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Discussion Starter · #1 ·
My '99 V8 has a sometimes problem shutting down cylinders #2 and #3 which I've traced to the ECU so it'll need to be replaced. Any good sources for ECU? Any real difference in the red box over the standard 918 box?
 

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How did you figure this out and why do you think it is the ECU? There are services that can rebuild/repair your ECU and you can have it programed by Lotus USA. If you do not have the HTU (High Torque Upgrade) upgrade you need to have it reprogrammed.
David Teitelbaum
 

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Discussion Starter · #3 ·
I tapped into the circuit board of the ECU of the ignitor circuit corresponding to output to Cylinders #2 and #3. Then hooked up a voltmeter with wires leading to the cab. While driving voltage normally runs 13.3 volts but is dropping to 0 to 3 volts. When this happens car stumbles slightly. It doesn't do this all the time and I'm afraid if I get it(the ECU) repaired it will test normally as most of the time it works fine. It could be the pick up but I doubt it as the other cylinders are sparking fine. I've looked for bad places on the ECU circuit board and cracked solder joints but 'can't find any. Some component of the circuit board is failing intermittently in my opinion
 

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That is a pretty big leap of faith. Your test leads could be the problem or more likely a bad sensor is causing the ECU to drop out. For example if the ECU doesn't see the crank or cam sensor it will shut down the ignition. The ECU is usually the LAST thing to suspect. Most of the time it will be a wiring/connector problem or a sensor. You need to watch the sensor outputs and see if you caught any stored codes. It can also be bad ignition coil packs. My bet is on a wiring/connector problem. Check if you have the HTU program. If you don't then get it out to Lotus USA and have it checked and reprogrammed. If you still have trouble then you know it isn't the ECU. Intermittants are tough. You have to try to catch it in the act or get lucky or get it to be consistent or constant.
David Teitelbaum
 

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Discussion Starter · #5 ·
Everything post ECU has been replaced including coil packs. The only things left are the ECU or the signal to it is defective. 'Could be a slightly bad pick up from the crank(but not bad enough to trigger a code). The weird thing is the pick up works fine for the other 6 cylinders. The whole engine isn't shutting down, just the 2 cylinders controlled by a single igniter. I might just replace the crank sensor first as it's not too expensive. If I reset the ECU it doesn't help. If I simply remove the ECU and put it back in I can go 60 miles of so trouble free (usually). The connection coming from the ECU has been bypassed without effect. Any other ideas are very welcome.
 

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The first step should be to see if there are any stored codes. If it is the one coil pack I would suspect the wiring to it first. There should be some codes, if not from a sensor causing the problem then from another sensor noticing the misfires. Get a scanner and see what is going on. It also could be a problem "on the other side" so to speak. Maybe you have a high tension lead breaking down or a spark plug that is misgapped. At least you seem to have narrowed the problem down so that is a good thing. You could try swapping coil packs and see if you can move the trouble.
David Teitelbaum
 

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I tapped into the circuit board of the ECU of the ignitor circuit corresponding to output to Cylinders #2 and #3. Then hooked up a voltmeter with wires leading to the cab. While driving voltage normally runs 13.3 volts but is dropping to 0 to 3 volts.
You are describing normal coil operation. The primary winding is charged and the voltage removed to induce a current in the secondary winding.

Have you changed the sparking plugs in cylinders 2 and 3?
 

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Do you have spark in the cylinder you mentioned?
If the spark is weak, you probably has spark driver issue.
That can be fixed.
 

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Discussion Starter · #9 ·
I have a great spark when it sparks but it is cutting out. The ECU is not sending voltage to the coil pack all the time when it should. It's a problem in the ECU or the ECU is not receiving a signal to fire. Everything (coil packs, wires, plugs) post ECU has been replaced. The ECU wire to the designated coil pack is not sending voltage to the coil at times - this I'm sure of. It's not in the ECU to engine wiring harness though it might be an incoming wire from the crank sensor. There are no codes except the O2 sensor due to unburnt gas. The o2 sensors have been replaced as well as cats.
 

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Where do you live?
Is there anyone in the area can lend you a V8 ECU?

I have the same issue a year ago, the spark driver resistor in the ECU cooked.
 

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nothing much to add other than to keep in mind just because they are new parts doesnt make them good parts. I get bad crap all the time working in the field. be it a spark plug or a control module.
 

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Discussion Starter · #12 ·
The ECU must pulse 12+ volts 1,000 times per minute @4,000 rpms to fire plugs #2 and #3.The ECU just isn't doing this consistantly - I've measured it. Talking to JAE yesterday Jeff says it sounds like a bad quad drive on the ECU. I know it's tempting to always blame the ECU but believe me this is the LAST thing I wanted to replace. On the bright side I now have a new fuel pump, plugs,wires,vacuum wastegate actuators, injectors, fuel filter,coil packs, and the knowledge of the sneaky wires on the underside of the plenum that break rather too easily. Thanks for all the advice - I'll let yall know if the ECU fixes things.
 

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The ecu grounds the coil 4000 times a minute at 4000 rpm. It does sound like you may have an ecu issue as you seemed to have eliminated everything else.
 

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You need to find someone locally that has a oscilloscope and look at the primary voltage signal going into the coil pack, otherwise you are just guessing. Based on what's been replaced and the primitive voltmeter reading it is probably an intermittent ECU driver. Where are you located?
 

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Discussion Starter · #15 ·
The ECU has four wires each controlling 2 spark wires hence the 1,000 per 4,000 is for a single wire (#49) controlling #2 and #3. I'm in southern Virginia. The folks at JAE have been good at locating me a unit from Lotus cars USA. They swap out your old one for the price of a small vacation. The new units are programmed to put out a bit more power they say but this might be wishful thinking. ECU's rarely go bad and I hope this doesn't happen to anyone else - the REAL bitch was the intermittent nature. I can fix broken much easier than sort of broken.
 

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A four stroke engine fires a cylinder’s sparking plug once every two revolutions so for a V8 there are 4 sparks required every revolution. There are 4 wasted spark coils on the Esprit V8 so each coil fires once per revolution and therefore at 4000 rpm the coil is fired 4000 times a minute.
 

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Discussion Starter · #17 ·
You're correct Sailorbob - I get confused easily. Anyway the ECU WAS the problem. JAE/Lotus Cars USA sent me a rebuilt one from a company aptly named Injection Correction. The turnaround was amazingly fast. They supply a standard EPA approved unit for your year of mfg. Thanks for everyone's help!
 
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