%^#@!!!!!!!!!!!

Bought a new ICM. Swapped it in. CEL still flashes. Code 73, random misfire in cylinder 4. Swapped another spark plug wire onto 4. Same thing, misfires.

It doesn't feel like it's misfiring though. And the idle straightens out at anything over 1000 RPMs. One of my neighbors came out and listened to the loudness of each spark when he slightly pulled the plug wire out. Cylinders 1 and 2 popped loudly. Cylinder 3 sounded ok, but cylinder 4 was quieter. Does that now point to the coil? Rotor or cap? Or something internal to the distributor?

 

What does a worn out ignition rotor look like? I was looking at pictures of a brand new rotor on Auto Zone's website and the actual contact was spaced out somewhat from the rest of the plastic. I don't think mine is. I think it's flat with the plastic. I don't know if that's normal for the brand of rotor or if my rotor is actually toast too. Sigh, I'm still a noob after all these years.

[edit] I guess the rotor is fine judging from this picture. Looks ok.



Cap looks fine as far as I can tell too.

 

Misfiring primarily at idle you should consider the valve adjustment. That cap and rotor looks like new but that doesn't necessarily mean it's good.

 

Code 73 is misfire in cylinder 3. Check it for spark quality and whether the fuel injector #3 is pulsing fuel or clogged. The next step would be to compression test the cylinders.

 

Let's go waay back to post #6 two weeks ago...

Ever take care of that?

When your manifold is cracked that fools the O2 sensor and throws the A/F mixture off. You could try disconnecting the sensor to force the ECU to run open loop and see if it runs better.

 

@RonJ, typo. Code 74. Will check the spark plug on 4 for spark color/quality. Is there anything obvious to look for when checking the injector? How do I tell if it's pulsing? (Compression test will happen tomorrow when this engine gets pulled. I'll call it a "post mortem".

@mk378, the manifold is still cracked, but there's a brand new one on the new engine, waiting to be put in. I will try pulling the primary o2 sensor plug to see what happens. I probably won't adjust the valves because the engine is coming out tomorrow. I just need to verify that the ignition components are good before swapping the distributor over.

I started the engine this morning and there was no CEL, no flashing, and it drove beautifully. But it was 74 degrees this morning, versus 98 with a 105 heat index yesterday.

 

Please don't put those Duralast wires on your new engine.

You could also try swapping the fuel injectors around (I'd swap #1 with #4, since they are 180 apart in the firing order) see if #1 misfires instead.

 

I have no choice. Funding is nonexistant. I've spent too much on this and I still have to move to a new apartment next week. The wires will be one of the first things I replace once I can afford it.

I'll add swapping injectors into the mix if I have a chance today.

 

WellFedHobo,

Did you ever find you smoking gun? My Nephew is having the same type problem, heat related. We've changed the dizzy, checked the MAP, the TPS, batt. connections, had the head machined, new head gaskt.

No indicator lights, starts cold everytime, runs great. Turn it off for a couple minutes and NOTHING, engine spins, but not start. I clampped my timing ight to #4, and a noid on inj#1. Injector was pulsing, but spark from #4 was erratic, like anything it wanted to. Including fireing once or twice after the switch was turned off. An ideas?

 

Whew, that was awhile ago. I honestly do not remember.

Since this thread, I swapped in a completely rebuilt engine, using the same ignition components and wires. I did notice that the pintle cap on injector #2 was broken, but that wasn't the one that was misfiring. The car ran like a champ until it was totalled 2 weeks later. Sat for a month, bought it back, rebuilt it, but had to replace the distributor cap and plug wires due to damage. It hasn't misfired or bogged since the swap.

I do know that changing the ICM did help a little with the issue. You might try having that checked first.