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cold start misfire Pages: 12

mhamilton on Fri January 25, 2008 6:52 PM User is offlineView users profile

Year: 80
Make: Chev

Another one of those "what now" problems with my Malibu 229. This just started happening last week.

In the morning, go out and start the car. It fires up like normal, and revs up to the high idle. I usually wait a few seconds before kicking it down. But now after running ~15 seconds, the car starts shaking terribly, black smoke out the exhaust, sounds like a cylinder is missing, and I hear a light knocking sound from the LH side. Giving it more throttle does not help. Letting it idle down and shakes less, but seems like it will stall. If I hold it at a lower rpm for 15-30 seconds, it will smooth out and run fine.

Never happens the rest of the day, and doesn't happen when it's over 50 degrees. I changed the plugs (thinking the old ones got damaged with all that recent pinging), and checked the wires. They have lower resistance than when new, just one slightly higher than new (7.5k ohm vs 7.3k when new). The choke is working fine, I can't think of what else would cause a miss like this. Sticking lifter? This problem happened with the old and new plugs, and it is the same exact problem every time.

CorvairGeek on Fri January 25, 2008 7:23 PM User is offline

Sounds like a choke unloader/pull off failure (or loss of vacuum) to me. You said the choke was fine, but without an unloader/pull off they will literally drown in fuel. The popping may be from the fuel exploding in the exhaust manifold with the A.I.R. is directed there on startup.

Picked up a Corvair for parts ($45) that had one failed on each carb, had filled the crankcase with gasoline (winter time). A "professional" told the owner the engine was shot. Ended up being one of the most fun and cost effective cars I ever owned.

-------------------------
Jerry

mhamilton on Fri January 25, 2008 7:40 PM User is offlineView users profile

Thanks for the reply! I am hoping that it is just a choke adjustment, because of the fact that the problem starts and stops in short order.

The unloader itself is working, but it is possible the choke is not opening fast enough. The other morning I had the air cleaner cover off to see what it was doing. For a few minutes when it was first started, the choke stayed at the unloader setting (the coil hadn't advanced far enough to open the choke more).

The choke has a 2 stage heater, so that in cold weather only half the heater runs, opening it slower. It may be normal operation. I guess the test will be to start it and when it starts missing, open the choke by hand (there is no adjustment for the choke). I have the old choke heater, so I can swap that in.

But what gets me is why it wouldn't have had a flooding problem any time before now?

CorvairGeek on Fri January 25, 2008 7:56 PM User is offline

I know the heaters can burn out, but the oil/choke light is supposed to stay on if it does. Your symptoms sounded so classic of the unloader/ pull off because of the over night cold occurrence. My other thought was a sticky mixture control solenoid. Does yours have an audible "clicking" when the key is first turned to on for a number of seconds?

I hate carburetors. I've had an intermittent flooding condition when below 20F with the 1 barrel on my '78 292. I just went through it again, carefully checking EVERYTHING, and it now runs better than it ever has. Still don't know if the flooding is solved, it is at least better. It's not like there is much to those big 1 barrels either.

-------------------------
Jerry

CorvairGeek on Fri January 25, 2008 7:59 PM User is offline

Sorry, I believe you are a 49 state car. No mixture control solenoid 'til '81!

-------------------------
Jerry

mhamilton on Fri January 25, 2008 8:27 PM User is offlineView users profile

Right, no CCC for my year.

I will check on the power piston, to be sure that is not sticking. I looked back in my service records, I replaced the carb last January, and had no cold start problems back then. Though, one thing I did not like, was that when fully hot, the choke had a loose feeling. It could be pushed closed slightly and would not spring all the way open--as though the choke was adjusted rich. I do not recall my old choke having a loose feeling, will take a look at that as well.

The choke warning light is slightly above useless. The way it's wired the choke heater can burn out, short, or the wire fall off the carb completely, and the light will not come on. It relies on the heater coil itself to provide the ground for the bulb. Only if the choke fuse blows (or oil pressure goes low) will the light will come on.

NickD on Fri January 25, 2008 9:28 PM User is offline

Corvair calls it a choke unloader/pull off, I tend to call it a choke vacuum pull off, a vacuum diaphragm that sits on the choke side of the carburetor with linkage going to the choke vane. In operation with a cold engine, you hit the gas pedal to the floor, just once then hit the starter, this action releases the tension on the choke vane so it snaps shut, also pulls on the cold idle cam for fast idle. As soon as the engine starts, intake vacuum is applied to that actuator that pulls the choke open, generally about the size of a 1/4" drill bit or whatever the manual says to adjust it to. Then as the engine warms up, either the bimetallic coil or the electric heater finishes the job to fully open the choke.

Just trying to give a more detailed description, is your choke vane acting this way? If that choke vane is not opening, even that 1/4" or so, your engine will be starving for air, run extremely rich, and blow black smoke out the exhaust. But as the heater heats up, the other means opens the choke. You would be running less rich at lower throttle, hit the gas pedal, it would really run rich with a fully closed choke. The pure force of the engine sucking air tends to open the choke vane some. Could be the actuator or the choke heater itself binding the operation of the choke. Something to check out.

Agreeing with Corvair, just trying to make it more clearer, if that helps.

I use a hand vacuum pump to both check the actuator and hope it works as they are hard to find and to adjust the choke opening, has a small bleed off hole, and they sometimes corrode shut, linkage is normally adjusted by bending the linkage rod to whatever the book says.

Edited: Fri January 25, 2008 at 9:33 PM by NickD

mhamilton on Fri January 25, 2008 9:45 PM User is offlineView users profile

Yes, everything works as you describe. It did work fine all year, up until it got really cold (below freezing) in recent weeks.

One day last week it was 50-ish, the car started up fine and was no problem. The more I think about it, the more I agree that it has to be choke related because of the direct temperature dependence. There's a bimetallic switch in the choke, when it senses the ambient is warm, it runs both sections of the heater and opens the choke quickly. When cold it only runs half the heater to open slowly.

I know for a fact from watching it the other day, when it's cold the choke just sits there with the small gap from the pulloff for quite some time. Seems that the heater is not opening it quickly enough, or the pulloff is not opening wide enough. Once the choke started opening, the engine smoothed out and the idle went up.

Don't know why I didn't try opening the choke by hand while I was looking at it last time. Now that you've both pointed it out, it just seems too obvious. I had never had reason to watch the choke before, so I didn't think it was closed too long. I have to look at it tomorrow, but I think the coil is holding the choke closed too tightly. I also have my old carb/choke to test and see how long that takes to open.

NickD on Sat January 26, 2008 7:31 AM User is offline

Watching the choke open fully on cold start up was always a very important task when doing a tune up that reminded me that I must have a few dead brain cells trying to recall when vehicles switched from manual to automatic chokes. Think manual chokes were almost standard in the 40's with a switch to automatics in the late 40's to early 50's, but do recall the early automatics were a PITA and the easiest way to repair them was to buy a manual choke conversion kit that was a very popular accessory at the time.

This kind of goes along when the starter switch was on the floor and moved to a push button on the dash, didn't make any difference if the ignition was on or off, clutch pedal up or down, engine running or not, if you kicked the starter it would engage and really make a grinding noise, had to be awake. Also had to be wide awake when trying to start an engine in subzero weather with a manual choke, and each car was a bit different, if you didn't pull it out far enough, could grind all day, too far and the engine would flood, normally pulled it out all the way while cranking and as soon as you heard a pop, to push it in a tad. A tad is a unit of length measurement the seat of your pants would memorized as to how far to push it in, and gradually push it in as the engine warmed up. Was not very easy back then to teach a girl how to drive, parking brake on, clutch engaged, one foot on the gas pedal with your toe on the starter, just had to switch the ignition on and forget about that, pull the choke all the way out, listen to the engine when cranking and push the choke in a little. If you just left it completely closed, would flood the engine, moisture on the plugs would freeze, and you were dead. Had to pull the plugs, bring them in the house and heat them on the gas range.

I remember a relative having lots of problems starting his 76 Chrysler, had some kind of power enrichment carburetor, I set it up according to the book, and all he had to do was to slowly push the gas pedal to the floor, release it slowly and leave it, start the engine, and leave it. He would also pump the gas pedal and if the car did start, hit the gas that would lower the cold engine speed and kill the engine, had to let it warm up at least two minutes before putting it in gear on cold days. But would go out there and pump the gas, flood the engine and grind it all day, finally had to yell at him and say what in the hell are you doing? My 82 Chevy is set up the same way, and have to think twice when starting the engine to use the same procedure, FI is quite a bit different.

Learning to start an aircraft engine was a different story, no choke, mixture and a primer and have to learn exactly how hard and fast to pump the primer after the engine popped. My old 165 HP Franklin was really a cold weather starter even in 20 degree below zero weather, used to piss off the mechanic as he was standing there with his engine heater and booster cables with a cash register strapped to his back. It had an electric starter, but you could forget trying to start a Champ or a Cub in that kind of weather, had to be hand propped. Didn't want to fly either on those days as these planes had no heater, and if it did start with 20 below on the ground would be about 35 below at 5,000 feet.

My 82 Chevy has the bimetallic coil that you can adjust rich or lean, not much in the book about that, have to play that by ear. But it does have up to three batteries to crank it over and have to let it run at least ten minutes before trying to take off. Snow thrower has both a choke and a primer, took awhile to learn that if you want to blow snow, have to pump the primer on warm up, until it settles, but not too much or will flood the engine, just enough to keep it going and remember to push the choke all the way in as it warms or it will carbon up the spark plug and kill the engine. Fun.

mhamilton on Sat January 26, 2008 9:37 AM User is offlineView users profile

Have the '47 Cub tractor with an updraft carb. Have to play with the choke any time you want to start it, hot or cold. Else you'll be cranking until the battery goes dead. Remember a '46 Olds had an automatic choke, probably one of the earlier models to get that feature. Was the typical exhaust-heated-air coil spring. Chevy used that up to 1979, but finally went with an electric choke for 1980.

My '80 has been very good for a long time, this was the first time I had trouble with starting. I push the gas twice in the winter, per the owner's manual (usually only need 1-1.5 in the summer). Crank, and it fires right up to 1600 rpm, wait 30 seconds for it to smooth out, and kick it down. The choke takes over the idle, so with it still half closed will keep the idle over 1000 rpm. Run back inside while the interior warms up. 3 minutes later the window is defrosted and the car is warm, put it in gear and go.

That's one good thing about this engine. Between the air injector, exhaust crossover, and small block, it gets heat in a hurry. The only issued I have ever had was in very rainy weather. It likes to stall after I kick it down,s o have to keep it on a higher idle longer. But once up to temp would be fine.

I have not had any experience with the Chrysler products, but sounds like a similar setup to FOrd and some upper division GM. Some of the DualJets (Buick, for one) had an extra pulloff that would take the car off high idle after a short time. So you could crank the car and run back inside without waiting to kick it off high idle.

mhamilton on Sat January 26, 2008 12:59 PM User is offlineView users profile

Well, so far so good! This morning I played around with my old carb, and found the old heater took just as long to go from a below-freezing position to full open. Seems GM wants the choke to be just at the pulloff level for a few minutes while the coil heats up.

Knowing that, I gave my current choke pulloff 1 turn of adjustment (can hardly see any difference) so it opens slightly more. Low 40s F right now, it started up just fine with no stalling, so that's good. It reved up, and kept running just fine. Exhaust smells very rich, but that's no surprise. As long as it doesn't start sputtering and missing. The real test will be Monday morning when it's 20F.

The bad news--while watching the engine idle, I noticed that the damper and crank pulley were vibrating up and down. I don't think it was a trick of the light... and I do not think I will keep this crankshaft when I rebuild this engine. Torsional vibrations or not, this looks terrible. No way that can be "acceptable" operation.

NickD on Sun January 27, 2008 8:42 AM User is offline

Wonder if I am missing the boat on carb tune up, just can't start my 454, put it in gear and drive away, engine will die, it does start instantly, yes the exhaust is rich, but the engine just doesn't have any power until it warms up a bit. Is better than my old 72 Ford motorhome, recall being late and trying to leave a camp ground that had a steep hill to climb, just couldn't make it until it was much warmer. 86 Civic wasn't nearly as bad, could get rolling without killing the engine, but with about 40% power.

Feel it's those cold droplets of fuel not burning properly until it warms up, perhaps one improvement of FI vehicles. My 72 Ford just had a straight air cleaner where the 82 has the exhaust manifold heated air cleaner, but the exhaust manifolds are ice cold on start up, everything on it checks out. But even on a 60*F morning, had to start the engine, then do my walk around, then it was okay to go. Was told I could convert my 454 to FI if I could find all the parts, but that gets away from the simplicity of the system. Just have to let it warm up first.

You live in NC, right? That 40 degree temperature sounds like a heat wave, I do have a couple of close friends living in NC, they tell me can have a nice home, but drive a ten year old car and get by paying low taxes, sounds interesting. WI is going nuts with new taxes, just about had it with this state, we seem to have three unions here, the police, teachers, and government workers with full health insurance and 75% retirement at 55 years of age, screw them, I have to work at close to 70 years age just to pay my property tax bill. Can you give me a city near the ocean? Spent three hours yesterday chopping hungs of ice that the city snow plow dumped in my driveway, doesn't do a bit of good to complain, same old crap. New politicians claim to lower taxes, but get in and raise them, same old crap. Use to be a good honest state, but not anymore.

mhamilton on Sun January 27, 2008 10:06 AM User is offlineView users profile

Does your 454 have an EFE valve? I know my car was hard to get going when that did not work. When I got the car, the vacuum to it was simply disconnected, reconnected it and it worked fine. No more cold stalling. Not sure about your power loss when cold, I'm sure all the weight of your RV makes a big difference. My 229 has the EFE, heated intake, and the aluminum intake manifold. Even after just 2 minutes of running I can feel the heater hoses are warm. I'm sure the intake gets hot very quickly. But, this car was designed for people who wanted to turn the key and go. I let it warm because I don't want to sit in a cold car, but if it's the end of a long day I only wait 30 seconds or so before taking off.

40 is still below average for us, here's the 5-day. Guess I won't get much chance to check out the cold start operation



Central NC has all the big cities and jobs: Raleigh, Durham, Research Triangle Park, and lots of big suburbs in Chapel Hill, Cary, Apex. If you live in the city, still have to pay city taxes. Though they're usually not as high as NJ where we were paying $10,000 a year for postage stamp lot. If you live outside the city, will only pay county property taxes, and those are pretty small. The coast of NC is beautiful... have both the coast and the Outer Banks, but don't know about the job market out there. And there's the occasional hurricane to deal with, those hit the coast pretty hard.

NickD on Sun January 27, 2008 8:08 PM User is offline

Yeah it has EFE, early fuel evaporation, but if we are talking subzero weather, it's not early enough as is the thermionic air cleaner. My insulated garage seems to stay well above 20 degrees even in subzero weather, so in an FI car, just get in, and go, maybe a ten second warm up while I put on my better to be safe than sorry belt.

Can you recommend a city in NC, just to look at.

mhamilton on Sun January 27, 2008 9:29 PM User is offlineView users profile

I'm sure in below zero weather, "cold start" takes on new meaning. I would not likely be fooling with this old DualJet if it were that cold.

Well, there's quite a variety of places. Raleigh is a large urban area, not sure if that's what you like. Durham is a big city, but not overwhelming.... and like most has good and bad areas; has Duke University. Chapel Hill is a college town, with UNC, and lots of yuppies, Starbucks, etc. All are close to the big businesses, universities, etc, and have many suburban developments in between. If you want a small historic town, Hillsborough is quaint, but still near enough to the city to be convenient. These are all smack in the middle of NC, about 3 hours to the coast, 3 hours to the mountains. Of course, go 20 minutes outside any of these and you're in rural country. Can buy 100 acres for peanuts, no neighbors or city ordinances to bother you.

I know, that really doesn't answer your question for "one" place to look at. But, except for a few bad neighborhoods, all the towns around here are very nice. If you're looking on a map, find Raleigh... all the places I mentioned are west of Raleigh within 2 counties.

Edited: Sun January 27, 2008 at 9:30 PM by mhamilton

NickD on Mon January 28, 2008 6:36 AM User is offline

One buddy lives in Lexington, the other in Raleigh, the one in Raleigh is getting hitched in June and did invite us down, it's kind of a tough decision as my entire family lives around here. Our gross income is way much higher than the poverty level before taxes, darn near poverty after, makes a guy wonder what we are working for.

Forgot about the routine of having to add a block heater to any vehicle I purchased with carburetors and still have one of those battery chargers on wheels that kicks out close to a thousand amps for those cold mornings, haven't used that in a long time, wonder if it still works.

mhamilton on Mon January 28, 2008 1:32 PM User is offlineView users profile

Lexington is further west, south of Greensboro and Winston-Salem. I'm not very familiar with those places, other than they are both are pretty big cities, but don't have the large corporations and universities like Raleigh/Durham. I'm sure it's a nice place. If you visit your friend in Raleigh, I'm sure he can show you plenty of nice areas. From Raleigh all the way west to Chapel Hill/Hillsborough is only about 30 minutes on the highway.

This morning everything was frosty when I started the car, and thankfully it did start without issue. I could feel roughness as it reved up, but nowhere near the violent shaking and sputtering of last week. Maybe needs another 1/2 turn adjustment. I let it high idle for 30 seconds or so, then kicked it down. No heavy black smoke, and no stalling. All that, and just a single turn of the pulloff adjustment. I don't know why it never showed up as a problem before. Had the carb last winter, and nothing like this occurred. But, as long as it works now, I'm happy. Thanks again Jerry and Nick for pointing out the obvious to me!

CorvairGeek on Mon January 28, 2008 2:50 PM User is offline

Glad to hear you've made progress! As I've said, I've learned to hate carburetors. Living at high altitude with this crap, volatile fuel has even colored my perception more. God forbid I put fuel with alcohol in my carbureted vehicles or lawn mower in hot weather. My '78 292 has consistently lower emissions (we test back to '65 in only the northern part of our county) on non-alcohol enriched fuel than with 10% ethanol (I have to test it in August).

-------------------------
Jerry

NickD on Tue January 29, 2008 6:24 AM User is offline

Looks like you are guessing at the choke adjustment, guess I did too with my four barrel, manual called for a couple of J tools that I don't have, an angle meter for the choke vane and a thickness gauge that I don't have, mine bends a rod for adjustment, just used a bit of trig and measured the distance from the center of the choke axis to the edge and with the choke angle specified, got the side adjacent, subtracted that from the edge distance and got the closest drill bit size, within a 1/64" and adjusted the rod so the edge of the choke vane was just touching it. Why does GM like to do things the hard way?

I had my 78 Caddy coming back from Astoria, Utah through Yellowstone and took I believe, US 30 east, what a beautiful road, got up to over 15,000 feet with black smoke pouring out of the exhaust. No mixture control on the dash of that car, did have some kind of an altitude compensator, but where it fit in the carb was an empty hole. Thought I was having engine problems at first, but all cleared up after going downhill for about 15 miles from 15,000 to more like a thousand altitude.

Aircraft carbs just used a tapered rod that when down would completely closed the main jets controlled by a pull out lockable knob on the dash that has to be adjusted constantly with any changes of altitude. Even back then the better ones had an O2 sensor for precise adjustment, I had to rely on my ears, tach, and EGT, if too lean the EGT would skyrocket. FAA said full mixture on take off, that didn't make much sense when taking off at even 5,000 feet, with brakes on, full throttle, just had to set the tach to maximum RPM, and remember that setting for landing, a lot less black smoke and a lot more power if you needed to make a go around. On a power climb, the tach would drop, had to pull out on the mixture control to get it back up again. When cruising, went as far back while watching the EGT so you could get some range, but had to push the mixture back in when descending.

My 88 Supra has a barometric sensor for altitude, not seeing that on my GM stuff, but wonder how they are compensating for altitude in FI vehicles? Or are they?

mhamilton on Tue January 29, 2008 9:56 AM User is offlineView users profile

I guess your '78 Qjet was a non computer model on Fleetwood. Some Qjets did come with the aneroid bellows for altitude control. Which models, I have no idea. I've never seen one. The C4 systems did include a baro sensor for altitude control, possibly CCC did as well. I seem to remember--but don't hold me to it--that those early systems used the difference between baro and MAP to determine engine load. But, OBDII did away with the baro on GM cars. I'm guessing the MAF compensates? Or the computer just sees the rich mixture and cuts back the injectors. The e-carbs could only drive the metering rods down so far, but injectors can be shut off.

Oh, I didn't even think of calculating the opening. I know the GM manual calls for that magnetic, self-leveling angle gauge. But, then again, this is not really a precision instrument, as long as it starts without stalling I don't see the need to keep playing with it.

NickD on Tue January 29, 2008 10:58 AM User is offline

Ha, did you ever thumb through the shop manual to see all the J tools you need to work on your car? Would need a 40' motorhome with the interior stripped out to carry them all.

I just look at them and say I can use a pair of pliers for that, and definitely a hammer for anything else.

Wonder if I could hook in my cell phone to read codes? Does about just everything else, except make calls if I go a tad too far into the woods.

CorvairGeek on Tue January 29, 2008 11:46 AM User is offline

Most CCC cars , at least through the early 90s, have a barometric pressure sensor in the interior behind the dash. They look just like a MAP sensor. Have seen an '82 with a "minimum function" ECM that used a terminal that was grounded for high altitude certification, left floating for low altitude certified models.

-------------------------
Jerry

CorvairGeek on Tue January 29, 2008 11:54 AM User is offline

I do love all the J tools called out in the manuals. Some are so neat while others seem so unnecessary for someone with any skill, or look like they would be next to impossible to use.

Having just gone through a carb made me notice that the opening of the choke position measurement point was changed after a certain year. Same carb, just measured in a different place. I had to wonder why.

-------------------------
Jerry

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