Rough Idle - Codes P0151, P0174, P0300

Hello,

This occurs when the engine misfires causing the oxygen sensor codes lets start with a compression test to see if the engine is okay before we go any further, here is a guide to help.

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run down this guide and report back.

Thanks for this post I had this problem and used the guide found the #3 cylinder had 30 psi time for a valve job. I love this site.

Started with a squealing belt now I am having problems idling.

belt and tensioner should be replaced at 60,000 miles due to losing tension and wear. do not a spray any soap or oil on the belt it will destroy it. then clean throttle plate on both sides and IAC hole with choke cleaner. if stalling continues check fuel pressure with a gauge auto parts rent it.

I have an 04 tahoe that was getting the SES error code of p0174. currently the light is off but the car is running rough at idel and it gets worse as the out side temp gets colder.

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

I have a 2000 Tahoe and a few months ago noticed that the engine was idling very rough and used the gas supplements a few times and the problem went away. Now it seems the problem is back and worse. I have tried the supplements, but no joy. Took the vehicle in to have the injectors cleaned and it seemed ok for a few days. But the problem is back. Since then I have noticed that while driving @ 45-50 mph the engine looses power and stutters. If I let off of the accelerator it stops stuttering. If I try to accelerate through and above 50 mph it has a hard time doing so. Please help me out. Thanks.

Is the check engine light on?

no, that would have helped. The guys at the auto part store said that it would be very costly to take it in because the check engine light is not on. Sorry, this doesn't help.

Ok, that usually means that all the sensors etc. etc. that are regulated by the computer are reading within spec.
There is a common problem with the fuel injection system on these engines. GM is VERY aware of this and has developed an upgraded fuel injector system for this problem. The problem is that a GM dealer must determine that this problem exists. The fact that you had the injectors cleaned and you had briefly positive results, leads me to believe that it is a fuel problem. A failing fuel pressure regulator is common and this may be your problem. However, this part is located under the upper intake manifold cover. Your injectors are also located and accessed under this cover. This cover should not be taken on and off a lot -- SO -- if you can get the chevy dealer to determine that the fuel injector system is to blame, they should repair this for free. And if a new upgraded injector system is installed they all come with a new fuel pressure regulator...Whoa!
OR LOL
Check your spark plugs. If you replace them or anyother ignition related item, make sure you use A/C Delco parts -- just trust me....If the gaps are good -- what do they look like? And be specific as to what cylinder they came out of....

I took it into a mechanic and her noticed a strange hissing noise coming from the PCV valve and took it out and said I should replace that and let him know how it runs. I did and it seems to be running good, other than every once in a while it still idles rough.

check the fuel pressure.

I have a 2002 Chev Tahoe and last winter/spring when the air temp was between 10-30 F the idle was rough then when the air temp warmed up for summer the rough idle went away and it idled great all summer, now that the air temps are falling the rough idle came back. This is odvusly a temptrature sensor failure of some sort. Do you have any sugestions of where to start (oxigen sensor? MAP Sensor? Fuel pressure regulater?)

Sorry, I didn't mention it. That was one of the things the mechanic checked also and said it was good.

I forgot to ask about the Idle Control Valve. Could this cause this rough idle. The rough idle is a rich fuel mixture.

Put some tectron fuel injector cleaner in the gas tank. Cheveron makes it. This may help. But as I mentioned before, check the spark plugs and wires, and make sure the injectors are pulsing (firing) properly. Did the mechanic check the fuel pressure regulator? This is a common failure.

On left front cylinder head fine engine coolant temp sensor if faulty will not signal PCM engine cold to rich fuel mix so rough idle.

I don't think he checked the fuel pressure regulator, but the spark plugs and wires are new. Just replaced them Yesterday.

What brand wires and plugs did you use?

I know that the plugs are AC Delco. They did not have AC Delco wires, so I told the guy at the auto parts store to give me the wires one step above them then.

the vehicle has this constant rough idle, so bad that at times it will drop to almost zero and then catch itself. i know there are a number of things that will cause this. any tips on where to start?

well your main things are to make sure each cylinder is getting what it needs (ie. spark and fuel)....so take out each plug and verify the condition and color..... make sure your filters are fairly new and unclogged (air,oil,fuel) and if need be check the timing as it could have slipped ....also check all your vacuum lines to look for tears or breaks and make sure your PCV valve is in good order......good luck lemme know :)


ps...... whats the engine and milage?

I have a 2002 chevy tahoe that idles rough when its cold then when it warms up it stops. Check engine light came on and we had it checked and they said it was had codes of 106 BMP, 300 Misfire, 171 Lean and 172 Lean. They have cleaned the throttle body and MFAS but it didnt help. They also checked for vaccum leaks and all good in that department. Tried starting it this am and same problem exists and sevice engine light back on. Any suggestions on where to start the diagnosis.

Has the temp sensor been checked

Not that I am aware of. What would that do and is the temp sensor something that I could do?

IT tells the computer the ambient and coolant temp. From that, the computer decides how rich or lean to make the fuel mixture.

OK is this something that I can just replace or check myself because they are saying for me to replace the fuel pump. It lloks as though this part is not very expensive AC Delco part #155632 $4.47 ea.

This part isn't very expensive, and yes you could replace it. However, if someone is is saying the fuel pump is bad, you may want to check it yourself. There are directions on our homepage under the DIY section.

rough idle when im warming it up for the first time that day. it lasts for approx. 7 minutes. im in ny and lately the temp outside has been in the single digits, I was reading the manual and had read something about a plugin heater for the engine, is it good or is it a waste of time and money.

Ok thanks for the great information. Just to clarify you are talking about the intake temperature sensor.

-Its a good idea to install one-inline type on the heater hose or block heater on the freeze plug-Also have the idle air control valve and coolant temperature sensor-checked

It could be mounted on the intake, but that isn't its name. Tell them you want the ambient temp sensor.

2003 Chevy Tahoe idles rough when outside tempurature is cold. Even after engine comes up to normal operating temp. It only occurs during the winter and clears up in warmer months.
Ideas?

check for holes in the air duct leading to the throttlebody. if the service engine light is on get it scanned for codes.

107,000 miles 5.8 liter. Have several issues that may or may not be related. SES light (p0420 code) has been going on and off but the vehicle was running fine. Recently, I noticed a rough idle when A/C compressor comes on. Then today I heard a strange sound when i accererated from a stop. Sounded like a rush of air from under the hood, maybe from passenger side, lasted about one second. Happened four times in one trip to the store.

Hold on to you hat...er should I say cat. It should be a 5.7 motor. You need to get the OS sensors wave patterns looked at. You probably need a CAt...or Cataylitic converter. Heres the bad news, they are not only together, but are part of the front pipe. A shops' cost is around $390. Check for exhaust leaks in front of the cats..and hope you find one as that will throw the o2 sensors a little loopey.

The upper pic shows the front o2 sensor being flat lined (bad) and the rear o2 flat-lined (good) after the replacement, The front has a sin wave pattern-(good)

2001 Tahoe LT 5.3L 156,000 mi.

11/8: In AM, cold start, after driving not even two blocks, idle became very rough, engine was surging and tahoe was lurching forwards, kinda like a dog wanting to pounce on someone. Thought car was running out of gas (gas meter messed up) so filled up a few gallons but engine started after 4 tries (would idle at 500-600 then die). SES light came on, and still stays on

11/8: Afternoon to PM, would start the car in park, and there would be a rough idle, engine surge. Took it out on the freeway a couple times to see if it can still perform on freeway, and noticed SLOW accel. But car would not die. At night, drove on freeway again (3rd try, dist. of approx. 3 mi.), going 60-65 mph, RPMs started to fall almost to 0. Stepping on gas did nothing. All of a sudden, RPMs jumped to 2k-3k and stayed like that for abotu 4 sec. before dropping all the way to 0 and engine dying. After 6 tries (ignition and immediate idle and die) I was able to take it back home (drove in 1st gear w/o mashing on pedal b/c engine would die if pedal was floored). Started car in parking lot, at times idle would be normal and sound ok, and then randomly start sounding rough, engine died 2 out of the 8 times i started/idle it.

11/10-Present: Spray cleaned MAF, poured in Fuel injector cleaner into gas tank, cleaned throttle butterfly/lip. NOW, car will start just fine, RPMs at a little over 1k, then after 5 seconds, drop to 200 and fluctuate btwn 200-900 before dying. 2nd time (at idle this time) that RPMS shot up to btwn 2k-3k and staying like that for a few seconds before dropping again to almost 0.When rough idle, headlights and interior lights flicker. Can't even drive to back it out b/c engine dies so quickly.

Any advice would be great, thanks very much!

Last tune was? Think basics then get that code read! Autozone will read it free...Sounds like a vauum leak...read code and post result..

Have been having an issue with a rough idle. Started after the truck down shifted going up a hill the rpm's went to about 2700 and started running very rough to the point I could not drive it. The idle is still rough but not as bad as it first was. It is now drive-able. The idle is rough and stays generally down in the 500 to 600 range. I do not notice much of a difference between the idle in park or in gear. There also seems to be a dead spot in the peddle at times while driving where the truck seems to bog and will cough and sputter at times. Have done a tune-up (cap, rotor, plugs, wires,). The fuel pressure at idle is about 62 was hard to get a perfect reading. Checked for vacuum leaks but have been unable to find any, also when I block off the throttle body air the truck will die immediately. When the issue started I did not get any codes. Also generally at idle or low speeds for a bit the exhaust smells very rich. Cleaned the mass air flow unit and throttle body.