Drivability Issues '77 CIS

[T77911S]

no need to suck.

I would have to look to see if all 77s have retard, but I think they do. you know the CA guys, they make things difficult.

easy way to test vac advance/retard is to remove the retard hose at idle. RPM should go up.
connect it to the advance port. idle should go up again.

vac advance is only used for mid RPM. as RPM goes up, vacuum goes down thus the vac advance comes out or retards, but you still have mechanical advance. I think I use to set mine around 30 degrees.
check mechanical advance with vac hoses removed.
no advance can make for a bad driving car like you describe. vac advance more so at low RPM if upper RPM is good.

[Bob Kontak]

Originally Posted by T77911S

no need to suck.

I would have to look to see if all 77s have retard, but I think they do.

I am pretty sure they do as well. Vacuum advance is "newish" Thanks for putting that to bed.

[Jameel]

You mentioned new ignition components. And when I saw your car in May I remember an aftermarket coil, and maybe new CDI box? I don't know enough about ignition tech to offer any answers, but perhaps those items aren't playing nicely with your stock dizzy? Might want to post exactly what you're running for ignition.

[rwest]

Hi guys,

The distributor has vacuum retard and I did check it with a vacuum pump and it moved the plate smoothly.

When I baselined the FD last summer, the injectors sprayed a nice cone type pattern, no dripping and equal volumes.

Jameel,

I have an MSD 6 CDI box and their coil, I think it is the blaster II. I took the resistor out of the rev limit rotor.

I did just order a new MSD 6AL, so I can use a standard rotor and the box does the rev limit.

I'm going to send it to Partsklassic for a rebuild. Ran out of time today to call them for instructions; will try tomorrow.

Thanks,
Rutager

[T77911S]

did you check vacuum advance AND mechanical advance.
they have to be checked separately

[rwest]

Originally Posted by T77911S

did you check vacuum advance AND mechanical advance.
they have to be checked separately

Sort of! I've done some "hey, that appears to be working tests".

My 77 has a vac retard and not advance. I've applied vac and the arm moved and engine bogged down.

I've moved the throttle connection while the timing light was on and saw a smooth advance, but did not quantify it with numbers.

I'm just going to get the thing rebuilt for peace of mind-it has been spinning around for forty years after all.

[T77911S]

look to see if you have a timing mark around 30-35 degrees,. timing should advance close to that mark.
you need to look up the timing spec for your car. some set it for idle, others full advance.
I would try setting full advance to the 30degree mark and let idle fall where it may then drive it.

it not hard to pull that dist apart and check the weights to make sure they are not stuck.

you might post the engine number or specifics about you car so someone can look the spec up,
I want to say there is one that sets the timing to 15 ATDC and one sets it to TDC, don't hold me to it.

[rwest]

Hi,

Just a quick "midterm" update. I installed an MSD 6AL along with a standard resistorless and non rev limiting rotor a couple weekends ago (was planning on doing it anyways to get rid of rev limit rotor). Car took a lot of cranking to start up that day, most likely because I had also done fuel tests and there was probably some air in the lines.

After it was running, I checked timing and weirdly it was several degrees back from the factory 5 degree BTDC and about 5 degrees back from where I had set it a tad advanced before the change out of ignition box (was an MSD 6)! I reset the timing to factory and next day it started up excellently, just a few turns and it caught.

Road test revealed no change in the drivability situation; distributor has been sent out to be rebuilt, we'll see what happens.

[pmax]

Originally Posted by rwest

Cold Control Pressure 1.3 bar electrical disconnected.

The cold pressure appears low.

[rwest]

Agree, from chart it looks like I should be closer to 2 bar.

Okay, back at this thing and with a new problem!

Had the distributor rebuild and the curve paper they sent along looks perfect. Got it yesterday, installed today and set static advance. Went for a drive and it appeared slightly smoother past idle, but bucking/stutter still exists- no change.

Drove to the freeway and turned back at the next exit everything behaving as before, then when I took the exit ramp and stopped at the bottom, idle dropped real low and engine sounded awful- thought maybe a diesel truck pulled up behind me with straight pipes. Drove slowly and carefully the few miles back with small backfires out the exhaust.

Got home checked ignition still seemed good and with timing light and operating throttle by hand, it advanced, so not a stuck weight or advance spring problem.

Hooked up the LM-2 at the tailpipe and I was pumping oxygen! 15-20 AFR. Visually nothing appeared to have disconnected, airbox seams looked fine- sprayed brake cleaner fluid into intake and car almost died. Sprayed it along airbox seam, fittings, injectors throttle body, boot and intake- no change in idle; doesn't mean no leak, but seems fine.

So besides a big vacuum leak, what could cause such a lean condition to develop "suddenly?" I have had some slight tailpipe backfires before this, so is it possible a component has gradually been failing, WUR or FD?

Thanks for everyone's help,
Rutager

[T77911S]

what was the CP?
sounds like the WUR heated up and the CP went up as it should. could just be mixture setting but check WCP first.
get timing correct, set WCP, then set mixture.

make sure the LM is calibrated in open air. should read 20.3

[rwest]

Couple weeks ago when I did all the tests, cold pressure at 75 degrees was 1.3 bar, which from the chart is a tad low, but once warmed up, it was good.

Going out to the garage now to poke around with the mirror and flashlight to see if a hose in back came loose.

I didn't calibrate this time, but I have before- smell out the tailpipe agreed with the lean reading.

[rwest]

Double checked LM-2 calibration and it was spot on at 20.9

Car still was running 15 plus AFR cold. I poked around best I could and couldn't find anything that came undone. I slowly removed the booster vacuum line and engine started to die, so that isn't already sucking air.

Sprayed brake cleaner heavily around back of engine and AAR, no change in idle.

Picture my finger and thumb squeezing a blade of grass; that is how close I am to getting the Bitz kit.

I also did the slightly raising and pulling down the arm on the FD unit and both actions caused the idle to drop.

Any ideas?

[Dave Kost]

I'm sure you have done these checks but let's confirm.....
Ignition-
What spark plugs are you running??
Have you visually checked them?
Copper I hope ?
Gap?
What does MSD recommend for the gap?
What type of ignition wires?
Points? Have you changed them lately? I would.

Mixture setting- Sounds like you are running lean, so I would turn the mixture screw clockwise 1/4 turn. This will richen the mixture. (The 3mm amen screw)

Also, If it were me I would go back to the CDI box. Maybe you could borrow one from a local.

[Dave Kost]

Set the AFM between 13.94 (CO 1.5%) to 13.35 (CO 3.0%) at 950 RPM. This is done by turning the 3mm allen adjusting mixture screw at idle.

Let us know if this helps.

[rwest]

Hi Dave,

Pretty much the whole ignition has been replaced within the last year, just got the distributor rebuilt with new points and before that had put in a new set this year. Wires are Clewitt and less than 5,000 miles. MSD box just replaced two weeks ago. Not sure what type of plugs, but from Pelican and gapped to slightly bigger than stock as read in several places here. Dwell and timing spot on- well at least static timing, car started running bad on my drive to warm up, so I didn't do a 6,000 setting.

Car was running 13 AFR a couple weeks ago and then suddenly, like when it dropped from idle off the freeway went lean and started backfiring out the tailpipe, so something failed or false air is getting in to cause my problem. I did move the 3mm screw about 1/8 turn with no change.

Can't find a vac leak- doesn't mean there isn't one, or a component has failed- not sure which one?

I'll probably order the Bitz in the next day or so- so many things could be messing up my driving fun from CIS, that unless I want to keep chasing this thing and throwing money at it, I think that's my best move.

Thanks

[Nux]

Originally Posted by rwest

Double checked LM-2 calibration and it was spot on at 20.9

Car still was running 15 plus AFR cold. I poked around best I could and couldn't find anything that came undone. I slowly removed the booster vacuum line and engine started to die, so that isn't already sucking air.

Sprayed brake cleaner heavily around back of engine and AAR, no change in idle.

Picture my finger and thumb squeezing a blade of grass; that is how close I am to getting the Bitz kit.

I also did the slightly raising and pulling down the arm on the FD unit and both actions caused the idle to drop.

Any ideas?

After two blown Airbox'es due to backfires and vacuum issues, and a troublesome WUR - I was really tired of CIS.

Installed the Bitz kit during a weekend last year. Very easy. Runs flawlessly. Hugely improved throttle response. Nice gain in HP. I'll recommend Tony's kit to anyone.

[rwest]

Originally Posted by Nux

After two blown Airbox'es due to backfires and vacuum issues, and a troublesome WUR - I was really tired of CIS.

Installed the Bitz kit during a weekend last year. Very easy. Runs flawlessly. Hugely improved throttle response. Nice gain in HP. I'll recommend Tony's kit to anyone.

Placed the order this afternoon!

I just don't need a "parttime job" trying to track down the problem, I spent over a grand last year replacing the airbox and all the hoses, seals and gaskets and have hooked up gauges and tested components several times without finding a obvious issue.

I'll be interested to see if I find anything blown or disconnected when I remove the CIS.

I'll update and possibly start a new thread on my Bitz install.

Rutager

[Saadi996tt]

Eagerly waiting to see how this CIS issue turns out, please keep us posted.


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[rwest]

Originally Posted by Saadi996tt

Eagerly waiting to see how this CIS issue turns out, please keep us posted.


Sent from my iPhone using Tapatalk

I decided to remove it all and install the Bitz EFI- I will investigate the CIS once removed to see if something came loose or a hose split.