engine surges when in idle in drive?

Is the Check Engine light on? If so, the stored daignsotic fault code will indicate the circuit or system with the problem, not the specific part. This sounds typical of a defective trottle position sensor.

caradiodoc

Hi, I saw a post that is exactly like the problem I am having. The engine is surging and is having a rough idle and also a rough time when traveling. The gas pedal can also be real touchy when it is acting like this. So far I have replaced the O2 sensors. The dealer also said it was the throttle positioning sensor. I have that, and I can't find it on my engine. I have been doing some research and my throttle sensor doesn't look like the ones i have seen online. Is there any way that the engine is fuel injection? It is a 5.7 hemi 2500.

It sounds like an idle air control motor. As far as the TPS, check on the throttle body.

Let me know.

joe

My truck surges while in drive at various speeds, sometimes when I'm at stop lights and in park with engine running. Is it something with my engine or could it be my transmission. Please help

It doesn't sound like the trans. Has the check engine light ever come on? To me it sounds like the idle air control valve or throttle position sensor.

Let me know.

The check engine light has not come on.
and taking it out of overdrive does not help.
I will check out the things you mentioned and let you know. Thanks!

My husband took your advise and cleaned the idle air control valve. So far no more surging, but I have not got it out on the highway yet. That will be the true test. Thanks for your help! Lovin' my truck once again

Great! If that took care of the problem, we now know where the problem is coming from. If it starts doing it in the future, I would recommend replacing the it.

Take care, and let us know if you have question in the future.

Joe

Engine Mechanical problem
2002 Dodge Ram V8 Four Wheel Drive 150000 miles

My truck surges from 2000 rpm to 2500 rpm while driving on the freeway or even when sitting park. The fuel pump has been replaced two times and the problem is still there

Have you checked the idle air control valve? Has the check engine light come on?

no I have not checked the idle air control valve and no the engine light dont come on.

Try disconnecting the IAC to see if the engine dies.

Let me know.

We have installed a new fuel pump, fuel filter, new coil pack, new spark plug wires and plugs. The car runs fine when cold. once the engine is totally warmed up at normal running temp the engine quits quits and will not start until the motor cools down. what would cause this to happen

I was on the interstate and used the cruise control, I noticed the Tach surging occasionally, only moved 1 or 2 notches. I then took it out of O/D and cruise and it still does it. What do you suggest?

Are you getting spark when it doesn't start? Have you checked for fuel pressure when it doesn't start?

My cousin cruise control intern on the truck is getting faster and faster

We have installed a new fuel pump, fuel filter, new coil pack, new spark plug wires and plugs. The car runs fine when cold. once the engine is totally warmed up at normal running temp the engine quits quits and will not start until the motor cools down. what would cause this to happen?

not searching it just keeps gaining speed

Please understand, without a check engine light and trouble code, it becomes a guessing game. My first guess is the crank sensor. Have you had that checked? Also, when it doesn't start warm, have you checked to see what is missing, fuel or spark?

ok,, so we tried all those new parts and the check engine lite has been on too. so we will get a price and try the sensor. thanx

Let me know what you find.

Joe

my dodge ram 1500 5.9l surges up about 100 to 200 rpm while driving then goes right back to where it was, whether it is in cruise or using gas peddle the truck seems like it runs fine otherwise i have replaced both 02 sensors and have checked for vaccum leaks but did not find any? i also have a cool air intake system, replaced the fuel filter fairly recently along with the throttle body gasket.

Ok I took your advice and took the car up to a machanic and he hooked it up to a machine to see what was wrong and sure enough.... it was the crank sensor. So we replaced it yesterday an our daughter took it home last night and we have not gotten a call yet so we are assuming all is well. An just so you know..... we replaced the TPS on the dodge ram and it is also running with no surging. So............ thank you sooooo much for all your help guys!!!!!

The torque converter is unlocking intermittently. The most common cause is the brake light switch is out of adjustment. Less common, there could be a bad spot in the throttle position sensor. First try holding the brake pedal up with your foot. If that helps, readjust the brake light switch. Mechanics use a scanner to view live data, and that will show the state of the brake light switch, the signal voltage from the throttle position sensor, and other things that can cause the torque converter to unlock.

When this problem is not occurring, you can replicate it by driving at a steady highway speed, (not with the cruise control), hold the accelerator pedal steady, then tap the brake pedal with your left foot. You'll see engine speed increase 200 rpm, then drop back down a couple of seconds later. You'll feel the torque converter lock and unlock too.

On Chrysler products, other than diesel engines, you'll never solve a running problem by replacing the fuel filter. They easily last the life of the vehicle.

You would do well to throw that cool air intake system away. Liquid gasoline does not burn. It has to be turned into a vapor to burn. One purpose of all intake systems is to warm the air so that happens faster. The thinking of the people who promote these things, as long as you have money they can get from you, is colder air is more dense so more can be packed into the cylinders, then you add more fuel to get more power. The rest of us do the same thing by pressing the accelerator pedal further. The only place there are real benefits to cooling the air is when it can get so hot as to promote preignition, or when too much heat builds up, as in diesel engines with turbochargers.

Great! I'm glad it took care of the problem. Let us know if you have questions in the future, and I'm glad it helped you.

Take care,
Joe

I just did a ride and held the brake pedal up with my foot and it worked perfectly above 55 mph, rpm did not move, thanks

Dandy. Be aware these brake light switches have at least two separate switches built into the assembly, and three if it has cruise control. When the switch is just slightly out of adjustment, one of those switches will change before the others, so the cruise control can kick out, and / or the torque converter can unlock, when you do not see the brake lights flash. That makes for a potential misleading clue.

One part of the switch is normally on, and it turns off when the brake pedal is pressed. That one can develop arced or pitted contacts and appear to switch off for just a tiny fraction of a second when driving on rough roads, even when the switch is adjusted properly. The best way to identify that is to use a scanner with record capability. I have a Chrysler DRB3 for all of my vehicles. Among other things related to the cruise control, it lists the "Reason for last cutout". If you're standing still, that will be, "vehicle speed too low", so you have to read this while on a test-drive. If "Brake pedal pressed" pops up while driving, you would know to suspect the brake light switch or its adjustment.

On some vehicles the scanner shows the reason for "Torque converter lock-up denied". That could be due to the engine isn't warmed up yet, or road speed is below 35 mph. If you see "Brake pedal pressed", again, suspect the brake light switch. The computer unlocks the clutch in preparation for it thinks you're preparing to come to a stop. Failure to unlock the lock-up clutch, (a Chrysler invention for better fuel mileage), would snub the engine off exactly the same as if you failed to press the clutch pedal with a manual transmission.

greetings, i'm having a problem with my truck. while cruising , speed does not matter, the engine surges anywhere from 2-400 RPM and the kickdown dosent seem to be there all the time when i mash on the throttle. when it started happening i could temporarily resolve it by stomping on the gas. I just got this truck and drove it to Oregon from California and it drove me nuts. I'm thinking it may be the TPS or IAC motor or maybe the cruise control unit??? but i've read alot of conflicting material in the last few days. Thanks

Check and test all the following below:

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)
Dirty or worn spark plugs
Bad plug wires
Weak ignition coil

i recently tuned up the truck. plugs wires cap button coil air and oil. before the tune up the truck ran smooth as silk. started it up after tune up and ran just fine at idol @ 800 rpm. ran engine up to @ 2000 rpm and held throttle steady. engine began to surge down to @ 1500 and then back up to 2000. also noticed a sulfer smell when i got out of the truck. any ideas on where to start looking?

If a vehicle idles erratically and surges (idle speed is not steady and increases and decreases), the problem may be a buildup of carbon or fuel varnish deposits in the idle speed control valve (also called the idle air control valve or IAC valve). The cure for this condition is to clean the valve with some aerosol throttle cleaner or engine top cleaner

Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires