---> '92 twin cam sedan, 296k

I bought this car at an auction to get a motor for my wagon. It had a broken CV shaft and couldn't be driven, but it ran and it was cheap. I replaced the axle, drove it, but it was missing.

I did a compression test, found it low in 2 cylinders, pulled the head and found 3 burned valves. Had the head rebuilt, put it back on, compression is 175 in all 3 rear, 165 in all 3 front, but it still misses. It drives exactly the same. It feels like it's running on 5 cylinders.

I pulled the fuel rail and cranked the engine, and all injectors are firing nicely. I pulled the plug wires, one at a time, and started it to try and isolate the dead cylinder, and each time it runs worse. I would think if it's only firing on 5, eventually I'd get to one wire that could be pulled without making any difference.

I have a 'check engine' light that comes on, and I tried to get a code but got nothing. I took it to a shop and they told me the only code they got out of it was ABS related.

Now I'm at a loss. I'm getting fuel, I'm getting spark, the timing has been checked multiple times and everything lines up. I've heard about bad ECU's, though suprisingly I couldn't find much doing a search here. So what are the symptoms? What's the cause? Any thoughts appreciated.
:puzzled:

Well with these it can be the coil or the control module. being there are 3 coils , and the 3 coils fire for 2 cylinders each. I have seen an ignition coil working (firing) on a cylinder but out of sequince, and had to replace the coil.

Also are yu undoing the spark plug leads at the coils? Sure the coil can be firing but wut if but the spark plug lead leaving the coil to the spark plug itself can be bad. a bettwe way would have been to remove the lead end frum the spark plug tube at the spark plug side and not the coil for many reasons. A main reason is that the coils are open grounded and also not self sheilded , so removing a lead at a time at the coil and then starting it , will cause issues as for the one removed will open arc against the adjacent coil assembly, the assembly is self grounded and the power leads are open connectors , so this would cause an the spark frum the coil to easily arc to the coil assembly and power terminal.

On Mitsubishi vehicles with Hitachi, ND and other non sheilded coils its not recommended to check for a mis fire this way , it will cause an open short in the ignition control module or damage the ignition coil.

What do you mean by saying the coil may be out of sequence? It's firing, but at the wrong time? How does that happen, and why would that mean the coil is bad? Doesn't the coil fire based on a signal from a crankshaft or camshaft position sensor or something? I guess if it were firing at the wrong time, that could be the reason the car had burned valves couldn't it?

I tested the coils today and all three tested within spec on both the primary and secondary. I put in new plug wires, and a new ignition/control module, and it still runs the same. I checked the timing again, and it's right on. I looked all over, again, for any wires or hoses that weren't connected, and nothing. This car is killing me, slowly.

The main things that are in effect for ignition timing and firing are the TDC-Cam position sensor and the Ignition Power Unit(ignition control module)

I have seen ECU's give hard start and no starting but have never seen them cause the vehicle to miss on DOCH units and units with a distributorless ignition system. Its a very odd circumstance.

I'll try a new cam sensor. It seems the only thing left. Thank you very much for your help.

So yuve checked the Ignition Power Unit(ignition control module?)

Yes, replaced it. I've been thinking about this some more and I guess what I should be looking for is whatever caused the valves to burn. I pulled the head and fixed the valves but never did figure out why they were burned in the first place. Whatever caused that is probably why it won't run correctly now.

too much unburned fuel on the cylinders, too much spar advance.timing to say the least will burn valves. plugged or restricted exhaust that is causing an uneven and low exhaust flow , to say the least

It's finally running. Timing and spark problems. It's a long story.

Anyway, it's idling nice, but down on power. I pulled the codes and got 41 (injector fault) and 71 (Traction control vacuum valve solenoid fault). In the process of getting this running, I pulled the fuel rail and watched all 6 injectors fire, so I'm wondering what "injector fault" means. Could it be something other than the actual injectors?

And the TC solenoid....where is it, and what is this code telling me? Just replace it, or clean it, or what?

Thank you. I appreciate your help.