Ford-six; Yes I removed the intake temp sensor (ACT sensor by my manual) checked and cleaned it. Used a hair dryer and ohm meter. The resistance changed with warming and cooling. It ws quite nasty but cleaned up ok. I wonder if cleaning the entire intake is worthwhile.
Most conversations point to the EGR valve. Having replaced both the EGR valve and sensor, I went deeper to the EGR valve solenoid (page 6-92 and 6-93 of the Haynes Techbook Fuel Injection 1986 thru 1999) The solenoid has voltage and vacuum in but less than 2 in Hg to EGR valve. This appears to be a dealer only item. The local dealer ordered one this morning and is due Monday. I will post the results.
Note - Local shop manager suggested a fuel pressure check while driving, but my gauge hose is too short. Found that the extension hose for a grease gun is a thread match. Should reach through hood. If a safe enough arrangement can be set-up, I may try it.

 

Update - (1) While waiting for new part I decided to check the EGR sensor installation. The new EGR sensor came with an o ring that went into a groove in the housing. The old sensor had a flat seal with a molded in o ring. I went to the box for the new EGR valve and found this type seal. I installed it between the EGR sensor and valve with a light coating of gasket eleminator. Test drive result gave only a slight improvement.
(2) Next day replaced many of the vacuum hoses. All the obivious and easy to get at, including brake and cruise hoses. This has given the best improvement to date. Somewhat of a suprise as the old hoses seemed fine. I used to replace hoses on Porsche 914's when they got to be 10+ years old with good results. It seems those hard plastic (nylon?) lines give up a bit after 14 years. It is also possible that messing with the EGR solenoid got it to work better again. There were past episodes when the problem cleared up for a while.

 

Installed the EGR valve solenoid Monday. Short test drive was inconclusive. Took a longer drive today, 120+ miles. Once up to operating temp the engine ran fine. Pulled hills well and was generally smooth.
However, from start up thru warm up, it seemed as rough as ever. Weak when pulling out while cold, had to slip clutch more than usual.

 

Update - turns out that the vacuum line to the EGR valve kept comming off after my last repair. The engine ran well when this happened. I wonder what the long term effect of a disconnected EGR valve might be?
I replaced that vacuum line and it stays in place. The engine bucks during warm-up (more noteable under the load of long pull of a hill near home), but is fairly smooth when warm.
I replaced most of the rest of the vacuum lines. I left the lines that run into and from the gang of fittings along with the EGR solenoid alone as there seemed no easy way to do so. Replacing vacuum lines will be among the first things I do if I run across another EFI system on a vehicle over 10 years old.
I checked the canister (looks like a coffee can) that feeds vacuum to the EGR soleniod. Pulled some vacuum on the manifold side and blocked the other opening. It holds a vacuum but begins to leak down right away. I watched the needle on the vacuum gauge go down slowly. Should it hold a a steady vacuum?
I also checked the oxygen sensor with propane and the readings, though erratic, landed around the normal range. Guess it's ok.
I can live with the way it runs now, but it did not buck and run this way for the previous 14 years and I do no like it. I will keep looking into it.

 

Check the voltage across the leads of the EGR control solenoid. My guess is that some voltage is being allowed through, or there is a short to ground, allowing some vacuum through, allow ing the egr to open a little- more than the engine can handle cold, but not too much when warm. I can't remember if the valve is controlled from the power or ground side, but checking across the leads will be a good indication. KOER and KOEO tests should both show zero volts at the leads.

 

Ford-six: I went to my notes and found there was 11.5 volts across the electrical connector at the EGR Valve Solenoid. The Haynes manual (page 6-93) says at KOEO a test light should light up across the two terminals.
7/29/03 - checked compression, 175 +- 3 psi on all cylinders. Checked resistance on wires and distributior cap(2.5k to 3.8k ohms). Changed plugs to Autolite 5125 from Autolite platinum on the habit of going back to the last job performed prior to a problem being noticeable. All this had no effect on problem.
8/2/03 - Made and installed an EGR valve resistrictor plate. Did a forum search on this site and read about it . Drilled a 1/8 " hole as suggested. Short test drive today was promising. I will post more results after a few trips.
Note - found that the fitting at the end of the pipe that supplies exaust to the EGR was not very tight at the manifold end, pipe moved around a bit. Had to disconnect battery as work was near starter and my 1 1/4 " wrench was long enough to touch the leads. It is tight now.

 

Update - The engine still bucks (like an extremely brief throttle shutdown or miss on all cylinders) during warm up. It ,so far, is running well once at operating temp. The only new obervation from the last few weeks is that it sometimes seems down on power on a hill. It will pull well and strong much of a trip and then will need a downshift that is out of character. It is smooth when this happens. I wonder if a knock sensor can retard the timming enough to have an effect like this?
- Installed a new temperature sender and while coolant was out added a new 195 degree thermostat. This put temp gauge back near the the normal reading. This, of course, had no effect on running problem.
- Rigged fuel pressure gauge to windshield wiper and went for test drive today. Used nylon ties to secure the hose and a 1/2 inch bit of plywood to keep the hood from pinching the hose. I drove as I usually do. Started from cold engine, waited till fast idle dropped from 1700 rpm to around 1000 rpm and drove up hill near home. As usual it bucked three or four times starting after about 1/2 to 3/4 mile. This is very predictable now. It does not always buck, but when it does it is around the same place (also is when first heat is felt from vents in cool weather). The fuel pressure held steady, around 58 psi under part throttle at 45 to 50 mph.

 

What did you replace your Vacuum lines with? I am having some rough running conditions(intermittent) and my lines are 10 years old. It is high time to replace them.

One comment with your problems, after you change sensors, are you resetting the computer's Adaptive Performance memory? There will also be some time needed for the computer to "relearn" before comparison testing can be done.

WHaynes

-93 F150 4.9-

 

whaynes - Sorry for the reply delay, I mistakenly blocked this site's notification e-mails on a spamblocker program. I have been trying to unblock for days now.
I used rubber hoses from Advance of suitable diameters. I picked thick walled types to avoid collapse under vacuum. I have not yet replaced all vacuum lines. The ones leading to and from the EGR solenoid form a gang and will be difficult to replace this way. I cannot locate the three way rubber ends and anticipate dificulty routing replacement hoses around the back of the block.
On resetting the computers Adaptave Performance memory, I have only disconnected the negative battery terminal. I read about a proceedure for clearing codes. If this is not the correct proceedure, please advise.

 

Update- Bucking problem during warm up gone for several days. I know what I did but do not understand why it worked. Unfortunately, I did three things at one time. Poor scientific method.
1)- Timing was retarded about two degrees. I set it to dead center of the deep V notch.
2)- Decided to adjust the TPS position by rotating counter clockwise and holding it while tightening the mounting screws.
3)- While TPS was out I found a thin O-ring that fit around the outside of the plastic collar that slides into the TPS. Also put very thin film of gasket eliminator on edge of collar that slides into TPS.
I had retarded the timing last summer by two degrees to help reduce detonation while running on 87 octane fuel.
The o-ring was to stop possible vacuum leak and the TPS rotation was mentioned in other posts at this site.
There is still a slight roughness in the engine at light throttle which clears up with more throttle.
The only other observation is the vacuum line that plugs onto the EGR position sensor will be off from time to time. I suspect exhaust system pressure from slight backfire.

 

Negative Wire removed with Lights on for a few minutes should do it. I usually leave it off for 10 or more. I have noticed that my truck takes a lot of time to "relearn" as of late. It runs rough for almost two tanks of gas before things smooth out. More proof I guess that something is wrong. I will have to get busy on those lines. I have heard of some people using refrigration tubing. Thanks for the reply.

WHaynes

-93 F150-

 

Bucking during warm-up not gone after all, merely reduced. After several starts bucking returned, but much less often. Engine was not running smooth enough also .
Having read several posts, I decided to remove coil to check for corrosion at ground. There was some corrosion that was cleaned. Decided to replace ignition condensor and coil, as coil is only $14.95. One short test drive thus far resulted in a single buck and a smooth engine. It often takes several days or a long drive for problem to be apparent, so I will continue to observe.
WHaynes - I am curious as to why the lights are to be turned on with the battery disconnected as mentioned in your post.