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Can any one tell me how to adjust the potentiometer and TPS on the 1988 range rover 3.5 efi with the help of a voltmeter.
Potentiometer and TPS settings
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57 Posts
Connect volt meter to between the red and green leads at the potentiometer electrical plug. Rotate the potentiometer clockwise or anti-clockwise, until the volt meter reads 290 + or minus Mv.
Tighten the potentiometer securing screws. Recheck voltage.
Very little movement is required when turning potentiometer.
Tighten the potentiometer securing screws. Recheck voltage.
Very little movement is required when turning potentiometer.
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Potentiomenter settings
Thanks for the tip. How about the TPS. How do i set this. Actually the problem is that my range has a serious missing at around 850/900 rpm and this obviously becomes magnified when the vehicle is moving. Have changed the plug wires, alternator, ignition coil,plugs, but the missing is still there. One of my friend says it could be the pickup coil in the distributor. Can you shed some light on this problem.
Thanks for the tip. How about the TPS. How do i set this. Actually the problem is that my range has a serious missing at around 850/900 rpm and this obviously becomes magnified when the vehicle is moving. Have changed the plug wires, alternator, ignition coil,plugs, but the missing is still there. One of my friend says it could be the pickup coil in the distributor. Can you shed some light on this problem.
amplifier
We just experienced the famed break down of the amplifier resulting in a weak spark, poor ignition. At higher RPM the amplifier produces a larger spark. At idle a small to nothing spark. We witnessed the spark by cranking over with a sparkplug in the boot grounded to the motor. Very poor spark!! We installed the new "remote ampllifier kit" and all is well. They break down with age and heat. Kind of expensive but worth the fix.
We just experienced the famed break down of the amplifier resulting in a weak spark, poor ignition. At higher RPM the amplifier produces a larger spark. At idle a small to nothing spark. We witnessed the spark by cranking over with a sparkplug in the boot grounded to the motor. Very poor spark!! We installed the new "remote ampllifier kit" and all is well. They break down with age and heat. Kind of expensive but worth the fix.
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amplifier
Is this amplifier you are talking about, the same thing as the ignition module which is connected to the pickup coil in a distributor or is this something else.
Is this amplifier you are talking about, the same thing as the ignition module which is connected to the pickup coil in a distributor or is this something else.
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3,225 Posts
The potentiometer and TPS are one and the same, just different terms to describe it. Earlier EFI engines (yours) used Lucas 14CU computers, but the 14CUX (developed for the US market) eliminated the adjustment of the TPS, so when it goes on, in won't rotate. A rouugh running spot in the rpm range is a good indication of a TPS with a bad spot in it's winding. It's just a variable resistor, like a volume control pot (potentiometer) in a radio. The spot in the winding most often hit, idle and cruising speed, is usually where it breaks down. The Ign. amplifier, mounted to the side of the distributor, does break down with heat related aging. It is intended to act as a switch, like an old set of points, getting it's impulse from the Hall effect pickup coil, which can't handle the current of a ign coil. They almost always just quit, no inbetween. Often the truck will start when cold, but as soon as it heats up under the hood, they pack it in. Pick-up coils do occasionally go, but more common is a break in the flexible wire from the pick-up to the side of the distributor where the amp lugs in. This is beacuase of all the flexing it does when the advance unit rotates the breaker plate (everytime you step on the gas).
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My mechanic says that the problem with my range is the ign. amplifier, but after what you have described, i am now doubtful about my mechanics claim, as my car runs fine even after warmup. The only problem is that it has become very sluggish and lost its throttle response. The problem becomes worse when i swithch on the lights and the A/C. The car starts missing even more. After installing an Excel super coil, there is some improvement, but not much.
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3,225 Posts
Provided that your alternator is puting out what it should, 13.8-14.5 volts at 2000 RPM, the symptoms you're describing could go either way for the IGN amp, but the TPS,if faulty, will be faulty at any voltage above 12.0 volts.
The TPS is very easy to check for bad spots o the winding. The manual describes taking voltage readings, but in my experience, I findusing an analog ohmeter is more reliable. connect one lead from the ohmeter to the center wire (sorry, I never remember the colors) and the other lead to eother outside end of the winding. If you connected it to the high end, it will read full resistance, then, by hand, open the throttle, slowly and smoothly aand the ohmeter should go down smoothly in a linear fashion. If you connected to the inside winding, the meter will only slightly move, but smoothly move up the scale as you open the throttle.
I don't have any test method for the IGN amp. When I'm sufficiently suspicious of it, I swap it out for a known good one.
The TPS is very easy to check for bad spots o the winding. The manual describes taking voltage readings, but in my experience, I findusing an analog ohmeter is more reliable. connect one lead from the ohmeter to the center wire (sorry, I never remember the colors) and the other lead to eother outside end of the winding. If you connected it to the high end, it will read full resistance, then, by hand, open the throttle, slowly and smoothly aand the ohmeter should go down smoothly in a linear fashion. If you connected to the inside winding, the meter will only slightly move, but smoothly move up the scale as you open the throttle.
I don't have any test method for the IGN amp. When I'm sufficiently suspicious of it, I swap it out for a known good one.
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