Runs rich and high idle after restart

[FastWoman]

Definitely calibrate the AFM! That may be it. However...

Here's a somewhat esoteric bandaid approach that I've never seen tried:

If all else fails -- if all your EFI components (except the ECU) are all good, if there are no leaks, your valves are in adjustment, engine is timed correctly, distributor advance isn't sticking, and you STILL have a rich condition (just like the '78s tend to have that lingering lean condition), then you might consider the following adjustment to the CTS circuit:

See if there's some way to accommodate an additional CTS sensor in the thermostat housing. There may be other years, or perhaps California versions, that have additional bungs that would allow you to screw in another sensor. Or maybe there's some other temp sensor for a different vehicle that has a lower resistance that you can substitute for the one you have. (You'll have to get creative here.) Then wire the two CTS sensors in parallel. That would give you half the resistance, while still being responsive to temperature changes. This would lean the mixture. As the mixture might end up being too lean, you could then richen it slightly (to fine-tune it) with a potentiometer in series.

Or.... Keep your eyes on the ZFuel thread. The cavalry might be coming to our rescue right now. Soon we'll have the ability to toss our deteriorated ECUs and get our engines running straight with whatever components we have installed. I think that's the ultimate fix.

[Zed Head]

Looking for the odd clue, as superlen said, in Post #28 - "kind of falls off at about 4200RPM". That doesn't seem right, especially for an engine running rich. The stock L28's accelerate/rev to 5000 RPM easily. Maybe a restrictive exhaust system?

On the subject of rebuilding - have you confirmed correct cam timing via the notch and groove?

[Zed Head]

Can't edit - cam timing would also explain the loss of power at 4200 RPM. Too advanced, I believe.

[mjr45]

Zed, the cam/notch timing has been checked 3 separate times. Falls off was poor terminology on my part it just flattens out above 4200. The exhaust is new from the manifold back with 2 1/4" pipe and new muffler, no cat. or resonator.

Edited February 5, 2014 by mjr45

[mjr45]

Ok, today I pulled the AFM and ran all the tests in the FSM pg EF 51 and 52, the tests of the potentiometer were the only ones that are off, Test 1 reads 204 ohm and test 2 114 ohm so its put them both off by 14% the voltage dropped when I opened the vane as it was supposed to.. I then calibrated the AFM using the Atlantic Z write up(Thanks Blue), it was off slightly to the lean side. The test of the CTS showed 4.5 ohm completely cold and 0.47 after getting up to 150°. Now I can only wait for the Hellfire to come out soon!

Edited February 6, 2014 by mjr45

[rcb280z]

I'm with you Mike! I can't wait for the Hellfire to be ready also!

[mjr45]

Len,

I have another ECU, untested and untried, that I may put in to see if it makes any difference, but I'll wait until I get 100 miles on her after the AFM cal. just to see, I'm not expecting much but we'll see. Thanks, I'll be in line for the Hellfire when its done!

[superlen]

I've got some spares too if you think yours is suspect. Although the state of my extras is dubious as well if your are trying to get back to perfect factory stock operation.

[mjr45]

Len, I just want it to run well or at least better. If you want another ECU, I'll be glad to send you my spare, but from what I've been reading on your ZFuel thread, it sounds like you have plenty, I can't wait for your project to be completed, the idea of being able to diagnose problems and tune sounds awesome.

Mike

[superlen]

Mike, thanks for the offer, but save yours as everyone will need a core ECU to send in. I have about a dozen spare ECUs of various vintages. Some are 1979+ or jaguar, bmw, ect. I wish I had more as I would like to have 10 Early Z-specific units stocked up and ready to ship when someone orders. That way, unless they just have some emotional attachment to *their* core I can just exchange. Otherwise, there will be a few days while I gut & prep theirs.

FYI, I have a little more on the house list today (currently installing door jambs and trim on the babies room) & then it's out to the shop. I've had the heater going for an hour now. It was 22F outside and 35 in the shop this morning. Hoping to get to a 70ish temp and then gather some data from a run. Look for an update on the main thread this evening.

Lenny

[mjr45]

Lenny, its a balmy 45 up here @ 9000', just went down and ran the Z to warm it up, my garage stays about 30° all winter and I have to run the kerosene stoves to get some heat down there.

Mike

[mjr45]

Just to close this out, I adjusted the AFM per Atlantic Z and I've only been able to take it once due to snow, which I don't drive the Z in. It "seemed" to run better, smoother if you will, but haven't put enough miles on it to tell if its still running rich on top of that, I'll be getting a HellFire, so maybe it doesn't matter any more!