Newly purchased GT350 flawless 150 miles. Now sputters out every few miles.

[1690]

All good suggestions.

Last addition....I did not see this mentioned: Was the gas tank and fuel lines replaced or are they original?  How is your fuel?

[mark p]

Another vote against synthetic oil for break-in. Run regular 30 weight for first 100 miles. Drain and 30 weight again to 1000 miles. Then Mobil 1 forever. With a flat tappet cam you'll feel better if you add some zinc too but I've found Mobil 1 is a good enough lubricant not to need it with stock valve spring rates. New cars come with semi-synthetic oil not full synthetic. I also use a filter designed to work with synthetic oil.

FWIW, new Fords use that 5W20 Synthetic bland (per some buddies), new GM uses 5W30 Sythetic "Dexos" ONLY specified for my Acadia. Not sure about FCA or them furrin brands.

[deathsled]

Once you get it sorted, that Jaguar will be experiencing this instead of smiles and laughter. Remember B production champions from 1965, 1966 and 1967!

[s2ms]

Some great advice here.

One thing I haven't seen mentioned is the coil. Probably unlikely in your case but in my experience failing coils can cause very weird, intermittent problems, especially when hot. Can't explain how using the choke would make things better unless the denser fuel charge helped with a weak spark?? Anyway, something to consider, especially if you're using one of those lousy repop yellow tops, and easy enough to check.

Dave

[sg66]

After about 100 very gentle brake-in miles 2148 started acting like it was running out of fuel. I discovered that if I pulled  the choke out when it started coughing and sputtering, it smoothed out, but when I pushed the choke in, it coughed and sputtered out and will die unless the choke is pulled out a bit

With no choke: it dies and off to the side of the road I go.

If I let it die, and sit by the side of the road .....for 5 minutes or so, it fires right up again and might run fine for several very controlled throttle sensitive miles; then it sputters and coughs and dies unless I pull out the choke and try to tease it on homeward bound.

Could it be a gas tank that has debris inside clogging the fuel system? The tank looks like it was replaced at some point because it looks spotlessly shinny tin on the exterior which would perhaps explain several cut wires right above the tank, and the fact the fuel gauge doesn't work, except a barely perceptible "movement " when the ignition is turned on. Im thinking the gauge itself works but the sending unit doesn't work.

Re-reading this today, it sounds like the first 100 miles had no issue? This would likely mean the float levels are probably not the cause....but still worth checking. The car is dying due to lack of fuel which you can temporarily correct by pulling the choke. So the question is whether there is a piece of debris inside the carb which temporarily is blocking normal fuel delivery or if the issue is outside...filter, pump, fuel line, sending unit. Check the float levels at idle first and then go for a drive. If/when the car dies, pull over. Do not try to crank the motor over yet. First open up the plugs on the fuel bowls. Does any fuel come out of the bowls? If no, shake the car side to side, any fuel? If no, now you know you have an issue getting fuel into the bowls. I say "bowls" because you would also need to check the needle and seat in the carb. If fuel comes out when you first open it, your issue is very likely a foreign object inside the carb which is preventing proper fuel delivery into the intake. 

I have a lawn tractor that was doing the same thing and turned out the gasket on the fuel cap had eroded and pieces of rubber had fallen into the tank and found their way to the outlet blocking most of the fuel from entering the line to the filter. Moving the throttle to choke would help it run for a couple seconds but eventually it would die. After sitting for a minute, the rubber would float away and the engine would run fine. Filters should prevent this from happening inside your carb but if it was rebuilt and a piece of gasket or something is floating around in there, it could have the same effect. Ethanol fuels are not friendly to many parts. Fred Ballard rebuilds the fuel pumps for these cars and uses parts that will not deteriorate from ethanol. The other oddball thing to consider is vapor lock but I was in Palo Alto a few weeks ago (right by the McLaren dealer) and it didn't seem hot enough where ambient temperature would contribute to vapor lock. That also usually takes more than 5 minutes of cool down time to go away.

My personal experience with a bad fuel pump was at SAAC 10 when there were a bunch of us doing burnouts outside the hotel parking lot. After a few, my engine would no longer rev beyond ~ 3,000 RPM's due to fuel starvation. I drove it home over 200 miles and had no issue as long as the RPM's stayed low.

I also had a friend with '58 MGA with a similar problem to what you describe. Carbs were getting fuel at idle, new filter but after driving, crapped out. Traced it back to an electric fuel pump with a canister like on '65 pumps that had filled up with rust and sediment from the fuel tank. When the rust settled, it could pump enough fuel but once the car started to move, it was enough to kill the fuel delivery.

[NC TRACKRAT]

Like sg66, I vote for trash in the tank.  You start off fine but, after getting up to operating temp, the sediment or rust in the tank sloshes around and gets suspended in the gas, then clogs the pick-up in the tank.  You sit for a while, the crap settles and you can drive o.k. until it stirs up again. If they didn't replace the tank when they did the restoration, this is the first place I would investigate.   Drain/siphon the gas, take out the sending unit and look in there with a flashlight.  Many years ago, this same thing almost ruined a day for me at Summit Point

[corbins]

Certainly sounds like a fuel delivery issue,,  not a damn thing to do with oil. Especially after 150 miles of "carefree" driving.  Either float levels are off , or something is clogging up the filter /needle and seat. Sediment, rust, deteriorated seals/gaskets , etc as has been suggested already. Good luck ! Try the easy stuff first

[98SVT - was 06GT]

Once you get it sorted, that Jaguar will be experiencing this instead of smiles and laughter. Remember B production champions from 1965, 1966 and 1967!

This same scene with the same cars was repeated at Monterey Historics - until 5R001 broke.
I vote for carb. Not delivery as when you pull the choke it runs better so there is fuel for it to run it's just not being metered through the carb right. Pull the bowls and make sure there isn't crude floating around. Also if it's ever sneezed it probably blew the power valve so change that while you are in there.

[zray]

IMHO I and many others just install Brad Penn brake in oil and be done with it.  Run it up and down the rpm with a slight load in both directions  - up and down the rpm range.  Yes this can be seen as old fashion but has served many well for 60 plus years

I'm with you 100% on the slight load / up and down rpm range. Fastest way to seat rings, and end up with the most HP.
note:  .....didn't know Brad Penn made brakes, but I'm usually uninformed about these  "braking" developments, nevertheless,  I want to be there when you put the brake(s) in the oil. .....don't just love spell check  

Another vote against synthetic oil for break-in. Run regular 30 weight for first 100 miles. Drain and 30 weight again to 1000 miles. Then Mobil 1 forever........"

using a straight 30 wt. for a break in oil is great for accelerated wear vs. any multi viscosity. However, there is a difference between breaking in & wearing in. A multi-viscosity oil will reduce wear during start up and during the warm up phase, where much of the wear occurs. After an engine had reached full operating temperatures, a straight 30 wt. and a 0w-30, 5w-30, or 10w-30 have have the same flow properties,

https://www.blackstone-labs.com/oil-viscosity.php

".......FWIW, new Fords use that 5W20 Synthetic bland (per some buddies), new GM uses 5W30 Sythetic "Dexos" ONLY specified for my Acadia. Not sure about FCA or them furrin brands.

a partial list of a few of the cars using full synthetic oil from the factory:

note: The Fords listed below use this full synthetic oil for a factory fill, and recommended  thereafter:

Motorcraft 5W-50 Full Synthetic Motor Oil. Part number is XO-5w50-QGT  ( likely a re-branded Mobil 1 5w-50 ):

Ford GT
Ford Mustang Shelby GT500   5.4 S/C engine
Ford Mustang Shelby GT500   5.8 S/C engine
Ford Mustang Boss  5.0 4v engine
Ford Mustang GT Track Pack  5.0 4v
Ford Mustang GT350  5.2 4v
Ford Focus RS  2.3 EcoBoost

most of the following use Mobil 1  as a factory fill:

Chevy Corvette, Corvette C7.R & Camaro Z/28
Mercedes,
McLaren,
Porsche
Aston Martin,
Nissan GT-R
Bentley
Chrysler,
Jeep,
Dodge,
Ram,
etc.

....back to your regularly scheduled program.



Z

[6s1802]

The steel fuel line that ran from the tank to the pump on my '63 406 Galaxie rusted on the inside giving me the same symptoms you describe. I would look at the entire fuel system.

[2112]

I believe Motorcraft 5-50 full synthetic is made by Conoco

[zray]

I believe Motorcraft 5-50 full synthetic is made by Conoco

We say Conoco-Phillips in my neighborhood


Z
Bartlesville, Oklahoma, home of Phillips 66,
(& one block south from the Frank Phillips mansion)

[papa scoops]

probably just a cracked block. phred

[SFM6S1348]

Some great advice here.

One thing I haven't seen mentioned is the coil. Probably unlikely in your case but in my experience failing coils can cause very weird, intermittent problems, especially when hot. Can't explain how using the choke would make things better unless the denser fuel charge helped with a weak spark?? Anyway, something to consider, especially if you're using one of those lousy repop yellow tops, and easy enough to check.

Dave

I had a coil problem one time and it sounded somewhat like what is described here, except the choke. Mine would run for various times short and long. After being towed home by AAA I discovered the power wire to the coil was not pushed all the way down. It was loose causing power and no power. Pushed it down in place and have not had any problem.

Les 6S1348

[Steve McDonald Formally known as Mcdonas]

I went trough 6 of the "new" reproduction coils. Finally gave up and cleaned and repainted my old crusty, nasty, crudy, beat up looking coil. Hasn't missed a beat since. Before that I changed the carburetor twice, 4 sets of points and condensers, 8 sets of plugs, set of wires, cap and rotor, two sets of intake gaskets, check, compression, leak down, camshaft.
Car would run good one day, bad the next, fiddle with the crab, ran great, drive it 20 minutes, starting surging, popping back through the carb, running rough.
When I first put the car back on the road it wouldn't start, the new coil was bad. I can't belive how many of these coils I went through before going back to my old coil. May not be concours, but it never has failed