When driving car runs rough, acts like it struggles when accelerating. Shift into neutral and seems fine. I replaced the points and set timing, no change. Replace carb (was going to replace regardless) and same thing. It ends up backfiring from both ends after about 15 minutes. Plugs, wires, cap and rotor are a year old. New aluminum radiator. Today started the car idled for 1/2 hour, temp stayed at 180, didn't miss at all. Ran it at about 2500 for 5 minutes and everything ran fine and stayed cool. Drove maybe 2 miles and started acting up again. Throw into neutral and is fine. No hoses colapsing, nothing arching, no pinging, just sounds normal. Get back home and temp climbs to 230, throw into neutral and cools down in about 4 minutes. Backed out of driveway and go 100 feet and temp jumps, back into garage and in neutral all is fine. I'm thinking torque converter. I just don't think it is ignition or fuel issue.
I'd have to stop and add up how many of those engines I've had since Dec 1968 and the only one that ran hot that didn't have a bad thermostat was late on timing. Have you changed water pump or belt systems on it? This acts the same as a Camaro that I worked on that had come with Serpertine belts but someone had swapped an older 350 in it with V belts and when a shop replaced water pumps they put the pump for the year of the car rather than for a V belt engine on it and it would idle cool but heat up as soon as you got to moving down the road. A coil acting up as Saxman suggested would cause the rough running but not the overheating.
Thermostat was replaced last year when I installed new radiator, belts are no more than 2 years old. I had water pump off 2 years ago when I had overheating problems. Pump was in good shape as was the timing chain.
A bad converter could cause it to overheat but I don't know that it would cause the backfiring. I've never had a bad converter so I am not the voice of experience, but wouldn't you be seeing some other trans related symptoms?
I researched it the last few hours and I do have a couple symptoms. Bad fuel mileage, lurching and some chatter at light load. I thought the chatter was drive shaft too straight after air bags were installed, maybe not. Doesn't hurt to get it checked out.
definitely check for vacuum leaks, not sure which trans you have, but it may have a vacuum modulator bad or bad line to it. Running lean with a vacuum leak could cause these problems including the backfiring/overheating/stumbling. Check every source of vacuum (was the intake ever off?)-rick
Could be bad spark plug wires, as well, as a coil breaking down under load. Thing is, dont' just go off changing stuff just guessing. Do some diagnostics. See if all cylinders are firing. On old cars you can do it by pulling plug wires one at a time. Check the condition of the plugs, read the color. Do compression checks. Double check timing, and if it still acts like a timing issue, do a TDC check. Check timing mech. advance and vacuum advance. Put a vacuum gauge on it. Spray for vacuum leaks, close off vacuum accessories to check for leaks there. If you can get a non contact thermometer, check exhaust ports for cold , or too hot cyls.
The last time I messed with a 350 Olds that wouldn't run right, we put it on an engine analyzer which showed the distributor was worn out. On an analyzer the plugs should be firing straight up and down on the scope. These readings showed the plugs firing all over the place. Replaced the distributor and it ran great.
Results were short in ignition wire at a connector, timing off and a piece of chromium in the new carb according to the shop. I just ran out of time so I took it in, work is going nuts. Ran good for a couple hours, then crappy again. Now I was at Back to the 50's, limited tools. Found a bad spark plug wire, got pissed and changed out the cap, rotor and wires, ran better and didn't die but the idle would drop way down at a stop. Loaded up Sunday and headed home. Monday after work started it up ran it in and out of gear for more than a half hour and everything was great. Took it for a spin and everything was fine. Only thing I can come up with is crap in the gas tank, plugging the outlet to tank. I'm going to put a mini camera to see if there is crud in the tank. Any other ideas would be appreciated.
Sounds like a V8 I had and someone had reversed the coil polarity/terminals. It ran fine with no load, but bucked and snorted when you put it in gear and tried to drive away.
I'd look in the float bowls for crud that's floating around plugging up jets randomly. Also: This mechanic sounds like a flake to me. if somebody told you there was a short, and you didn't smell burning wires or blow fuses, I'd be thinking about a different mechanic. he doesn't know the difference between a short and an open circuit. I can believe they re-set the timing. If they only changed it 1 degree, to them it was "off". That had zero to do with your random drivability problem. Chrome in the carb? A big chunk? Is something flaking off the air cleaner? It had to come from something, but if you don't see flaking chrome under the lid maybe it came from his own beat up screwdriver. What part of the carb was it in? Did they open the float bowl?
I have chased problems before that I would swear were electrical only to find out later a lifter was hanging up every once in a while causing an intermittent miss in the engine. When I finally fixed the problem I realized that a lifter that is hanging up from time to time feels just like an electrical problem. I always believe that you should try and easy fixes first such as adding one quart of Marvel Mystery oil in the crankcase first. If I had just done that one simple fix first I would never have replaced the spark plugs, plug wires, vacuum lines, distributor, and wasted day's chasing what I thought was an electrical problem. If you think you have an electric problem always start at the battery first. I also think it could be a coil on the way out. Just My Opinion. Jimbo
The 350 olds had a vac hose that looked like a chicken foot . It always split in the v and would open, leak and close, making it hard to find.One side usually went to the vac. modulator the other to vac. advance. A lot of transmissions were overhauled because of this hose leaking.
New carb, but you suspected crud in the gas tank, so if it's lean at times I'd look in that bowl. How did that flake get in the idle port? Are you SURE there's not a spoonful of flakes floating around in the bowl? Unless you lift the lid you're not. I understand not wanting to crack open a new carb, but this one is totally suspect in my mind. Once you find one bit of junk inside a new/rebuilt component, it's time to take a real hard look at what you have. My OT Bonneville had something like that too. Went to the fuel pressure reg, and would leak vacuum if you touched it. I fixed it by soaking in Crazy Glue & drying overnight. Cost $1, but Pontiac wanted way more +tax & shipping. My kids have the car now, and it's still OK 4 years later. Crazy Glue will fill in pores in old porous rubber parts. It won't look pretty, but hot gasoline will not dissolve it. I'm told water will eventually dissolve it, if you soak it long enough. I've never seen this happen though. I fixed a high pressure power steering line on the road, with crazy glue and twine wrapped around the hose 100 times. It had split wide open in the middle and it was 1 AM on a Saturday. I found a mini-mart with some ATF, a ball of twine, and Crazy Glue, and that got me from Baker CA back to Fresno just fine. I used gasoline to clean the rubber before applying the glue, then I soaked the twine wrap in glue after. I had to use ATF in the steering pump but it works fine in cool weather. (A bit thin at 100F though...)
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