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OKIE-JET
01-28-2007, 08:28 PM
I need some help here fellas, I have a 2000 new body Tahoe with the 5300. My trouble is the idle, it fluctuates between 7-800 and 2-300 and acts as though it cant "find" its idle setting, almost like the compressor kicks in and out but its not. The fuel filter is changed regularly and otherwise no other engine running issues. I was thinkin throttle pos. sensor but dont know much about the newer stuff, any help is greatly appreciated. Thanks

Kachina26
01-28-2007, 08:34 PM
Don't go replacing parts willie nillie. Without looking at it, you might wanna clean the throttle body, as that can cause a fluction in idle. Take it to autozone and check it for codes. Do not buy parts based on the code! If it has a code, post it up and we'll go from there. Leaking fuel pressure regulator is pretty common as well, but you usually have an extended crank condition as well. Does it take longer to fire up (first start of the day) than it used to?

BoneDaddy
01-28-2007, 08:34 PM
How many miles are on it?
Is the compressor kicking on? Have you looked at the AC pump and pulley to see if it is spinning as one whole piece?

OKIE-JET
01-28-2007, 08:38 PM
Fires up quick as always, and sometimes will idle perfect no matter temps, problem shows itself no matter temps. 165,000 miles. Compressor is working properly.

76ANTHONY
01-28-2007, 08:45 PM
check the tps, throttle position sensor. in the manual it should give you the ohms to check for, its not that hard ta do...sounds like the issue

Kachina26
01-28-2007, 08:46 PM
It'd be much easier to diag with a scan tool plugged in. :D Seriously, clean the throttle body, it's cheap and easy. If that doesn't help, you might have to take it in.

OKIE-JET
01-28-2007, 08:48 PM
Will clean it up and check ohms tommorrow, see if that helps. What would an extended crank issue be?

BoneDaddy
01-28-2007, 08:51 PM
It'd be much easier to diag with a scan tool plugged in. :D Seriously, clean the throttle body, it's cheap and easy. If that doesn't help, you might have to take it in.
If you clean the throttle body make sure you use "throttle body and manifold cleaner". It will not damage the other components like carb cleaner will. I think you also need to make sure you don't get any on the Mass Air Sensor.

Kachina26
01-28-2007, 08:52 PM
check the tps, throttle position sensor. in the manual it should give you the ohms to check for, its not that hard ta do...sounds like the issue
Short of scanning it, the best way to check it would be to backprobe the signal wire at the tps with a high impedence dvm. You will be looking for around .4-.8 volts at idle and a smooth transition to 4.6volts as you open the throttle to full open. You can do this with the key on and engine off. You can also "massage" the harnes while it's running to try to induce the condition. This will help you locate wiring issues like broken wire or poor connections.
Come to think of it, check the positive battery cable connection. Make sure it is clean and tight.

JAY4SPEED
01-28-2007, 09:31 PM
If its drive by wire (no throttle cable) clean the throttle body. Kachina26 is right on the money with that one. You'll see a buildup right where the thottle blade meets the bore. Get that squeeky clean and your good to go. We see this one a lot.
If the thottle is cable actuated, carry on with checking for codes TPS sensor and IAC position actual vs. commanded. Let us know what you find.
Jay

scooooter7
01-28-2007, 09:37 PM
If you use a K&N filter and have cleaned and reoiled it recently, you might have put too much oil on the filter and fouled your system. Remember a little goes a long way.

shockwaveharry
01-29-2007, 01:44 AM
Check the basics first... Look for open/cracked vacuum lines. Vac leaks are the most common cause for an erratic idle.
...What would an extended crank issue be?
Like Kachina26 said, a leaking fuel pressure reg could cause that.
The old Vortec motors with the spider injectors were famous for that. The regulator was actually inside the manifold and they'd leak down when the engine was off and fuel would pool in the intake manifold and cause a very hard start. Yours is external but fuel could leak back in through the vac line from the reg into the mani.

Kachina26
01-29-2007, 08:45 AM
Kachina26 is right on the money with that one.
Jay
I would hope so after 14 years with GM :D . I kinda miss doing diagnostics, but I don't miss chasinig a flag sheet.

BowTie Rick
01-29-2007, 09:10 AM
If you use a K&N filter and have cleaned and reoiled it recently, you might have put too much oil on the filter and fouled your system. Remember a little goes a long way.
Impossible. They work even when exposed to a direct spray of oil from an air brush. We have even soaked them overnight in a bucket of oil. It does not "foul" them. This is an internet legend started by competitors more than likely. These are the same ones that go on the diesel boards acting as regular peeps with years of experience and knowledge when they are actually company reps toting their own product line. Sad part is people believe them. Everything you read on the internet is NOT true. When we get a claim regarding filter oil and a MAF sensor, we imediately contact the dealership or repair place. We offer to pay for the repair if they send the old part back to us. Once we get the sensor back it is placed on a voltage signal machine and compared to a brand new sensor. More than 50% of them pass at this point!! That means the diagnosis is wrong half the time. If it fails, it is then put under an electron microscope. The "hot wire" is looked at for signs of contamination. Then the sensor is sent out for spectrograph analysis to determine the chemical make up of the contamination. Guess what? 100% of the conatmination can be traced back to the potting material inside the sensor breaking down. At this point, we go back to the repair place with the results and ask for reimbursement. Customer is happy their vehicle is fixed and we get our money back plus the cost of testing. Once enough dealerships get hit with these charges, the word will get out, don't F with K&N. :D Want more deatils... http://www.knfilters.com/MAF/massair.htm

IMPATIENT 1
01-29-2007, 09:18 AM
k&n air filters that are over oiled will damaged mass air flow sensors, i've replaced dozens of them because a customer got crazy with the oil spray.fuel pressure regulator will make it hard to start when hot and idle surge, pull off the vaccum line, turn on key, if fuel squirts out regu., replace it.
if its hunting for idle, i'd look at the intake gaskets.i replace at least 4-5 sets a weak on tahoes and trucks. take some brake cleaner or carb cleaner and spray around the intake gasket area (between intake and head).if it revs up or starts to idle rough, its the intake leaking. the gaskets get warped and compressed over time and start leaking. i always look a fuel trim numbers, if they're both over(rh and lh banks)over 10% on the positive side, the intakes leaking!i'm a gm master tech in 7 areas,just my .02:D

BowTie Rick
01-29-2007, 09:44 AM
Then how do explain the fact that analysis shows 100% from potting material and zero incidents of filter oil? No dealership in the country has the ability to test a sensor. How many people on this board have had to change an MSD module because it went bad? What made it go bad? Potting material breakdown. Same thing for the MAF sensors. Did you happen to notice the potting compound is directly above the hot wire? Where do you think the residue goes? Furthermore, aren't all new vehicles closed crankcase systems? Shouldn't there be some oil vapor present in the intake tract then? Toyota has hydro-carbon traps in the lids of the air boxes of their vehicles to capture oil vapor and meet future emissions regulations.

Kachina26
01-29-2007, 10:23 AM
Impossible. They work even when exposed to a direct spray of oil from an air brush. We have even soaked them overnight in a bucket of oil. It does not "foul" them. This is an internet legend started by competitors more than likely. These are the same ones that go on the diesel boards acting as regular peeps with years of experience and knowledge when they are actually company reps toting their own product line. Sad part is people believe them. Everything you read on the internet is NOT true. When we get a claim regarding filter oil and a MAF sensor, we imediately contact the dealership or repair place. We offer to pay for the repair if they send the old part back to us. Once we get the sensor back it is placed on a voltage signal machine and compared to a brand new sensor. More than 50% of them pass at this point!! That means the diagnosis is wrong half the time. If it fails, it is then put under an electron microscope. The "hot wire" is looked at for signs of contamination. Then the sensor is sent out for spectrograph analysis to determine the chemical make up of the contamination. Guess what? 100% of the conatmination can be traced back to the potting material inside the sensor breaking down. At this point, we go back to the repair place with the results and ask for reimbursement. Customer is happy their vehicle is fixed and we get our money back plus the cost of testing. Once enough dealerships get hit with these charges, the word will get out, don't F with K&N. :D Want more deatils... http://www.knfilters.com/MAF/massair.htm
Hate to bust your bubble, but oil on the sensor does cause problems. Sensor replacement is not necessary, however. The sensor can be cleaned with a good contact cleaner and put back into use. I've done too many of them for you to say any different. I've never had the same condition occur with a stock filter. Not knocking K&N in any way. People just have to follow K&N's instructions on filter oiling.There is no way you could soak a MAF sensor in oil and have it work properly. I understand your position in relation to techs replacing sensors when they are fine, but please don't try to tell folks that an oil soaked sensor will perform the same as one not soaked in oil. I could post a bulletin which speaks to maf sensors fouled by just plain dirt due to improper filter installation. If dirt covering the sensor wire can cause problems, so can oil (which attracts dirt).

Baja Big Dog
01-29-2007, 10:28 AM
This is unbielieveable....even the guys that sound like you know what your talking about attempting to diagnose the problem without a scanner....the computer will tell you what your problem is, if it is the correct scanner, you can monitor conditions that could lead to the problem. If in doubt and unless you want to change alot of parts to make the engine pre:mad: tty Id take it to a professional...not the dealer, but some one that makes a living fixing cars.

Baja Big Dog
01-29-2007, 10:31 AM
Then how do explain the fact that analysis shows 100% from potting material and zero incidents of filter oil? No dealership in the country has the ability to test a sensor. How many people on this board have had to change an MSD module because it went bad? What made it go bad? Potting material breakdown. Same thing for the MAF sensors. Did you happen to notice the potting compound is directly above the hot wire? Where do you think the residue goes? Furthermore, aren't all new vehicles closed crankcase systems? Shouldn't there be some oil vapor present in the intake tract then? Toyota has hydro-carbon traps in the lids of the air boxes of their vehicles to capture oil vapor and meet future emissions regulations.
You guys better listen to Bow Tie, I think he knows his shit. And Ill bet he is finacially tied to K&N.....
But now you have pissed him off:mad:
Ive heard K&N's are shit...but somehow I feel bad trusting our $15K off road motor to a K&N!!!

Kachina26
01-29-2007, 10:36 AM
This is unbielieveable....even the guys that sound like you know what your talking about attempting to diagnose the problem without a scanner....the computer will tell you what your problem is, if it is the correct scanner, you can monitor conditions that could lead to the problem. If in doubt and unless you want to change alot of parts to make the engine pre:mad: tty Id take it to a professional...not the dealer, but some one that makes a living fixing cars.Not trying to diagnose, just giving a few quick checks. You are correct, the best course of action is to scan the vehicle. But if he insists on trying to figure it out on his own, I figure the least I can do is offer up the most common problems I saw as a GM tech of 14 years. Notice that I did not recommend replacement of any parts in my posts, as a matter of fact, I warned against it. I didn't make a living fixing cars, I made a living repairing them, and correcting the fock ups that the guys who "fixed" them made. When all else fails, even the good shops send it to the dealer:D I worked alongside a very reputible shop from time to time, because the fact of the matter is, the dealer just has better access to information.

Big Kahunaa
01-29-2007, 11:05 AM
the iac will cause that problem also

BowTie Rick
01-29-2007, 11:11 AM
Correct, if you were to soak the thing in oil overnight, it would need to be cleaned. But would it be destroyed, no. When words like "damage", foul", "ruin", etc. are used, that is untrue. And why not use a K&N on a 15K off road motor? Plenty of teams do. We are not new at this. BTW, no disrespect to you Kachina 26, I think you know what I am trying to say. Who sponsors you Baja Big Dog?

Baja Big Dog
01-29-2007, 11:28 AM
Correct, if you were to soak the thing in oil overnight, it would need to be cleaned. But would it be destroyed, no. When words like "damage", foul", "ruin", etc. are used, that is untrue. And why not use a K&N on a 15K off road motor? Plenty of teams do. We are not new at this. BTW, no disrespect to you Kachina 26, I think you know what I am trying to say. Who sponsors you Baja Big Dog?
I screwed that post up. I meant to say we DO trust our $15K motor to a K&N, hope I bunch up your panties:D
Best Buy, Yellow Frt

IMPATIENT 1
01-29-2007, 11:34 AM
i've got 1 in my hand rite now. the oil from the k&n gets on the little resistor looking things between the "bars". once its on there, they heat up and turn black, start setting maf performance codes.
if you've ever worked at a dealership long enough, you'd notice how most vehicle lines will have a defect that most of the vehicles in the same car line will also have.the fuel pressure regulators are a good example, or the bumping ass steering shafts that sound like a shocks coming off. the intake gaskets are another thing i see all the gm trucks, and suv's with v8's will be lineing up needing. if 1 truck has a defect, chances are there's thousands with the same.at @60-70k, your gm 99-04 4.8,5.3, or 6.0l will be needing them wether or not your "good mechanic" says so or not.its in the trim #'s, and o2 sensor values, most techs today can't tell because its not a code telling them to replace this part.

BowTie Rick
01-29-2007, 11:36 AM
LOL, they were in a bunch but now we are back to free ballin' status :D Do you know Damen Jeffries? We are stepping up big with him. If you need anything for the race team, let me know.

BowTie Rick
01-29-2007, 11:39 AM
[QUOTE=IMPATIENT 1;2363845]i've got 1 in my hand rite now. the oil from the k&n gets on the little resistor looking things between the "bars". once its on there, they heat up and turn black, start setting maf performance codes.
QUOTE]
Send it in for chemical analysis. Black = Potting compound. The filter oil is actually leaves a light red/tan color and is easily sprayed off. The black crap from the potting compound is there for good.

IMPATIENT 1
01-29-2007, 11:40 AM
k&n filters are awesome, i love em, just not on gm trucks with a maf.i've seen a maf take a dump from a spec of dirt.anytime your dealing with a maf with heated elements,oil, water, dirt will kill em.our oil changer cost the service dept. 1k last yr., when he changed out a benz air filter and got alittle dirt in the intake tract, which ended up on the maf.they're more delicate then people think.

OKIE-JET
02-07-2007, 10:52 AM
If its drive by wire (no throttle cable) clean the throttle body. Kachina26 is right on the money with that one. You'll see a buildup right where the thottle blade meets the bore. Get that squeeky clean and your good to go. We see this one a lot.
If the thottle is cable actuated, carry on with checking for codes TPS sensor and IAC position actual vs. commanded. Let us know what you find.
Jay
Cleaned TB, removed and cleaned cables (very little), retorqued.....good to go for days now...Thank You fellas, your expertise is greatly appreciated, hope to return favor one day with a few brews.:D

Kachina26
02-07-2007, 11:37 AM
Cleaned TB, removed and cleaned cables (very little), retorqued.....good to go for days now...Thank You fellas, your expertise is greatly appreciated, hope to return favor one day with a few brews.:D
Good news, happy to hear it was cheap and you didn't toss a bunch of parts at it.

OKIE-JET
02-07-2007, 11:41 AM
Good news, happy to hear it was cheap and you didn't toss a bunch of parts at it.
I never throw money away....ever.:D Thank you for your help.:)

Beer-30
02-07-2007, 12:14 PM
I firmly believe the K&N oil theory is complete bull. I have ran 3 K&Ns on vehicles with MAFs to over 100,000 miles each. None have had any problems, and I serviced (cleaned/oiled) the filters every 20K. I have never had a problem. The whole intake tract was clean and oil free / as were the sensors and throttle bodies.
I can't even imagine how much K&N oil you would have to spray to get it all the way up the tract thick enough to foul a MAF sensor. One would pretty much have to REMOVE the air cleaner and spray it directly in the screen for a few seconds.
Who in their right mind would ever use THAT MUCH filter oil?
OH, and for the idle problem. I would definitly hook it up to an OBD-II reader. My 496HO was surging up and down at idle. Hooked it up to the reader (not OBD-II, but same thing) and it showed TPS out of spec. Sure enough, new TPS, idles fine.

JAY4SPEED
02-07-2007, 01:08 PM
Cleaned TB, removed and cleaned cables (very little), retorqued.....good to go for days now...Thank You fellas, your expertise is greatly appreciated, hope to return favor one day with a few brews.:D
Glad it worked out for you. The advantage to being a dealership tech is that we know everything about a few car lines and one make. Independants can only know a little about every car line and every make. So we tend to see the same issues over and over.
With your situation and the vehicle being drive by wire (throttle is motor driven instead of cable driven), the throttle body blade is controlled by the engine computer. To idle up the ECM opens the thottle blade a little more to allow more air in. Over the life of the vehicle, the ECM "learns" the sweet spot on where to position the thottle blade for idle. That way, everytime you start your vehicle, it doesn't have to go through the learning process all over again. Over time carbon buildup fills in the little gap between the thottle blade and bore. The ECM has no way of knowing that the airflow is being restricted and keeps the thottle body blade in its normal position. The result is erractic idle because when the engine moves the blade a little bit, its affects the idle a due to the restriction.
I've worked at an independant before becoming a dealership master technician. I've become a 100% better tech due to the information I have available and the special tool avaliabilty. I've been there I've seen the difference. I wonder how many indepentants can fix that one without throwing one sensor after another at it until its fixed. There is a huge difference in a technician (one who diagnoses cars before attempting a repair) and mechanics (hangs parts on a car until it works).
Anyways, glad it worked out for you!
Jay

JAY4SPEED
02-07-2007, 01:11 PM
I firmly believe the K&N oil theory is complete bull. I have ran 3 K&Ns on vehicles with MAFs to over 100,000 miles each. None have had any problems, and I serviced (cleaned/oiled) the filters every 20K. I have never had a problem. The whole intake tract was clean and oil free / as were the sensors and throttle bodies.
I can't even imagine how much K&N oil you would have to spray to get it all the way up the tract thick enough to foul a MAF sensor. One would pretty much have to REMOVE the air cleaner and spray it directly in the screen for a few seconds.
Who in their right mind would ever use THAT MUCH filter oil?
OH, and for the idle problem. I would definitly hook it up to an OBD-II reader. My 496HO was surging up and down at idle. Hooked it up to the reader (not OBD-II, but same thing) and it showed TPS out of spec. Sure enough, new TPS, idles fine.
The issue is not with K&N filters themselves but the misuse of K&N filters. Obviously you know how to clean and oil your filters therefore you didn't have any issues.
The problem comes in where people who don't know any better think that if a little oil on the element works good, than a lot of oil will work better. Thats when the problems begin....
Jay

Beer-30
02-07-2007, 01:15 PM
The issue is not with K&N filters themselves but the misuse of K&N filters. Obviously you know how to clean and oil your filters therefore you didn't have any issues.
The problem comes in where people who don't know any better think that if a little oil on the element works good, than a lot of oil will work better. Thats when the problems begin....
Jay
That makes more sense. I would imagine some people spray oil on the INSIDE of the filter as well as the outside. I could see several drops getting spread downstream with each cleaning, and eventually start sticking to the MAF.
To say that simply bolting on a K&N WILL gum up your sensors is just ridiculous.
I agree with your terminology. Well put.

brianthomas
02-07-2007, 01:48 PM
So do the 8.1 liter 496s have MAF sensors also even thought they operate in an open loop program without an 02 sensor? So does fogging oil really hurt them if sprayed into the air intake?

OKIE-JET
02-07-2007, 02:13 PM
Glad it worked out for you. The advantage to being a dealership tech is that we know everything about a few car lines and one make. Independants can only know a little about every car line and every make. So we tend to see the same issues over and over.
With your situation and the vehicle being drive by wire (throttle is motor driven instead of cable driven), the throttle body blade is controlled by the engine computer. To idle up the ECM opens the thottle blade a little more to allow more air in. Over the life of the vehicle, the ECM "learns" the sweet spot on where to position the thottle blade for idle. That way, everytime you start your vehicle, it doesn't have to go through the learning process all over again. Over time carbon buildup fills in the little gap between the thottle blade and bore. The ECM has no way of knowing that the airflow is being restricted and keeps the thottle body blade in its normal position. The result is erractic idle because when the engine moves the blade a little bit, its affects the idle a due to the restriction.
I've worked at an independant before becoming a dealership master technician. I've become a 100% better tech due to the information I have available and the special tool avaliabilty. I've been there I've seen the difference. I wonder how many indepentants can fix that one without throwing one sensor after another at it until its fixed. There is a huge difference in a technician (one who diagnoses cars before attempting a repair) and mechanics (hangs parts on a car until it works).
Anyways, glad it worked out for you!
Jay
Your analogy is exactly the way it went in my mind once you guys brought it to light...took about 20 min at a cost of one razor cut from the bore edge.:idea: :D

Beer-30
02-07-2007, 04:49 PM
So do the 8.1 liter 496s have MAF sensors also even thought they operate in an open loop program without an 02 sensor? So does fogging oil really hurt them if sprayed into the air intake?
IF you are referring to MARINE applications: There is no MAF sensor. The aircleaner is attached directly to the inlet of the throttle body.
Pickup versions would have a MAF between the filter and the throttle body.

JAY4SPEED
02-07-2007, 07:54 PM
So do the 8.1 liter 496s have MAF sensors also even thought they operate in an open loop program without an 02 sensor? So does fogging oil really hurt them if sprayed into the air intake?
Like Beer-30 asked, is this marine or automotive? I don't know much about the marine end of it, if your referring to the automotive end, I may be able to explain, but automotive uses both O2 and MAF.
Jay