Lousy mpg -7-???
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
TPS test results + ???
TPS voltage: closed throttle = 0.9v., WOT= 4.5v., reference voltage 4.1v., steady increase from closed to WOT.
TPS resistance:closed throttle = 3.5K ohms, WOT = 500 ohms, steady decrease from closed to WOT.
Reference voltage should be approx. 5V. Is 4.1v close enough or is this a problem? (battery was a little weak)
WOT resistance should be 350 ohms. Is 500 ohms close enough?
Unless reference voltage slightly low or WOT resistance slightly high is a problem then the TPS looks OK. Comments anyone?
TPS resistance:closed throttle = 3.5K ohms, WOT = 500 ohms, steady decrease from closed to WOT.
Reference voltage should be approx. 5V. Is 4.1v close enough or is this a problem? (battery was a little weak)
WOT resistance should be 350 ohms. Is 500 ohms close enough?
Unless reference voltage slightly low or WOT resistance slightly high is a problem then the TPS looks OK. Comments anyone?
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Well, 500 ohms didn't seem that far off from 350 ohms, which is supposedly just right, especially when it starts at at 3500 ohms, but I sure don't claim to know for sure. Would that much difference at WOT mean the TPS is bad?
Posting Guru
Joined: Apr 2011
Posts: 1,119
Likes: 1
From: Hartland, WI
Funny thing about TPS signal is it can command increased pulse width (more fuel) or clear flood mode (no fuel). During cranking 100% TPS (4.9v, 5v is almost unattainable) injectors will not fire, "clear flood mode". Engine running, 100% TPS commands maximum pulse width (80% is maximum; it's realistically continuous on). TPS isn't the only fuel commander, it only tells the ECM what the driver demand is. the MAP (or MAF if equipped) tells the ECM what engine load is, and also helps dictate fuel mapping.
Freshman User
Joined: Oct 2011
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Another thing about the TPS is that it can have intermittent problems which may or may not be revealed by testing it..... The fact that the computer set a code means that something is going on...
I'd say for the 5$ and 5 minutes that it takes to replace with one from the junkyard, that you might have a cheap gamble towards knocking this problem out.
Good luck!
I'd say for the 5$ and 5 minutes that it takes to replace with one from the junkyard, that you might have a cheap gamble towards knocking this problem out.
Good luck!
Elder User
Joined: Jan 2008
Posts: 635
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Keep us posted. I am experiencing similar issues with no codes though. I tried replacing my O2 sensor but found the threads and sensor are cross-threaded so I need to fix THAT before replacement.
Very curious to see how the O2 sensor affects the truck.
Very curious to see how the O2 sensor affects the truck.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Should get the O2 sensor installed in the next day or two. My biggest confusion is that the poor mileage seems to be the only issue except for a very slight stumble off idle (and I mean very slight). After the O2 sensor I'll see if I notice a difference in how it runs. If not then I guess it is time for a TPS install. I'll keep you informed.
Elder User
Joined: Jan 2008
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Should get the O2 sensor installed in the next day or two. My biggest confusion is that the poor mileage seems to be the only issue except for a very slight stumble off idle (and I mean very slight). After the O2 sensor I'll see if I notice a difference in how it runs. If not then I guess it is time for a TPS install. I'll keep you informed.
exact same secenario with my truck. EXACTLY as you describe
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Posting Guru
Joined: Apr 2011
Posts: 1,119
Likes: 1
From: Hartland, WI
An O2 sensor can cause fuel economy problems. If it's stuck lean the ECM will command more fuel to try to achieve stoich. An EGR valve failing to open will cause a drop in highway fuel economy. The inert exhaust gases displace fuel and oxygen, lowering combustion temperatures and lowering NOx emissions.
Easy way to check is to apply vacuum to the valve at idle: the engine should stumble or stall depending on how much vacuum you apply. A stuck closed valve or clogged passage will not cause any change to the idle. A stuck open valve will cause a poor idle or no idle condition.
Curious- have you ever done a top-end cleaning? If you take off the intake tubing and look into the throttle body with a flashlight, there will most likely be PCV and EGR deposits on the throttle blades, the throttle bores, and the inside of the intake. Berrymans B12 chemtool is a fantastic cleaner for the throttle body, and Seafoam is great for cleaning the intake via vacuum source.
Smell the oil for fuel as well. A leaking injector (or a few) can cause a drop in economy as well. Obviously a clogged air filter or obstructed intake system will do the same.
Easy way to check is to apply vacuum to the valve at idle: the engine should stumble or stall depending on how much vacuum you apply. A stuck closed valve or clogged passage will not cause any change to the idle. A stuck open valve will cause a poor idle or no idle condition.
Curious- have you ever done a top-end cleaning? If you take off the intake tubing and look into the throttle body with a flashlight, there will most likely be PCV and EGR deposits on the throttle blades, the throttle bores, and the inside of the intake. Berrymans B12 chemtool is a fantastic cleaner for the throttle body, and Seafoam is great for cleaning the intake via vacuum source.
Smell the oil for fuel as well. A leaking injector (or a few) can cause a drop in economy as well. Obviously a clogged air filter or obstructed intake system will do the same.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
How much effect would a crack in the exhaust manifold have on O2 sensor readings? I notice that the drivers side manifold has a crack in it. O2 sensor is in a crossover between dual exhaust pipes on the other side of the engine. It would seem that a crack should result in exhaust gases going out rather than air coming in, but I have also heard that a cracked manifold will cause burnt valves which would seem to imply air coming in through the crack. So will a crack in the manifold cause a lean reading on the O2 sensor?
EDIT TO ADD: On further checking, crack does not seem to be all the way through. No exhaust gas escaping that I can detect, so it is probably a non-issue. O2 sensor does not want to come out. Will saturate with PB Blaster repeatedly and see how it goes.
EDIT TO ADD: On further checking, crack does not seem to be all the way through. No exhaust gas escaping that I can detect, so it is probably a non-issue. O2 sensor does not want to come out. Will saturate with PB Blaster repeatedly and see how it goes.
Laughing Gas
Joined: Dec 2007
Posts: 959
Likes: 8
From: Imperial, MO
An exhaust leak forward of the O2 sensor will typically cause a lean reading, which the EEC will attempt to compensate for by richening the mixture. In other words, exhaust leaks forward of the oxygen sensor are bad for gas mileage.
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