i never had those problems (85 CJ)....and the midwest gets way colder than that....so im guessing its not a design problem.

you might want to:
-check injectors, make sure they are giving a good spray,
-check for manifold leaks
-check Timing, i think Timing does different things in Dif Temps.

I did have a kinda similar problems, in any weather, because my exhaust was shot and didnt have much back pressure (lost Cat and Muffler to rust...fell off on the highway somewhere) ....ran fine when warmed up, but cold ran like crud.

if those dont take you anywhere maybe check O2 sensor

 

Do you normally let your Jeep warm up to full operating temp before driving?

 

There's no reason it shouldn't run perfectly in the cold. Not to say this is the cause, but there should be two temperature sensors. One in the block to tell the system what temperature the engine has reached (and enriches the mixture during warmup), and another near the intake or air filter to tell it the ambient temperature of the air to correct for density. Maybe one of them has gone bad?

 

The Howell performed perfectly for me down to -45*C... that's darned cold... I'm surprised they told you to change the MAP, as it doesn't come into effect until the engine warms up.

 

Mine runs great in the cold, well, as well as it does in the warm. I drove it a couple times this past week in below zero temps. My rough idle problem is an issue of a tired motor though. Mine runs a bit on the 'fat' side of 14.7:1 as well, but it's fine until the motor gets re-built. If I still have any issues with it I will address them then.
'83 CJ7 Auto, 258, 187,000 miles and never apart.

 

Are you running the Stock chip from Howell?

Without any tweaks for mixture?

 

FINALLY.. thanks to Rich, MY PROBLEM has been found. This is one for the records. My cold running problem looks to be all related to the Coil pick up. During below frezzing temps, one or both of the wires must be breaking or coming loose. Once warm they are more flexiable. I disconnected the vacuum advance and my CJ7 ran perfect in 27 degree temps..
Thanks RICH.... i can finally stop having nighmares..

 

CONFRIMED THAT DID IT..
The coil pick in my HEI distributor up was breaking down during the extreme cold temps, I guess the wires where to stiff. i repalce the coil pick up last night, this morning 24 degrees ran perfect. Very strang and very interesting problem. So after about 10 chip changes, it proved out not to the Howell set up at all. Just a critical feed to the Howell ECM.
Completely owe the solution to Rich. thanks again..

 

Just so everyone knows the logic behind it.
On a telephone conversation Roger mentioned a key factor. He was watching down the throat when it was doing it's stumbling.

---- (Please, please, please - whenever you do that wear safety goggles, all it takes is a backfire to permanently blind you.) ----

As he cracked the throttle the fuel shut off for a split second, it stumbled, then fuel started squirting again.

Ony a few thing happen just "off idle."

Hmmmm, TPS? No, he'd already swapped in another one. The likelyhood of two being bad at the same spot is -- awful!

MAP sensor? But it's not on a hard snap, just "ease into it off idle," a hard snap it's OK. The MAP sensor doesn't see enough vacuum drop on a soft "ease into it." It should also do it at higher speeds too, not just "off idle."

Could the Tach Sync signal to the ECM be getting lost for a split second? What would cause that? How does the engine know it's trying to accelerate? It gets it's RPM info from the tach input signal - from the module.
The module gets it's sync info from the pick-up coil.
The vacuum advance just barely moves at about 1200 RPM, right when the stumble occurs - could it be the PU coil wires themselves?
Tried something -- Disconnecting the vacuum advance made the cold stumble go away, proving it! I've seen the pickup coil wires go bad before, but it's a very uncommon problem. And never as a temperature related problem.
(Those tiny wires have to bend every time the vacuum advance moves - think about it - it's mind boggling how many times those tiny stranded wires have to move in 100,000 miles. Suprisingly, it's not a more prevelant problem.)

Just thought it was interesting how greenlighting this came up with the answer --- He He -- I HOPE!


Roger has had quite a few issues with the Howell swap.
Those contemplating it maybe can avoid a few by knowing what he went through.

- First he had a problem with the adapter for the throttle body. There's a big gap at the side -- Howell said plug it with silicone. Silicone "unsticks" with gasoline - causing a severe vacuum leak. The cure he did - there's a flat area on the adapter next to the hole. He simply used a blob of JB weld to extend the side of the adapter out a little to cover it. Used a file to make it flat on the bottom, and made a new larger gasket. Simple, easy.
Helped quite a bit.

- His HEI had the wrong vacuum applied to it - manifold vacuum suggested by Howell, instead of ported vacuum like an HEI distributor needs. Simple, hook it to the right vacuum source. Helped even more.

Since the HEI distributor was not from a TBI type vehicle, the ported vacuum from the TBI was not compatable with the distributor. Wrong curve, probably too fast coming in, too much too soon.
Using the correct vacuum source and re-curving the distributor correctly with an adjustable vacuum advance did the trick. All he needed was a timing light to do it.

Now the stumble, rough idle, tip in, ping, and other issues were gone. But still performance was not what it could be.

Then, disconnecting the vacuum line to the EGR helped even more. Roger said that alone made a huge difference in performance - now that the other issues were gone. Smoother and more power.

All the above - each trouble accentuated and masked the next one - it took addressing them one at a time. Sometimes we look for one simple answer instead of thinking multiples - fooling ourselves.

Everything worked great for a few months. But then it got cold outside. Only on very cold mornings did it stumble, 25 degrees or less, but as soon as the engine warmed up for a moment it no longer stumbled, ran fine the rest of the day. This didn't happen until recently, but was it? Since it never got that cold before who knows.

More chip burning from Howell. They've been very helpful and willing to try, but their focus of attention is on the computer aspect of it, not the entire engine.

All the first issues were due to the matching/mismatching of components from different vehicles. Two problems were introduced by Howell, vacuum source and silicone. They kept trying to overcome mechanical problems with chip burning.

Now this most recent one was actually from a defective part.

Hopefully this will save someone from headaches, or help someone improve performance on what they have now.

You have to look at the whole thing as a "system." ALL the individual components all work "together" to make it a "System."

 

Almost forgot. During the course of all this latest round, Roger did add propane to it during the stumble. No help, that's why burning a richer chip made no difference. The propane even slowed it down a bit - showing it was already rich.

Since it was the pick-up coil breaking down, he was losing both fuel AND ignition at the same time!

I learned alot during this too - Thanks Roger.

 

Thanks Rich you sum it in pretty good. hope fully now my ECM can start to learn again at help me get the most out of my 4.2 as i can get. Especially better MPG, this maybe dreaming here. but so far it's running great!

Once i removed the Coil sensor, interesting enough if i got it real cold, in the frig and then did a omm test, the numebrs were all over the board. Once it got warm, very little but there was some, on an extreme move, lost all signal. the new AC delco, strong contection at any position.

thanks again..
i can say that based on months of troble shooting, i would have most likely given up and accepted teh systems as is. Then teh coil pick up would have completely quit one day and left me stranded.

By the way now even my wife is happy,its fixed.. now she thinks there is now more time for yard work. Guess she doesn't know there is always something to do on a jeep, and its not always bad..

 

FYI, I found that my jeep was more likely to ping without the EGR.

do you still run the evaporative canister? mine runs much better without it. But it think my canister is busted. I pulled the ported vacuum purge input off canister and the line from the canister had manifold vacuum on it. thus tying the ported vacuum to manifold vacuum.

 

""""FYI, I found that my jeep was more likely to ping without the EGR.""""

The EGR cools down the combustion temperature slightly, stopping the ping. But it also often inhibits some performance too.
You might try an experiment. Try disconnecting the vacuum advance AND the EGR line at the same time.
If no more ping, check to make sure the distributor advance is not advancing too fast, and the total advance, with vacuum does not exceed 35 degrees.
The vacuum advance portion should not come in full until about 2500 RPM. If it "slams' in too fast - ping.
Or if the total advance is too much - ping.

Trying it without the vacuum advance and no EGR you might wake up some extra ponies that have been asleep. Without the vacuum advance working, mileage will suffer, but power may improve. (You'd be on the power curve all the time.)

If it really helps, you might want to go with an adjustable advance diaphram.

Is it HEI? Or what type distributor?

-- Sounds lke that charcoal cannister is history. Easier to find another than try to get the check valve. Or just leave it off if you don't need it to pass smog testing.

 

"Is it HEI? Or what type distributor?"
duraspark. I wish I could smog it with an HEI on it.

 

[ QUOTE ]
"Is it HEI? Or what type distributor?"
duraspark. I wish I could smog it with an HEI on it.

[/ QUOTE ]

Smogging and daily running are two different things... It only takes 15 minutes an one bolt to swap/time a GM HEI for the FOMOCO.

Not that I'm advocating anything here that would be against the California CARB regulations...

 

Absolutely! That only needs to be swapped back every two years anyway - in California!

A definate improvement, well worth the effort!!!!!

But, same things apply for the timing and EGR.

 

do you still run the evaporative canister?

yes i am the ecm requires it. Helps my set up..

is your timing to high?