Help me troubleshoot this simple problem
Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
Help me troubleshoot this simple problem I'm tying to fix a simple problem without wasting a lot of time and money on parts. This is just a daily driver...
It is a 5.3 in a 07 Tahoe, Has 120k on the OD, totally stock.
It recently started having a shake at idle when in Drive. CEL came on, shows Misfires and TPS error. Seems to run fine otherwise, does not do it in N or when moving.
Trying to decide where to start the troubleshooting/repair process.
Off the top of my head, I'm thinking:
1. Plugs (the are the originals)
2. Wires (also original)
3. De-carb procedure with Sea Foam
4. Check Fuel pressure
Just looking for some insight. Is 120k just time for new plugs or do they usually last longer on daily driver soccer mom Truck?
It is a 5.3 in a 07 Tahoe, Has 120k on the OD, totally stock.
It recently started having a shake at idle when in Drive. CEL came on, shows Misfires and TPS error. Seems to run fine otherwise, does not do it in N or when moving.
Trying to decide where to start the troubleshooting/repair process.
Off the top of my head, I'm thinking:
1. Plugs (the are the originals)
2. Wires (also original)
3. De-carb procedure with Sea Foam
4. Check Fuel pressure
Just looking for some insight. Is 120k just time for new plugs or do they usually last longer on daily driver soccer mom Truck?
TECH Fanatic
Joined: Aug 2006
Posts: 1,407
Likes: 63
From: Knappa, Oregon
I would do 1 and 2 first if you are getting multiple misfire codes. The plugs might still be good but 100k is usually their expected life. Wires get old and crack and you can't really tell by looking at them if they are good. If you try just replacing the plugs but not the wires you may break one taking it off anyway. The LS1 engine has short wires and individual coils and don't go bad often. The 3800 V6s I had had long wires and went to the 3 coil pack and I had problems that turned out to be the plug wires on two separate cars. I'm not familiar with the wires on your 5.3. Change the plugs and wires, they need it anyway.
I would forget the Seafoam for now as it isn't going to solve the problem. There are various opinions here as to the value of the upper end Seafoam treatment and I am in the don't do it camp. I do like the product and use it in the gas. But it isn't likely to solve your issue.
Step #3 for me would be to clean the MAF sensor. If you don't know what this is, there is a wire or 2 somewhere in your air intake, after the air filter but before the throttle body opening. Get a can of MAF cleaner and spray the **** out of these wires and let them dry. Be sure the power is off and don't touch the wires. Again, some people use a Q-tip and alcohol, but they are very careful. Just get a can of spray. On second thought, move this up to step number 1.
If your vehicle runs find while driving I would not worry about the fuel pressure, at least until I had done the above.
I would forget the Seafoam for now as it isn't going to solve the problem. There are various opinions here as to the value of the upper end Seafoam treatment and I am in the don't do it camp. I do like the product and use it in the gas. But it isn't likely to solve your issue.
Step #3 for me would be to clean the MAF sensor. If you don't know what this is, there is a wire or 2 somewhere in your air intake, after the air filter but before the throttle body opening. Get a can of MAF cleaner and spray the **** out of these wires and let them dry. Be sure the power is off and don't touch the wires. Again, some people use a Q-tip and alcohol, but they are very careful. Just get a can of spray. On second thought, move this up to step number 1.
If your vehicle runs find while driving I would not worry about the fuel pressure, at least until I had done the above.
Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
Thanks for the input. Forgot to mention I already cleaned the MAF sensor. It did not help.
The wires are very short on the 5.3. Just like the 5.7, 6.0, 6.2... variants.
I think I will start with the plugs and see what happens.
The wires are very short on the 5.3. Just like the 5.7, 6.0, 6.2... variants.
I think I will start with the plugs and see what happens.
the 2007 and up tahoes have been known to have faulty TPS sensors. I recently had the one on my 2011 5.3 tahoe replaced by the dealer free of charge even though warranty was out. This is because there is a bulletin out for that part. Worth looking into.
Staging Lane
Joined: Jun 2012
Posts: 88
Likes: 0
From: Raleigh, NC
Just to throw in, you might wanna clean the TB. Those things get gummy and like to stick open or shut. Just grab a can of carb/TB cleaner and go to town. If you really want to get in depth pull the TB off and clean boths sides.
Teching In
Joined: Sep 2006
Posts: 33
Likes: 0
From: Melbourne, FL
also, you want to clean the back side of the MAF. JFYI. the wire is shielded.
The stock fuel pump only lasts till about 120K. Got misfires from that one, BIG TIME - like a ghost in the system. gotta drop the tank. Get the right delco GM part --
don't waste $ on aftermarket junk.
Also, bad knock sensor finally showed up at 110K via a code. I thought my transmission was bad -- it even affects the shifting.
On my TA I got misfire codes from a PCV vacuum leaks around where they plug in.
The stock fuel pump only lasts till about 120K. Got misfires from that one, BIG TIME - like a ghost in the system. gotta drop the tank. Get the right delco GM part --
don't waste $ on aftermarket junk.
Also, bad knock sensor finally showed up at 110K via a code. I thought my transmission was bad -- it even affects the shifting.
On my TA I got misfire codes from a PCV vacuum leaks around where they plug in.
Last edited by cold_surfer; Dec 27, 2013 at 08:43 PM.
Trending Topics
07' is DBW IIRC. Clean the TB. Make sure you don't get any solvent into the side with the motor.
If it's original and has 120k on it it's about 40k overdue for a plug change.(Hate on people I don't care)
If you don't want to spend the money on Delco Iriduims look at the NGK's. For wires the red GM stock replacements are good and so are the MSD's.
Make sure you gap the plugs. If you use platinum still gap them but don't gap them like you do a copper plug.
If it's original and has 120k on it it's about 40k overdue for a plug change.(Hate on people I don't care)
If you don't want to spend the money on Delco Iriduims look at the NGK's. For wires the red GM stock replacements are good and so are the MSD's.
Make sure you gap the plugs. If you use platinum still gap them but don't gap them like you do a copper plug.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
It seems like cleaning the TB fixed it.
But now it is acting a little crazy and needs a re-learn. It self adjust to ~650 RPMs when in gear and stopped. But starting with the key in, and it revs up to 2k out of gear. Starting with remote it acts normal.
It also wants to go about 30mph without touching the gas.
If anyone knows a way to force a complete idle relearn without a techII please chime in. I have an HP tuners scanner, but it does not seem to support an idle relearn in the rev I hvae. It seems my issue is common after a TB clean, but I can't find a solution besides getting the dealer to use a techII and trigger a re-learn.
But now it is acting a little crazy and needs a re-learn. It self adjust to ~650 RPMs when in gear and stopped. But starting with the key in, and it revs up to 2k out of gear. Starting with remote it acts normal.
It also wants to go about 30mph without touching the gas.
If anyone knows a way to force a complete idle relearn without a techII please chime in. I have an HP tuners scanner, but it does not seem to support an idle relearn in the rev I hvae. It seems my issue is common after a TB clean, but I can't find a solution besides getting the dealer to use a techII and trigger a re-learn.
make sure you clear any DTC's first.
Start and idle the engine in PARK for 3 minutes.
With a scan tool, monitor desired and actual RPM.
The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
Ignition OFF for 60 seconds.
Start and idle the engine in PARK for 3 minutes.
After the 3 minute run time the engine should be idling normal.
⇒X If the engine idle speed has not been learned the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations and extended idles.
After the drive cycle, the engine should be idling normally.
⇒X If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds and repeat step 6.
Once the engine speed has returned to normal, clear DTCs.
Start and idle the engine in PARK for 3 minutes.
With a scan tool, monitor desired and actual RPM.
The ECM will start to learn the new idle cells and Desired RPM should start to decrease.
Ignition OFF for 60 seconds.
Start and idle the engine in PARK for 3 minutes.
After the 3 minute run time the engine should be idling normal.
⇒X If the engine idle speed has not been learned the vehicle will need to be driven at speeds above 70 km/h (44 mph) with several decelerations and extended idles.
After the drive cycle, the engine should be idling normally.
⇒X If the engine idle speed has not been learned, turn OFF the ignition for 60 seconds and repeat step 6.
Once the engine speed has returned to normal, clear DTCs.
Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
I have driven it, but only around the neighborhood .... Not much at speed above 50. I will try that tomorrow, when I get out on open road.
I updated my HP Tuners to the latest rev, and it now has something in the scanner VCM controlls called Throttle Cleaned Reset. It seemed to do the trick on the first start (after running that), but then reverted back to the high idle on a second start after a short drive.
It does not seem to lean once it gets in this mode. It just idles at 2k and stays there until I cut the motor. It will drop to 1500 for a sec, but then back to 2k. And like I said before, it does not do this when started with the remote or put into drive. It is really odd. I have found lots of info about others having the same issue after cleaning and the solution seems to be many miles of driving. I don't mind driving it like this a little while, but I need it resolved quickly.
Hopefully, driving at speed and getting into some decel conditions will do the trick. Will report back tomorrow after trying that.
I updated my HP Tuners to the latest rev, and it now has something in the scanner VCM controlls called Throttle Cleaned Reset. It seemed to do the trick on the first start (after running that), but then reverted back to the high idle on a second start after a short drive.
It does not seem to lean once it gets in this mode. It just idles at 2k and stays there until I cut the motor. It will drop to 1500 for a sec, but then back to 2k. And like I said before, it does not do this when started with the remote or put into drive. It is really odd. I have found lots of info about others having the same issue after cleaning and the solution seems to be many miles of driving. I don't mind driving it like this a little while, but I need it resolved quickly.
Hopefully, driving at speed and getting into some decel conditions will do the trick. Will report back tomorrow after trying that.
Last edited by QuickSilver2002; Dec 31, 2013 at 08:49 PM.
Thread Starter
TECH Apprentice
Joined: Apr 2002
Posts: 308
Likes: 0
From: Austin, TX
The high idle seems to be slowly resolving on its own now after about 70 miles of driving at speed.
Initially, if I tapped the throttle in park after starting, it would shoot up to 2.5 k and just stick. Now it comes back down, but not as fast as it should. Also, the truck wanted to go at least 35mph with my foot off the gas initially, now it is more like 15. All indications are that it is slowly learning its way out of this mess.
Another odd thing is that I scanned it and the PCM was clearly demanding the high throttle position. You could see it stick at ~30%.
In the end, it looks my original problem was a combination of plugs that needed to be changed and a throttle body that needed to be cleaned.
Also, I think one cylinder has questionable rings based on what the plugs looked like. They all looked great except #1. It seems to be getting some contamination, but nothing crazy. I did not bother to do a leakdown or anything on it, since this is just a daily driver that I will be getting rid of shortly. It might just be that #1 gets the brunt of the crap from the PCV.
Initially, if I tapped the throttle in park after starting, it would shoot up to 2.5 k and just stick. Now it comes back down, but not as fast as it should. Also, the truck wanted to go at least 35mph with my foot off the gas initially, now it is more like 15. All indications are that it is slowly learning its way out of this mess.
Another odd thing is that I scanned it and the PCM was clearly demanding the high throttle position. You could see it stick at ~30%.
In the end, it looks my original problem was a combination of plugs that needed to be changed and a throttle body that needed to be cleaned.
Also, I think one cylinder has questionable rings based on what the plugs looked like. They all looked great except #1. It seems to be getting some contamination, but nothing crazy. I did not bother to do a leakdown or anything on it, since this is just a daily driver that I will be getting rid of shortly. It might just be that #1 gets the brunt of the crap from the PCV.