My truck is running well but it wasnt real smooth, I noticed it mostly when I was letting out the clutch when taking off from a stop. It also would surge slightly at cruising speeds. After reading these posts I plugged off the EGR hose and WOW what a difference!!!!!! Now its super smooth on take off and no more surging. But my check engine lite hasnt come on yet ?
Remember, it is not a faulty EGR valve that causes the bucking and hesitation... it is the emissions laws that Ford had to meet to sell trucks... so they made the EGR feed a lot of exhaust gases into the engine to reduce emissions. This causes the fuel mixture to be too lean, so the engine bucks.
If the truck runs well when the EGR valve is not working (e.g. when you remove the green vacumn hose and plug it), then you should make the restrictor plate and install it. Do not replace the EGR valve itself. It is not the problem. Also, the CEL does take a while to come on, so I wouldn't worry.
I can't comment if you can drive the truck with the EGR vacumn hose disconnected for several weeks... that's your call. Personally, I didn't want a temporary fix but a permanent one, and the restrictor plate seems to be a permanent fix. It is simple to do, and has lasted for three years now, so it seems permanent.
I, for one, wouldn't use an aluminum can for the metal, but that's just my opinion. I got a small sheet of aluminum at a hardware store, and it was probably four times as thick as a can, and should hold up a lot longer.
I have a" 92"--f150 extended cab--300cid--efi--274k miles.
a year ago my truck had the same problem--got comp--code
that said "improper air flow in the egr "
I replaced the limiter ---it fixed it up untill 2 weeks ago-
replaced it again--nada--also found out that it did run better with
the vac hose off the egr---but i did not plug the hose--when cold
would spit--cut out and die. hard to restart[like it was to rich] pluged the hose back in-same problem
read about the restrictor plate--makes sence-- thanks
will try the restrictor plate .
????--do you put the hose back on the egr after the plate is installed?
p.s.this has been a very good truck--great engine
bring back the 4.9s
I have had my 91 F-150 since it was brand new.
I have lived with this problem the WHOLE TIME I have owned this truck, I am making a restrictor plate this weekend. I will let you all know how it turns out.
>There was vacum there. If I remember there should NOT be any >vac. when cold.
Thats correct. There should be no vacuum when the truck is cold. That means your EGR valve is likely good being it lets gas flow when vacuum is applied. Your fix is to find out why the vacuum modulator is feeding vacuum when cold. You need a manual so you will have diagrams and descriptions of the emission eqpt. It's hard to guess on the internet. I'd be looking at temp sensors, etc. first.
IE: a temp sensor could be flaky. If the car thinks it's warm all the time, the computer will let the EGR operate. It will also not run properly when cold as it has no way to know it's cold. So it will be too lean. You need to do a through check of the whole emission system, and check for any codes. Myself, I always prefer to fix the real problem rather than using fixes which can sometimes cause other problems. IE: the EGR block method. This can work, but like one said, just pulling the hose will do the same thing. No vacuum, no EGR valve operation. The problem I have with disabling the EGR is the possibility of excess combustion temps, due to the lack of the cooling exhaust gasses. This could cause excess pinging, high NOX scores, etc in some cases.
The newer engines runs so lean, they usually need the EGR or the NOX output goes thru the roof. I have a hunch many of the bucking with EGR problems are actually excess lean conditions to to half plugged injectors, carbon, vacuum leaks, etc. But, heck, if it works, and the truck doesn't ping, don't let me stop anyone from doing it. The older engines that run richer, it probably doesn't make a heck of a lot of difference if you block the EGR. "as far as pinging" My 68 has no EGR at all. Never did. A PVC valve is the only smog gear on the truck. BTW, all the times I've had bucking ford trucks, it was due to a bad running engine at idle and lower speeds. Usually carb, vacuum leak related. If the engine misses at low speeds, the truck will buck if in a high gear. To be expected really if the rpm is fairly low, or you are close to the lugging point. :/ The smoother the idle and low rpm operation, the less the bucking. MK
Yes, after installing the EGR restrictor plate, put the vacumn hose back onto the EGR. This will make the EGR work again, and the check engine light will go out. Now you are limiting the amount of exhaust gas the EGR is trying to throw into the throttle body, and everything should smooth out. Be sure to remove the negative battery cable for a few minutes after installing the restrictor plate so that the computer has to relearn its settings.
As for testing for this condition by removing the EGR vacumn hose, if the truck still bucks after removing the EGR vacumn hose and plugging it, then your problem will not be solved by creating a restrictor plate. I would look for another cause... a vacumn leak, clogged injectors, clogged fuel filter, etc.
Be sure to remove the negative battery cable for a few minutes after removing the EGR vacumn hose to test for this condition and also after putting in the restrictor plate if you make one.
Removing power from the truck computer will make the computer relearn its fuel mix and adjust to the new setup. If you just remove the EGR vacumn hose and plug it without removing the battery cable to reset the computer, the computer is still using its old fuel mix settings, so you'll get a rich mixture which will cause a hard start or possibly bad combustion.
Last edited by paulghenderson; 09-22-2003 at 12:13 PM.
Wow, I installed the restrictor plate and my truck runs as smooth as a babys butt. I can't believe I lived with this condition for over 10 years without hearing of it before, I have changed burned up lean spark plugs every 10 or 20 thousand miles since I bought this truck in 92.
Thanks for the tips on restrictor plate, I used galv steel from a stove pipe with a 1/8" hole drilled in the egr port. with a new egr gasket on each side of the plate. Highly recomended for any truck that is helped with egr vac hose disconnected.
Hey Scott... glad it worked out for you. Like you, I lived with the bucking for years, and if it weren't for this bulletinboard, I'd still be living with it.
You make a good point that I forgot to mention... use a new gasket on each side of the restrictor plate. You can get them at your local parts store or Ford agency for a few bucks each.
I fixed my truck at 65K miles, and now, at 112K miles, it is still running very, very smoothly. It also passes the emissions test in NJ with no problem.
The inline-6 is a very sweet engine. Ford had been making them since around 1960, but by the early 90's, it was a 30 year old design and was having a lot of trouble meeting emissions standards. That's why they made the EGR push so much exhaust into the throttle body... they needed to lean out the mixture and also reburn the exhaust somewhat.
At 65K miles, I was ready to sell the truck and go to the dark side and buy a Chevy. But I knew the Ford was a much better truck, so I found this board and found the solution. 57K miles later, the truck is still running perfectly.
Yeah, The plate is working well, My son thinks I tuned up the truck LOL. while I was ordering my egr gaskets, the parts guy goes, "really I have a 300 6 cyl that bucks and jerks like a big dog". I told him about my restrictor plate, and now he's going to do it to his as well. does this work only for efi vehicles or earlier carb models too,? cuz his is early 80's w carb...
It may work for a carb engine, I don't have any experience with anything but EFI, so can't tell. In principle, it should work for any type of fuel system. Hope the parts guy can solve the problem.
Yes, just remove the green vacumn line from the EGR, tape the vacumn line off, then drive the truck for a while. The check engine light will come on, but ignore it. If the symptoms you have experienced disappear, then make the restrictor plate.
>BTW im experience the same basic symptoms, but mines more >at idle and 1/4 throttle or less
Shouldn't be any EGR flow at idle. So it shouldn't have an effect there unless the valve is leaking a lot. Could be a problem at part throttle though. Make sure there is no vacuum to the valve at idle. If there is, there is a problem. "Unless maybe they intended some EGR flow at idle on that year engine". Which would be a bad idea.
I sort of doubt they would do that. You've have to expect drivability problems. MK
Where were you guys 12 years ago? I finally went to my friends shop, cut out a restriction plate out of some stainless steel and bolted it up. I didn't think it was going to work at first. It bucked going up the hill from his place. The next weekend I hooked up the boat and went to the lake. Everything worked perfect. I think the computer learned the new readings and smoothed everything out. The old beast thanks you guys. (Me too) Wade
azhound60... as you found out, the computer will learn new settings over time. To force it, however, disconnect the battery negative cable for a few minutes after installing the restrictor plate. This forces the computer to relearn the engine setup, so it starts out fresh right off the bat.
Glad it worked out for you. Enjoy your truck!
(let me see, 12 years ago I was living in a small house with no children, no mortgage, and a live in girlfriend... I guess I was in heaven ;-)