is the idle air control.

Just my $0.02
 

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Was the efi pulled from a vehicle running/running well? What are the qualifications of the mechanic who performed the conversion? Codes?

As far as the gas gauge goes, if tinkering with the ground doesn't help, you can always drain the tank to see what it reads @ actual empty and @ actual, say, 1 gallon? Mine stays on "Full" until it's pretty darn low & then starts moving to 3/4 where it's @ actual empty. I wouldn't settle for a haywire gauge reading without at least replacing the sender & gauge after ensuring that it's not simply the ground.
 

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Discussion Starter #4
Great questions cowboy. I was told that everything was good on the engine it came from but I cannot confirm that. I have been driving it each day to work out the bugs and there are some specific symptoms that have become consistent:
1. when sitting overnight the truck struggles to idle when I crank it in the morning. It will hunt for a consistent idle and then, once the engine starts to warm, settle in and smooth out. It does not stall if left alone during this process but can stall if I tap the accelerator
2. once the engine is warm it runs well and seems to maintain a good idle
3. Once warm and running more smoothly it is still possible for me to quickly press and release the gas pedal and cause the truck to stumble. it corrects itself after stumbling and does not stall
4. When parked for several hours and the engine cools down it may still run a little rough upon start but transitions much faster than when sitting overnight.
5. The idle hunting does not feel like a traditional misfire and I do not get any noticable blue or black smoke out of the exhaust

I am leaning towards a throttle body or idle control valve issue - any additional thoughts from the experts?
 

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First things to check for are vacuum leaks. These can be a missing or cracked hose, a bad seal between the plenum housings, or even a stuck-open stepper motor. Vacuum leaks will give you fits, making you think you have all kinds of problems when you really don't.
Next is to be sure that you are getting good fuel flow. Starvation from low fuel pressure can also make the engine run poorly.
Lastly check on things like missing or inoperative sensors, road speed sensor, map sensor, etc. Also be sure that you have a good battery that you're not experiencing low voltage or bad grounding issues.
That should give you enough to poke at this evening...
 

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A stepper motor and/or a MAF sensor problem is sometimes just that your existing ones need cleaning, right? And there is also something for those EFI systems called a "pvc kit" - would a pvc kit address some of the problems that 02batsea listed?

No expert, but I have been stalking similar symptoms on a '91 RRC oem efi...
 

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You really need to take the workshop manual and go through a check of each item. Anything else is hunting in the dark. The troubleshooting guide in the manual is easy to follow and you will rule out each item.

Are ALL of teh sensors from the original vehicle installed?
 

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Discussion Starter #10
Red90, I don't really know the answer to your last question. I will try to find out. I am going to try to take a look / clean the MAF and stepping motor as well as check fuel pressure. I am starting to wonder if I have a problem with the fuel pressure levels dropping over night. Will let you all know if I find anything out.

On a different note, I am very new to dealing with defenders. I have driven a 1995 RRC for the last 12 years and have very little issues with them. I am mechanically inclined and pretty analytical when I can dedicate time to things, but have little experience with working on these trucks. Where can I get a correct workshop manual? Those are very helpful and I restored a 65 mustang when in high school by using one.
 

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Lets test the amplifier and coil to see if the spark is consistently strong. Parts that you will need some day that are well worth buying include Dizzy cap. plug wires and rotor.
Mine stumble and stalled at cold. Ran ok with slight misfire when warm. Utimately cured with new cap and rotor.
 

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Ok,
I have a 3.9 EFI installed with ZF auto in my 1988. Since the conversion we have had a problem with the engine progressively running worse over time. Unplugging the battery to reset the system results in better operation for a short bit and the cycle continues. We thought the primary issue was that we did not have a transducer installed resulting in too rich a mixture. Added a transducer and it does appear to be better but still having some issues. When starting the truck cold it seems to stumble and search for idle. It eventually evens out but once I put it in gear and apply a little pressure to the accelerator it wants to stall. It acts starved or flooded, hard to tell. More pressure applied gets it going relatively smoothly but if I quickly take my foot of the accelerator or come to a stop it tries to stall. It appears to get better as the truck warms up. I have only driven it about 50 miles since the transducer install so it could still be the same problem as before. Will drive more today to see if it evens out, stays the same or continues to progress in the evil cycle. Any ideas?

Also, the fuel gauge is not functioning properly. It goes to empty when the car is off but seems to read 3/4 full regardless of fuel level when on. I know the mechanic had a fit getting the gauge to read at all but not sure this is any better. prior to the engine and transmission replacement the gauge worked fine - a quick search shows that it is likely a grounding issue. my question here is how many of you have fuel gauge issues? Seems that many of us defender owners just use our miles trip counter?
Air idle control valve is a very common fault that would lead to the symptoms you decribe.

You can unplug it and unscrew it from the plenum and give it a spraying with a copious amount of carb cleaner ... often that will clean the residue that makes it sticky.

alternatively non-genuine spares are cheap.
 

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In the past you had replaced yours with AICV from Autozone? Is still holding well, or you had replaced them with something else? Is the AICV located on the top left corner of the plenum when facing the plenum?

Air idle control valve is a very common fault that would lead to the symptoms you decribe.

You can unplug it and unscrew it from the plenum and give it a spraying with a copious amount of carb cleaner ... often that will clean the residue that makes it sticky.

alternatively non-genuine spares are cheap.
 

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In the past you had replaced yours with AICV from Autozone? Is still holding well, or you had replaced them with something else? Is the AICV located on the top left corner of the plenum when facing the plenum?
I cleaned my original and put it back in after using the autozone one for a while. Both work equally well. And yes it's where you describe.
 

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You really need to take the workshop manual and go through a check of each item. Anything else is hunting in the dark. The troubleshooting guide in the manual is easy to follow and you will rule out each item.

Are ALL of teh sensors from the original vehicle installed?
^^^
Very good advice. Like most have said clean the stepper.

What vehicle is the engine out of? I can you a link to download the RRC 87-91 which covers the 3.9 and should provide all the info for trouble shooting this engine.
 

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Nah... I like hunting in the dark! ;)
 
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