Idle quality issues. Boy I sure talk alot.


New Member
Jul 31, 2015
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kewanee, Illinois
Hello All,

So I finally got around to doing some more digging on my Newport and have not been able to diagnosis a rough idle issue i have (guess I have an idea I just don't want to face it). I think the best place to start would be with what I have done to the car and what I have tried in diagnosing the issue.

When I purchased the vehicle it already was a lean burn delete, looks like an old Chrysler kit as it has proper connectors and a five pin ignition box. It had also had installed a vacuum advance electronic distributor. The car idled fine but was gutless even for a heavy metal sled with a stock 400. I noticed that it still retained the lean burn T-quad and none of the ports supplied any reasonable vacuum off idle with the gauge.

My first step then was to replace the carb. I went to the Uremco web site and used their carb look up tool to figure out which stock T quad I should purchase for a Lean Burn deleted system. Then took that part number to Summit and bought the in house brand reman carb for my vehicle. Installed the carb, and Bam! Still gutless.

Ok next step tune up as the vehicle had sat for long and long. Cap, wires, plugs, drained fuel, replace fuel filter, added fuel filter at the carb, topped off tank with premium fuel and a treatment of sea foam. Quick internet search of timing specs lead me to 5deg BTDC at idle, timing in tolerance +or- 2deg. Watched about two hours of T quad tuning videos on you tube, broke out the vacuum gauge again and set the carb for performance not emissions. Fired right up, ran smooth, still a dog when I put my foot in it. AHHHHHHHHHHHG!

Fine, fine I think maybe it just needs drove kinda work the kinks out. Put a 1000 miles on it and all of a sudden it won't start without splashing a bit of fuel in the carb. Look close and the accelerator pump isn't pumping. The fuel bowls are full ( I tried to fill manually but wouldn't take any more) fuel pump was working, pulled accelerator pump jets and those were clear.

Rewatch T quad youtube vids, learn to take apart carb without destroying it, practice on old T quad. I pull the top half only of carb, discovered check ball wedged in the brass puck in the bottom of pump. This had caused the pump to suck the seal right off the pump shaft. Was unable to dislodge ball from brass puck without damaging it. So I bought a reman kit and replaced the brass puck and accel pump. The ball in the old pump was really misshapen. I wish now I would have contacted Summit and tried to warranty the carb but I guess hindsight is always 20/20.

I fill the bowls, pump the gas, turn the key........Vroooom! Repeat carb tuning steps. Drive car, still a dog, and now it has a very light but noticable surge. All of that accompanied with a feeling that in gear it wants to die. Engine is so quite I can't hear it running, but you know how when your driving a car the vibration and little ques tell you it's falling off?

Alright relax I say to myself. I take the car to a few people and ask questions. None of them believe I screwed up anything in the carb but that the issues are ignition related. These problems are coming to light as things are being fixed. So it is recommended to me that I check my tune up, compression check the cylinders, test the coil, check the charging system as voltage and spark health are big parts of the Chrysler system.

Lets see. Battery brand new and load tested good. Coil replaced and ohm'ed out good. Alternator charging and when voltage drops below 12 it kicks on and charges up to 13.5ish good. Compression all cylinders but 1 over 120, low cylinder was 115 all within 5% tolerance. Plugs were fuel fouled and a bit oily, I replaced them. One plug wire had a burn so I taped and covered section with rubber fuel line then rerouted to prevent same from happening again. Replaced fuel filters again. Checked timing and did another internet search, discovered that when you do the lean burn swap that there should be 38ish deg mechanical timing overall and another 20ish deg vacuum advance timing overall. All the while I'm doing this the idle quality is deteriorating but the engine is coming alive like never before off idle. So I retime the engine taking new numbers into account and wow this thing would rip the tires off, secondaries would open and you heard that T quad song. You could just feel it press you into the seat like a rocket on a roller skate. Holy snikeys it did not idle worth a crap. It sounded like an old Massey Fergussen tractor. I had to feather the foot feed to get it to run right when I drove it and the only time it felt really happy was at WOT.

At this point I'm at a loss. No mechanic in town will touch the carb. All the old carb guys I remembered were dead or retired. I am leery about digging back into the carb as it's obvious that I screwed something up. I do not want to spend another 300 plus on another carb or another 300 plus to mail out to a specialty shop that won't turn it around until next year some time. For the same price I could buy another carb. The waits were unrealistic on some of the sites I looked at.

If there is something I missed I could sure use the insight. I'm sure I'll have to tear back into the carb. I just dont want to. Any links documentation or good old fashioned common sence that I might of missed would be appreaciated.
I fought with my TQ for years.
It felt like it was on the bench more than on the engine.
Had it restored by Scott Harm.
Looked at every YouTube video.
Read everything on the net.
Bought the specialized tools.
Ran like CRAP!
Bought a 650 Edelbrock, plopped it on as is out of the box. No adjustments.
Engine runs so smooth it feels like fuel injection.

What can I say....
Welcome aboard. I'm sure some of the less technically challenged here will pipe in and offer advice. What raised my antenna was your description of the plugs as fuel fouled and a bit oily,.
Were you able to keep cruise and all the stock linkages?
Buy the:
1. Adapter plate so you can mount the Eddie onto the stock manifold.
2. Chrysler throttle linkage adaptor.
3. Chrysler Cruise Control adaptor.

Five minutes to remove the TQ.
Five minutes installing the Eddie.

Have a beer and feel as defeated as I did because I insisted that I was so smart I could make that TQ work.

Well, I actually did make that work a dozen times.
Each time for about a day...
Im assuming here and we know what that does to people, but the fuel was from something I had done in the carb. The oil I'm hoping can be traced back to some really failed valve cover gaskets. I replaced the gaskets and and the PCV valve in the D/side Valve cover. I also cleaned the vent that connects to the breather on the P/side of the car. I was cconcerened that I was sucking oil into the intake.
Oily plugs =
1. Rings, or...
2. Valve guides.

Compression test will determine which it is.
From everything I've ever known or heard about T-Quadz, They either run fine 'til they don't anymore or they've already reached the "'til they don't anymore" stage. You're right tho'. Most tecz that could work on them and win the battle are retired or toez up lookin' at the brown side of the sod. Personally I'd follow Stanz lead on this one. The 650 Eddelbrock is a real close re-pop of the old Carter AVS only better 'cuz all the little partz for rebuilding are readily available and the end of sales on 'um iz no where in site. You'll be so happy you'll have your head out the window smillin' so big you'll be catchin' bugz in your teeth
ok carb, linkage (throttle and cuise),adaptor plate all ordered. Hopefully this will fix the idle issue. On a positive note, Summit rep said call tech support on monday they might warrenty the old cab.
just over 120 psi on all the cylinders, one was at 115 maybe above a little. I question guides though in this instance. I know I could be wrong, I've been doing things wrong my whole life, but this was a 1 owner car under 18k miles when i got it. It did spend a lifetime in a garage though not running. Do these 400's have umbrella seals like GM products? I guess thats still a guide leak.
The seals on the valve guides go rock hard with age so hearing that the car is one owner low mileage it probably hasn't had the rocker covers off its entire life. Once you have the carb and idle issue sorted, see how it runs then. If the plugs are still oiling then have a look at the guide seals. The compression is acceptable but not great too, it shows though there is no failure on any of them, 5psi difference between cylinders is acceptable and normal.
Morning Everyone,

So got the eddy carb installed on the Newport, Summit was super cool and will warranty the thermoquad once it gets back to them. This is the second one that I had bought, which also was a failure. Cruise, throttle and kickdown all hooked right up to the Chrysler adaptor for the throttle. Just needed the old throttle linkage clips and throttle rod.

Moral of the story here as another person that has learned the hard way about the thermoquads. Buy an eddy with the right parts and put that on the car. Take your old thermoquad and put it on the shelf till you need to sell your car. I wanted so bad to keep the car as stock as possible. I wasted a month of not being able to cruise and drive my car. When I did drive it I was unhappy with everything about it. The experiance was truely miserable.
I'd have a closer look at the spark plug wires just to be sure they're working as they should as well.
The single biggest issue on the Tquads is the lack of parts for them. They were designed before modern fuels and in order t "run perfect" in some cases they have to be modified without having parts to do so. From what you're saying - the idle circuit may have had a blockage, or it might have just been too lean for the engine and fuel combination. That, is VERY common. The peformance carbs from any manufacturer are designed to hve richer idle circuits (referring to air bleeds and emulsion tubes/orifaces - not mixture screws) and that tends to make everything better. You needed a Thermoquad expert - because the Quadrajet guys have access to parts ao they tend not to really have much Tquad experience.
Regardless - hopefully this cleans it up for you. I wouldn;t worry too much about the compression numbers at this point. Watch the plugs. If they get oil up, or you see blue smok out the pipes, then you will want to look into engine repairs.
The seals on the valve guides go rock hard with age so hearing that the car is one owner low mileage it probably hasn't had the rocker covers off its entire life. Once you have the carb and idle issue sorted, see how it runs then. If the plugs are still oiling then have a look at the guide seals. The compression is acceptable but not great too, it shows though there is no failure on any of them, 5psi difference between cylinders is acceptable and normal.

That's right, and was the case on mine. The intake stems had a positive seal and the exhausts had an umbrella. I replaced all of mine on-car after the plugs kept was a ***** but well worth it. I used two different types of spring compressors plus an extra hand to do the job and had to be extremely careful not to loose any keepers!

And, after that operation, I was still getting oil fouled plugs, though not as bad. It was still not idling that well but performed good on the highway. So, two weeks ago I pulled the intake manifold and installed a new gasket. The intake showed big sighs of leakage - oil in the ports, exhaust burn patterns on the valley pan underside, etc.
With a new gasket and valley pan installed, it's like a new engine! It idles smooth as ever now, and the Plugs are staying clean.
Thermoquad is a better doorstop than a carb. My buddy's battling his. I told him put an edelbrock on it and be done. He's freakin stubborn. Anyways , I would have used a vacuum gauge and adjusted idle air mixture for maximum vacuum reading. JM.02. Rs59
I like my T-quad. 850 CFM and it idles smooth. All of the idle problems I had previously were the fault of the engine, distributor, and wires. Not to say I haven't had carb issues, though.

The T-Quad spent some time on the bench the past three weeks. Hard starting cold and hesitating when cold. Ran well when hot, though.
As expected, it was the accelerator pump. It's not the carb's fault, the fuel is to blame here. The "new" fuel is causing the plunger seal to shrink. I am fortunate to have a 50+ year old carb shop less than 10 miles from where I live, complete with "old guys" that know how to work on stuff like this. They were able to supply me with new pump seals (or cups) which solved the problem. Also had some insight on how the new fuels are attacking various parts here and there...
Yesterday I found some fouled plugs, however. Might have been a too rich condition, not sure yet. The jets were changed to a bigger size temporarily to (unknowingly) compensate for a vacuum leak. Now that it's all fixed, we'll see how the plugs do...

Pump Cups.jpg


plugs 2015-11-08.jpg

Plugs 2015-11-08 (2).jpg