Car Is Acting Weird
Thread Starter
Pro
Joined: Feb 2005
Posts: 616
Likes: 2
From: Sedalia MO
Car Is Acting Weird
My car has been running great except after it warms up, around 195-200, and I am at a stop sign or stopped in traffic, the car starts to sputter to the point that I have to left foot the brake and keep pressure on the gas or else the car will sputter and die. Anyone have any ideas on what it could be?
Race Director
Joined: Feb 2006
Posts: 12,239
Likes: 19
From: Chino CA
My car has been running great except after it warms up, around 195-200, and I am at a stop sign or stopped in traffic, the car starts to sputter to the point that I have to left foot the brake and keep pressure on the gas or else the car will sputter and die. Anyone have any ideas on what it could be?
Exactly what, I can't say.
Race Director
Joined: Dec 2004
Posts: 10,332
Likes: 63
From: PARADISE
St. Jude Donor '09-'11-'12-'13-'14
How long does it take after coming to a stop to begin acting up?
At that same engine temperature does it ever sputter while at speed?
Is this a new problem or is it since the weather warmed up?
At that same engine temperature does it ever sputter while at speed?
Is this a new problem or is it since the weather warmed up?
Melting Slicks
Joined: Jul 2010
Posts: 2,503
Likes: 33
From: McGrady NC
St. Jude Donor '15-'16
This time of year as the weather moderates and suppliers start shipping summer-blend fuels sometimes we get a load of "bad gas" for the weather that day. Gas is blended differently for the temperature of the seasons. I'd get a fresh tank of gas at a different, big name brand gas station and see if your condition improves.
Cruising
Joined: Apr 2008
Posts: 10
Likes: 0
From: Knoxville Maryland
I would also check your EGR and make sure it is not sticking, after all the cold of winter vacuum lines can take a beating as well. I would not rule out carb either, all the ethanol they use these days can have some devastating effects on carbs, gaskets etc.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,112
From: Crossville TN
Could be a temperature controlled vacuum switch with a hose off or some other such problem. While cold (below its set temp), there is no connection made to the vacuum system. Once that temp is reached, you then have a vacuum leak (excess air into the induction system) which is wreaking havoc with controlling your idle.
Research the vacuum lines on your engine and focus on those that are connected to temperature activated switches.
Research the vacuum lines on your engine and focus on those that are connected to temperature activated switches.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Could be a temperature controlled vacuum switch with a hose off or some other such problem. While cold (below its set temp), there is no connection made to the vacuum system. Once that temp is reached, you then have a vacuum leak (excess air into the induction system) which is wreaking havoc with controlling your idle.
Research the vacuum lines on your engine and focus on those that are connected to temperature activated switches.
Research the vacuum lines on your engine and focus on those that are connected to temperature activated switches.
The 78 has 2 TVS switches and also thermac in the intake. Thermac is a controlled leak, but should be accounted for in setting your base idle.
TVS1: in thermostat housing, connects to AIR and EFE if I remember right.
TVS2: on intake, connects to EGR and PCV. Shouldn't be active at idle because the input is ported vacuum.
Thermac: connects from small nipple on rear of carb baseplate (next to power brake fitting), goes to 1 input on the air cleaner. Other side goes to flapper valve/valves on snorkels. When the spring heats up enough, the vacuum bleeds into the air cleaner. This is an intentional vacuum leak and should be compensated for with mixture screws.
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Pro
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Likes: 3
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??? Timing chain stretch allowing timing to change when in gear and warmed up??? Had a funky semi related symptom that lead to a bad timing chain in my situation ... Just throwing ideas out there ... It would idle just fine, die when I put it in gear, had to power break it to put load on the engine... Could even drive it while keeping Rpms up... But it would always idle like nothing was wrong, right until it was warmed up and dropped into gear... Which made it hard to diagnose and find...