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STILL having issues!!!


mjr45

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This is about the 80th time I've posted with the same problem on this car its driving me stone crazy.

Problem: Stumbles and bucks above 4K under load. Runs great up to 3800. Occasional miss at idle. It ran great with very very slight stumble above 5200RPM after re-doing the fuel pump.

Whats been done: I've run all the checks and tests suggested by Zed Head, Fastwoman and others, kudo's to all for their help. Fuel pump rebuilt(new O rings and check valve) makes 37-38psi at idle, drops to around 30 under load, new injectors, new fuel line clamps, new fuel lines, new pressure regulator. No rust in the lines or at the pump. AFM calibrated per Blue at Atlantic Z. TPS adjusted. New CTS and Thermotine, checked OK per EFI Bible, new spark plugs and wires, new rotor and dizzy cap, timing at 10°. Has a 79 dizzy and ignition module. Vacuum is at 14.5", compression average 120 (this is at 9000'). New rubber boots on the intake. Spark plugs are black, tailpipe has lots of black soot, exhaust smells a little like fuel. Gas mileage is about 15mpg. You can see the miss at idle on the vacuum gauge( gauge is steady then drops about 1/2" then back to steady), doesn't happen with every engine cycle just occasionally.

My guess is ignition but at this point I don't really have any good guess's.:angry:

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Considering the time, effort and aggravation you've spent so far, maybe a trial of a GM HEI module would be worthwhile. $25 and some wiring versus $75 for a new ZX module. High RPM weirdness is a typical failing module sign.

It could also be the distributor though. Have you checked the gap between the iron rotor and the pickup points? Described n the 79 FSM. The rotor needs to be perfectly centered. The pickup coil magnet tends to break on the ZX distributors also. I've seen it but don't know if they still work when broken.

If you're not in to wiring or electronics, maybe $100 for a spare distributor would be worth the money. Or, maybe you could borrow a spare from somebody.

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site, I've got a new Accel coil on this b***h.

Zed, I've thought it might be the ignition module, so' I'll gladly spend the $25 for the GM HEI and give it a try. Up where I live there is only one other Z around and I've only seen it once last year. There are a few more in Colorado Springs, but no one I know. I've got an old(75) dizzy, but I'd have to hook up the old ignition module, ballast resistor etc., or could I use the old dizzy with GM HEI?

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The old 75 distributor will work great with the GM module. Here's a diagram that I spent a few days putting together. Connect the red wire to W, the green wire to G, and B and C as shown. Make sure that the mounting grommets are electrically grounded.

Missed the internal part. There's not enough room inside for the GM module. But, if I was going to do another one I might mount it in the cabin where the old ignition module was. The red and green wires from the distributor run all the way there, along with the old coil positive and negative wires. You might need to fabricate a mounting plate. It would take some time with the wiring diagram.

For a test though, it might be simpler to just run jumpers from your ZX distributor. You can take the ZX module off of the side and the two wires you need will be right there. Choices.

post-20342-14150828304837_thumb.png

Edited by Zed Head
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Thanks Zed. I'll have to dig thru my boxes of Z stuff and find the old dizzy. What can I use for a heat sink and being real electrical savvy, how much of the module has to be covered by it?

Mike

Edited by mjr45
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Im having a problem with mine atm. It misses or more like hits a rev limiter when its under load. Starts and drives great, its only when you accelerate hard that it starts playing up. Its not the same problem your having, but its starting to be a pita.

I had problems with water in the fuel an thought it might have been something to do with the efi. Now starting to check the ignition system.

I checked the dizzy and noticed the dizzy shaft has a lot of sideways movement. About 2.5mm. It also has a compensating spring on the opersite side of the pick-up. Not sure what the purpose of this spring is.

Not sure if that can cause problems on an electronic ignition system. It can cause problems with dwell on points dizzy's. There is nothing in the 1977 FSM about sideways tolerences.

It will be interesting to see how you go with the 75 dizzy.

Chas

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Euro, I'll probably just stick with the 79 dizzy and wire in the GM module. The dizzy is so tight in the holder that to remove it I have to undo the bolts that hold it to the block. You're right, PITA.

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Mike

If you are interested I will send you my dizzy complete with coil module everything that worked perfectly before I took it off a month ago.

I would suspect your ignition, but this would eliminate that part of it.

PM me if you want to try it.

I believe my set up is from an 81

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After speaking with madkaw, I ended up advancing the static timing to 16-17° to get full mech advance to around 31-32° and no vacuum advance(the vacuum advance dash pot is toast). Leaving the vacuum off, the car runs great up around 5500 RPM which is good enough for me. Checking the plugs after a short 35 mile run, they were starting to get to the tan/brown color except for #3 and #6 which were still sooty looking. I changed the plugs to the BPR6ES-11(for the 79 dizzy) and I'll check later today after a 130 mi. trip and see if getting the timing sorta right will help with the mixture. Thanks for all the help, I know I'll be back with more questions(issues?).

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Back again! Yesterday I took the Z for a short trip to town, car ran as usual revs up to 5500 with no stumble, no nothing. Stopped and got fuel and one other short stop, car starts right up only now the tach starts bouncing all over at anything over 3000 and sometimes stumbles sometimes doesn't, sometimes I can hear the engine revving but the tach is bouncing all over the place. It appears to me that something electrical gets warmed up and things go haywire, but what exactly, ign, module, coil, wiring? I'll check the module and coil today, but the coil is a brand new Accel. I'm beginning to think I have garage gremlins that just like to mess with my head!

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Thanks Arne, will do, there is one condenser mounted on the coil bracket which I left in place when I changed to the 79 dizzy, but I'm not sure if it is in the ignition circuit, but I'll definitely take it off and see what happens. It did the same thing this AM ran great until it got a little hot under the hood, then boom back to weirdness.

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If the engine runs fine and it's just the tachometer that's weird then a condenser/capacitor might help. But if the engine runs weird also, that is a sign of a bad ignition module. Mine would run fine until I too it over ~3000 RPM, then it would behave (the ignition module) like you describe. The tachometer read too high, and the engine ran rough and would barely idle. If I turned the engine off, it would fix itself, until I took it over 3000 RPM again.

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Arne, I took off the condenser and ran the car and it ran fine with no issues, but I only ran it for about 10 minutes(long enough to get heat under the hood). The tach was steady up to 5500. Thanks.

Zed, I read somewhere this AM that the module should read 400 Ohms +/- 40 and mine read somewhere around 1200, I think its bad. I also checked my TPS and it failed(wouldn't read any continuity or continuity) when checked at the ECU connector, and while that may not have much to do with the goofy running, it sure might help with the rich running condition.

Edited by mjr45
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Arne, I took off the condenser and ran the car and it ran fine with no issues, but I only ran it for about 10 minutes(long enough to get heat under the hood). The tach was steady up to 5500. Thanks.
Is just a guess. I fought a similar problem on my 240Z with electronic ignition, and finally determined that the original condenser on the coil on my car was either bad, or connected wrong. Once I eliminated the condenser all was good. Not certain this applies to your situation, but it sounds much the same.
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  • 2 weeks later...

Back again, took the Z out yesterday and the gremlins are back, ran OK yo to about 3500 then the tach went crazy and al kinds of stumbling from the engine. When it got warm after a 10 minute drive, the problem got worse, so I'm going to town and try to get a GM HEI module and see what happens. Wish me luck. I know I'll have to retard the timing a bit, getting some light backfires thru the exhaust.

Mike

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Just as a way to close out this thread, I bought a GM HEI module, but I thought that before I wired it all up, I would pull the e12-80 module off and give a real close look over. I cleaned up all the connections and the ground points and then noticed that one of the connectors in the wire harness was kinda goofy looking, so I made a new wire harness and connected it up, I retarded the timing slightly to about 15-16° and voila' the car ran great, two days in a row with nary a miss or stumble, just goes to show, pay attention to the small details first. Thanks for all the help.

Mike

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