Addressing bucking / missing problem in 1990 4.9L I6. to make your restrictor plate I used the gasket for the EGR valve as a pattern. If you haven't a whole gasket, do a pencil rub on the base of your EGR valve with a piece of paper and pencil. Then cut it out and use that for a pattern. The bold holes are 3/8" dia. 2 7/8" c to c. The hole in the plate for gas to pass through is 1/8" centered in the area where the stock hole is. I used a piece of .035" aluminum I had on hand and installed it with a gasket on each side of the plate. I just drove 100 miles today after putting the plate in yesterday. No miss, no buck. After several unsuccessful and costly attempts to remedy this problem this was the one with no cost and it worked. I read a post somewhere that said that if you blocked off the EGR entirely your engine would run too hot. I watched my temperature gauge like a hawk today. No change. Hallelujah!
rudyrides

 

Engine will run hot when running lean. Will also run poorly-miss, buck, etc. Good running=good mixture=temp ok (if no other problems).

 

Thank you Bigblue88,
You're absolutely right. When I pulled my plugs to check for gap etc. a few weeks back they were almost bright orange. Too Lean. It will be interesting to see how they look after a few miles on them with the restrictor plate in place. As I said, I read a blog on the other Ford website that went into great detail about how the EGR was supposed to keep the temperature in the engine down so as not to over heat. It sounded like an environmentalist justification for the EGR valve. Didn't overheat today and she had plenty of opportunity to do so. We'll see. Thank you for your input.
rudyrides

 

The function of the EGR has to do with cooling the flame front in the combustion chamber to reduce NOX. It has nothing to do with cooling the engine.

 

Thank you.

 

Alright here goes... I recently rebuilt my 351 and still have the same problem as I did before. At speeds between 30-60 mph my truck does exactly what you have all been sayin, it feels like im about to bounce into space. I have new injectors, 80% of my sensors are new, new plugs, recent wires/distributor cap/rotor. Although it is a different motor than you have all been posting about, the problem and concept are the same, so.... i pulled and plugged the EGR vacuum line to no great affect. The problem is now not AS BAD at cruising speeds but continues violently with light accleration. Any ideas or info are much appreciated.

 

Big Red Windsor,
Did you read my reply #91. After I had made and installed my restrictor plate between the EGR valve and intake manifold a very knowledgeable friend cautioned me about possible spark knock (pre ignition pinging). I made a 1/8" hole in my plate where the stock 3/4" hole was. I have no knock and my truck runs better than ever. No missing at all. If I were you I'd try a slightly larger hole, 3/16". If that wasn't successful try 1/4". You have to have some exhaust gas going into your manifold, so I was told, or you will get a "check engine light". I make no claim to be an expert here, but a novice at best. I wish you success. Lord bless,
rudyrides (a Victory Kingpin)

 

I installed the restrictor plate but with 1/8" holes, I will have to try changingt the hole size. Never thought of that. Thanks

 

Big Red Windsor
You said "holes" plural. I said "hole" singular. Just one. Your 351 may need a larger hole(one) or multiple. I have no knowledge nor experience there. I used two gaskets, one on each side of the restrictor plate. Let me know how it works out for you.

 

Since pulling the EGR vacuum line didn't effect the hesitation then I would think it is not the egr causing your problems. I would look elsewhere in the ignition system. Last tune up, proper timing, then go to fuel pressure, filters. If there are any engine codes that would be the best place to start. Sometimes the codes are there, and there is not Check Engine light, any autozone should be able to read them for you for free.

 

Good advice from Wolfy. I also plugged the EGR valve, with no change whatsoever before putting in the restrictor plate. The restrictor plate did it for me. Thanks to everyone who contributes to this blog.

 

Interesting! good to know that it worked for ya. So that could still be the ticket. Not sure with the 351, never had one

 

I know this is an older thread but I just found it. I have similar problems, engine bucks like it is gonna tear out the rear end under acceleration. It will also smoke black when acting up. There is also a strong smell of fuel or unburnt fuel like it is getting way to much fuel.
Engine is a fuel injected 300 six in a 95 e150.

I live in oklahoma and we do not have emmision inspections.
I have cut off the catylic converter, replaced the o2 sensor, new rotor, cap, plugs and wires.

I have read this entire thread, tried unplugging the egr valve to see if it helped before I made the plate. It did not change anything. Only thing it did was cause the engine to run hot after a 10 min drive. Still had huge amounts of black smoke and still had bucking under acceleration.

I can not find any vacuum leaks, and seems to me if it is getting to much fuel how could it be a clogged fuel filter or injector.

I have been to Autozone to have the codes read, they told me they could only read 96 and up. I took it to a mechanic, he said his machine would not read the codes either but claimed that I had an electrical problem. He gave the van back said he could not help. So I tried another mechanic. He seemed to think it was plugs and wires.So he changed them all along with the green vacuum hose to the egr ( it was cracked).He told me it was fixed charged me $150.00 and sent me home. I drove the van for five minutes and it started acting up again, Thats when I found this thread.

Can anybody help or is this van going into retirement?

 

Amazon.com: Equus 3145 Ford Digital Code Reader: Automotive

 

corytcline,
You did not mention anything about air intake. What does your air filter look like? Are the intake passages clear. I had mice store an amazing amount of nesting material in the heat/defrost system of a Dodge pick up. I am but a beginner, but with black smoke, etc. sounds like you're not getting enough air. What color are your spark plug electrodes? I probably sound pretty outrageous here, but sometimes an answer lies in the simplest solution. I can empathize with your frustration.
Lord bless,
rudyrides