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  #1  
Old August 15th, 2013, 03:15 PM
scolvus.x
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John Lomax
94 ST
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Idle Issues: TPS?

Short story: My truck idles around 525 most of the time. It will occasionally wander +/- 50. Normally, if I'm driving at speed and clutch the rpm's will drop down to 1k or so then as I come to a stop fall to 750 then back to 525 after coming to a stop. However, around 50% or the time (or more) when I clutch while underway, the rpm's drop to somewhere between 250 and 400 immediately, then will wander around a bit before recovering to 525. It doesn't stall though. Could this be a bad TPS?

When it does this behavior, 2 more things happen: The truck seems to run rich for a second, you hear a light gurgling/popping/sputtering sound from the tailpipe, and when I try to accelerate after awards (even after coming to a complete stop) it is boggy. These issues don't seem to crop up if idle steps down correctly.

Check Engine Light works, and it's never thrown a code.

I also had (have?) issues with stumbling under load and high idle shortly after purchase, thus many fuel system parts have been replaced. The following work has been done:

NEW
Stepper Motor
Plugs
Coil
Vac Advance
MAF
injectors and o-rings
Fuel Filter
Air Filter
PCV Hoses and trap
Coolant Temp Sensor
Timing reset to factory
Silver Relays
Battery

Long Story for those who care -

When I purchased the truck, I soon had issues with high idle and stumbling under load. The truck had seen 4 independent LR mechanics (and 2 of the twice for 6 total visits) with no resolution. This lead to the stepper, battery, air filter, and Vac Advance getting replaced at the suggestion of the mechanics. No change.

Eventually I purchased and installed a new MAF. Truck drove great for 1 day, no stumbles, acceleration great, idle like a rock. Then something went amiss and the truck would begin to run so rich it would flood and choke out. I was told by one of the shops it was leaky injectors, so I took my truck home and changed all the injectors and o-rings with OEM parts. No difference, still flooding. I change the rest of the parts listed above and still no change.

Last resort I put my original MAF back in and truck no longer floods, but it goes back to stumbling w/ high idle, running just like it did in the beginning. At this point I also found that the CTS was bad and got it replaced. I return the new MAF and get a replacement. Now it doesn't flood like before, it doesn't stumble, it just has this crazy idle/throttle issue.

Original MAF = Stumbles under load and High Idle
Replacement MAF = Flooding engine w/ fuel
2nd Replacement MAF + new CTS = Crazy idle under clutch but no stumbles
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  #2  
Old August 15th, 2013, 03:36 PM
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Bill Adams
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You did everything except for what you should have. New ignition amplifier module should bring it back into snuff. While you are at it do a new cap, rotor and wires. Oh and buy the Lucas one not the aftermarket ones. Trevor at Rovahfarm has them.
Read Lav's posts about what is pretty much identical symptoms and story...

PS TPS has very little to do with the engine's overall happiness. Your ECU needs to know 2 things. How much air is coming in and am I keeping the mixture right. MAS tells it the first and the o2 sensors tell it the second. All the other sensors are there to help tweak the overall mapping.
Spark is generated by the distributor, which also tells the ECU when to squirt. Your engine is bank fire, so it is squirting all the right side injectors then all the left side injectors. Quite rudimentary as far as injection is concerned since most have gone to SFI nowadays.
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  #3  
Old August 22nd, 2013, 03:06 PM
scolvus.x
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John Lomax
94 ST
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Thanks for the help. I just received my ignition relocation kit, but had one more question. I need to know the size of the crankshaft bolt, I don't have any sockets large enough to fit it and need to know what size to buy. This is for a 94.
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  #4  
Old August 23rd, 2013, 07:05 PM
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Phillip
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Old August 23rd, 2013, 08:35 PM
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Jason England
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Rover gauge. Make some actual diagnosis.
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  #6  
Old August 24th, 2013, 02:27 AM
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John Lomax
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Quote:
Originally Posted by leastonce View Post
Rover gauge. Make some actual diagnosis.
So I've heard of Rover Gauge and it sounds great. Unfortunately it doesn't seem to have an Apple version which would mean me buying a laptop just for the Defender. I guess it's not a bad investment. Thanks for the suggestion and I will consider it if this fix doesn't take.

Have you or anyone else used it on a Windows tablet like a Surface?
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Old August 24th, 2013, 09:46 AM
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Jason England
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Quote:
Originally Posted by scolvus.x View Post
So I've heard of Rover Gauge and it sounds great. Unfortunately it doesn't seem to have an Apple version which would mean me buying a laptop just for the Defender. I guess it's not a bad investment. Thanks for the suggestion and I will consider it if this fix doesn't take.

Have you or anyone else used it on a Windows tablet like a Surface?
The cable investment is cheap ... maybe $20 ... perhaps you could try it?

The alternative is to perform so measurements of the outputs of various voltages from the sensors in the engine bay ... I've posted the 14cux pdf links several times so have a little search.
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  #8  
Old August 24th, 2013, 11:41 AM
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John Lomax
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Quote:
Originally Posted by leastonce View Post
The cable investment is cheap ... maybe $20 ... perhaps you could try it?

The alternative is to perform so measurements of the outputs of various voltages from the sensors in the engine bay ... I've posted the 14cux pdf links several times so have a little search.
I suppose I'm confused. I understood that it required an inexpensive cable, but isn't Rover Gauge itself a windows or unix based software? I don't own a laptop or tablet that runs on either of those OS. Don't I need a windows laptop to run it? Can I run it on a windows tablet?

Thanks again
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Old August 24th, 2013, 12:08 PM
MonLand
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Loic Fabro
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Quote:
Originally Posted by scolvus.x View Post

I suppose I'm confused. I understood that it required an inexpensive cable, but isn't Rover Gauge itself a windows or unix based software? I don't own a laptop or tablet that runs on either of those OS. Don't I need a windows laptop to run it? Can I run it on a windows tablet?

Thanks again
I never went as far as actually making this work, but in theory, this should compile run on MacOS as well.
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  #10  
Old August 24th, 2013, 12:35 PM
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Russell
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While the Rover Gauge is a cool tool, it did not diagnose my issue that was very similar to what you are describing. My fix was another stepper motor replacement, first replacement not fixing the dropping idle issue. Other than the stepper, the only other area checked was for vacumm leaks to which there were none.
How is the idle right after starting the motor cold vs. warm? If worse when cold, check that stepper again.
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Old August 24th, 2013, 03:13 PM
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Jason England
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Quote:
Originally Posted by scolvus.x View Post

I suppose I'm confused. I understood that it required an inexpensive cable, but isn't Rover Gauge itself a windows or unix based software? I don't own a laptop or tablet that runs on either of those OS. Don't I need a windows laptop to run it? Can I run it on a windows tablet?

Thanks again
I've not idea if you can run it on a windows tablet ... But if you have one why not try it?

Rover gauge would give you ...

Rpm read out , engine temp, fuel temp, stepper position, throttle position, maf readings etc wtc. you'd know what value the ECU reads.

For example if the ECU saw an engine temp of 30 degrees F because the sensor was faulty but it was really 180 F then the ECU would add more fuel to try and warm the engine. Without making a measurement how would you ever know this?

This is a trivial example, but my point is you have no idea what the ECU is reading and if the readings are in the right range.

As for not owning a windows laptop ... Do you maybe know someone who would be willing to lend you one? Places of work often have cupboards full of old laptops. Rover gauge will run on pretty much any windows laptop.
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