WallyP

Check for a coil wire touching metal or a wire harness; check the rotors for pinholes or burn-thru, check the caps for carbon tracks or cracks.

Bill Ball

I will look at the caps and rotors. They aren't very old. I did pull the coil wires and check them. Nothing notable and they don't appear to be leaking current.

The tank vent system is hooked up and working. No evidence of vacuum in the tank.

I didn't swap the EZK as I was thinking fuel. But I have a spare, so I should do that tomorrow.

danglerb

Not sounding like a fuel issue to me, my bet is something ignition related. Since it works fine at the top end, maybe that points to an issue with some input to the brain?

Bill Ball

Maybe Sharktuner will show the problem.

Mrmerlin

Bill from your info i would be suspecting an ignition issue,
remove the air intake tubes and run the car up to temp in the dark look for fireflies.
Inspect the CE panel for the 4 running relays LH, EZK, fuel pump, ignition,
remove each one and swap in a good relay one at a time,
smell the removed relays for burning or melted solder

rbrtmchl

Bill, in your original post you say that replacing the O2 sensor fixed the problem for five days. Could the new O2 have failed, or could there be a continuity problem with the O2 wiring?

danglerb

My thoughts too.

Charley B

It sure sounds like an ignition problem but the only time I had a similar problem it turned out to be a failing outer fuel pump.

If you need an LH or EZK for testing, let me know and I'll run them over to you right away.

Bill Ball

It is odd that the O2 sensor "fixed" it for 5 days. It would be nice to see if there is a disparity between the wideband and narrowband, perhaps due to a problem in the narrowband harness, but I don't know of a way to read that at the LH. Sharktuner just sees the wideband.

Charley, thanks, I've got spares.

Tim Murphy

If you have a Shark Tuner, plug it in and check the voltage readings for both the LH and EZK. This will expose any voltage issues to the LH and EZK.

jorj7

Tim,

I went over today with the Sharktuner. It seemed to work as Bill had the car fixed by the time I
got there.

Tim Murphy

That's good to hear.

I had a bad connection at the battery terminal that feeds direct power to the EZK/LH and caused me all kinds of headaches of an intermittent problem. So, every time I hear about these types of troubles it brings me right back to what was happening with my car.

So what was the fix?

Bill Ball

OK, now I feel real stupid. I said I had checked the ignition system, and I had, but apparently only the right side. That's not how I remembered it. I must have gotten distracted halfway through my check and never got to the left side. Anyway, the right side distributor cap and rotor and wires were fine. Here it is:



But the left was not. I hate leaving my car outside overnight, but last month it sat outside for the entire month including some heavy duty rain and wind. I've noticed that the underhood plated parts get corroded rapidly when the car is left out like this. And I have had corrosion on coil wire ends before. I put dielectric grease on the caps, but that doesn't seem adequate. Water appears to get in from the cable side of the boot which is harder to seal.

Here's the coil wire lower ends from the right and left sides. The left has a good amount of green/blue corrosion caked on it.



Here's the bottom of a new distributor cap and the left side cap.



It gets worse... Here's the left side distributor cap with a new one above it. Note the corrosion on the 1st, and 3rd connectors.



And worse yet, look what happened when I tried to remove spark plug cable end 8 from the cap. NASTY!





I thought, no problem, I'll just replace the distributor cap and the end connector for plug wire 8 as I have a bunch of good spares. But here's what I saw when I tried to unscrew the wire end. The crimped end came off exposing a lot of green wire!



So, there's some good evidence the water is getting in via the wire side of the boot. Needless to say I replaced the entire #8 plug wire.

With that the car is running like it did before its stint outside. BWAAAAAHHHH!!!!

The problems weren't evident immediately after pulling the car back into the garage from the month of exposure, so I didn't make the connection to sitting outside for a month in the rain and wind until today. Plus the lean AFR and the apparent resolution with the new O2 sensor lead me away from ignition to fuel, but it shouldn't have as Ken pointed out. Since the O2 sensor measures oxygen and not fuel, if there is a bad ignition misfire, the mixture will appear to go lean from the extra unconsumed O2 sent downstream from the msfiring cylinders.

Thanks for your help. Maybe my misadventure and incorrect assumptions in diagnosing what many of you correctly said sounded more like an ignition problem than fuel will help someone else with a stuttering engine. Time for a celebratory burnout!

Speedtoys

I remember saying as we pulled up to the parts store for my R134..


"Id go with cap/rotor..old normal cars with caps/rotors always run funny on throttle tip-in."

sendarius

Would wrapping the wire side of the ignition lead boots with self-fusing rubber tape help with the water ingress issue?

Surface suitably cleaned first of course.