lean codes, possible vac leak on IAC hose?
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lean codes, possible vac leak on IAC hose?
Hi, long time lurker, first time poster here. Been searching your forums for a long time now for good answers.
History:
2003 Ford F-150 XLT V8 5.4L
Sat in a field from 2007-2010, brought back to life in late 2010.
Numerous mouse nests removed, all fluids changed, removed the insulation on the hood as it was chewed to bits and was part of a large mouse colony, new brake pads, repaired a brake line leak. But has since always thrown P0171 and P0174 lean codes.
At any rate I've been trouble-shooting these P0171 and P0174 codes for some time now. These are system (fuel) lean bank 1 and 2 respectively. So either too much air or too little gas. I've already done the following since:
1) two rounds of fuel injector cleaning (via gas additive)
2) changed fuel filter
3) cleaned MAF sensor
4) verified MAF with code reader that it was reading values in line with specs
5) hand and visually checked the vacuum hoses, felt the lines for brakes or inconsistency, checked the boots, connections, etc nothing stood out as being faulty
and finally...
5) performed a poor mans vacuum leak test
What I did here was disconnect the air filter box on the throttle side, and rigged a sealing plug that had air compressor connections on it to fit in the intake end. This was just ahead of the MAF. Then I put ~5psi of pressure on and listened/felt for air leaks with the engine off. What I found was air coming out the IAC hose connection off the intake just in front of the throttle.
Problem is it looks fine from visual inspection, the connection is not deformed or chipped in any way. So if I bought a new IAC hose I'd likely get the same result.
In retrospect, I should have opened up the throttle manually when I did the pressure test because its blocking air from hitting the other vac hoses. There could have been other leaks behind the throttle that would have leaked ahead of this. I'll have to give this a go when I'm back at my garage. But I'm also thinking a professional smoke test would have flagged this as a faulty connection, 5psi is not a whole lot of pressure. Given the history of the vehicle, I'm expecting to find a mouse bite on a rubber vac hose somewhere causing the leak but haven't found it yet. Its possible its not a leak at all but something else.
History:
2003 Ford F-150 XLT V8 5.4L
Sat in a field from 2007-2010, brought back to life in late 2010.
Numerous mouse nests removed, all fluids changed, removed the insulation on the hood as it was chewed to bits and was part of a large mouse colony, new brake pads, repaired a brake line leak. But has since always thrown P0171 and P0174 lean codes.
At any rate I've been trouble-shooting these P0171 and P0174 codes for some time now. These are system (fuel) lean bank 1 and 2 respectively. So either too much air or too little gas. I've already done the following since:
1) two rounds of fuel injector cleaning (via gas additive)
2) changed fuel filter
3) cleaned MAF sensor
4) verified MAF with code reader that it was reading values in line with specs
5) hand and visually checked the vacuum hoses, felt the lines for brakes or inconsistency, checked the boots, connections, etc nothing stood out as being faulty
and finally...
5) performed a poor mans vacuum leak test
What I did here was disconnect the air filter box on the throttle side, and rigged a sealing plug that had air compressor connections on it to fit in the intake end. This was just ahead of the MAF. Then I put ~5psi of pressure on and listened/felt for air leaks with the engine off. What I found was air coming out the IAC hose connection off the intake just in front of the throttle.
Problem is it looks fine from visual inspection, the connection is not deformed or chipped in any way. So if I bought a new IAC hose I'd likely get the same result.
In retrospect, I should have opened up the throttle manually when I did the pressure test because its blocking air from hitting the other vac hoses. There could have been other leaks behind the throttle that would have leaked ahead of this. I'll have to give this a go when I'm back at my garage. But I'm also thinking a professional smoke test would have flagged this as a faulty connection, 5psi is not a whole lot of pressure. Given the history of the vehicle, I'm expecting to find a mouse bite on a rubber vac hose somewhere causing the leak but haven't found it yet. Its possible its not a leak at all but something else.
