1988 F-150 4.9L

Computer code came up for EGR valve. Removed valve and plunger moves freely (no buildup). EGR Tube intact.

The EGR is piggy backed by a sensor. Is there a way to test the sensor without having to buy a new one? Dont really have the money for that.

Looked at VCM? If thats what it is. The valve the vacuum line of the EGR runs to, which runs through more valves, into the coffee can, into the main vacuum source. If it is a possible vacuum problem (which I think it all looks good) could I run the lines to bypass the coffee can?

 

I had to change out my EGR sensor also, there's no real way to test it that I've heard of.

 

Of course there is.

http://lmgtfy.com/?q=ford+evp+sensor+test

 

Well it looks like I just got schooled, can you test any of the sensors like that?

 

Almost every sensor can be tested in one way or another. Usually a voltmeter is all you need, but some of them (like the PIP sensor) you need some fairly specialized equipment.

 

I need to get me a voltmeter, is there any place to get a cheapy, the ones I've seen cost over 200 bucks, unless I'm looking in the wrong place.

 

I bought one at harbor freight a few years ago, it was on sale and I think I paid less than $5.

 

Yep, I'm looking in the wrong place then. Shows how much I know

 

{edit: took me quite awhile to type all that out and the thread really
moved along while I was fartin around LOL}

http://shop.oreillyauto.com/ProductD...goryCode=3389B

------------------------

SubFord drew this up...
http://www.panix.com/~alvinj/file12/egr-SubFord.jpg

While testing your sensor, realize that the upper left diagram is of the
harness-plug, not the sensor. ;) ...so the left and right positions are
reversed.

The sensor I am measuring now has got 3400 ohms from circuit 351 to 359.
To get a 2000 ohm reading from circuit 351 to 352 the plunger is pushed in
a little less than half way (3/4" -> 7/16").

At 3/4" out, mine reads 100 ohms from 352 to 359 and only takes pushing
the plunger down from 3/4" to 11/16" to get 400 ohms. Reading that half of
the potentiometer with the plunger down around 7/16" it reads 1500 ohms.

Something don't add up. ;)

I believe the circuit was designed and drawn up with eliminating the EGR as
opposed to testing the silly sensor. LOL ;) I don't know about where you-live
but rain-rinsed heavily-laden-NOx-air is -good- for the soil and plants here in
the desert. YMMV

This sensor might be messed up too tho, since it's off my junky old '90 parts
truck and never drove it enough to find out much about it. :)

Alvin in AZ
ps- When I get around to testing the one off my '91 F150 with only 73k miles,
I'll hunt this thread up and post the readings. ;)

 

Thank you for your responses. I knew anything can be tested I just dont know that much about electrical to understand the resistances and whatnot. I just hook things up (with common sense) and repair em. Appreciate the help! Ill check back for anyone else that adds or updates.

Umm, I understand the testing but one last thing: Do I use the voltmeter to jump across the plug and harness? I know what readings I need to look for now, just not how. I read about a vacuum pump in the one link.

 

theres another way to test it. i disconnected the coffee can and checked for vacuum on that line. it passed. hooked it back up, check for vac on the EVP, none, that proved it was my coffee can. If you have vac to the solenoid, you can check the line going to the valve, but you have to have someone else in the truck holding the idle kinda high and wait for the CEL to come on, because the EGR system isn't constantly running. There was a list on here somewhere that explained when it kicks in but i'm not sure entirely. The voltmeter way is quicker, but I didn't have one, and mine wasn't the EVP anyway. Sry for the rant

 

Actually Neptoees, ill try that. Cant hurt. I was playing with the vacuum line into the EGR and it only has vacuum on it whenever there is a load of any kind on it, so in other words, at idle its shut, it opens gradually from there. I didnt think about it until this second that I could have messed with the good old fashioned cable operated throttle control. When im at work and need to get things done, I think about this diagnosing stuff a lot better than im showing on here, ha.

Well, I took the EGR valve off my truck today, blah blah, and determined there is no significant problem with it. I reinstalled it so I can drive again and whatnot and the CEL stopped coming on upon hard acceleration... It could be a temporary thing but right now its off. The truck has always been slow so I cant determine if thats done anything and I didnt drive enough to check gas mileage. (I get 9mpg, I cant afford to test drive long distances). I still want to know how to check the sensor just in case.

 

a 4.9L getting 9 mpg is either having some problems or in serious need of a tuneup

 

HAHA! I KNOW! I had an '87 that got 16mpg. The 4WD cant make that big a difference. The truck has 33's on it but my friend has one with 31's and he gets 17mpg. I did plugs, wires, cap and rotor, seafoam. I dont know what it could be to be truthfully honest but the EGR code is the one coming up. I dont even know if a possible CAT clog could cause this kind of problem.

 

cat clog would seriously rape your mileage as would a clogged fuel filter. just like a human doesnt work good without food(fuel) or without an ability to get rid of waste(exhaust)