Repair Topics / Choke

• How does a choke work?
• How does a carburetor work?
• How does emission control systems work?
• Why does black smoke come out of the exhaust system?
• How to test a fuel injector

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Car Choke Questions and Answers - This category contains featured questions as examples. They relate to most vehicles.

Question: 1968 Ford Mustang mileage: 38,000.  Car starts fine in the morning (automatic choke).  When stopping on the first stop sign, the engine dies and will not start again.  After resting for at least an hour or so, will start readily and behave fine all day long.  Since it is first morning start, may it be choke's flooding?

Answer: It sounds like your choke may be hanging up.  A choke releases two ways, as the engine gets warm.  One way is by a small electric heater in the choke housing.    Another way is that it pulls warm air off the exhaust manifold.  Verify that the choke releases as the engine warms up.

Question: 1984 Nissan Sentra v4 mileage: 98,000.  When I woke up this morning and started my car, I noticed it was idling very high.  There is also smoke coming out of the tail pipe.  I turned the car off and checked my oil.  It was low but uses oil fast for some unknown reason.  I put a quart of oil in and tried to start it but it made a loud noise in the engine.  I turned the ignition back to off then waited a minute, and it started, but it was still idling high.   I put it in gear to move it to the driveway and the engine went down to normal as I moved, but increased again, when I stopped.   I heard it could possibly be something with not having enough anti-freeze, but it did not freeze last night.  Any help is appreciated.

Answer:   Check the choke linkage, it may be hanging up.

Question: 1999 Mazda Millennium mileage: 65,000.   My Mazda has an automatic choke.  When I start the car, it starts immediately and the engine runs 1500 RPM.  However, when the engine warms up the choke keeps active.  When the engine is warm, the engine speed is 2000 RPM or more.  Can you help me with my choke problem?

Answer: Your car does not have a choke. It sounds like your have a vacuum leak or a tear in a intake boot. Insect to replace as needed.

Question: 1989 Pontiac Firebird 2.8. Hi guys, a friend replaced the serpentine belt. He also messed with and messed up the coil wire. He put a coil wire on that did not fit my car. On the way home that night my car died three times. I would place the coil wire back on the center of the distributor cap each time and that would get it going again. But, the next time I drove it I had to put the coil wire back on 10 times at least and then even that did not help it run again. I bought a new distributor cap, rotor and coil wire. Now my car will go 1 to 2 miles. Then it starts cutting out, backfiring and dies. The plugs and wires were checked and were firing correctly. "They" say it's the fuel filter, timing, and the last opinion was the catalytic converter getting hot (since it runs ok briefly). What do you guys think? I figured out how to get the ECM codes to display. The codes are: code 22, throttle position sensor, voltage low or fuel cut off relay circuit open or shorted to ground. And, code 34, manifold air pressure sensor voltage high, pressure high/vacuum low or MAF signal high--flow low. The code descriptions indicate to me something isn't flowing right, not grounded, pressure/vacuum problems.

Answer: You may have a faulty manifold air-pressure sensor or possibly even a faulty fuel pump.

Question: 1985 Delta 88 5.0 mileage: 160,000. I washed the motor using a degreaser. I also cleaned the carburetor with carburetor cleaner. The car started a few times and it sputtered and then died. I haven't been able to start it again. Can you give me some troubleshooting ideas?

Answer: Check for water in the distributor, especially the bottom side of the distributor cap. Also, check the plug wires and shorting out.

Question: 1997 Ford Escort LX 1.6 mileage: 22,000. Hi There Bob & Ken, I've been searching the Internet for a couple of months now in the hope of finding a solution to a problem I'm having with my car . . . but without success. The car concerned is a 1997 Ford Escort 1.6LX 16v Zetec, which I have had from new, and which has clocked up only 22,000 miles. The problem occurs only on "first" starts on cold and/or wet mornings and is as follows: The engine always fires up without fuss and initially it runs perfectly at idle. The tick-over is slightly faster than on subsequent "warm" starts, so the auto choke is definitely "coming on". There is no sign of any misfire at this stage. The car pulls away and drives ok at first. But when I bring it to a halt, at a road junction just a quarter of a mile along the road from my home, the engine either cuts out immediately I dip the clutch - or it begins to misfire, and then it dies. If I get through the junction without having to stop the car, there's a period when the misfire causes reduced power and rough running, but this lasts only a very short distance before returning to normal running. When the engine does cut out, the re-start is always instantaneous and driving carries on perfectly normally from then on - with the tick-over slightly increased, indicating that the auto choke is still (back?) on. I have replaced the plugs and the HT leads without any change in the situation and I've almost convinced myself that the problem is caused by the auto choke cutting out too soon. But that wouldn't cause the misfire would it? Or is it the misfire that's causing the problem in the first place? I've had the car in three repair shops, with the express intention of getting this fault cured. And, although all have been aware of this problem's existence ("it's a common Ford Escort trait", I've been told on a couple of occasions), nevertheless no one has yet been able to effect a cure. It recently passed its MoT with flying colors so the catalytic converter must be doing its job ok by the way. The car is perfectly adequate in all other aspects, including performance and mpg, the average being around 40 mpg from being new to the present time. I would be most grateful to hear what you think the problem is being caused by - and just as importantly what I can do to cure it (it's driving me mad!) Tony

Answer: In your questions, you did not indicate whether there was a scan for trouble codes. This is where we would have started. If no trouble codes are present, you may possibly have a faulty ECM.

Question: 1989 Dodge Aries K 2.5 mileage: 41,000. My car starts and stops fine but after driving for a while on a highway or above 40 mph, it has a tendency to die after coming to an immediate stop. If I'm driving on the highway for 15 minutes and I stop at an intersection, it will sputter a little, and gradually die off... Especially when I start up again uphill and to the left. It's not an evil car, but this one defect will probably be the death of me. To fix it, my friend tried upping the rpm's a smidgen... It worked a little. He said that it idled slowly and that the carburetor suffered from blow-by. Unfortunately, this only made the problem more an unpredictable annoyance. Have I a lost cause?

Answer: From what you tell us, your dying problems may be caused by a faulty oxygen sensor or idle speed motor.

Question: 1989 Chevy Cavalier Z24 2.8l V6 mileage: 122,000. I recently had the exhaust replaced (catalytic converter on back) because the car was extremely loud & the noise seemed to be originating from the converter.  Shortly thereafter (within the same week) the car would sputter and sometimes stall when coming to a stop.  Then had the MAP sensor replaced.  This seemed to improve the condition somewhat, but it still will sputter & hesitate from time to time.   I've had problems with the TCC solenoid before and it almost has the same "feel", but it doesn't happen often enough to really tell.  Before the first time the TCC solenoid was replaced, I was told by the mechanic that the easiest way to tell if it is the TCC solenoid is to UNPLUG it and drive around that way for a while.  What does unplugging the solenoid do, and will this harm your transmission in any way?  Also, would replacing the exhaust have any effect on the MAP sensor, or was the timing of this failure just a coincidence?

Answer: You may want to check for a plugged catalytic converter.   In addition, it is okay to unplug the connector to the transmission and drive the car.  This will let you know if the TCC solenoid is hanging up causing your problems.

Answer: Your “hiccupping” problem is more than likely caused by a faulty ignition coil.  We do not think the oxygen sensor is your problem.  However, replacing it after 68000 would be good preventative maintenance.

Question: 1989 Chevrolet/Celebrity 2.8 liter V6 mileage: 220,000.  Ok, well I’ve been having this problem for a long time.  My car will be running fine for a while and then all of the sudden it starts backfiring in the engine, stalling when I come to a stop, it stalls and chugs even when I’m doing 70 Mph on the freeway!  It's weird because if you let my car set for a couple of weeks without driving it it'll run like new for about a week.  And then it just gets worse the more you drive it!  So the first thing I did was changed the fuel filter.  Didn't work.  So, I went out and bought one of those code readers, and the code read that I needed to replace the oxygen sensor.  So I did and nothing!  So just recently, I went out and had a brand new Catalytic converter and new muffler and I was sure that was the problem!  But it isn't... HELP PLEASE!

Answer: Without actually “seeing” your vehicle and driving it, it is difficult to diagnose the problem.  We are guessing based on what you have done and described, that your stalling problem may be cause by the fuel pump.  Replacing it and the fuel filter should fix your problem.

Question: 1991 Oldsmobile Cutlass Calais 4 cyl mileage: 95,000.  After driving car for a few miles, it bogs down, sputters & then dies.   After letting it set for a few minutes it starts up, but in a few minutes it starts over again.  I have replaced the computer, had it hooked up to a computer at the service station & checked spark plugs, it is very hard when u come to a stop light & it just gets worse as you drive.  Thank you for your help

Answer:   Check the catalytic converter to make sure it is not “plugged” or restricted.  To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter.  Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge.  With the gauge inside the car, drive up a hill or accelerate and read the pressure.  Normal is 2 to 3 pounds, restricted 4 pounds or higher.  The drawback to this method is the small hole will need to be welded shut after the test; a minor job if you have a welder.

Question: 1988 Dodge Ram Minivan 3.0 V6 mileage: 125,000.  Under load the engine, "cuts out". There are no codes when taken to a Dodge mechanic and the van was put on computer.  Have new fuel pump/filter, dist cap, rotor button, and plugs, plug wires.  The engine runs like a top at idle, no misses or anything, but when put in drive and powered up it" dies" momentarily.  Mechanic said maybe, ignition module or bad distributor assembly.

Answer:  Yes, your mechanic may be right.  The ignition module may be causing your problem.

Question: 83 1983 Dodge D-150 225Cyl mileage: 145,000.  When I stop for a light or a stop sign the engine dies on me.  It only dies when my truck is going up hill fully warmed up.   It also dies when I hit a bump or go around a curve slow.  It does not die when it is on the level.  About a week ago I took my truck to, Goodyear they tested it out and said there was nothing wrong.   Every time I drive it, it always dies on me.   Could it be the fuel pump?  Could it be the carburetor?

Answer:   Check the float level in the carburetor and check the float itself, it may have fuel inside.  Replace the needle and seat when the carburetor is apart.

Question: 1991 Nissan / Axxess 2.4_mileage: 150,000 km. I recently purchased a used 91 Nissan Axxess FWD with 150k, 2.4, 5 speed. The vehicle has this intermittent problem (every 2 days) whereby the vehicle, in every gear, once you reach 2500 rpm's, the car jerks severely and the engine will not go above this rpm. However, shutting the car off and restarting will solve the problem until it returns again. We have changed, mass airflow, vehicle speed sensor, distributor & cap, plugs and wires, rotor, ecm and coil. We have had 3 different mechanics look at the problem and everyone agrees that it is electrical. We desperately want to solve this problem, any suggestions or have you heard of any similar problem?

Answer: When we read your question two things came to mind. The pick-up coil in the distributor or the alternator is failing. We know what your thinking, the alternator? What maybe happening with the alternator is a diode is "leaking" A.C. (alternating current) into a system that requires D.C. (Direct Current). These "spikes" of A.C. will temporarily shut down electrical components.

Question: '86 Toyota 4x4 22R 160,000 miles. During acceleration, (stock-carburetor) there is a point where no more acceleration occurs, pedal on the floor. Let off gas slightly and reapply acceleration continues slowly. However, recently there is a "bump," like hitting a small pothole and then I have excellent acceleration. Is the lack of acceleration a function of the vacuum and emissions system? And what is causing the "bump" sensation? Is the "bump" an indication of a serious problem?

Answer: Check for dirt in main jets of the carburetor. The downward angle of the jets makes them prone to the problems you describe. A new fuel filter is also in order. This should cure your "bump" sensation.

Question: I bought a Mazda 626 with Automatic Transmission recently. I have a problem with the car choking and dying whenever I put my gear in any forward position "D, S or L". Reverse is fine. I can drive the car (reverse only). Idle is fine (can rev). Trans is fine (fluid is red). No oil leaking. No AC. No "check lights" on. I did step on the gas and put gear in D. It drove chopping, choking and revving up and down like crazy. However, when I come to a stop it chokes and dies. I suspect the fuel system. I think it is the filter (but looks new). Could I be in the big hole on this? Fuel injectors or dirty gas tank?

Answer: Wow, you do have a strange problem. After some thought, we would suggest carefully checking the wiring in the engine compartment. What may be occurring is the engine moves or "rocks" in one direction in reverse and the other direction in drive. This engine movement may be pulling on the wiring causing the engine to die. Check for broken motor mounts also.

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Repair Topics / Choke