2010 F150, 4.62v, been battling lean,rough idle issue for some time, but long story short,here is my question. Has anyone noticed if your idle drops when you apply your brake ? Warmed up, in P, normal idle sits around 6-700rpm. IF I put on E brake, put in D and allow it to hold on E brake only the RPM holds pretty steady. When push the brake pedal, the RPM drops noticeably, to 500RPM or lower and rises when I let off. This would seem to indicate either an issue within the booster itself, or a borderline amount of manifold vacuum at idle, which is not enough to supply the booster. And yes, I have been all over every hose, fitting, PCV valve etc under that hood at least 3 times recently and using all the usual methods, WD40, throttle body cleaner,smoke and even was desperate enough to try ether (cold engine start up mind you) in an attempt to find even the smallest leak. I even just replaced the upstream o2 sensor , drivers side, based on recurring engine light and code. I seem to feel that the issue still remains and that sensor was a waste of time/money, as the idle is still rough at it's lowest, especially with the AC on. You may not notice it as a passenger, but as the driver who has put all 142,000 plus miles on her...I notice it and it's different than before. Plugs are new platinum, couple months old..MAF replaced about 6mos ago, throttle body cleaned regularly (I'm a maintenance freak) Just grasping at straws for ideas to try next. Any and all help greatly appreciated !
Brake and RPM question
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My 2008 4.6L 2V does this exact same thing when hot and it is completely normal. I don't have AC either, this specific truck is a stripper model. The reason for the rough idle at higher temperatures could easily be attributed to higher ethanol fuels, are you using 87 octane?
87,89,93 and all aforementioned grades in their 100% gas, no ethanol varieties. Plugs look lean as all get out, the o2 sensor I just removed was white as chalk....going for fuel pressure next, as well as checking the o-rings on injectors sometime this week. That's an easy check at least.
Interesting. I know my truck does the exact same thing you describe and my dealership assured me it was completely normal for a healthy 4.6L 2V. I'm off warranty too, and if there was a fixable issue rest assured they wouldn't hesitate to bill me for a repair. I'm only at 69,000km too I should add. New fuel filter last week, original plugs/coils and original O2 sensors. I replaced the PCV valve at 60,000km too.
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Well,like I said, I have put every mile on it and it's not normal.
Mine started at about 50k or so on miles and has been an issue for this whole time. No codes early on, so stealership says " no codes, feels fine to me" standard answer and I gave up on them pretty quick. Mine is very pronounced with the AC on, so I'm just waiting now to see if the engine light comes back on after clearing codes on new o2 sensor. I fully believe that it will and that the "problem" still exists. I don't use the AC that much anyway, and I have plenty of time to chase it this week (vacation) so maybe I can find the gremlin.
Mine started at about 50k or so on miles and has been an issue for this whole time. No codes early on, so stealership says " no codes, feels fine to me" standard answer and I gave up on them pretty quick. Mine is very pronounced with the AC on, so I'm just waiting now to see if the engine light comes back on after clearing codes on new o2 sensor. I fully believe that it will and that the "problem" still exists. I don't use the AC that much anyway, and I have plenty of time to chase it this week (vacation) so maybe I can find the gremlin.
Have you pulled a vacuum on the brake booster to see if the diaphragm has a leak?
Smoky
Smoky
Smoky14, I have not. Was more curious at this point if anybody else was seeing the same thing.The brakes themselves work great, actually very strong, but not sure at this point how that factors in. If I go to the trouble of pulling it, I will be replacing it,since with this many miles on it and probably as much again to go before I trade it, what could it hurt..except my wallet if that's not the issue.
I didn't mean to pull the brake booster, but to apply a vacuum to the booster to see if it leaks.
Smoky
Smoky
Is the pedal hard 1/2 hour after shutdown? If so the booster leaks.
I'm pretty sure you have a leaky brake booster diaphragm .... that would explain the lean idle condition too.
Try pinching your brake booster hose with nose pliers .... see if the idle improves.
Try pinching your brake booster hose with nose pliers .... see if the idle improves.
Don't have the ability to put vacuum on it (no hand pump) but I can pinch with pliers and also check 1/2 hr after shutdown. Thanks to all the replies, let's hope I can get some clear results !
Okay, the plot thickens. No , the pedal does not change to hard after 1/2 hr or so of off time, stays "normal". Additionally, I removed the brake booster vacuum hose and performed the same tests as described above. When idle was higher, due to fact that I just started it for the first time in 6 or 7 hrs, there was no change in idle speed. After it was up to temp, booster hosed removed, in Drive holding against the Ebrake , when I pushed the brake pedal..the RPM STILL drops down to 500RPM or less ! I now fear it may be something related to torque converter, or the CPU is reducing the idle on purpose for some reason when brake pedal is pushed, with zero speed, at idle. I am waiting on my Bluetooth adapter to arrive for my Torque App , then I can see in real time , what the throttle angle is and what RPM the CPU thinks is happening, etc, etc. Stay tuned...more to come
Travlnman, I really got thinking about this problem. It may be possible we both are experiencing a sticking EGR valve.
during a run, say cruising down the highway, the EGR valve opens up allowing exhaust to enter the intake manifold. Under idle the EGR valve is supposed to be closed. If the valve opens at operating temperature/cruising, than is unable to fully close when you are once again idling it may act as a vacuum leak and cause the rough idle we are both experiencing.
With my own truck, this is an intermittent problem I have had for over two years. It only occurs when ambient temperature is very hot (+30 Celsius or more) and after a long day of driving. When this problem does occur however, and I place the truck in park, than manually increase the revs with the accelerator pedal, it resumes a very smooth and normal operation.
The brake booster requires vacuum during normal operation, and by using the brakes we may be amplifying the problem which could vary well be a vacuum leak (caused by the sticking EGR valve). I'm pretty confident this is our problem, and I stopped by a local Ford dealer to order a new EGR valve/gasket. It will be a few weeks before I can get the part though, and I have no idea when I will even find the time to install it when it does arrive. If you google EGR valve sticking you may find some other info to bring clarity.
Nothing is certain however, and if this doesn't fix it I'm giving up, some things just act as they are when they age.
during a run, say cruising down the highway, the EGR valve opens up allowing exhaust to enter the intake manifold. Under idle the EGR valve is supposed to be closed. If the valve opens at operating temperature/cruising, than is unable to fully close when you are once again idling it may act as a vacuum leak and cause the rough idle we are both experiencing.
With my own truck, this is an intermittent problem I have had for over two years. It only occurs when ambient temperature is very hot (+30 Celsius or more) and after a long day of driving. When this problem does occur however, and I place the truck in park, than manually increase the revs with the accelerator pedal, it resumes a very smooth and normal operation.
The brake booster requires vacuum during normal operation, and by using the brakes we may be amplifying the problem which could vary well be a vacuum leak (caused by the sticking EGR valve). I'm pretty confident this is our problem, and I stopped by a local Ford dealer to order a new EGR valve/gasket. It will be a few weeks before I can get the part though, and I have no idea when I will even find the time to install it when it does arrive. If you google EGR valve sticking you may find some other info to bring clarity.
Nothing is certain however, and if this doesn't fix it I'm giving up, some things just act as they are when they age.
Actually, I had considered this . I was counting on , possibly falsely, the DPFE sensor setting a code if the EGR flow was ..well, wrong. I had this on a previous Ford , and it gave me a code and CEL, I replaced the EGR valve, still had light. Turns out it was the DPFE sensor that was bad...
. I guess I could take EGR pipe off and block it temporarily to see if that helps...if I do, I will let you know how it goes.
Much appreciated, and thanks in advance for your time and effort.
CurtisB, no chance today to attempt a blockoff...realistically, it could be the weekend before I get it done, hang in there.
Do you by any chance have any additional electrical loads when applying the brakes (such as electric trailer brakes etc.) which could load the alternator and cause a RPM drop?
Todd, nope no electrical loads, she's a bone stock plain jane truck.
CurtisB, I did get a chance today to remove my EGR valve and piping. Saw no obstructions, and with the valve removed from engine , could not force any air through it in either direction, so it appears to be sealing/closing well. Unfortunately, I was almost kinda hoping it would be the problem,as I'm outta ideas. I guess it could still be the valve being help partially open by improper vacuum..but did not have time to block off and run engine...summer evening shower chased me back inside
I feel, if that is not it, it is either a deliberate change by the ECM , reducing the rpm for some crazy reason, or lastly, it could be related to an issue with the torque converter/transmission. The search continues...
CurtisB, I did get a chance today to remove my EGR valve and piping. Saw no obstructions, and with the valve removed from engine , could not force any air through it in either direction, so it appears to be sealing/closing well. Unfortunately, I was almost kinda hoping it would be the problem,as I'm outta ideas. I guess it could still be the valve being help partially open by improper vacuum..but did not have time to block off and run engine...summer evening shower chased me back inside
It looks like your EGR is electronically controlled. Any chance the PCM is incorrectly calling for EGR at idle? Have you tried your idle test with the EGR disconnected?
Todd, I have not tried that. Just received my Bluetooth adapter today and have been playing with settings etc. I can try that for sure. BTW, idle speed, per Torque in P or D with foot off the brake, is 620-630rpm. With brake applied, drops to between 515-520...for what it's worth.
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