I can't figure out this sound coming from my engine.

[eXplicit]

First, I'd like to preface this with the fact that I've been getting a constant P1221 error code and reduced engine power at random times. It's only seemed to have been getting more frequent when this sound started getting louder. I can tell that it's coming from the driver's side of my motor, so could possibly be coming from the AC compressor or alternator. Can anyone tell me if they've heard this sound before, or know what it might be? Also, could it be related to the P1221 code I keep getting? And if it's not, ideas on where the P1221 code might be coming from? It usually happens when I'm at a stop light after driving on the highway, and the idle will start to get a little rough, and progress within a 30-45 second time period to the point to where it'll come close to stalling, and sometimes actually stalling, giving me the Reduced Engine Power light.

[video=youtube_share;nVchUzV8-VY]http://youtu.be/nVchUzV8-VY[/video]​

Thanks in advance.

 

[dmanns67]

P1221 relates to the throttle position (TP) sensors. Electronic Throttle Control serial data present and the PCM detected the TP Sensor (2) signal disagreed with the TP Sensor (1) by more than 75% for less than 1 second.

Do you still have the whine with the A/C on? How many miles are you at? Have you replaced your fan clutch?

 

[MAY03LT]

Does the noise change it you rev it up?

 

[djthumper]

It almost appears to have an electronic sound to it...

 

[eXplicit]

P1221 relates to the throttle position (TP) sensors. Electronic Throttle Control serial data present and the PCM detected the TP Sensor (2) signal disagreed with the TP Sensor (1) by more than 75% for less than 1 second.

Do you still have the whine with the A/C on? How many miles are you at? Have you replaced your fan clutch?

It does continue with the AC on. I'm at around 150k, and I have replaced the fan clutch, just before replacing the head gasket about 4 months ago.

Does the noise change it you rev it up?

It seems to go away most of the time when I rev it, but not all the time.

It almost appears to have an electronic sound to it...

It does. It almost sounds like it might be coming from the PCM.

 

[djthumper]

Do you have a mechanic's stethoscope? It should help narrow it down more where the sound is coming from.

 

[Texan]

If you take off the serpentine belt and run the engine, does the sound change?

 

[eXplicit]

If you take off the serpentine belt and run the engine, does the sound change?

Will the engine run without the belt?

 

[Playsinsnow]

Will the engine run without the belt?

Yes and it is the most effective way to isolate a worn pulley or noisemaker. Idling in your driveway/garage is fine. Just don't drive across town, or anywhere really!,with the belt off. I've done ita few times and nothing blew up.

 

[Texan]

Yes, for a short time with out setting a code ( 3 min. +/- ).

 

[eXplicit]

Anyone know what this is? I noticed that when I pulled it apart, there wasn't anything attached to it. And it's a VERY high power vacuum. I capped it and it's been running much better. Not 100%, but that sound has almost completely gone away after having it capped for a few miles. I can't seem to find where it connects.

View attachment 33139​

 

[moneypit]

Takes a 90 back 8" then a 90 to front of tbi(or whatever ya wanta call it/air horn?) I believe..hard to trace when assembled...

 

[eXplicit]

Takes a 90 back 8" then a 90 to front of tbi(or whatever ya wanta call it/air horn?) I believe..hard to trace when assembled...

Haha, you're telling me that's for the horn? It's causing all these issues?

 

[bobdec]

It's used as a vacuum line to the rear HVAC on the EXT only. I've read that some SB's have that port permanently plugged and others have a plug over the fitting. My '07 Envoy has the port opened and I have a cap on that fitting. Your signature indicates SB so that port s/b capped.

 

[eXplicit]

Yeah, I capped it last night. I noticed that it's kept the engine from stalling and getting sluggish on me. And the noise went away for a little while, but I just went outside and started it up again (I drove it to church this morning, and back home) and now it's got the sound again. As loud as it was before. Could it be another vacuum line leaking, or does it sound like it could be electrical?

 

[IllogicTC]

Yeah, I capped it last night. I noticed that it's kept the engine from stalling and getting sluggish on me. And the noise went away for a little while, but I just went outside and started it up again (I drove it to church this morning, and back home) and now it's got the sound again. As loud as it was before. Could it be another vacuum line leaking, or does it sound like it could be electrical?

Have you double-checked that your cap has stayed? Is it absolutely air-tight?

And did you remember to hook up the hose that connects to the bottom of the intake resonator when reassembling?

Then again, the engine stall issues and the noise could be entirely unrelated to each other at least one is fixed so far. It sounds sort of electrical but not really electrical to me. Sounds more like a test tone to me, or like if the "60hz hum" you hear near large electrical equipment was instead following something that takes PWM on the engine, but we aren't dealing with that kind of electrical power and the highest-running thing I can think of is the CPAS at 128hz.

Does the sound scale linearly with RPM, exponentially with RPM, or stay the same tone no matter what the speed?

 

[eXplicit]

Have you double-checked that your cap has stayed? Is it absolutely air-tight?

And did you remember to hook up the hose that connects to the bottom of the intake resonator when reassembling?

Then again, the engine stall issues and the noise could be entirely unrelated to each other at least one is fixed so far. It sounds sort of electrical but not really electrical to me. Sounds more like a test tone to me, or like if the "60hz hum" you hear near large electrical equipment was instead following something that takes PWM on the engine, but we aren't dealing with that kind of electrical power and the highest-running thing I can think of is the CPAS at 128hz.

Does the sound scale linearly with RPM, exponentially with RPM, or stay the same tone no matter what the speed?

Yeah, I put a 1/4" cap on it, which was pretty tough to get on there it was so tight (giggity).

The bigger hose on the bottom of the intake is connected and tightened as well.

The sounds stays pretty much the same as the engine is revved. It does sometimes sound like it wants to stall when I press the gas, and the sound goes away as it begins to do that. I guess you could call it a hesitation. I really only notice it when I'm sitting in park.

 

[Texan]

If you take off the serpentine belt and run the engine, does the sound change?

Have you tried this yet?

 

[eXplicit]

Have you tried this yet?

Not yet. Been busy all day getting my newborn's room ready for him. Might give it a shot tomorrow.

 

[jsheahawk]

Not yet. Been busy all day getting my newborn's room ready for him. Might give it a shot tomorrow.

Grats on the baby. You may never get to this!

Jared

 

[IllogicTC]

Any chance on having a code reader with live data readout to look things over such as the fuel trims?

Doesn't have to be a super-fancy thousand dollar one that reads all the stuff, even just covering the basics like fuel trims, MAP/MAF, etc would help.

 

[eXplicit]

Grats on the baby. You may never get to this!

Jared

Thanks. Yeah, I've got a 6-year-old daughter, and my son is due in a few weeks. I'll get around to it today, hopefully.

Any chance on having a code reader with live data readout to look things over such as the fuel trims?

Doesn't have to be a super-fancy thousand dollar one that reads all the stuff, even just covering the basics like fuel trims, MAP/MAF, etc would help.

Do you think I could get one of those bluetooth ODBII plugs and the app and get this information? Would I be able to make any adjustments with that, or will I need my PCM reprogrammed?

 

[IllogicTC]

Do you think I could get one of those bluetooth ODBII plugs and the app and get this information? Would I be able to make any adjustments with that, or will I need my PCM reprogrammed?

Torque Pro? Yeah you can get codes and a ton of live data which is very helpful, but unfortunately it's not a two-way device, meaning you can't command things to arbitrary values like with a Tech 2 and some of the other shop/dealer-level tools.

 

[eXplicit]

Alright, so I found the sound. It was the hose on the intake manifold that goes into a different part of the manifold. The hose we used when we put it back together was some 5/8" heater hose. It ended up separating on the inside and restricting the airflow. The sound was because of the small area of the air passing through. So, to temp fix it until I can order the correct hard-rubber hose tomorrow at the dealer, I just put another piece of heater hose. How, being that the hose flexes, it is somewhat kinked. The new hose has more air flow through it, but not as much as the molded hard-rubber one. My truck is still running a little rough when I come to a stop, and sometimes feels like it wants to sputter. Would this be because I don't have the right hose on there? I'm it runs perfect again when I get the right hose.

 

[IllogicTC]

Alright, so I found the sound. It was the hose on the intake manifold that goes into a different part of the manifold. The hose we used when we put it back together was some 5/8" heater hose. It ended up separating on the inside and restricting the airflow. The sound was because of the small area of the air passing through. So, to temp fix it until I can order the correct hard-rubber hose tomorrow at the dealer, I just put another piece of heater hose. How, being that the hose flexes, it is somewhat kinked. The new hose has more air flow through it, but not as much as the molded hard-rubber one. My truck is still running a little rough when I come to a stop, and sometimes feels like it wants to sputter. Would this be because I don't have the right hose on there? I'm it runs perfect again when I get the right hose.

It could be, considering the vacuum is being restricted. If you had a long length of spring of the appropriate length you could run it into the tube to keep it from collapsing as part of the temporary fix.

 

[eXplicit]

It could be, considering the vacuum is being restricted. If you had a long length of spring of the appropriate length you could run it into the tube to keep it from collapsing as part of the temporary fix.

Eh, it'll do until I can get it ordered. Hopefully it won't take long to get it.

 

[jsheahawk]

Alright, so I found the sound. It was the hose on the intake manifold that goes into a different part of the manifold. The hose we used when we put it back together was some 5/8" heater hose. It ended up separating on the inside and restricting the airflow. The sound was because of the small area of the air passing through. So, to temp fix it until I can order the correct hard-rubber hose tomorrow at the dealer, I just put another piece of heater hose. How, being that the hose flexes, it is somewhat kinked. The new hose has more air flow through it, but not as much as the molded hard-rubber one. My truck is still running a little rough when I come to a stop, and sometimes feels like it wants to sputter. Would this be because I don't have the right hose on there? I'm it runs perfect again when I get the right hose.

Sweet. Glad you found the sound. Hopefully fixing it fixes all of the problems.

Jared

 

[eXplicit]

So, I was able to find the tube at my local dealership. To me, a great $14 investment. It was a pain trying to get the thing on since the factory clamp was near impossible to close (it was one of those locking ones). But I finally got it and drove it around a little last night. Felt like it was getting better (maybe relearning)? Then got up this morning, drove to the office, and it was MUCH better.

I think I'll celebrate my victory by finally washing the thing since the weather is nice today and I'll have more daylight after work.

 

[jsheahawk]

:wootwoot:

Jared

 

[eXplicit]

Well, leave it to my wife to get my truck to throw another P1221 code. It ran fine all day. She took it to the store and came back, and as she pulled into the driveway it sputtered down and got the SES and REP lights. Any ideas?

 

[dmanns67]

I am assuming your have already thoroughly cleaned your throttle body based on your pic from above? Since the sensors are internal to the throttle body have you checked the wire harness running to the throttle body to see if any wires are cut or insulation is exposing wires shorting them out or maybe a loose connection?

If you do not find any issues with the wire harness, maybe a failing throttle body.

 

[eXplicit]

I am assuming your have already thoroughly cleaned your throttle body based on your pic from above? Since the sensors are internal to the throttle body have you checked the wire harness running to the throttle body to see if any wires are cut or insulation is exposing wires shorting them out or maybe a loose connection?

If you do not find any issues with the wire harness, maybe a failing throttle body.

The wiring cover that covers the wires to the throttle body is still pretty much intact. Would I need to cut back the cover to inspect the wires, or should I only be looking towards the connector side?

 

[dmanns67]

The wiring cover that covers the wires to the throttle body is still pretty much intact. Would I need to cut back the cover to inspect the wires, or should I only be looking towards the connector side?

You would want to see as much wire as to see if any is damaged. Do you have a meter? I found a thread with some good trouble shooting steps on the voltage you should be looking for.

How handy are you with a voltmeter?

With the ignition ON and the engine OFF check the following on the TB connector:
1
Meter black lead to the black/white-stripe wire
Meter red lead to the Light-blue/black stripe wire
You should see +5V
2
Meter black lead to the black wire
Meter red lead to the grey wire
You should see +5V

While I'm still leaning towards an electrical issue you can easily check for a physical problem with the throttle body with the ignition OFF:

Take off the intake so you can see the throttle plate. It should be about 20% open. Carefully move it fully closed and fully open.
You should feel spring pressure for the entire movement in both directions and it should always return to its original position. There should be no binding or sticking.

For the sake of completeness since you're going to be in there anyway:

If tests 1 and 2 come back with +5V check 3 and 4 below. These have to be done with the throttlebody connected, ignition ON, engine on or off. If you cant get the meter probe into the back of the connector you can poke a pushpin through the insulation.

3
Meter black lead to the black/white-stripe wire
Meter red lead to the purple wire
You should see a reading greater than 0V and less than 5V
4
Meter black lead to the black wire
Meter red lead to the dark green wire
You should see a reading greater than 0V and less than 5V

If you have a helping hand have them press the gas pedal up and down while you have the meter connected, the readings should change.

Do you have the ability to clear codes (Tech tool or TorquePro app)? You can unplug the fan clutch connector then clear the codes and start the engine. See if p1221 comes back.

 

[eXplicit]

You would want to see as much wire as to see if any is damaged. Do you have a meter? I found a thread with some good trouble shooting steps on the voltage you should be looking for.





Do you have the ability to clear codes (Tech tool or TorquePro app)? You can unplug the fan clutch connector then clear the codes and start the engine. See if p1221 comes back.

I'm not very good with a voltmeter. I actually don't even own one. But my father does, and I'm sure he could help me with it.

And I do have a code scanner that I can clear codes with. Problem is, the P1221 only happens at certain times. Like for instance, I used to notice it when I'd put the truck in reverse after driving forward for 30 miles (I know, odd situation. It's how I parked when I get home from work). Or sometimes when I'd start to roll the windows down, it'd bog down real bad and occasionally threw a code. Then there were times when I'd be driving on the highway and it'd just happen randomly. But most of the time, it'd be me sitting idle at a stop light. It wouldn't take a specific amount of time to do it, it'd just be random.

Quick question, though. Could my battery cause this issue?

 

[eXplicit]

I'm not very good with a voltmeter. I actually don't even own one. But my father does, and I'm sure he could help me with it.

And I do have a code scanner that I can clear codes with. Problem is, the P1221 only happens at certain times. Like for instance, I used to notice it when I'd put the truck in reverse after driving forward for 30 miles (I know, odd situation. It's how I parked when I get home from work). Or sometimes when I'd start to roll the windows down, it'd bog down real bad and occasionally threw a code. Then there were times when I'd be driving on the highway and it'd just happen randomly. But most of the time, it'd be me sitting idle at a stop light. It wouldn't take a specific amount of time to do it, it'd just be random.

Quick question, though. Could my battery cause this issue?

Bump for suggestions?

 

[IllogicTC]

Bump for suggestions?

1. Faulty wiring
2. Faulty voltage regulator (needs to be +5V)
3. Screwy battery, alternator, or ignition switch.
4. Bad accelerator pedal position sensor.

I'm kinda feeling 1 or 2 myself, or maybe number 4. Number 3 is just a wild last-resort guess, I'd start with the other ones first.

 

[gmcman]

I would attach a vacuum gauge and see what it's pulling at idle. You can use that port that you capped since it draws manifold vacuum.

I would also see what the voltage is at the battery measured with a volt meter when the engine is idling.

Have you ever changed the plugs? Have you ever changed the fuel filter?

 

[eXplicit]

I would attach a vacuum gauge and see what it's pulling at idle. You can use that port that you capped since it draws manifold vacuum.

I would also see what the voltage is at the battery measured with a volt meter when the engine is idling.

Have you ever changed the plugs? Have you ever changed the fuel filter?

I've changed the fuel filter, not the plugs. Plugs were gonna be next. I might actually take them out today and inspect them.

 

[gmcman]

Be careful with the coil bolts, use an inch-pound torque wrench and tighten to 89 inch-pounds, not foot pounds.

Spark plugs use only AC 41-103, tighten to 156 inch pounds

Use very light film of anti-seize on threads, I generally hit the last 3-4 threads about halfway around, let the threads spread it around.

I would also highly recommend changing the upstream O2 sensor with the plugs, if the sensor has 80K or more miles on it.

This tool works well on the O2 sensor. With a cold motor, idle the engine for about 1 minute to loosen the clamping force on the sensor threads from the manifold. This tool works well.

Just throwing out maintenance ideas if you are unsure of the history.

 

[eXplicit]

I've been doing a lot of research lately for stuff that could be causing this issue, and there are A LOT of things to cover. I'm going to start today by checking the condition of the harness that plugs into the TB. And I'll probably pull the mass airflow sensor and clean it just for the hell of it. And if I can get around to doing it, I'll pull the plugs and check them as well. I probably should've just changed them when I had the head out of the thing, but I was already behind in getting things done, I needed to finish getting it together. I'm sure I'll pay for that now that the engine is put back together

Anyways, I'll keep in mind of the O2 sensors as well. I'm sure with a truck this age, it needs a lot of this stuff if it wasn't regularly maintained (which the guy assured me it was at the dealership he worked at).


You know, it's funny that I can drive the thing without throwing any errors. It'll run rough, but won't bog down. Then I'll park and sit with the engine running for a few minutes and after a few minutes it'll start to bog down real bad, then jump up, then bog down again, then jump up, then bog down real bad and then throw the SES and REP lights. I'm so puzzled.