New to me 78 NYB on its way but please Don't tell my wife

[73 T&C]

Notes on engine and car after last night.

Car ran right up to 80 on the expressway with dead on tracking. Brakes even and straight. Very slight drift to right with slope of pavement.... normal.

Engine at speed was glass smooth and required only the least amount of throttle to maintain speed. Engine responsive, if a bit weak, at part throttle when at speed.

Full throttle from standing start results in bad bog which clears immediately if released to part throttle (just before opening of secondaries) no backfire and no popping.... and no stumble but a 1/4 second bit of a delay.... more of a feeling.... like a modern drive by wire. Not like the wagon where it is crisp and instantaneous.

Pulled over and leaned out the idle screws back to 3-1/2 turns out from closed. This had no effect on idle speed but resulted in slower rpm with tranny and A/C engaged.

Items to check:

Thinking timing, vacuum leak inside carb or past carb into manifold.

Install spare carb???

Set basic idle engine timing 10* BTC and rpm per FSM.

vacuum to cruise control.

Check fuel filter for debris. Change to transparent unit.

Check secondary choke plate operation... may be coming in too quick/spring not adjusted properly.

Spray carb cleaner to look for leak under manifold and at manifold/head.

More as I think about it.

 

[Carmine]

Pardon me for not re-reading the whole thread, but have you ever looked at the car's ignition pattern on a scope? How about t-chain stretch? I think a smoke generator would be helpful as well.

You're doing a very high-level diagnosis and I'd want to be absolutely certain there was no potential mechanical issue.

 

[Carmine]

Couldn’t resist.

It should be noted that any good Michael Jackson song is really the work of Quincy Jones.

 

[73 T&C]

Pardon me for not re-reading the whole thread, but have you ever looked at the car's ignition pattern on a scope? How about t-chain stretch? I think a smoke generator would be helpful as well.

You're doing a very high-level diagnosis and I'd want to be absolutely certain there was no potential mechanical issue.

Smoke is a good idea..... hmmm

I hand turned the crankshaft and didn’t feel any play between the crank and valvetrain. Also, the heads were obviously done fairly recently and compression test was very good.

I’m thinking the scope will only show they are all firing evenly. But not a bad idea.

 

[73 T&C]

Great clear article on troubleshooting the ELB system. Best I’ve read so far. Unfortunately, it is for the first more complicated version though the checks and operation are the same. In 1978, mopar went from the initial double system (for run and start with basically two computers as a failsafe) to a single integrated computer. The updated system used in 1978 was much simpler and less complicated but the testing procedure was the same. I’ve been reading and comparing the 1978 and 1977 FSM to compare the testing and troubleshooting procedures. Finally, in 1978, mopar also deleted the centrifugal advance system for better control of overall spark timing.

The author takes great pains to get the two testing procedures correct and addressing both versions of this early spark control system.

Popular Mechanics

Here’s part 2 of the above article:

Popular Mechanics

 

[Carmine]

I’m thinking the scope will only show they are all firing evenly. But not a bad idea.

Scoping secondary ignition systems | Search Autoparts

Some of what's covered above as a bad injector in an individual cylinder would apply evenly to your engine, such as a lean mixture being harder to fire. Granted, you don't have a proper baseline to judge against, but perhaps you'll turn up a large KV difference from off-idle under load (obviously with the brakes on, etc.)

 

[73 T&C]

Scoping secondary ignition systems | Search Autoparts

Some of what's covered above as a bad injector in an individual cylinder would apply evenly to your engine, such as a lean mixture being harder to fire. Granted, you don't have a proper baseline to judge against, but perhaps you'll turn up a large KV difference from off-idle under load (obviously with the brakes on, etc.)

Believe it or not. We’ve got an old sun diagnostic computerized tester with an oscilloscope.... I’ll hook it up to see if I can trace the cause of the rough idle. But as you know, it could be anything at this point. From a weak or failing coil to a bad or improperly set pick up to carbon tracking in or on the new cap.

Having changed the computer and cleared the backfire issue, I’m thinking what is left is probably....,,stupidly simple.

 

[cantflip]

I'm going to back Carmine up on this... use the scope. The biggest challenge with reading a pattern is the realization that more than one issue could be the cause of a pattern change. With all the tinkering that you do, I believe you will benefit greatly by comparing the changes as you continue to work on her.

"But as you know, it could be anything at this point. From a weak or failing coil to a bad or improperly set pick up to carbon tracking in or on the new cap."

Those are perfect issues for a scope to assist in the diagnosis. I would also recommend that you print or take a picture of the screens for reference. I think it will help you see differences as you get her running better, or worse, and make why more clear. There are several folks in here who would like to see the patterns and I'd enjoy getting to see what I can learn from the others, like Carmine, who have a solid background. I will be willing to assist with whatever I can too.

 

[cantflip]

I also keep thinking this car would benefit greatly from a smoke tester...

 

[commando1]

I also keep thinking this car would benefit greatly from a smoke tester...

He will never, ever, get rid of the stumble, bog, cough, farting, or whatever you want to call it, flooring it from dead idle. The TQ has never been able to transition smoothly from the idle circuit. I was able to once for about a week.

 

[Carmine]

He will never, ever, get rid of the stumble, bog, cough, farting, or whatever you want to call it, flooring it from dead idle.

If you read the link to the government testing that Javier posted, the Feds call it "stretchiness", which is hilarious because only the Federal government could create an automotive term that i've NEVER heard used in the real world.

 

[commando1]

If you read the link to the government testing that Javier posted, the Feds call it "stretchiness", which is hilarious because only the Federal government could create an automotive term that i've NEVER heard used in the real world.

I saw that, too. Made me scratch my head. I'm just assuming that's gummint-speak for, Runs like ****.

 

[73 T&C]

If you read the link to the government testing that Javier posted, the Feds call it "stretchiness", which is hilarious because only the Federal government could create an automotive term that i've NEVER heard used in the real world.

Was wondering how long it would take one of you to pick up on that observation and term..... my money was on Stan.

 

[cantflip]

He will never, ever, get rid of the stumble, bog, cough, farting, or whatever you want to call it, flooring it from dead idle. The TQ has never been able to transition smoothly from the idle circuit. I was able to once for about a week.

I was thinking about vacuum leak diagnosis... By my observation, Javier will have to create a 30 page thread on the mastery of the TQ before he gives in to an Eddie.

Was wondering how long it would take one of you to pick up on that observation and term..... my money was on Stan.

Nah.. I saw it first and bit my tongue

 

[commando1]

Actually I'm enjoying Javier's dedication to beat the TQ.
I like to watch.

 

[73 T&C]

I was thinking about vacuum leak diagnosis... By my observation, Javier will have to create a 30 page thread on the mastery of the TQ before he gives in to an Eddie.

I don’t think 30 pages wouldn’t cover it.... but I do admit it took me a good bit of time and careful checking to get the TQ’s in my ‘73 wagon and my ‘73 Road Runner to work well. But they now both work just fine. Very responsive with no bog. They do require a good bit of adjustment on the car to get them “dialed in” but not more than the Holleys or Quadrajunks I’ve had to wrestle with in the past.

On both those cars I even connected and evaluated the orifice delay on the advance before I eventually bypassed them.

Because the TQ’s run fairly lean to begin with, smooth idle is the hardest part to get right because they are so sensitive to even minor vacuum leak and choke issues.

Obviously, timing is also a big issue, a little bit more advanced (2 degrees or so) than spec seems to work best over base stock setting.

There are lots of books and articles out there and I have collected quite a few. Here are some of which I’ve collected to help me over the years as well as valuable help I’ve gotten on this forum.

So.... back to my ‘78 NYB.

Because it’s version of the TQ is even more lean running, it’s an even bigger challenge to get right.

But that is only one part of the problem I’m seeing now.

The idea from Carmine, with Jeff’s support, will have me put it on the old Sun diagnostic computer this weekend to look at the spark and ignition on an oscilloscope the help me wade through the issues that surround the TQ.

You will recall that, other than a stumble, I had her up and running fairly well early on. In part, that is what is driving me forward now.

If I do “give up” after everything else is ruled out or repaired, I may go with an earlier TQ (as much to unify the fleet as anything else) and adapt the ELB sensors (TP transducer and idle stop switch).

If after that, if I don’t like how the ELB works, I would probably go to the earlier, simpler, Electronics Ignition module and swap out the dizzy to a centrifugal/Vacuum advance module. And that would be that....

Either way, it should be an interesting ride... which I will do my best to share with you guys.

Like Stan said I also “like to watch” ..... which has taught me much around hear.

And what should be compleyely obvious to you all by now is.... I love Puzzles!!!

If I haven’t said it before, let me say now how much I appreciate the support and interest I’ve gotten here with this little project.

Thanks to you all!

And there I go again.... another perfectly good early lunchtime invested on my puzzle.... Writing about it to help me think it through.

J

 

[73 T&C]

I woke up at 4:00 am bolt straight upright in bed with a possible epiphany as to my 440 troubles.

Will verify tomorrow.... and play with the scope.

Clue..... it was something I did different when I rebuilt the TQ the last time....

Here’s a picture of the carb numbers. It’s correct for a ‘78 440.

Here’s the master carb list...

A Carter Thermo-Quad Guide

 

[commando1]

Here's my guess..
You need a thinner rod.

 

[73 T&C]

Started a little late today because I had my road runner being worked on for some minor but important body rust issues and l,..... my friend Costas need my help with checking the sunroof panel.

 

[73 T&C]

Costa’s shop (TSA motors) is down the street from Ivan’s shop so I was still able to get there around noonish.

Started by checking voltage at all the sensors switch’s etc.... all good. Getting ready for the old Sun Diagnostic computer testing.

One final thing to do was to check and reset/verify basic timing. FSM calls for 12 degrees +/- 2. I set it at 14 and proceeded to check the fast idle at 1400 per FSM.... setting the fast idle to that.

My epiphany was that I changed the carb base plate gasket to a brand new one I had.... the last time..... when all the issues started happening.

When I woke up last night, I remembered I had done that. And the following memory... That’s when it hit me.... Sherlock Holmes....

“When all the possible options are ruled out, the answer must be the impossible.”

So...... This is what I wanted to check... the impossible... that the carb base plate gasket was bad.

Well... here it is:

While doing the fast idle check.... I observed this:


Waiting for it to cool down to change it now.