Trying to figure out my loping problem

[nativebroncofan]

I posted this in another thread and have had no action on it. So I'm re posting it by it's self.



The bracket that contains the map sensor also contains the EST module and another device that has a tube from the EGR and a tube from the back side of the TBI unit. It has an adjuster screw inside of an air filter. What is this part??
I think I figured this one out. Is it the EGR solenoid?
I have had a lopeing problem with this truck since I've had it. The emissions control stuff has been removed by the PO.
Replaced several different items, The IAC valve, o2 sensor, knock sensor, ESC sensor, fuel pump relay, thermostat, ignition control module, ignition coil, MAP sensor and generator, cap and rotor. The EGR valve holds vacume and it has new, correctly gapped plugs. All the vacuum/coolant hoses have been replaced in the last year.

I also replaced the one way check valve on the drivers side of the engine. Then I happened to unplug the MAP sensor and Viola, the lopeing problem vanished. With the Map sensor plugged in it barely wants run.
The ECM has always had a code 44(lean exhaust) I have been able to eliminate other codes by replacing the parts that I stated above.
Now I have a fuel pressure tester that I plan on hooking up this weekend to test out the fuel pump.
Am I doing any harm to the system, running it with out the MAP sensor plugged in? I get a strong sulfur smell as it gets driven.

I don't have any computer stuff for it, Just a paper clip and a
Haynes manual. Wish that I could afford all that technology but that will have to wait for now.

So what do you guys think
Thanks in advance,
nativebroncofan

[grinch4om]

see if you have vacuum at the EGR valve at idle. this can cause these conditions...start there. when you unplug the MAP sensor the computer goes into "fail safe", a rich fuel map to save the engine and to get you home. an energized EGR valve at idle will mimick a vacuum because that is what it is, a vacuum leak into the exhaust system. this leak beyond what the computer can compensate for at idle. Just a place I would start first

[glock35ipsc]

Along with that, see if the EGR valve might be stuck, or sticking. It may be stuck open just slightly. Use a small pry bar or screw driver and see if it moves freely. Maybe even take it off to see if there is a piece of junk holding it open just a little.

[nativebroncofan]

Originally Posted by grinch4om

see if you have vacuum at the EGR valve at idle. this can cause these conditions...start there.

The very day you replied to my post i had to make a run of about 30 miles. The MAP sensor was still unplugged during this trip. On the way back home the SES light went away!?!?
I figured that The ECM went out. I plugged the Map sensor back in and with a short 5 mile drive it was still operational. Tonight when I took it to work (14 mile drive) I checked for vacuum at the EGR with the engine at idle there is no noticeable vacuum at the hose. There is vacuum at the MAP sensor. Neither of the two hoses running to the EGR solenoid have any noticeable vacuum to them. I had the EGR tested the weekend before last like I posted and it held vacuum no problem. I still need to check whether or not the engine speed decreases when the EGR is pushed in. From what I can remember it increased the engine speed when manually pushed up.
Does the testing of the EGR valve only test for one function of the valve it's self? Does it perform anther action that is not readily testable? I can see where the EGR valve would get suction power from the engine, just don't understand why it has "no" vacuum.

when you unplug the MAP sensor the computer goes into "fail safe", a rich fuel map to save the engine and to get you home. an energized EGR valve at idle will mimick a vacuum because that is what it is, a vacuum leak into the exhaust system. this leak beyond what the computer can compensate for at idle. Just a place I would start first

I take it that running it with out the MAP sensor plugged in is not a good thing to do to the engine?

glock35ipsc I have taken the EGR valve off and cleaned it and had it tested. It holds vacuum when applied to it. When I cleaned it I used diesel and let it soak overnight. It was a suggestion from someone. I just soaked the bottom half not the hole thing. It moved freely up and down and was cleaned to the Haynes manual specs.

So what's the next suggested step? New EGR valve or EGR solenoid.
Thanks for your help guys,
nativebroncofan