Ok, about a month ago I picked up a '97 with the 4.6L. It has a "sluggish" feel. Almost like it is missing. Changed the plugs and wires, fuel filter, air filter new exhaust and still the same. I have cleaned and checked the EGR valve and the MAF sensor. I have no CEL and there are no vacuum leaks. In park or neutral it revs up strong and feels fine. As soon as I drive it it gets the missing sound and feel. I am now thinking fuel injectors. Any other thoughts? Thanks for any help.

 

Transmission?? it does not have the problem until it's in gear right? if you find out please post. Good luck.

 

No the tranny is new and in tip top shape. I'm dead certain it is the engine. Spits and sputters at times under acceleration

 

Check fuel pressure while driving under a heavy load(up hill) good is 36 at idle 40 to 45 under load a slight difference won't be a big deal but if it drops like a rock under load most likly a fuel pump, I would stat there. Good luck keep us posted.

 

That's what is happening. Only under load. Fuel pump eh? Great. I'll check pressure. Thanks

 

Just a quick question. Any chance it could be the coil packs? It does have 145,000 on the odo. And if it isn't making sufficient spark then it would spit and sputter, correct? I'd rather try those first because it doesn't hurt to replace them at my kinda mileage anyways. That and it's a little cheaper route.

Man, by the time I get this thing figured out she should run like a champ. New fluids and seals all around and damn near everything under the hood. Thanks guys

 

HI!... Do a compression test.

 

Try cleaning the injectors withn the type of cleaner that attaches to the fuel rail. I had this done on my 01 at 60k and was amazed at the difference. And I did not use cheap gas. Always Amoco.

 

Where can I get some of that? And what is it called? Thanks

 

Most shops have the equipment for that. If you want to do it yourself, you can purchase the setup and cleaner, probably at any auto parts store. Personally, unless you are going to do it for everyone in the neighborhood, I would just let a good shop or the dealer do it.
That doesn't mean it will fix it, especially if the injectors are bad, but my 90 had the original injectors in it when I got rid of it. I had had them cleaned a couple times like that, and it still ran fine.

 

Right on. I'll give that a shot

 

Well after about 300 bucks I finally fixed it. I went ahead and did coil packs and no change. Then today I changed the O2 sensors. Wow!!! Not only did it fix it but man is there power. Before I had to power brake to bust 'em loose but now at a dead stop she'll go as long as I let her. Now everything is brand new with the exception of injectors. Now I am proud of the old 4.6. Thanks for all the help guys!