OK Guy's heres your chance to armchair diagnose my FI problem and let me continue to enjoy the best damn truck I ever owned!

1993 F150 302 Automatic trans

When driving normally and you accelerate without causing a downshift, the truck will miss and buck badly (similar to when you are running out of gas). If you accelerate as if you have an egg between your foot and the accelerator it responds normal. This condition is worse as the outside temperature increases and as the engine gets hotter. On a 95 degree day the truck is almost undriveable. If you kick it into passing gear the problem seems to diminish signifigently and instead of bucking it pings badly.

In addition to this problem if you let it idle for awhile (like at a long light or left parked with the engine running for a while) the inside of the cab gets a horrible acrid smell to the point you have to roll down thew window and put your head out for fresh air. Once you begin driving the odor tends to go away, however it will return when you stop for any period of time.

I believe both of these problems are related as from the best of my memory they started about the same time.

My local mechanics have been unable to fix this problem and are sending me to the dealership. We originally thought the fuel filter was the problem. Replaced it with no change. The next guess was ignition. Changed plugs, wires, distributor cap and rotor with no change.

I was discussing my problem with a fellow owner the other day. He has a 95' and had the same problem with the bucking. He told me his mechanic changed out a device located to the right of the throttle housing cover that controls the EGR valve and that solved his problem. Unfortunatly my truck is a little different and does not have the device he was referring to.

In my humble opinion this truck is running too lean especially in the 30 to 50 mph range.

Help - I just can't afford the $1,000.00 bucks the dealership is probably gonna charge me.

 

Pull the codes first with a code reader or volt meter. That will give you a better idea on what could be wrong. your local mechanics should have already done this though. Repost us with your findings.

 

My mechanics are telling me that they do not get any codes out of it. We aklso changed the fuel pressure regulator.

 

With no codes, anyone correct me if I am wrong, perhaps your cat(s) are plugging up. check for a good exhaust flow. sometimes this is easily overlooked.

 

The mechanic checked the exhaust when we were looking for the source of the bad smell and it was tight and flowed well.

Ok - I know someone out there has had this problem before - Help

 

I have a '93 also. Have had similar problems. Here's what I would do:
1. buy a haynes manual and check the codes yourself. It's quite easy to do. It will flash the codes on the dash using the "check engine" light.
2. Check that the plug wires are in their looms. When i bought my truck my wires (forget which cylinders) were not in the looms and I was experiencing what the mechanic called cross-fire induction. When I would try to accelerate up a hill or underload ..the truck would buck!! the original mechanic thought the torque converter was going out so he replaced it. the second mechanic put on a new set of wires in the looms and it was fixed.
3. my throttle position sensor caused this problem too. codes should tell you.
4. if it's running real rich, i would look strongly at the oxygen sensor. you probably need to replace it anyways with 150,000 miles on it. this could very well be your problem and doesn't always give you a code.
5. check vacuum with a vacuum gauge.

let me know what you find. Kent

 

How to pull codes with a paperclip.

The full code list.