Engine stumbling and bogging when you pull away from idle--77 Newport with a 400 and TQ carb

[70bigblockdodge]

I wonder if that little plastic tube from acc pump to discharge nozzle isn't leaking.
After 40 years and ethanol gas.

 

[kmccabe56]

I've experienced this a few times. Might not be the same for your car, but it sounds to me like there is a small vacuum leak. Check the valve on your Power Brake booster, also look at all the hoses coming off the intake. A slight leak will cause the stumbling you are mentioning.

Agree. Also need to bite the bullet and pull the intake to check the crossover passage. If it plugs up then you have a hell of a time with warmup and then once it's finally hot, then you get fuel percolation from the heat boiling the carb dry.

 

[Pclancy]

Wow, all this great advice. I am in Conakry Guinea now, and the Newport is in a garage.

In three weeks or so, I will have it driven to my mechanic and:

Ask that we check again for vacuum leaks, paying special attention to all the tips you guys have given;
Failing improvement, replace the TQ with an eddy 1406 reman
Look for a place to buy non ethanol gas (not sure where to find that in DC)
Not sure how much work is involved in pulling the intake. Perhaps best done when replacing the carb?
I will give my mechanic a printed out version of this chain and ask that he read it.
I go back for some R&R second week of March and will look forward to an empty wallet but also a smooth running Newport.

Thanks

Peter

 

[cantflip]

Wow, all this great advice. I am in Conakry Guinea now, and the Newport is in a garage.

In three weeks or so, I will have it driven to my mechanic and:

Ask that we check again for vacuum leaks, paying special attention to all the tips you guys have given;
Failing improvement, replace the TQ with an eddy 1406 reman
Look for a place to buy non ethanol gas (not sure where to find that in DC)
Not sure how much work is involved in pulling the intake. Perhaps best done when replacing the carb?
I will give my mechanic a printed out version of this chain and ask that he read it.
I go back for some R&R second week of March and will look forward to an empty wallet but also a smooth running Newport.

Thanks

Peter

Peter, if you Mechanic is worth even a fraction of what you pay him... by all means print the thread and give it to him, but please allow him to diagnose the issues. No self respecting Mechanic will want to follow the Internet's directions to do his job, but no wise one would ignore a little good advice so long as it didn't cut into his time too much.

It is an unfortunate reality that the number of professionals out there who are familiar enough with our older cars to be able to competently diagnose and repair them is getting fewer every year. Couple that with the lack of available parts and poor quality of many of the parts that are available... be patient, they may need a few days to make things right.

BTW, once in a while a sharp young guy is the one who will do this job best. I am pretty sure the generation who worked on these when new are retired or trying to be, but a younger person who loves the cars may have all the skills and time working with them necessary to do excellent work. Nobody can really make flat rate workout right on stuff this old, so it really comes down to how much they give-a-crap.

 

[commando1]

Ask that we check again for vacuum leaks, paying special attention to all the tips you guys have given;

The tips given shouldn't be needed. A real mechanic would have done all of the tips given already.
Seems silly that YOU have to research what a mechanic should be doing.
How many Nissans and Toyotas are in his shop?

 

[Pclancy]

Thanks for those two comments Commando and Can'tflip. The vehicle has been to this particular garage many many times, and the mechanic has had plenty of time to diagnose the issues. He's in his fifties and he has managed to fix issues on the vehicle that another mechanic gave up on. Like getting the valve covers to finally stop leaking. Or getting the front brakes and alignment such that she drives perfectly straight with no pulling or drifting at any speed. I get the fact that any decent mechanic doesn't want a knucklehead like me giving him internet wisdom. So I tread very carefully and it is not me that determines what to try next. The last time he attempted to fix the stumble, he did not want to be paid if it was not right. I drove the car a couple of hundred miles and it was not fixed. I paid him anyway, as it was clear to me that the time he put into the car far exceeded his bill. The garage I use fixes all makes and models, and I picked them because they like older American cars.

I had earlier suggested that we switch carbs, but we are both a bit shy about cheap replacement parts. An earlier experience with the ICM caused no end of hassle. A new one put on that turned out to be bad.

In any case, I will keep you guys up to speed on what transpires on the next visit. But I will not agree to a third carb rebuild, and nor do I think he will suggest that.

This has got to be the luckiest Newport in existence. I have poured thousands into it. Many faults have been fixed. I am determined, no driven, to have it run well.

 

[cantflip]

This has got to be the luckiest Newport in existence. I have poured thousands into it. Many faults have been fixed. I am determined, no driven, to have it run well.

And bring it to Carlisle...

 

[Pclancy]

And bring it to Carlisle...

So we are finally now about to put in the eldebrock. Most folks here have recommended a 1406. But my mechanic says that runs even leaner than the TQ it would replace. He was thinking about the 1405. What do you guys say? Plus he says the 1405 comes with an electronic choke.

 

[Dobalovr]

So we are finally now about to put in the eldebrock. Most folks here have recommended a 1406. But my mechanic says that runs even leaner than the TQ it would replace. He was thinking about the 1405. What do you guys say? Plus he says the 1405 comes with an electronic choke.

Umm no the 1405 is a manual choke the 1406 is an electric choke. I also don't agree that a properly set up 1406 runs leaner than a TQ. Suggest your man reviews their website.

Here is the owners manual. Page 23 shows you how to make a 1406 run richer but your engine is a low compression smog motor so it is designed to be lean.

http://www.edelbrock.com/automotive/misc/tech-center/dl/carb-owners-manual.pdf

 

[Snotty]

The Eddys do tend to run lean out of the box, but there are plenty of kits available to change jets and spring rates.

 

[Tsarofcars]

I have had nothing but problems with my ignition system and carb. No doubt due to some problems that came with the car, mistakes made by my mechanics and/or bad parts that we have put in. Or some evil combination.

About 6 months ago, we removed the lean burn. Everything worked well for a couple of months, but then the ignition began cutting off at random times. We diagnosed that as a faulty orange box (ICM). Put in a ICM made by standard and that stopped producing spark after a couple of weeks. Completely. Now we have put in a chrome ICM made by Mopar. That problem seems to be solved, and the spark is strong. Starting is either instantaneous (just after shutting down) or after just a bit of cranking when cold. I can live with it. The choke works well.

But the engine runs a bit rough at idle, especially when warm. Barely noticeable, but it is there sometimes (and sometimes not when the engine is cold). Feels like a very tiny rumble/misfire. And the engine stumbles and bogs just a little bit when you accelerate very gently from idle or a stopped position (on the flat). Or when you go up a hill, very slowly, from a stop. As you speed up past 10-20 MPH or so, the engine smoothes out and runs perfectly. At highway speeds, she runs like a champ. Smooth.

To fix this, we have rebuilt the TQ (original) carb. Twice. We have replaced the spark plugs. We have installed a new ICM. We have checked and adjusted the distributor. We have readjusted the choke and the vacuum advance. All wires and connections have been checked. Everything has been gone over twice. I'm sure I am missing some stuff.

You guys know by now that I am not a mechanic. But I choose my mechanics carefully, and the guy I have is good. But he seems to be stumped. And like all of us, he isn't perfect. The latest theory was that we replace the spark plug wires.

Any ideas? Thanks as usual!

Peter

 

[Tsarofcars]

May be off base but a similar "bog" problem with my old Carter was a sticky accelerator pump.

 

[Rick Saucier]

Is the vacuum advance hooked up to a ported or manifold source? It has to be manifold (constant).


cheers

 

[Pclancy]

An update to all who contributed to this thread:

Indeed my mechanic was able to eventually get rid of the flat spots via a combination of boring out the jets, adjusting the metering rods and also messing ever so slightly with the timing. The engine now runs 9/10, with no hesitation and smoothness all the way through its power band (or mine, anyway).

This completes an arduous, lengthy and expensive transition from lean burn. Two new ICN boxes installed before one worked well. New spark plugs, wires, new distributor cap, ballast resistor (two tried), and several carb rebuilds. Endless fiddling.

But she runs very well now and I could not be more pleased. Thanks to all for the great advice.

 

[1978 NYB]

Glad you got her sorted out.

Happy motoring!