Hello:
I'm hoping someone out there can help me as I am, at this point, totally lost as to what to do.
A little background - I purchased and installed a Megajolt system for my bone stock 1995 Range Rover with a 4.2 litre V8 about 2 years ago (the distributor was done and my son convinced me to go the Megajolt route). The installation was pretty straight forward as I bought a complete kit from Trigger Wheels and I had little trouble getting the truck back up and running. It was a vast improvement over the distributor, but to my dismay, failed it's first rolling road air care inspection. I went home, dialed back the advance considerably (to the point where the max advance was about 15 degrees) and managed to get it to just squeak through the smog test (I was hoping for better, but was happy to have passed). I have, since then, been chasing what appears to be a very confounding problem. Using a very simple inductive pickup timing light (no timing advance function or anything) I connected it up to each of the spark plug wires in turn, and got some really funny outputs. Some of the wires were firing as I would expect (rapid timing light flash) but would momentarily (very momentary!) drop out. Other wires appeared to be firing at about 1/2 rate, and again, would drop out momentarily on a random basis, others were very intermittent in their firing. Since then I have replaced the spark plugs (twice) with new units, the plug wires (three times!) with new units, and both coil packs (three times) with new units - none of which had any substantial effect on the missfire. I have tried running the truck in the limp home mode (Megajolt disconnected) and again, the missfire is still there. I have replaced the EDIS 8 module with a new one, and no change. I then tested the output of the VR sensor, and with the engine cranking I could only read 0.5 volts AC - so I figured I had a bad VR sensor - replaced it with a new one, rechecked the alignment and spacing of same (it varies from about .66mm to about .85mm depending on the trigger wheel position) but on rechecking the output with the engine cranking I could only get about .5 volts AC. In a desperate attempt I then replaced the trucks battery with a new unit, and on rechecking the VR sensor output it is now up to about 0.7 volts - better, but nowhere near the 2.5 volts the manual says I should see - cannot figure out why this might be, but have a feeling that it is not the cause of the missfire. At this point I do not know what to do next. I have checked and rechecked the wiring many times, and even went so far as to put in a relay for the power supply just to make certain that I was getting a good supply, but it has not helped. The one area that I am not certain about, and one which could potentially be the problem is the 'tach driver'. On the 1995 Range Rover the tach is actually driven off a signal from the alternator, but the ECU, which controls the fuel injection, needs to receive a signal from the coil, otherwise it will not operate the fuel injectors and the truck will not start. I originally overcame this by simply using the 4 diodes and a zener setup described as a tach driver and the truck ran, but with the missfire. I have since changed this to the four diodes and four resistors setup hoping that would fix things, but there was no change. Could the trucks ECU be doing something with the 'tach driver' signal that somehow causes the coils to cut out? Any help would be very much appreciated!! At this point I am seriously considering buying a new distributor, but would really hate to have to abandon the Megajolt - it seems like such a good thing!!
Regards,
Rob
Megajolt and '95 Range Rover - HELP!!
Moderators: JeffC, rdoherty, stieg, brentp
From your description I'm not convinced that there is anything wrong with your ignition at all. Inductive timing light pickup can get confused by wasted spark and also interference from other leads in close proximity giving the illusion that there is a problem.
That you are struggling on the emissions might is more likely to be a failing lambda sensor in my experience.
That you are struggling on the emissions might is more likely to be a failing lambda sensor in my experience.
Official Megajolt distributor for UK and Europe.
Complete Megajolt packages, EDIS kits, Trigger wheels and everything else you need for your megajolt install
www.trigger-wheels.com
Complete Megajolt packages, EDIS kits, Trigger wheels and everything else you need for your megajolt install
www.trigger-wheels.com
Thank you very much for the reply!
I did have some concerns about the accuracy of the 'timing light test' if only because the truck seemed to be running better that I thought it would have with all the misses. I have purchased a couple of O2 sensors and will get them in the truck - hopefully that will take care of my problem (that would be absolutely wonderful!) - will let you know how it goes.
Regards,
Rob
I did have some concerns about the accuracy of the 'timing light test' if only because the truck seemed to be running better that I thought it would have with all the misses. I have purchased a couple of O2 sensors and will get them in the truck - hopefully that will take care of my problem (that would be absolutely wonderful!) - will let you know how it goes.
Regards,
Rob