Rough idle

Try cleaning throttle plate on both sides disconnect the battery first. Here is a guide to help:

https://www.2carpros.com/articles/throttle-actuator-service

Please run down this guide and report back.

Cheers

Thanks! Worked perfect for my car. I love this site.

Six cylinder two wheel drive 92,000 miles.

Recently the check engine light came on. I took the vehicle to the shop and they said they needed to change the fan clutch and gas sensor sending unit for the gas pedal. When the light was on, the engine was running rough when in drive. Once I received the vehicle back, the check engine light was off but the rough idle was still there. I took it back to the garage and now they are saying that the water pump needs to be replaced due to the bearing being bad. The water pump is not leaking at all.
My question is, can a worn water pump cause rough idling? They said they checked the engine on the computer and the engine is not missing. Help!

The water pump cannot cause an engine miss. Have you checked for vacuum leaks?

This guide will help us.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Please run down this guide and report back.

Engine idle is somewhat rough. Ehen A/C is turned on the engine will shut off. Replaced coil and plug on cylinder six based off misfire code.

Try cleaning out the idle air control valve and test the throttle position sensor and manifold absolute pressure sensors.

My vehicle has an issue with the idle and taking off. At times the idle will be at 900 which I have been told is normal. While idling at this rpm everything is fine. At other times it will drop down to 600 and wants to stall. When you give it gas it bogs down and tends to stall. Also, when the idle is this low it also hesitates on take offs. I am also getting a lean engine code. I have changed the intake gasket, cleaned the throttle body, changed the O2 sensor, MAP sensor, cleaned mass air flow sensor and also added fuel injector cleaner to my fuel. Would the secondary air intake cause this problem or is there anything else I can check?

Possibly, but at this point I do not think that is your problem. Check your idle air control valve for faultiness.

I have the same problem with my 2005 Trailblazer. Is the Idle Air Control Valve the problem? Could it be the coil(I was told it is a common problem) or even the fuel filter?

When A/C is on idle is below 1,000 rpm and stumbles like it is going to stall out. Does this year have an idle air control and could that be the problem?

Check for any vacuum leaks first. Then check air filter. It sounds more like it is having a hard time keeping up. I do not think it is any switches. When was the last time you did a tune up? Any check engine lights come on?

My vehicle is idling rough. I did a tune up and even had my fuel system cleaned with the three step process at Tires Plus. It is still doing the same thing. Yes my engine light comes on for a day and goes off for a few days and then comes back on and goes off in the same manner. I was told that my catalytic converter is bad. I had an after market catalytic converter put on at the beginning of the year though. And as I was driving last night my lights began flickering and my battery needle was moving up and down every time the lights flicked. What could the problem be? I have done a lot of traveling and I have 144,000 miles on my vehicle. This did not start until about three trips to Texas and back from Georgia.

First step here is have the computer scanned for code/s, you have a problem within the engine management system that caused the CEL to turn on. This is your starting point of diagnosis, finding out what is going on.

Hello, I have the EXT model. No work done to motor other than oil changes. Engine idles very rough when cold, even stalls occasionally, but after a couple minutes of driving (when warmed up) it runs just fine. Is this a sensor problem, and if so, which?

Test the resistances on the coolant temperature sensor hot and cold. Also clean out the idle air control valve.

GM Coolant temperature sensor

Temp Resistances

-40 100.7
40 7.5
100 1.8
210 185

Thanks for your blazingly quick response. I did a check on the IAC and learned that 2004 is the first year Chevrolet assembled it with the entire throttle body so it is no longer a separate component. I can see it visually on top there but don't see a way to clean it. Any suggestions?

Also, on the coolant temperature sensor. Where is it located exactly?

The coolant temperature sensor is located on left front of engine block near the alternator/generator as for the IACV you have to remove it form the TB and clean out. Does yours looks like this?

It has a rough idle when I start it and leave running for a minute. When I drive about fifty mph it acts like it is losing power. Not sure what is wrong.

Hey ALEX,

It sounds like you have a catalytic converter that is partially plugged. Have you replaced the spark plugs recently or the fuel filter?

Here is a couple guides you can use for testing:

https://www.2carpros.com/articles/how-to-change-a-fuel-filter

and

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

and

https://www.2carpros.com/articles/engine-has-low-power-output

and

https://www.2carpros.com/articles/how-to-change-spark-plugs

Please let us know happens so it will help others.

Best, Ken

I changed the plugs and fuel filter with no change. I took to AutoZone they hooked up diagnostic machine and it said mass air sensor was bad, but my vehicle is not equipped with a mass air sensor. What should I try next it idles rough and has no power when you push on gas.

It is in the air intake duct right by air filter. It is a four wire connection, but make sure the duct work is connected and no holes in hoses or grommets on engine. Clean throttle plate on both sides with choke cleaner.

I had Walmart replace battery, has run very rough ever since, after some research I removed and cleaned the throttle body, still running bad, also removed negative terminal side of battery for about forty minutes, no results! This thing ran absolutely great prior to new battery! Any thing I am missing? Any help would be greatly appreciated! Thanks, Clint.

Http://www.2carpros.com/articles/engine-stalls-idles-too-high-low-after-dead-or-replaced-battery

I have also seen with some computerized vehicles, that getting on a lightly traveled road and getting your vehicle up to 60 mph or so, then letting go of all of the pedals and letting it coast down to basically nothingness will aid in the idle relearn process.



The medic

hi, i am a one-owner of a 2004 trailblazer 6 cylinder. i have been having a problem with missing and rough idle. the problem has been gradual and getting worse. the service engine light stays on and intermittently flashes when the miss is really bad. i have had a tune up. coils, plugs, converter change, fuel pump and filter, secondary air pump, and camshaft sensor all changed. the secondary air pump was filled with water when he changed it. during a diagnostic run i had over 500 misfires in cylinder 3 and over 60 in cylinder 4. i am at my wits end. no one has been able to know what my problem is and how to fix it. i have spent literally thousands and feel like it is driving worse everyday. could this be egr or any ideas?

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.

Check the crankshaft sensor, its the one that detects missfires.

i just bought a 04 trailblazer and it has 106000+ miles on it and it has a rough idle the code read p0302 missfire number 2 cylinder i took it to the shop and he told me that this engine was inherant for intake gasket leaking and that he had just fixed one with the same problem i tried to put new plugs and coil boots on all coils and i switched the number two coil to a different spot to rule out the coil and now it reads p0300 random missfire detected i'm going to have the gasket checked for leaks you might try it as well good luck with it !

where is the crankshaft positioning sensor?

Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P030... Information on Engine Misfire MIL/SES Light Illuminated or Flashing DTC P0300, P0301, P0302, P0303, P0304, P0305, P0306, P0307, P0308, P0420 or P0430 TECHNICAL SERVICE BULLETIN Reference Number(s): 06-06-04-046,  Date of Issue:   September 12, 2006 1999-2007 Cadillac, Chevrolet, GMC Full-Size Pickup and/or Utility Trucks; with Affected 4.8L, 5.3L, 5.7L, 6.0L or 6.2L VORTEC GEN III, GEN IV, V-8 Engine (VINs V, C, Model(s): T, Z, B, 3, M, 0, J, R, U, N, Y, K, 8 - RPOs LR4, LY2, LM7, L59, L33, LC9, LH6, LMG, LY5, L31, LQ4, LQ9, L76, LY6, L92); with Active Fuel Management(tm) and E85 Flex Fuel Related Ref Number(s): 06-06-04-046 ARTICLE BEGINNING SERVICE INFORMATION The wire terminal (G103) attaches either to the front or to the rear of the right side cylinder head, depending on the model year of the Full Size Pickup and/or Utility Trucks. If the ECM ground terminal has been found to be corroded, then follow the service procedure outlined in this bulletin to correct the corrosion issue. Fig. 1: Engine Wiring Harness Ground Terminal Location (2007 Full-Size Pickup and/or Utility Trucks) Fig. 2: Engine Wiring Harness Ground Terminal Location (1999-2006 Full Size Pickup and/or Utility Trucks) 1. Remove either the nut or bolt securing the main engine wiring harness ground terminal (G103) to the right cylinder head. Refer to the above illustration to determine where the ground is located on the vehicle (1). 2. Remove all rust from the ground terminal, the cylinder head and the retaining nut or bolt. 3. Position the main engine wiring harness ground terminal and install the nut or bolt. Tighten:: Tighten the retaining nut or bolt to 16 N.m (12 lb ft). 4. Apply some type of electrical moisture sealant to protect the harness terminal from further corrosion.

I have a code p1345 cam crank sensor correlation and very rough idle with stalling. When I look at the engine sensor data it appears that both cam and crank sensors are functioning and communicating with PCM. There are no PCM attempts to re-sync with either sensor.
Also, this engine was operated very low on engine oil and when I first evaluated it was three quarts low. My guess is a stretched timing chain, but this is a huge repair. Any ideas?

You should check the freeze frame data and check whether a code p0014 has set as well. this could also be a cam phaser stuck or failed that has caused this. i would think that would be more likely then chain stretch.

If it is the cam phaser, the solenoid is working and my scan tool shows that it is not advancing. Because of the code p1345, the PCM stops cam phasing when it sets the code. However, I am interested to see what kind of sludge is in and around the physical advancer. Sludge? The solenoid is good.
Unless I have overlooked a check that can be done without removing at least the valve cover and inspecting and then possibly going farther to remove timing cover and checking timing, I feel like thats i my next move.
Advancing solenoid, cam and crank sensors are good. have I missed an easy test?

i do not think so. it could be chain stretch but they have tension-er's on them to keep stretch to a minimum and i have seen a lot of these go many miles before having this issue. if it is sludge you could always try choke cleaner to clean it off and free it up maybe. But as you said in the initial post this was run low on oil for a while so i guess your next move is go over everything and pull the cover. i am sure you will find something from doing that.

I have a 2003 Chevy Trailblazer that has started ideling rough over the last couple of weeks. The car runs fine down the road and my wife says on some warmer days it seems to idle fine, just not on cooler days. I had a friend check the code and it came back with a "128", which has something to do with coolant temp if I was told right ? There is also another code of "1345", or (P1345), which said something about cam / crank issue, possibly the variable cam timing sensor ?

I changed a temeperature switch yesterday, not the sender for the guage / light, but another one which is located behind the altenator on the left side becasue we were told that was the problem more than likely. After completing that task I started the vehicle and it seemed to run fine, but a few minutes later we took it around the block and it started idleing rough again. This morning my wife left for work in it and it sounded fine again and she said it was running fine later in the morning. If it begins to idle rough again do you have any suggestions ?

I was told by another online mechanic that the 128 code was going to be the thermostat sticking, is this a possiblity ? I have not noticed the guage getting higher (hotter) than normal. Would the thermostat sticking have anything to do with a rough idle.

It acts like an older carb engine with a choke and the choke not working correctly.

Thanks and any and all help is greatly appreciated.

Tom

Hi You replaced the ECT which sends engine temp to PCM. The P0128 is thermostat not closing for engine to reach op. temp.. That would cause rough idle. The P01345 does cause concern but first replace thermo. and clear codes see what happens.
Thanks for donate

At a stop while in Drive, car idles low and rough. When you accelerate, car sputters for a few seconds and then accelerates normal. Any idea?

I am having the same problem, but it was only after changing the original factory plugs with Bosch Platinum 2+.

Have you received an answer yet?

no platinum in trailblazers book says not

I also started having problems with the engine nearly stalling in idle or gear a few days ago with the AC on. I finally decided to buy a new set of plugs, this time ac delco, all of my problems have been gone now and it has been 3 days.

Engine Mechanical problem
2003 Chevy Trailblazer 6 cyl Two Wheel Drive Automatic

My vehicle idles very rough when in gear. If you move into park or neutral it idles normally.