Author Topic: '81 Z28 E4ME Issues  (Read 1771 times)

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
'81 Z28 E4ME Issues
« on: August 23, 2021, 02:36:18 PM »
So I had a thread previously after rebuilding my '81 CCC carb a couple years ago, but I figured I'd start fresh, though I'll recap that one a bit.

Ran incredibly rich and I couldn't get the MCS dwell reading to go higher than 3. To be certain it wasn't the timing light I was using (that measures dwell), I went and bought the pinnacle of technology in 1981: the OTC Monitor 2000. Connected it up: still 3. Long story short, adjusted the idle air bleed a bunch and suddenly I had varying dwell and could tweak it to exactly where it needed to be. The Monitor 2000 also told me that my TPS was reading nearly 5V at idle, with no change at all no matter how you adjusted it, so I replaced that and was able to set that to the correct voltage as well. I had also replaced the O2 sensor with a new one, so that is new, as well, just in case.

So, that's where I am at now: New O2, new TPS, and have a tool that can confirm all necessary readings and thus tweak everything in closed loop to the proper spec, and have. However, all isn't exactly well.

One of the bigger issues I have is that when this thing is in open loop, it runs like absolute trash. If you have it warmed up and running in closed loop and it then falls back into open loop, it'll try to die. Suddenly starts idling lower and lower. If you bring engine speed up and bring the engine back into closed loop - back to perfect. But this also means cold starts usually require throttle input to keep the thing from dying. When you rev it so it doesn't stall, it sounds like it's breaking up. The throttle response is far from great during all this as well, so it affects drivability as well - end up doing a lot of chirping gears when trying to shift because you really don't know if the throttle is going to act the same was as 2 seconds prior.

The other issues are somewhat more minor. When warmed up and driving around, full throttle usually feels like two stages - it'll kinda just sit there and make a lot of noise and then it starts to pull. Sometimes this even happens with just moderate throttle (part of why driving the car can be so difficult sometimes, as it lacks any kind of consistency). Even when warm, blipping the throttle to rev match on a downshift produces varying results. Sometimes you get a great rev and things sound great - other times it basically does nothing and you end up chirping the tires as you let out the clutch. The full throttle issues may very well just be related to the secondaries being out of adjustment, but the throttle response varying so widely might be more related to the initial issue (or not).
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #1 on: August 23, 2021, 02:37:25 PM »
Had to split my post in two because I tend to ramble ;D:

Since I have the fancy Monitor 2000, I can see basically everything the computer can see, and that was a major help to fixing the initial issues I had in 2019 and 2020, but clearly I have a long way to go on this thing and really don't have a clue where to start. I have the idle mixture screws in the throttle plate set to the base of 4.5 turns out, and the service manual states those really shouldn't need adjustment unless you can't hit the varying dwell in closed loop (which I can). I've also noticed that the next time I'll drive the car after dialing it in...it won't be anymore. This should be a "set it and forget it" kind of thing, but it doesn't appear to be that way.

Any help would be appreciated - if we need to work through it in stages, that is fine as well. I have a feeling I am dealing with a few different issues here that may or may not be connected.
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5347
Re: '81 Z28 E4ME Issues
« Reply #2 on: August 24, 2021, 05:04:37 AM »
Full throttle is basically not computer controlled other than ignition timing.  Issues there can be related to the choke pull-off release time for transition.  Once past all that it should pull strong clear across the engine load/speed range.

What size fuel inlet seat did you install during the "rebuild"? 

Did you install a new secondary plastic cam and spring?....

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #3 on: August 24, 2021, 05:32:28 AM »
I installed whichever seat was included in the rebuild kit I ordered from here, likewise with the secondary cam/spring.
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5347
Re: '81 Z28 E4ME Issues
« Reply #4 on: August 24, 2021, 02:34:53 PM »
If you bought one of my kits I supplied the high-flow .135" non-windowed N/S assembly for the CCC carburetor.

So any issues once you are past transition at full throttle are going to be fuel delivery related.

I didn't see anything mentioned about the M/C solenoid.

It may be time for a simple test which is nothing more than removing the top and the primary jets, metering rods and setting it up to run straight off a smaller set of jets.

I've corrected issues with troubled CCC set-ups quite a few times with that move.  You'd be surprised how well the engine will run set up in that manner once you nail down the most ideal jet size for it........

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #5 on: August 25, 2021, 06:01:06 AM »
What specifically regarding the MCS?

When I installed it, I set it to backed out 3.5 turns, and I think it only requires adjustment if you can't hit the correct varying dwell in closed loop?

Just for my own refresher - the lean-stop is that "screw" mentioned above, and the further you back it out, the less the metering rods can sit in the jets and thus the "less lean" it can go, overall. Likewise, the idle air bleed screw is the rich stop, which only allows the metering rods to come up and out of the jets a certain amount (so screwing that in would make the mixture less rich).

The MCS seems to function properly, at least in closed loop when you're able to tell - I can get varying dwell within the range it needs to be. But in open loop, I'm not sure it's possible to tell. I don't think it clicks rapidly, unless you have the "OBD" pins jumpered to read codes, but it might once the car is in open loop. I don't remember for sure, but I don't expect it'd do anything in open loop, since it doesn't factor in the O2 reading there, so I assume it's some kind of "base" setting?
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5347
Re: '81 Z28 E4ME Issues
« Reply #6 on: August 25, 2021, 04:40:57 PM »
The M/C solenoids can be troublesome.  I would set it up to run straight off the jets (about 7-8 numbers smaller than what's in it and see if it helps some?......

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #7 on: September 17, 2021, 10:55:47 AM »
Sorry, I went on vacation and totally forgot about this!  ;D

So would there be any kind of signs to look for, specifically, that would tell me the solenoid is having issues? Is it possible that maybe those two idle screws on the bottom don't like where they're at, so even though I can "hit" the intended varying dwell in closed loop, when it falls back to open look, it's not getting enough air or something?

I also need to do something very simple, but important, and make sure I'm not just chasing my tail here (or dealing with a second issue), and check my plugs. It ran really rich for a while there when I first rebuilt the carb, so it's entirely possible I fouled a plug or 7. I checked one and it was fine, so it's not likely that's the case, but it's a relatively easy thing to check.
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #8 on: September 27, 2021, 01:46:53 PM »
Out of due diligence, I checked 7 of the 8 plugs (didn't get to number 6 due to it looking like more of a pain in the ass than even number 5 was, due to the primary, though one plug out of eight won't cause the car to try and die at idle) and they all seemed to be pretty clean. Nice tan color - plug 7 did smell a little funky, but looked to be the same color. None of the others had the same smell.

So plugs do not appear to be an issue and thus likely aren't influencing anything.

Figured I would update on those, at least.

So as far as going with a jet change test, where would I find myself those - are they specific to the Qjet? Do they just unscrew? I didn't mess with those when I rebuilt the carb, aside from poking them with some wire to make sure they weren't blocked (they looked clean - the whole inside of the carb did), since I had read it was very easy to screw em up.
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5347
Re: '81 Z28 E4ME Issues
« Reply #9 on: September 27, 2021, 06:30:19 PM »
The CCC carbs used a different style of jet but they are same thread as earlier models so any jet from any year will screw into the holes and tighten up fine......

Offline MP81

  • Carb lover
  • ***
  • Posts: 73
Re: '81 Z28 E4ME Issues
« Reply #10 on: September 28, 2021, 04:58:12 AM »
Okay, cool. As I don't know the jet size in there (without disassembling it first), I should be able to just get a kit with all of them, similar to "regular" carbs, correct?

Or, do you have an idea what the E4ME would be running stock and thus could recommend the jet I need (and I believe I can purchase them from you as well, correct?).
-1981 Camaro Z28 - 305 ci LG4 V8 - Headers, Dual Exhaust, GW U/LCAs, Hotchkis Springs/Swaybars, DD HDX Cluster
-2007 Cobalt LT - 2.2L L61 I4 - M62 SC, FE5 Suspension, Much More
-2014 Cruze Diesel - 2.0L LUZ I4 TD - MSR Wheels, UR Rear Bar, Trifecta Tune
-2017 Volt LT - Voltec Gen 2 + 1.5L I4

Offline Cliff Ruggles

  • Administrator
  • Qjet Hero
  • *****
  • Posts: 5347
Re: '81 Z28 E4ME Issues
« Reply #11 on: October 10, 2021, 06:01:14 AM »
Correct, I can spec out the jets and supply them with the kit....