I need some real honest advice. When I start my van up cold, it idles fine for about 1 minute then idles down to almost a stumble blowing carbon out the back and blacksmoke and almost wants to stall. After it has warmed up it runs very strong but when stopped and put in park the engine will idle up and down several times and then smooth out, also the engine check light will come on and off after warmup. This happend all of a sudden and now my fuel mileage has been cut in half. It has been put on a computer check and a few sensors have been replaced and everything says passed. It blows black smoke while cold and the exhaust pipe is black, it even leaves a carbon buildup on the driveway, it's like holding out the choke on the old carburated engines. The engine has been tuned, has only 80,000 miles and does not burn any oil, but man when you first start it cold you think it was on 5 cylinders, I know it's getting way to much fuel fed into the injectors. Somebody has mentioned changing the fuel pressure valve which does not show up on the computer. I have already spent 500.00 bucks and it has not done a thing, and this van has never given me a problem until now. Is there such a thing and where is it located, in the back of the engine. I'm desperate and I thing my mechanic is taking me for a ride. It must be something simple. Help!!
Bill please email me at sccahonda(No Email Addresses In Posts!)

 

It does sound like it is your fuel pressure regulator. The exact same thing happened to my 89 F250 4X4 5l. It is relatively cheap to replace & only 3 bolts. It's at the back of the engine, drivers side next to the upper intake manifold.
Rich

 

on most vehicles the fuel pressure regulator is controlled by vacuum pressure. The regulator is a round metal object about 2 inches in diameter and it will sit on the fuel rail for the injectors. there will be a vacuum line going to the top of it. Check to make sure that this line is still attached and not crimped anywhere. What you have is an indication the the engine is running way too rich. When the vacuum line is off the regulator black smoke will come out the tailpipe. This is how I test for a faulty fuel pressure regulator. Another way of doing it is to attach a fuel pressure gauge to the schrader valve on the fuel rail. I don't know exactly how much pressure there should be but my best guess is probably around 60psi. Hope this helps.

Robbie

 

Thanks for the response. You both hit the nail right on the head. I replaced it and it's purring like a kitten. I can't believe the money I have spent at the garage.
Many Thanks
Bill