Rough idle, what's causing?

[tsmith1156]

Ok so I'm not sure what is going on with my tb, I have talked to a few other members about it, but my problem is a HORRIBLENESS rough idle in park, it idles rough a little bit when in drive at a stop light but not enough to really notice but as soon as I put it in park and sit in it, the car like shakes it is so rough. Today on my drive into work the RPMs stayed at 3000 almost the entire time even if I was not accellerating. Idk what is causing this, I have had an oil change, changed spark plugs and cleaned throttle body, replace cam position sensor. Can anyone diagnose what this is?

 

[xavierny25]

Just a thought but did you clean out your maf sensor. Although not really ever a issue with the gmt360's I have had other vehicles with rough idle and cleaning the maf did solve the issue.

2nd I'd try searching for a vacuum leak and double check all lines and hoses.

 

[tsmith1156]

Just a thought but did you clean out your maf sensor. Although not really ever a issue with the gmt360's I have had other vehicles with rough idle and cleaning the maf did solve the issue.

2nd I'd try searching for a vacuum leak and double check all lines and hoses.

To be honest I'm not sure what the maf sensor is and I have a check engine light for the secondary air system, that wouldn't cause rough idle would it?

 

[dkvasnicka]

Your profile says you have a 2005 TB. That means you don't have a MAF, your air intake system uses a MAP & IAT. Not sure how much cleaning those need, if any.

What is the exact code you're getting?

 

[mrrsm]

Some questions to consider:

(1) Can you post the Year/Make/Model....and Mileage of the vehicle?
(2) Did you change BOTH the CPS AND the CPAS Sensor/Solenoid or clean the CPAS?
(3) Have you driven through deep water or on the beach in the last week?
(4) Have you changed Gas Service Stations or filled up when a Tanker was unloading fuel?
(5) Does the Check Engine Light illuminate on Start Up and remain on?
(6) Have you ever changed the Fuel Filter? New Air Filter, too?
(7) Are you able to read any stored CEL Codes in the PCM and advise?
(8) Is there a fresh odour of gas under the hood?
(9) If you smell fuel vapours...it could be a leaking Fuel Pressure Regulator on the EFI Rail.
(10) Have you suffered from Low Power on acceleration? (Bad O2 Sensor or Clogged CAT)

Take a piece of laser Printer paper... tear it in half...lengthwise. Start the vehicle at idle and if will run in Park (with the Emergency Brake set)... Lay the strip of paper flat over the mouth of the Tail Pipe and observe that it should flutter like the wings of a humming bird...but...if the paper should suddenly or intermittently get sucked up backwards inside the tail pipe... it indicates for Bad Valves in the Engine Cylinder Head.

You should never fuel up your vehicles when a tanker Truck is present and off-loading fuel as this tends to churn up all the dirt, goo , water and crap in the bottom of the tank and leave this stuff suspended in the fuel long enough to be pumped inside your gas tank... A pint of Chevron Techron now would be a good idea to try and clean the system, emulsify any water and get it burned out in the engine during normal driving.

 

[tsmith1156]

Your profile says you have a 2005 TB. That means you don't have a MAF, your air intake system uses a MAP & IAT. Not sure how much cleaning those need, if any.

What is the exact code you're getting?

PO0410 is the code I get for my check engine light

Some questions to consider:

(1) Can you post the Year/Make/Model....and Mileage of the vehicle?
(2) Did you change BOTH the CPS AND the CPAS Sensor/Solenoid or clean the CPAS?
(3) Have you driven through deep water or on the beach in the last week?
(4) Have you changed Gas Service Stations or filled up when a Tanker was unloading fuel?
(5) Does the Check Engine Light illuminate on Start Up and remain on?
(6) Have you ever changed the Fuel Filter? New Air Filter, too?
(7) Are you able to read any stored CEL Codes in the PCM and advise?
(8) Is there a fresh odour of gas under the hood?
(9) If you smell fuel vapours...it could be a leaking Fuel Pressure Regulator on the EFI Rail.
(10) Have you suffered from Low Power on acceleration? (Bad O2 Sensor or Clogged CAT)

Take a piece of laser Printer paper... tear it in half...lengthwise. Start the vehicle at idle and if will run in Park (with the Emergency Brake set)... Lay the strip of paper flat over the mouth of the Tail Pipe and observe that it should flutter like the wings of a humming bird...but...if the paper should suddenly or intermittently get sucked up backwards inside the tail pipe... it indicates for Bad Valves in the Engine Cylinder Head.

You should never fuel up your vehicles when a tanker Truck is present and off-loading fuel as this tends to churn up all the dirt, goo , water and crap in the bottom of the tank and leave this stuff suspended in the fuel long enough to be pumped inside your gas tank... A pint of Chevron Techron now would be a good idea to try and clean the system, emulsify any water and get it burned out in the engine during normal driving.

It is a 2005 Chevy trailblazer LS with 140xxx miles, I haven't driven through water, I haven't filled up with a tanker present. And to be honest I'm not mechanically inclined so I'm sure what most of the questions are. I only replaced the cam position sensor I didn't clean anything

 

[mrrsm]

EDIT:

Check to see if your Plastic Intake Manifold Bolts-Fasteners are loose enough to allow for vacuum leaks around the intake ports... Remember when you were either removing, installing or cleaning the Throttle Body? It is entirely possible that the Plastic Intake Manifold was also being moved around a bit and that would allow the sealing "O" Rings the chance to be moved enough and cause the ports to break their rubber gasket seals and pull in ambient air to lean out the the air-fuel ratios and cause misfires as a result. You do not have to remove the IM...just go around and tighten up the fasteners...tight...but NOT TOO tight...and see what happens. Look up "How To R&R The Trailblazer 4.2l Intake Manifold" to find images...or excerpts from the manual.

Do you a desire to learn how to do any of these repairs...or can you engage the assistance of someone in your circle of friends who might be both mechanically knowledge-capable...and keen to help you with looking into these issues? We can hold your hand to figure out what is wrong to some extent...but eventually...it might be necessary to turn a wrench or two and get after things first hand.

Doing most of the "fixes' on the vehicle will not be over-whelming and if you visit Youtube and look for a GMT Nation Member named "MAY03LT" AKA @MAY03LT and view any of his many target specific repairs...you could develop your mechanical aptitude very confidently and quickly if your desire to save money and learn are present in equal measure.

Here is an interesting video on how to diagnose and repair your Secondary Air Pump PO410 code issue...even if you do not understand a word of what he is talking about...he will TELL you that the pump solenoid at the focus of his examination will need to be changed.:

 

[HARDTRAILZ]

Did you get a CASE relearn? If not, start there.

 

[tsmith1156]

EDIT:

Check to see if your Plastic Intake Manifold Bolts-Fasteners are loose enough to allow for vacuum leaks around the intake ports... Remember when you were either removing, installing or cleaning the Throttle Body? It is entirely possible that the Plastic Intake Manifold was also being moved around a bit and that would allow the sealing "O" Rings the chance to be moved enough and cause the ports to break their rubber gasket seals and pull in ambient air to lean out the the air-fuel ratios and cause misfires as a result. You do not have to remove the IM...just go around and tighten up the fasteners...tight...but NOT TOO tight...and see what happens. Look up "How To R&R The Trailblazer 4.2l Intake Manifold" to find images...or excerpts from the manual.

Do you a desire to learn how to do any of these repairs...or can you engage the assistance of someone in your circle of friends who might be both mechanically knowledge-capable...and keen to help you with looking into these issues? We can hold your hand to figure out what is wrong to some extent...but eventually...it might be necessary to turn a wrench or two and get after things first hand.

Doing most of the "fixes' on the vehicle will not be over-whelming and if you visit Youtube and look a GMT Nation Member named "MAY03LT" AKA @MAY03LT and view any of his many target specific repairs...you could develop your mechanical aptitude very confidently and quickly if your desire to save money and learn are present in equal measure.ir

Here is an interesting video on how to diagnose and repair your Secondary Air PO014 code issue...even if you do not understand a word of what he is talking about...he will TELL you that the pump his is examining will need to be changed.:

I will look at this

Did you get a CASE relearn? If not, start there.

I am not sure what that is Kyle, how do I do it?

 

[mrrsm]

Here is the best explanation from @MAY03LT :

 

[HARDTRAILZ]

I cant see what youtube video is linked, but the CASE relearn is a dealer/Tech2 thing.

 

[tsmith1156]

I cant see what youtube video is linked, but the CASE relearn is a dealer/Tech2 thing.

All this stuff is getting way to into it, I may have to take it to tirediscounters unfortunately

 

[HARDTRAILZ]

I am not sure i would trust a tire place for that.

 

[tsmith1156]

I am not sure i would trust a tire place for that.

They do all my oil changes and stuff like that. Who would you go to?

 

[HARDTRAILZ]

Oil changes are far different than reprogramming the computer to learn a crankshaft.

I went thru my buddy's dealership since I knew they would get it right.

 

[tsmith1156]

Oil changes are far different than reprogramming the computer to learn a crankshaft.

I went thru my buddy's dealership since I knew they would get it right.

So do it through a dealer, that sounds expensive

 

[HARDTRAILZ]

Or an actual mechanic.

I have no faith in the tire or oil change places. Typically an entry level auto job and not actual trained technicians with the knowledge or tools to properly do many things. I want someone with experience and tools and knowledge to mess with a computer, not someone that thinks they can or has seen it done and just picked up the tool.

 

[tsmith1156]

Or an actual mechanic.

I have no faith in the tire or oil change places. Typically an entry level auto job and not actual trained technicians with the knowledge or tools to properly do many things. I want someone with experience and tools and knowledge to mess with a computer, not someone that thinks they can or has seen it done and just picked up the tool.

That is true, I just want something that'll fix these problems, all I've had is problems recently

 

[HARDTRAILZ]

Then it take it somewhere better if it is something you cant do yourself. The cheap jiffylube/dicounttire are that for a reason...not because they are Good at fixing or diagnostics

 

[tsmith1156]

There aren't to many places around me other than a Midas which isn't very good

 

[HARDTRAILZ]

You live in Cincinnati. There are dealerships and mechanics galore. What side of town you on?

Edit: According to your profile city...Elite Automotive is close and has great reviews.

 

[tsmith1156]

I am now in maineville

 

[freddyboy61]

Just an aside, the OP did not change his crankshaft position sensor, so he does not need a CASE relearn.

As far as the rough idle in Park, maybe an issue with motor mounts.

 

[tsmith1156]

That's what another member I talked to said but I don't feel anything when I accelerate, wouldn't the motor be moving causing a vibration in the pedal if it was the motor mounts?

 

[HARDTRAILZ]

I thought motor mounts were most noticeable in neutral.

 

[tsmith1156]

I thought motor mounts were most noticeable in neutral.

I have no idea, believe me, I could be WAY wrong. And on the way home there was no rough idle in traffic or at stop lights and I sat in the driveway a little longer and it did nothing, I guess I'll see what it does in the morning

 

[dkvasnicka]

I thought motor mounts were most noticeable in neutral.

I thought in D with the foot on your brake. That way your whole driveline is in the game plus your engine has bigger load than in N.

 

[tsmith1156]

I don't know, but the roughest idle is in park with the car on after driving

 

[dkvasnicka]

Anyway, you have a code and your RPMs misbehave so it doesn't look like the problem is mounts here...

 

[HARDTRAILZ]

True. The mounts and RPM are un-connected

 

[tsmith1156]

Well this morning it was doing it but not as much as it has been. I'm thinking it may be bad gas? Or could the secondary air system messing up cause a rough idle?

 

[mrrsm]

If you were grounded and more comfortable with doing automotive repairs and investigative problem diagnoses... I would suggest introducing some light Propane Gas (unlit... NOT BURNING...low pressure...low volume Gas flow... with an ABC Fire Extinguisher Handy at your side) around the exterior areas of the Intake Manifold while the engine is idling... and observe to see if the engine RPM suddenly elevates from sucking in the Propane Vapours at any specific location where the In-line Intake Manifold Ports marry to the Engine Head.

If you did this...and the RPM began to rise suddenly... then you would have located the position of a/many vacuum leak(s) and confirmed that it can mimic a PO410 Code. This action ordinarily requires experience and extreme caution... as the idea here is verifying the problem of ambient air being ingested around the Intake Manifold Flanges...and NOT to make a Barbecue Pit out of the engine compartment. It follows on of course that the next action to fix the problem is to simply snug down all the Intake Manifold Fasteners and then starting the engine to see if it idles normally and without misbehaving.

 

[tsmith1156]

If you were grounded and more comfortable with doing automotive repairs and investigative problem diagnoses... I would suggest introducing some light Propane Gas (unlit... NOT BURNING...low pressure...low volume Gas flow... with an ABC Fire Extinguisher Handy at your side) around the exterior areas of the Intake Manifold while the engine is idling... and observe to see if the engine RPM suddenly elevates from sucking in the Propane Vapours at any specific location where the In-line Intake Manifold Ports marry to the Engine Head.

If you did this...and the RPM began to rise suddenly... then you would have located the position of a/many vacuum leak(s) and confirmed that it can mimic a PO014 Code. This action ordinarily requires experience and extreme caution... as the idea here is verifying the problem of ambient air being ingested around the Intake Manifold Flanges...and NOT to make a Barbecue Pit out of the engine compartment. It follows on of course that the next action to fix the problem is to simply snug down all the Intake Manifold Fasteners and then starting the engine to see if it idles normally and without misbehaving.

The code i get is PO0410 and it shows twice

 

[Mooseman]

PO0410 is the code I get for my check engine light

You have a code. Fix this first and then move on. It is possible that the SAIS is stuck open and causing the bad idle. Fix it, clear the codes and recheck.

 

[mrrsm]

"The code i get is PO0410 and it shows twice...'

Indeed... PO410...I mistyped the Alpha-Numeric code... twice actually... and so my replies and suggestions remain valid... Forgive this Dyslexic error... Please.

But... don't take my word for it... Just view this video at around 7:30 Minutes into the training... and see what he thinks about the problem of the PO410 Code... and what is REALLY going wrong here (even though the engine is different here...the principles are the same):

...and Part Two for Good Measure... First PROPANE...Then SMOKE...

 

[tsmith1156]

You have a code. Fix this first and then move on. It is possible that the SAIS is stuck open and causing the bad idle. Fix it, clear the codes and recheck.

I am going to, I'm gonna get a diagnostics ran on it just hoping it doesn't find anything else

"The code i get is PO0410 and it shows twice...'

Indeed... PO410...I mistyped the Alpha-Numeric code... twice actually... and so my replies and suggestions remain valid... Forgive this Dyslexic error... Please.

But... don't take my word for it... Just view this video at around 7:30 Minutes into the training... and see what he thinks about the problem of the PO410 Code... and what is REALLY going wrong here (even though the engine is different here...the principles are the same):

...and Part Two for Good Measure... First PROPANE...Then SMOKE...

I will look at these when I'm off work, thank you

 

[tsmith1156]

You have a code. Fix this first and then move on. It is possible that the SAIS is stuck open and causing the bad idle. Fix it, clear the codes and recheck.

Sorry for the double quote, so you think the code for the secondary air injection system is the reason for my rough idle?

 

[tsmith1156]

Ok fellow members, I just talked to tirediscounters about just doing the secondary air injection system that is throwing the code instead of a diagnostics and they quoted me $500 for the replacement of the air pump! They said that and I literally laughed and said what in hell is it that expensive for?! So my new question is, where is the air pump and the check valve at on the car? It may be a dumb question but I really have no idea and I'm doing it myself

 

[christo829]

Pump itself is on the frame roughly under the driver's seat, where the transmission crossmember mounts. The solenoid is up on the passenger's side of the engine, about 2/3 back. You can follow the black hoses from the pump up to the solenoid. Did that $500 include the parts? If not, you're better off getting replacements from RockAuto and doing 'em yourself. Or, if you're in the mood to get a custom tune, you can get the stupid pump deleted and block off the solenoid port.

Cheers-

Chris

 

[tsmith1156]

Pump itself is on the frame roughly under the driver's seat, where the transmission crossmember mounts. The solenoid is up on the passenger's side of the engine, about 2/3 back. You can follow the black hoses from the pump up to the solenoid. Did that $500 include the parts? If not, you're better off getting replacements from RockAuto and doing 'em yourself. Or, if you're in the mood to get a custom tune, you can get the stupid pump deleted and block off the solenoid port.

Cheers-

Chris

Yes the $500 was parts, labor, and shop fees. I plan on doing it myself, I just don't know what could make them charge that much for doing it cause what I've read it seems fairly easy. Do you even have to remove anything to replace the check valve or air pump?