Would a bad knock sensor throw lean codes?
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
Ill give that a shot first thing tomorrow morning, will keep you posted. My buddy keeps saying the cat is clogged, I'll be testing temperature tonight
Hotshot
Joined: Jan 2004
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From: St Louis
A clogged cat will not cause "lean" codes nor will the engine run right, it will be very low on power. You explicitly stated it "runs smooth, feels great" so that would eliminate that idea.
A clogged EGR system will not cause "lean" codes, it will cause a P0401 "Insufficient EGR Flow" DTC. Uncommanded EGR flow would be a possibility, ie EGR valve stuck open or similar.
And I gave the correction to that overly broad statement.
Unlikely to be effective. If you had a vacuum leak in the TB, the smoke test should have revealed it.
Because the system is dumping excess fuel and it isn't being burned in the cylinders, the fuel will be burning in the cats. You're going to get misleading temps if you do not know how to interpret both the system and the readings.
Now THAT is actually useful data. It suggests a weak fuel supply that can't keep up with the system's demands at higher RPMs. You really need a fuel pressure gauge on there and monitor that while putting the system under load.
Check and see if the EGR, port on the upper intake elbow is not clogged up, remove the throttle body and its the upper most hole on the elbow.
Another member on this thread alone said ... snip
I'm thinking of trying a junk yard throttle body and seeing if that fixes the problem, maybe that gasket has a break or something
I'll be testing temperature tonight
It appears long term fuel trim is fine below 2500 but when I hit 3500 it goes up to 14
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
A clogged cat will not cause "lean" codes nor will the engine run right, it will be very low on power. You explicitly stated it "runs smooth, feels great" so that would eliminate that idea.
A clogged EGR system will not cause "lean" codes, it will cause a P0401 "Insufficient EGR Flow" DTC.
And I gave the correction to that overly broad statement.
Unlikely to be effective. If you had a vacuum leak in the TB, the smoke test should have revealed it.
Because the system is dumping excess fuel and it isn't being burned in the cylinders, the fuel will be burning in the cats. You're going to get misleading temps if you do not know how to interpret the both the system and the readings.
Now THAT is actually useful data. It suggests a weak fuel supply that can't keep up with the system's demands at higher RPMs. You really need a fuel pressure gauge on there and monitor that while putting the system under load.
A clogged EGR system will not cause "lean" codes, it will cause a P0401 "Insufficient EGR Flow" DTC.
And I gave the correction to that overly broad statement.
Unlikely to be effective. If you had a vacuum leak in the TB, the smoke test should have revealed it.
Because the system is dumping excess fuel and it isn't being burned in the cylinders, the fuel will be burning in the cats. You're going to get misleading temps if you do not know how to interpret the both the system and the readings.
Now THAT is actually useful data. It suggests a weak fuel supply that can't keep up with the system's demands at higher RPMs. You really need a fuel pressure gauge on there and monitor that while putting the system under load.
Thread Starter
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
Here's another video, this one is from me driving, tell me what you guys think, sorry it's a bit shakey Pennsylvania roads aren't so great
https://youtu.be/NCnAzjT0B9k
https://youtu.be/NCnAzjT0B9k
Cargo Master
Joined: Apr 2013
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From: Central Florida
I’ll be watching this thread eagerly awaiting the “I told you so” moment 
have you checked your your air intake tubing? And the clamps on it? I mean REALLY check it- take it off and inspect every inch. Flex it back and forth as you go.
have you checked your your air intake tubing? And the clamps on it? I mean REALLY check it- take it off and inspect every inch. Flex it back and forth as you go.
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
As we smoked the whole system, we flexed the pipe back and forth to look for cracks, smoke came out of the front of air box, but no where else. When we smoked the EVAP system, only place smoke came out of was the charcoal canister vent. I'm big enough to admit when I'm wrong, if it's a vacuum leak I'll post it right away. Right now all I'm looking for is my truck to stop throwing lean codes
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Joined: Jan 2004
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From: St Louis
The second video is useless. It's rotated wrong, is out of focus and I cannot make out any of the data.
What would actually be useful would the to allow the codes to set and to get the freeze frame data so we can see the operating conditions under which the codes tripped. That way, the tech can check the system's operation under the same or similar parameters.
Vacuum leaks usually manifest themselves at engine idle speeds when manifold vacuum is at its maximum. Warm up the engine, verify it is in closed loop operation, then monitor your fuel trims. If trims are relatively normal at idle speed, then it's much less likely to be a vacuum leak issue.
Also, get MAF readings at hot idle and at 2500 RPMs. That MAF reading on the first post is suspect for idle speed. NOTE: It appears that the system was in open loop at that time sot he readings may not be useful. You need to ensure it's in closed loop before doing any diagnostic work related to the fuel control system.
BTW, have you inspected/cleaned the MAF sensor element? A contaminated element will skew the MAF data and cause shifts in the fuel tables. I'd suggest getting those readings and record them, then clean the MAF sensor elements, and repeat the test, recording the results. Report the before and after numbers.
Also, did you use the correct Motorcraft PCV valve or some aftermarket replacement part?
What would actually be useful would the to allow the codes to set and to get the freeze frame data so we can see the operating conditions under which the codes tripped. That way, the tech can check the system's operation under the same or similar parameters.
Vacuum leaks usually manifest themselves at engine idle speeds when manifold vacuum is at its maximum. Warm up the engine, verify it is in closed loop operation, then monitor your fuel trims. If trims are relatively normal at idle speed, then it's much less likely to be a vacuum leak issue.
Also, get MAF readings at hot idle and at 2500 RPMs. That MAF reading on the first post is suspect for idle speed. NOTE: It appears that the system was in open loop at that time sot he readings may not be useful. You need to ensure it's in closed loop before doing any diagnostic work related to the fuel control system.
BTW, have you inspected/cleaned the MAF sensor element? A contaminated element will skew the MAF data and cause shifts in the fuel tables. I'd suggest getting those readings and record them, then clean the MAF sensor elements, and repeat the test, recording the results. Report the before and after numbers.
Also, did you use the correct Motorcraft PCV valve or some aftermarket replacement part?
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Thread Starter
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
When I changed the PCV, I didn't use motorcraft, I used whatever they had at advance auto. Sorry about the last video, I took another video with freeze frame data showing the long term fuel trim and short term, I'll post that in a minute. I'll also get you the maf value in a few minutes
https://youtu.be/oMtlIRyfom0 this is for fuel trim
Thread Starter
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
When I changed the PCV, I didn't use motorcraft, I used whatever they had at advance auto. Sorry about the last video, I took another video with freeze frame data showing the long term fuel trim and short term, I'll post that in a minute. I'll also get you the maf value in a few minutes. The first picture is the truck off, second is at idle and last is at 2500ish, the blip in the graph is from me over shooting 2500 and having to drop back down
https://youtu.be/oMtlIRyfom0 this is for fuel trim
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Senior User
Joined: Feb 2016
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From: Royersford Pennsylvania
I assumed... Because the check engine light was on I assumed it had done it's thing, are those values off? Should it show anything when it's not running?
Hotshot
Joined: Jan 2004
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From: St Louis
Do only ONE THING AT A TIME. Retest after each.
1. Clean the MAF sensor elements. Re-check and compare the hot idle and 2500 RPM MAF readings before and after. Your current readings are too high and it appears the MAF is mis-reporting the intake air mass.
2. Install a Motorcraft PCV valve.
1. Clean the MAF sensor elements. Re-check and compare the hot idle and 2500 RPM MAF readings before and after. Your current readings are too high and it appears the MAF is mis-reporting the intake air mass.
2. Install a Motorcraft PCV valve.