Ok guys I'm in need of serious help from someone smarter than me. Been going at it for three weeks strong and can't seem to figure it out. I have a 4.3 tbi and these are the symptoms....cold start in the morning is really the only time firing is a problem,and I always smell fuel when its turning. It always fires just sometimes takes a few minutes. It will idol all day in park,but its 50-50 at red lights. From a dead stop I can get on it and it will drive great,but if I havr to slow down,like in traffic, and then try to get back on it it usually always surges,like pulling a boat,and makes a noise that sounds like someone is litteraly slapping my air filter. If I ease on the pedal and stay at the same throttle position though most of the time it wont surge. I have changed the map sensor,tps,distributer,distributer cap,rotor,button,checked vacuum lines constantly,the plugs and wires,fuel filter,pump,and ran seafoam through it. The check engine light will come on but it wont flash any codes so its no help at all. Tomorrow i plan on cleaning the egr,iac and injectors with cleaner. Any help on this would be much appreciated.

 

Have u done the fuel system diagnosis? U really need to test the pressure

 

No but the fuel pump hasn't been installed to long ago. I can smell the gas on cold starts and can see the injectors spray.

 

I think it's normal to see the injectors spray a little bit on TBI motors. My old 93 Chevy Cheyenne was TBI, and idling, I could see the spray hitting the blade.

 

Well I had the fuel pump replaced about a year ago. It had some similar symptoms as I listed but it never ran as smooth as it is now. I think at this point the fuel pump can't be ruled out and could actually be the culprit and it just hasn't got to the point it was at last time. Anyone know where I can get the schrader valve adapter so I can check it?

 

But in the spirit of things would a fuel pump have those symptoms? I guess it would be more of not being able to build pressure at certain times which I'm guessing could be the reason it jumps around at certain speeds and the injectors starving could be the reason for the slapping sound on the air filter?

 

I wouldn't rule out fuel pump, until u test the pressure.......u should be able to rent one from advance or oreilly auto parts....

 

What about the fuel pressure regulator? If that goes bad, it'll cause rough starts, but idle will seem fine. It'll also run in gear like you're describing. Check the fuel pressure, checking the iac is a good idea too. But maybe the fpr is the culprit.

 

My idol is only fine in park. But there are days when it fires right up and runs down the road like it's supposed to,that's why I suspect the pump. I've checked or changed everything else. I can hear the pump engage so I know the relay is good.