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Car Engine Runs Rough and Idles Questions

Question: 1999 Pontiac Transport mileage: 125,000. My van is intermittently jerking on acceleration. The battery gauge will go from normal to 18, all my lights will dim and go really bright, and the van will jerk. I've had the alternator replaced, battery replaced, fuel pump replaced, and my transmission was just replaced. Now these all needed to be replaced, but I was having the problem before these were replaced. I've dropped about $2,000 into this van, I just want it done.

Answer: Your problem is probably related to the 12-volt power system in your car. A main power connection goes through the firewall. Within that connection is the main 12-volt power supply. These connections get corroded and cause the kind of trouble you described. In addition, check the battery cables for corrosion and or poor connections. It is also advisable to check ground connections to the engine compartment.

Question: 2001 Toyota 4Runner mileage: 108,000. Last winter I started having problems with the engine running rough. Symptoms were usually - run fine at first then 3-4 miles later start running rough (esp between 45-50 mph) Would run better if speed changed to higher or lower. Repair shop over several visits did the following: tune up with new plugs, flushed fuel injection system. Symptoms continued and were worse thru winter with colder weather. Note: symptoms either would disappear or were milder with warmer weather. Not a lot of missing during the summer except when cold, damp, rainy. Now we are back to winter and symptoms are back and are worse. Runs rough most of the time when I start it up. Sometimes it smoothes out in 4-5 miles, sometimes not. Sometimes when I start engine it runs smooth but starts running rough in about 3-4 miles. And then continues rough for rest of drive. Last winter seemed cold related and speed related. Now can run rough at any speed, still worse when cold but also rough if 45 degrees or higher. When the engine is running rough, acceleration is extremely bad. Note: the tachometer is stable when running rough. We are tired of replacing parts.

Answer:   It sounds like it could be your spark plug wires. Replacing the spark plug wires and recheck symptoms.

Question: 2001 Dodge Neon mileage: 90,000. My son has put 10,000 miles on his Neon since buying it with a freshly replaced head gasket. Two months ago, it began episodically (sometimes it runs fine) losing power dramatically and running extremely rough. The roughness starts (sometimes) if you gun the engine a bit, and will frequently fix itself if you let the engine idle down for a few seconds. Took it to the dealer who said he had to replace the computer with a rather pricey upgrade, and lost the codes. Didn't solve it. Haven't taken it back yet Replaced the PVC valve, and a cracked exhaust donut on our own, as recommended by the dealer, which seemed to improve the episodic roughness, but now that's back. When running rough, the brakes have no power, so I suspect a vacuum problem. Since it sometimes runs just fine, I suspect a mechanically sticking something-or-other. Waddya think, and can you tell me where to look under the hood. Recently, it started overheating, and we found it about 1-2 quarts low of antifreeze. No known leaks. Oil looks okay. Engine runs nice and smooth except as noted above.

Answer:   It sounds like you have a ignition coil going bad and needs to be replaced. try replacing the main ignition coil with new to recheck system.

Question: 2002 Chevrolet Cheyenne mileage: 84,000.  I am a young mechanic, (18), but I have tried the following. I first noticed that it was hesitating during acceleration, and that it was "bucking" while driving down the road. I thought the fuel pump had gone week, so I replaced it. While this helped, the problem persisted. All of my hoses are tight, and the only thing I can think of that is left, is either a compression problem, which I doubt seeing as it came on suddenly, and not gradually with time, or the EGR valve, which as I can tell is still working properly. I have also tried an injector cleaner, and nothing. I reviewed the FAQ's, but none of them seemed to specify my persisting problem. I hope I am not too much of a bother to you. What do you think the problem could be? I have been working on this truck, making it perfect, for way too long to let this stop me.

Answer: Your car is ready for a tune up including spark plugs, spark plug wires, fuel filter and air filter. Replace as needed to repair problem.

Question: 2001 Ford Thunder Bird mileage: 60,000.  Engine was running a little rough, so I pulled plugs and cleaned/re-gapped and put 'em back in.  Ok, so I got out the book, checked the firing order, direction of crankshaft rotation, (what I shoulda done in 1st place I know!)  But now, when I turn the key, nothing, no movement at all!  No cranking, no click, click, from a dead battery; nothing but a clunk like sound seemingly coming from the vicinity of the ”High Current fuse Box”.  Did I blow a fuse/circuit breaker?  Or, Is the engine frozen from the timing chain breaking because of the misfiring from my bungled plug wiring?  Battery is fully charged, Int. lights are bright etc.  HELP!  Please, Thanks

Answer: It sounds like you have a bad connection at the battery, clean battery terminals to recheck system.

Question: 2003 Chevrolet S-10 Blazer mileage: 80,000.  My Blazer  runs a little rough and wants to stall when idling and when coming to a stop.  It will die and you to start it again and it won't.  If you let it sit 15-30 minutes, it will start again and will eventually stall again.  Any ideas!  Thank you.

Answer:  The fuel pump sounds like it is failing, check fuel pressure it should be between 55 - 65 psi. If not replace fuel pump with new to recheck system.

Question: 1999 Pontiac Grand Prix mileage: 91,000.  I got stuck in a traffic jam a couple of days ago and my car did something it never has done before, it felt like it was going to stall.  The rpm's kept going up and down.  Then the next day while driving normal I had another problem, I think is related.  When I drive at a steady speed, say 50 mph, the engine has a constant vibrating that makes the car shake.   The only way to stop the car from shaking is to step on the gas to increase the speed.  Also something I just noticed during this time was that my exhaust makes a putt-putt sound while the car is in park and running.  Are these 3 separate problems or interrelated?  Any help on this matter I would appreciate.  Could a tune-up possibly remedy any of this?

Answer: Check the ignition coil housing, sometime when coil housing short circuits they can cause a cutting out effect. Replace ignition coil housing with new to recheck system.

Question: 1999 Chevrolet Cavalier mileage: 65,250. The car suddenly started running rough and noisy with what sounds like backfiring through the intake manifold on acceleration.  Replaced plugs and plug wires, fuel filter, air filter and PVC valve.  This made no difference.  I added fuel injector cleaner to the tank and took it out on the road for a long drive at highway speed and the problem only got worse.  One point of note was that five plugs were normal and the cylinder on the back driver's side was covered with black soot.  Any ideas?

Answer: Check the ignition coil housing, sometime when coil housing short circuits they can cause a misfire effect. Replace ignition coil housing with new to recheck system. This is a common problem with this vehicle.

Question: 2002 Ford f-150 truck mileage: 79,000.  The problem I'm having is with the fuel system. This is a problem that started all of a sudden.  The truck runs fine first thing in the morning but when it heats up it, starts to run suggest like it's not getting enough gas.  At a high speed (60 mph) it has a bad vibration.  We changed out the spark plugs and fuel filter, which was pretty well clogged up.  It ran fine for a while but seems to be a reoccurring problem.  I feel that I may have got some bad gas when my problems first started.  Any advise?

Answer:   It sounds like you may have a vacuum leak, check the vacuum tube running from the intake manifold to the PCV valve. Repair as needed.

Question: 2002 Chevrolet s10 pickup mileage: 60,000.  I have reviewed your FAQ's and don't see this addressed: My son has had the exhaust system on his Chevy S10 modified.  They installed some type of smaller muffler and dual pipes with tips.  It sounds loud and drives like crap.  Engine is missing.  Can this exhaust modification be the cause of the misfiring?  Do not like the loud sound, is probably illegal anyway...please advise.

Answer:   When installing modified exhaust systems it is common to crack spark plugs and not know it. Remove spark plugs to replace with new, that should fix your problem.

Question: 1998 Suzuki Vitara 2.0 DOHC mileage: 60,531.  My car is trying to keep running after I shut the key off.  What would be causing this?

Answer:  Your problem may be that your idle speed motor is shorted and needs replacing.

Question: 2001 Chevy Lumina mileage: 54,000.  The #1 cylinder is not working properly, or at all.  I have had a tune up and plug wires replaced (electrical arc in the wires were found).   The new plug for the #1 cyl has some fluid on it after taking it for a test drive.  Any ideas what the problem may be?

Answer:  Check the injector for the number 1 cylinder to be sure that it is getting an electrical pulse. If so replace injector with new to repair problem.

Question: 2003 Ford F150 mileage: 78,786. When the weather got cold here in Wisconsin, the truck started running rough when it first was started, but then smoothed out as it warmed up.  This became more prevalent below 10 degrees F.  I knew the truck was due for a tune up and took it in.   The garage told me that my spark plug wires were bad, probably original equipment, and they replaced the wires, plugs, cap, and rotor.  Two days after I got it back, I had the same rough running problem when I started it and as I listened to it it seemed that the problems were similar to the choke sticking on an older carburetor type fuel system.  I called the garage and made an appointment, but was not able to get the truck in before it quit running.   We got a cold snap, I went out to start the truck, and it ran very rough for a short time and then quit.  I tried several times over the next 2 days to start it, but it would not start.  It would turn over fine, and it would try to fire, but just wouldn't go.  It emitted a strong smell of raw gasoline and I had it towed to the garage.  The garage had the truck for 3 days and called me up to tell me that they could find nothing wrong with it except that it was badly flooded. They told me they had to take the plugs out and dry them off and they had to change the oil.  There was less then 500 miles on the oil change. The mechanic stated that there was an extra quart of fluid in the crankcase and a strong smell of gas.  He said that after he changed the oil they put the truck on a diagnostic computer and they could find nothing wrong except that the computer found gas fumes still present in the crankcase.  I got the truck back last week and used it to drive to work on Friday and Saturday.  Both days it still had symptoms of running rough when it was cold but would smooth out as it warmed up.  Saturday I filled it with gas and my wife and I went out for dinner.  The round trip to the restaurant was about 28 miles.  The truck again ran rough until it warmed up, and seemed sluggish at city driving speed.  The truck used a quarter tank of gas on the 28-mile trip.  Can you tell me what might be wrong?

Answer:   It sounds like you may have a vacuum leak, check the vacuum tube running from the intake manifold to the PCV valve. Repair as needed.

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