car runs like complete crap when cold, ideas?

[KFunk]

Caught me by surprise yesterday morning. It was rough starting, had barely any power, and wouldn't idle on its own. It felt like when it had nasty gas after sitting all winter, like its only being powered by 2 cylinders. I took it around the block, no improvement.

I remembered that the night before I had pulled all 4 plugs to check them to see how carbs were tuned. So of course, I figure loose plug wires or out of order. Double-checked them, all seem well and tight. I take off again, and the car quickly improves. Feels strong when I get to work, which is about a mile away.

After work, car starts just fine, drives home with plenty of power.

This morning, I get up, feels like crap again. I take off driving, first half mile or so its still complete crap. Once the coolant gets close to 180 degrees, smooths out some, starts getting the power again, and tires start a spinning. Feels fine when I got it to work.

Background: 74 w/40 DCOEs, not currently tuned the greatest but plenty of power, chokes not connected, stock bottom end, high mileage, Carter electric fuel pump, electric fan, fresh timing chain/water pump/oil pump a couple years ago, fairly fresh oil, half tank of gas filled up on sunday. was driven hard with 2 co-drivers on sunday, but ran fine monday and tuesday.

So, where do I start looking? I'm kind of puzzled. Must be temperature dependent, but I've never used chokes with these carbs. Its kinda cold here for the season, but nothing worse than previous months when the car ran fine. It might correspond with the t-stat being closed when its colder, but how would that drag power down?

Or its just something else expandind and sealing off when it gets warmed up.. maybe in the dizzy? i dunno...

[Oshweeken]

Check your distributor. Sounds like you have moisture in your cap and rotor inspect for wear

[KFunk]

Good thoughts, thats the next place I'm looking. Just haven't had the chance yet.

I'm also running stock points/condenser in a mech. advance distributor.... which is soon to be investigated.

[Guest]

Sounds like there may be some water in your gas tank. Are you getting cheap gas? I have noticed ARCO stations in the Seattle area give you all the gas and some water too.

[KFunk]

Sounds like there may be some water in your gas tank. Are you getting cheap gas? I have noticed ARCO stations in the Seattle area give you all the gas and some water too.

where can i buy cheap gas these days? let me know! hehe.

I last filled up in Columbus from the same gas station I usually go to before and after autocrosses. It was 87 octane as usual. Never had a problem with it. Think it might be a Chevron, but I forget.

But it might not hurt to throw in some of that 'dry gas' stuff for a couple bucks. Perhaps some water has seeped into my tank sometime, wouldn't surprise me.

[Emyers]

Kfunk,

Sounds like carb icing. Temp and humidity have to be within certain limits. When the engine comes up to temp there is enough heat to keep the ice from forming in the carb venturi.

Earl

[KFunk]

it can get cold enough in there to form ice? its been cold here, but only into the 40s at night, and the car stays in an attached garage that gets a little heat. Does the vacuum help cool it down more or something?

[Emyers]

As air passes thru a venturi velocity increases, pressure decreases and temp decreases. If the ambient air is close to freezing and the humidty is right, the conditions are perfect. This is why carb heat is necessary on recip aircraft engines, and why the OEM carb setup had that preheater arrangement fitted to the nose of the OEM air cleaner assembly that you had to select either winter or summer position. If this happens again, and you can safely stop the car, look into the carb throats you should be able to see the icing.

Just a thought.

Earl

[KFunk]

Once again, ran great on my trip home.

Sounds like you've got the best explanation Earl. Does the moisture come mostly from the air or the fuel? Just wondering if I should still buy something to get rid of moisture in fuel, or just wait for the weather to change....

it has been really cold and rainy here lately, strange for this far into spring.

My Warneford sidedraft manifold may actually be adapted to allow coolant to flow through it. Someone is selling one in the classifieds that includes a box below it that appears to have a coolant inlet/outlet. I have no idea where I could find only the coolant box though... since my kit didn't include one.

http://www.brakefade.com/files/FS/bmw_m10_warneford_manifold_2.JPG

[dapbmw]

side drafts are like that when cold, it would help if you warmed up the car for about 5 mins, or install a choke cable on the carbs and use the choke when you start it and you will be surprised that it starts right up and has smooth idle, once the engine has warmed up push the choke back to closed position and drive. depending on you engine mods, you may want to switch to colder plugs if your engine is heavily modified or hotter plugs if stock. i think bosch plugs have the numbers as w7dc colder? w8dc hotter? or vice versa. and ngk would be bp5 or bp6.

[KFunk]

side drafts are like that when cold, it would help if you warmed up the car for about 5 mins, or install a choke cable on the carbs and use the choke when you start it and you will be surprised that it starts right up and has smooth idle, once the engine has warmed up push the choke back to closed position and drive. depending on you engine mods, you may want to switch to colder plugs if your engine is heavily modified or hotter plugs if stock. i think bosch plugs have the numbers as w7dc colder? w8dc hotter? or vice versa. and ngk would be bp5 or bp6.

I've had the carbs on since last summer, so I'm used to the typical cold frosty mornings and giving it a little extra gas, but this was beyond the normal.

I've been thinking about adding a choke cable, but it would require a really long cable since both my choke mechanisms would need to be pulled from the front. I've seen another 02 with 40s that had chokes that could be pulled from the back, could I find those somewhere or simply reverse mine?

In any case, even in winter, it hasn't been hard enough starting to bug me enough to do something about the chokes.

Oh, and in today's case, I couldn't just let the car warm-up for 5 minutes on its own, since it refused to idle. So I just drove it till it warmed up....

You're right on the dot on the plugs. I'm currently running the only plugs that fit that were at the local part store, which happen to be BP7s, i.e. really cold. I've got a set of both BP5s and BP6s currently on the way via UPS.

Also, I just put in a bottle of STP gas treatment, can't hurt I guess.

[Emyers]

The moisture content is carried in the air, I bet when the humidity drops, the freezing, if that is the problem, will subside.

Earl

[Guest Anonymous]

I have an idea you are not going to fancy. Let me tell you a story. I had a coupe with 10:1 compression and side drafts. The engine ran like a dream for years. Then one day, in the early fall I went to start the car and it ran like crap - until it warmed up. I tried reinstalling the chokes, starting fluid, larger plug gaps but nothing worked. This hard "cold" running continued on a daily basis for the better part of two months. The interesting thing was all the plugs looked immaculate with a hint of tan. One day after work I went to start the car again and warm it up but it took longer than usual. I pulled the plugs again and noticed barely perceptible water droplets on plugs from two adjacent cylinders. Do I have to finish this story? I drove the car home and it was fine. I even gave it a compression test and that made me question the coolant I thought I saw. It is also noteworthy that I had not been adding additional coolant.

I eventually bit the bullet and found a decomposing head gasket. The leaks were minimal but large enough to make a difference when things cooled down. I hope this is not your problem, but be warned!

Good luck (and have an extra gasket handy)!

[KFunk]

ahh, i dont believe that. but no big deal really, just a gasket and an afternoon. could probably do one in a couple hours.

car ran a bit better this morning. not awesome immediately, but ok. maybe the extra warmth, it was over 50, i dunno. but we'll see. no need to get up early tomorrow, so it might be a while till i see effects again.

[KFunk]

ahh poop, still pretty damn bad when i got it out today around noon... with it almost 60 degrees side.

inside of dizzy looks OK. oil is clean.

i'm beginning to suspect you might be right morris. i'm thinkin that maybe there could be some seepage of compression between two cylinders, and when head gets warmed up and expands, it seals off the leak.

Tomorrow morning, first I'll re-torque head bolts, then see if it still runs like crap, then I'll try to do a compression test when its cold. If I'm right, there'll no compression in 2 adjacent cylinders.

Then I gotta see if Autozone or another local store can get in a head gasket real quick, then I'll swap it in some night this week. I gotta get it going for a 2-day autocross next weekend....