I've got a 1999 truck with a 350. For the past couple of months it started rough and idled rough every once in a while. Now it seems to start rough and idle rough almost all the time. By starting rough I mean it cranks for a second or two and then sputters a bit, starts but has low RPM and a rough idle. Every once in a while it starts normally, crank it and immediatley it revs up to a normal idle. Back it out the driveway and it has a rough idle already. It seems to start better more often in the cooler mornings and the engine is cold (well, cool, it never really cools off in Houston Texas!). No matter how it starts or idles take off down the highway and it runs fine. I had the plugs, wires, distributor cap and rotor and fuel filter replaced and put in injector cleaner and fuel treatment all to no avail. My mechanic told me it may be the injector assembly although he says he looked at it and it wasn't gunked up. I've also been told it may be a vacuum leak, a gas tank sending unit (whatever that is! the fuel pump??), bad gas or even an engine temperature coolant sensor. There is no code and the engine light does not come on. What could be the problem? The injector assembly might cost $1000 and it may not even fix the problem.

 

Someone else had a similar problem with theirs. It turned out that it was the fuel pump not putting out enough pressure. You will have to have a gauge to check this, the light was not on on his either. I am going to assume it isn't bad gas as it sounds like you have been thru more that one tank. Check that but it could also be a knock sensor.
Good Luck.

 

I was doing some reseach on-line trying to figure out my missfiring problem I found this website about fuel-injectors. What you discribe is exactly what the web-site has for a faulty fuel injector.

http://www.thepartsbin.com/fuel-injectors.html

 

It turned out to be a worn out fuel injection spider. Replaced that and it's running like new again.

 

It turned out to be a worn out fuel injection spider. Replaced that and it's running like new again.

 

what is a fuel injection spider?

 

I imagine he's talking about the fuel meter body. It sits under the upper intake manifold and has four pairs of fuel lines looking a lot like spider legs coming out to the injectors.

 

Holy thread revival..LOl!

Here's a pic of the CSFI (Central Sequential Fuel Injection) unit/spider.
Unlike a normal injector...they are ball bearing 'poppet' stle units which can stick either open or closed due to fuel additives.
There was a recall in CA due to the fuel being sold at the pumps and the 'spider' was replaced with a 'Multec mini' injection system (which is the better choice if you ever have to replace injectors....costs about the same....MUCH better).
Here's a pic of the 'spider' and its poppets.