O.K. I've seen this thread more times than I can count, but I haven't really seen any solutions.
I have a 94 F-150 (300 I-6) with a bucking/misfiring/surging etc. problem. I've run the codes and recieved various ones and fixed all the problems. e.g. new EGR valve, TPS, plugs, wires, distributor cap, rotor, coil, ignition control module, timing, MAP sensor, and air filter. I still have the problem and I don't have anymore error codes.
When I start the truck it will die a couple of times before it catches on and begins its warm-up process. The truck will run O.K., including acceleration. Once I throttle back and cruise, it will start the bucking/misfiring process after 35 mph. It won't really do it before, and will continue to do it all the way up to about 75 or 80 mph. Not really on acceleration, but definitly while cruising. I've spent about a month on this and I've tried all the usual stuff, even spent the money to have the injectors cleaned. (A waste of money)
I'm out of ideas at this point and I'm pretty stuborn so I don't want to drop it off at the dealer.
Now, I'm sorry to ask this question, since it has been visited many times by forum members, but it has never been resolved. I would have loved to have found an answer to this one without having to post, but I haven't.
Is there anyone out there that can point me in the right direction?
The only things I haven't done are the following:
PCM
PIP sensor
Oxygen sensor
Coolant sensor
Knock sensor
IAT sensor
I get NO Check Engine Light and no codes so I'm assuming that those things listed are, most likely, O.K. The truck has 121,000 miles on it and has the original exhaust. The exhaust seems to be putting out the right amount of pressure, but I haven't really had it checked. The truck doesn't burn any oil, I change it every 3000 miles. Once it gets started and warmed up, it will idle very smoothly. Please help.
Thanks!

 

Try disconnection the vacuum line to the EGR valve, just leave it hang there it won't heart anything. Drive it and let me know if the problem surge is gone.

 

I've already tried that. I tried it disconnected and disconnected and plugged at both ends. I replaced the EGR initially because I got a code on the first one saying it was stuck open.
The truck still ran bad after disconnecting the vacuum line and after EGR replacement. Thanks.

 

Hah! I decided to take your advice and try it again. The first time I did it I was told to unplug it and cap both ends off. When I did that the result was the same bucking and missing that occured before.
I had to run up the road so I thought it wouldn't hurt to disconnect and leave it hanging as you mentioned. Well, it runs much smoother. Still not as smooth as it could be, but acceptable. Now, the check engine light comes on when I do this, so I assume the way to fix this is to make a plate that will block off the EGR and plug everything back in as normal?
I took the throttle body off and noticed that the intake is very dirty especially where the port from the EGR valve joins in. I'm assuming that taking off the intake and giving it a thorough cleaning is going to help quite a bit?
Thanks.

 

No need to block off the EGR just restrict it. Build a plate that will allow about an 1/8 in. of flow and the system will still function as it was designed. Cleaning the intake could help idle quality problems but I doubt it would have any effect on the EGR surge.

 

O.K. I just have to ask. What is going on that would suddenly require an engine, that has been running fine in the past, to need this modification? Am I treating a symptom that may be caused by a multiple of things, or does the engine require this because of age? The engine still dies a couple of times when I start it up in the morning. It runs fine throughout the day, however. Anyway, I can't argue that disconnecting the vacuum line is working, but I have to know why.

 

As I understand it EGR is nothing more than a calibrated vacuum leak. Allows exaust gas to pass thru a adjustable orfice to the intake. As the engine ages this program no longer adds enough fuel to keep the engine from stumbling. A lean misfire is the result. If the injectors were partially clogged this could cause the lean problem, but at $600 for a set the cutting back on calibrated EGR flow is cheaper. GM handles these problems with a prom in the computer that can be replaced or rewriten in newer models. There are hundreds of prom updates for GM vehicles. Oops, didn't look far enough ahead to see it was going to do that so here is how we are going to cover it up. Put out a TSB for a new prom. Only way Ford can do this is to change the whole computer with one that has been reprogramed for the problem.

 

Hmmm, can I assume then, since I found the intake to be dirty from the EGR allowing residue into it, that the injectors are also dirty? I've had the injectors cleaned, but after messing around with the caked on carbon(?) I'm guessing that the injectors would take quite a bit to get cleaned properly.
Would it be worthwhile to take the intake off and clean it thoroughly along with either an injector replacement or proper cleaning off the vehicle? I know this may not be the most cost effective method, but would it help?
Also, let me say that I appreciate your help so far. Thanks!

 

I have had the EGR restricted for quite some time and I suggest it - but I don't think restricting it will cure all of your problems.

I have two problems that have yet to be 'solved' by the helpful posts here at FTE - one a hard start when hot, the other a stumble and attempt to die when just idling when cold.

The EGR restrictor didn't do anything for the hot start problem, and the stumble and die when cold started up a while after installing the restrictor, so I'm thinking the main problem is elsewhere.

If you had the fuel injectors cleaned, and you cleaned out your plenum, that's about all there is to clean. The build-up that you saw and cleaned in the air plenum does not pass through the injectors.

I attribute my problems to problems with the fuel flow, and we might assume the same for yours. WHy this is is still a mystery though. I changed the FPR with Ford's new stainless steel regulator w/out effect.

Maybe it really is time for us to change the injectors?

One note of caution: unless you watched the garage hook an attachment to, and clean, the fuel rail, don't assume you got your injectors cleaned. One of my small local garages seems to understand 'injector cleaning' as air-plenum cleaning. I've never seen the guys hook a fuel injector cleaner to the fuel rail nor the individual injecotrs, and I've never heard them describe the process when selling, or doing, their cleanings.

I guess if I'm going to buy injectors, they will be 19# injectors to try to get some gains from the project. And I wish I would have changed out the fuel pump when I changed the tank last year...

 

Thanks for that. Initially, I was taking the ignition route, but I think this problem is all about fuel. I agree that there is an underlying problem as my truck also takes a bit of coaxing to get running in the morning. Nothing serious, but it dies a couple of times before she wants to rev up and start the warming process.
Thinking about it, I want to say that since all of the sensors and computers are working,(and no check engine light), the vehicle has the ability to calculate fuel and timing requirements. I totally agree that, because of age, it can no longer do it properly. But, is this due to wear on the engine or is it due to worn out injectors?
I'm not asking for alot out of my truck, just a reliable start and warm-up process and a properly running engine throughout its driveability range.
I'm of the opinion that the ability and efficiency of electronic fuel injection is greater than simple carberation, but it seems that carberation is just a whole lot easier to keep running decently well.

 

Hey guys,
I have a 92 F-150 with the inline 6 and I'm also having problems with hesitation, engine surging & sometimes it dies after a cold start. It also has the hesitation & engine surging at 65-70 MPH. A few weeks ago I also disconnected the vacuum line from the EGR and plugged it. The hesitation did stop, but the engine surging stayed. I brought it to my mechanic and saw the codes for the EGR so he replaced it. He said there is a chance that it might not be the EGR but could be the solinoid the EGR vacuum line comes from. Well the hesitation was back but worse. He did hang on to my old EGR and put it back on. So he ordered me a new solinoid from the dealer, he says he does not like to use after market soliniods because he has had problems with them in the past. By the way he did not charge me for the new EGR since it did not do the trick, he kept the old one for me so we could figure out what the problem is. When I get the new solinoid I'll post the results on how it runs.

 

 

Ok, had the solinoid replaced and it did the trick all is running great now.

 

ok, i have a similar problem on my 93. nothing to my knowledge has been changed/replaced. the only mod i have dont is k&n and took off the cold air intake tube. my problem is when it sits overnight or a long period of time when its cooler out ill start it and it will surge up, and as its coming down it will stall. i restart it and it will run like an aminal. when it is hot out, it wont stall but it runs like s@#$. i am going to replace the fuel filter eventually. if this doesnt solve my problem, should i restrice the EGR? if i do that, will i gain performance?