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  #41  
Old May 22nd, 2013, 12:30 AM
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Chris Davis
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New spark plugs, Champion RN11YC4, previously Bosch which looked excellent as well. All 8 checked and looking perfect. If it was a lifter, I would probably hear it or see some sign--not saying it isn't but the symptoms don't match a lifter issue.

What have a swapped? ECU, TPS, idle air control, all plug and coil wires, spark plugs, Coil, Ballast resistor, ignition switch, fuel pump, Unilite e-spark module. Also ran truck off battery in lieu of alternator (completely disconnected from system). Battery voltage is normal, battery charging and alternator producing 14v. Disassembled alternator and individual checked zenier diodes. Swapped fuel rail and injectors and fuel pressure valve.

What have I not swapped, but worth checking? MAF, O2 sensors, Fuel Temp Sender, Speed Sensor. The MAF, Fuel temp, and 02 show up on Rovergauge and look normal or at least functioning within what I am assuming is normal range. I am gonna disconnect speed sensor and see if it does anything different tomorrow. Checked fuel pressure, at 35 psi while running (checked at fuel filter, replaced fuel filter). No vacuum leaks.

Truck starts up perfectly. Never stalls. No hesitation. Accelerates and drives perfectly. I can usually force a bucking issue going up a hill and giving it partial throttle. I have a rather steep long hill that I can go up and when getting to the top, going about 65 in 4th gear, I can shift to 5th near the top and get it to do it's bucking thing. Also, after going down the back side of the hill and exiting the freeway, at the traffic light I usually take a left up a small hill. When I take off, and gently shift into 2nd, it likes to do it then, too. Yesterday when cruising down the freeway at 70mph, pretty flat and just cruising (rather hot day), it just started for no reason (no shifting or accelerating, just cruising). Rarely does it going down anything. Doesn't seem to do it until it heats up a little, at least 5-10 minutes of driving.
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  #42  
Old May 22nd, 2013, 12:49 AM
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Chicklet?
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  #43  
Old May 22nd, 2013, 12:58 AM
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Chris Davis
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I checked the chicklet, ohm's out just fine, scrubbed both sides to nice bare copper and made sure connections were tight. Measured it after driving, too---I believe it was 6.8 ohm---it was within spec, for sure.
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  #44  
Old May 22nd, 2013, 01:17 AM
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Quote:
Originally Posted by Davis View Post
I checked the chicklet, ohm's out just fine, scrubbed both sides to nice bare copper and made sure connections were tight. Measured it after driving, too---I believe it was 6.8 ohm---it was within spec, for sure.
O2s can do that. Intermittent alternator faults. Speed sensor.
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  #45  
Old May 22nd, 2013, 01:36 AM
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Alt is ruled out as it did it under battery-only operation. o2's are ~12 years old, seem to be doing their thing on Rovergauge at least, but I honestly don't know what to look for--usually trimming up and down from center depending on acceleration. Swapping them with my RRC would be such a PITA, that I'd rather just replace them if I can't find something else wrong. Don't want to throw parts at truck, but time is money too... I'll find another resistor for chicklet, but it appears fine. Speed sensor is next on my list...
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  #46  
Old May 22nd, 2013, 08:24 AM
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Quote:
Originally Posted by Davis View Post
Alt is ruled out as it did it under battery-only operation. o2's are ~12 years old, seem to be doing their thing on Rovergauge at least, but I honestly don't know what to look for--usually trimming up and down from center depending on acceleration. Swapping them with my RRC would be such a PITA, that I'd rather just replace them if I can't find something else wrong. Don't want to throw parts at truck, but time is money too... I'll find another resistor for chicklet, but it appears fine. Speed sensor is next on my list...
speed sensor shouldn't make a difference ... i'm running without one and the only occasional problem is it almost stalls on stopping at a junction. It only warns the ECU to prepare to idle the truck.
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  #47  
Old May 22nd, 2013, 08:43 AM
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Quote:
Originally Posted by Davis View Post
Alt is ruled out as it did it under battery-only operation
so it did the same thing with the alt disconnected ? so if the alt was bad it would do the same thing connected ......i would swap in a known good unit and try that I've seen alot of alt check out OK but when under load and hot it starts to do strange things .. not being able to sustain the correct amp and volt to run correctly .. just a thought also did you monitor the spark when it happens? you can also make a extended piggy back lead to the injector to monitor injection pulse . how many miles on the engine ? (possible slack in timing chain causing an event under load ?) .. just putting things out there its very hard to diagnose such a problem from a desk
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  #48  
Old May 22nd, 2013, 09:01 AM
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I'll skip the speed sensor, then. I'm pretty sure alt isn't an issue-- I ran thorough tests on it and replaced regulator when it was out just as a precaution (I have several spare regulators laying around from previous life). I'm running an odyssey 2150 battery, so volt/amp isn't an issue on battery only (huge battery http://www.odysseybatteries.com/battery/pc2150.htm ). I don't have an easy alt to swap in (mean Green, modified mount), plus problem isn't rpm specific which is usually diode leaking A/C causing injector miss function which I have experienced many a year ago... Maybe 10k on engine, runs solid when not in fault mode, timing chain should be awesome still. I monitored dwell only so far which drops from 35 degrees to into high 20's (needle fluctuates) when problem happens, so that should indicate that the ECM is getting a signal somehow to shut down the ecu/injectors, correct? Dwell doesn't change for normal driving/accelerating. I'll try and check injector/spark this evening.

I will also see if rovergauge's fuel map zone is fluctuating during problem. And I'll clean the MAf, although I am not specifically suspecting that. I am pretty sure I can swap my RRC's 3AM MAF into this truck to rule that out, too.

If I had to guess, it sure seems like ignition module (or at least loss of spark/weak spark under load). I had previously swapped in an old unit I had and the problem was the same, but that old unit was also slightly suspect. Testing this unit last night tests perfectly--12V at coil dropping to 1.3 volts when blocking sensor. I ordered a new one to rule that out for sure, though, in case it has issues when warm.

Would the engine temp sensor or fuel temp sensor cause anything like this? I'll check them out (the rovergauge monitors fuel temp, so I am fairly certain that one is good). I would think if the sensor failed, it wouldn't be an intermittent problem...
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  #49  
Old May 26th, 2013, 08:53 AM
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SOLVED. Sure enough, as I mentioned in the last post, both my ignition module and my spare were BOTH suspect. They test out just fine on a bench, but under heat/heavy use, seemed be sending out some sort of weak signal and/or missed signal. I put in the new module and so far, things seem golden. The module was one of the first things I checked, too, but I checked it with a crappy module that I thought was good (slightly suspect, even at the time in retrospect). Both of them pass the bench test when blocking the optical sensor, so Mallory's tech that said that "when they fail, the don't work at all" is just plain wrong (or my symptom is in remission and it isn't the module at all, but 100 miles in high heat says differently...

Thanks to everyone and their suggestions. I know more about how to check the various components that I ever did before which is awesome for the future. I also know that everything on the truck is working as it should right now which gives a great peace of mind. And I know to use only CONFIRMED good components when swapping pieces to troubleshoot. :-)
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  #50  
Old May 27th, 2013, 08:08 PM
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Trevor K
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What was your final wiring setup with the Mallory distributor and coil? Did you leave the ballast resistor in? My setup keeps cooking coils and I'm wondering if I should put the ballast resistor in with my unilite, or swap out the distributor
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  #51  
Old May 28th, 2013, 09:41 AM
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For any "standard" coil, you 100% need a ballast resistor. The only time that you don't use one is if you have a coil with internal resistance built in. The standard "land rover" coil that you would run with your old distributor requires a ballast resistor.

For the actual wiring, the green wire goes to the neg side of coil, the red wire goes to the positive side and brown goes to ground. The ignition white wire goes to the ballast resistor then to the positive side of coil. The ECU white wire goes to the neg side of coil.
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  #52  
Old May 28th, 2013, 11:22 AM
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Ballast resistor with an optical pickup? Huh?
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  #53  
Old May 28th, 2013, 01:55 PM
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Yes. See wiring diagram here: http://www.v8engines.com/faq-mall.htm
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