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Old 09-08-2008, 08:22 PM
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egr valve

I'm temporarily taking a break from the 35 chevy but do have a question about my work truck.It's a 99 ford f-150,standard,6 cyl. Lately it has been missing mostly at low rpm's. Occasionally it runs ok. Changed plugs,wires,air filter,etc. The old plugs were barely tan and looked lean.I took it to autozone and oreilly to put their equipment on it. It came back with 5 things. It was miss firing on no. 2 and no. 5, running lean, egr,fuel filter and pump. I capped off the egr and the line that was plugged onto it and now it runs good except it idles a little fast at times. What is the purpose of the egr and will this hurt the engine? I put my finger on the line going to egr and it felt like a mild pulsating vacuum. I also puy the line that had the most vacuum on it and it got worse. Does this mean the valve is bad or posible the little cannister the vacuum line connect to. I don't think the lines have a leak. For now I plan to leave it capped off because it runs good this way. Any advice would be appreciated. Thanks

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Old 09-09-2008, 07:11 PM
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egr

The EGR was added to make engines pass the smog regulations. adding exhaust dilutes the fuel -air mixture and usually decreased the temperature in the cylinder. Higher tmperature usually increased power and milage but also lets nitros oxide forms which caused smog. Mid 80's ford 5.0 4 barrel manifolds with egr can over heat the holly and cause fires. disconnecting the egr on some GM engines can cause mixture problems in the intake manifold and engine problems. In most smog controll states you are not supposed to disconnedt the system but the ford 6 is easy to find non egr engines and swap parts, usually when the egr is disconnedt carb and timing needs to be adjusted
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Old 09-09-2008, 09:46 PM
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Check all the vacuum hoses with a fine tooth comb for cracks. Fords are notorious for developing cracks on the underside of the hose where you can`t see it. The computer can`t tell you there`s a vacuum leak, but when there is it will give you all kinds of codes chasing the problem that you can`t solve until you repair the leak. My brother has a 98 ford that gave him very similiar problems as yours, his was due to a cracked vacuum hose. When these engines develop a vacuum leak, it knocks the whole system out of whack.
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Old 09-10-2008, 02:20 AM
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driving it without the EGR system working properly will cause a drop in fuel mileage.
you'll get some spark knock & the PCM will pull timing.
i'll break this up into 2 posts, first the lean codes.

like DoubleVision said, the lean codes can be caused by a vacuum leak.
any air the motor gets that does not come thru the MAF sensor is false air & the PCM won't add any fuel for air it doesn't see.
first things to check are the PCV hoses, the boots on the ends are known to collapse & tear. next check the crankcase breather side of the PCV system. if the hose doesn't fit tight, replace it. check the air boot between the MAF sensor & throttle body, the clamps being loose are enough to cause a lean code.
check the oil cap & dip stick.
the lower intake gaskets will also start leaking & can cause lean codes.

the MAF sensors are know to get dirty. dirt on the elements reduces the amount of air the MAF sees and the PCM won't add enough fuel.
if the elements are dirty, you don't have much to loose trying to clean them.
you can clean the sensor elements but you must be very careful, the elements are extremely fragile. pull the MAF out of the filter housing & look inside of it from the air filter side. there will be a channel where the elements are at. on most ford MAF sensors, you can see the elements, but on some you can't. if you can't see them, then you'll need to pull the sensor out of its housing to clean it. if you need to pull it, there are 2 torx screws holding it in. they may be filled with what looks to be JB Weld. you can dig it out or use a small pair of Vise-grips to remove the screws.
the least amount of dust on them can cause problems. get a can of starting fluid & a straw from a can of brake clean, with the straw stuck in the spray button, spray the elements with the starting fluid. you want to get close to the elements but not hit them, like i said they are very fragile.
spray carb cleaner will not work, it will only make it harder to clean the elements, so don't even try it.

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Old 09-10-2008, 02:24 AM
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now for the misfire.
a ford 4.2 that has a misfire at light throttle that goes away when the EGR is disabled, its a very common problem.
the good news, you can fix it. the bad news, the upper intake has to come off.

you have clogged EGR ports. the EGR feeds the exhaust gas to each cylinder, the cylinders that are missing will have the cleanest EGR ports. they are getting the EGR that the cylinders with clogged ports should be getting.
once you have the upper intake off, you'll see a small round hole in the intake runners.
there is one for each cylinder. with a small screw driver, clean the carbon out of the holes.

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Old 09-10-2008, 07:40 PM
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egr

Thanks very much for the detailed info. Seems to be running good for now, but when it gets a little cooler and I have time I'll try your possibilities. I would much be working on the 35 chevy although. I have a rolling chassis with motor, trans., rearend, etc and body sitting on frame but need to start doing the metal structure support. I'm anxious to get started on this time consuming project. I would really like to see this thing on the road in another year. Problem is time, I am so busy and my wife insists on alot of the remaining time.Oh I did talk her into going to the show in old town spring texas in two weeks.
Thanks againegr
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