CEL back on

[ih8chevy]

My original codes where PO172B-bank1 and PO175B-bank 2 too rich. As I posted before I changed the MAF sensor and CEL went off. After a week of driving the CEL is back on(came on yesterday). It figures that everything would happen when the Inspection is due. When it rains it pours. Anybody have a little magic 8 ball that could help out. I'm going out now to do some of the little tricks I've learned off this forum(thanks to all of you and your wisdom) but if anyone has any ideas I'm open to suggestion.

 

[Runnin'OnEmpty]

I'd suspect a faulty fuel pressure regulator (FPR). If raw fuel is inside the vacuum line going to the FPR, that confirms it, and a replacement is in order.....

 

[ih8chevy]

I'll give it a try. If there is no fuel in the vacuum line, what would be the next suspect? Thanks for your help.

 

[ih8chevy]

Well, I must not be seeing it. I've traced the fuel lines from the filler tube to the fuel rails and back to the tank. I didn't see anything that resembles what I know as an FPR. Where might it be? '99 4.0 SOHC.

 

[Turdle]

The FPR is a diaphragm device--much like a vacuum advance in appearance

It is attatched to the fuel rail, right before the return line--I think

Also
By chance, are you using a reusable type air filter?

 

[ih8chevy]

I did see a diaphram almost right above the a/c compressor with a vacuum line coming out of the top. Would that be it? And if you mean "reuseable" as the kind you pull out and check, shake out the big stuff, reinstall with the intentions of getting a new one on your next trip to town, then yes.

Thanks for the help. I'm losing my mind. The safety inspection was due at the end of the October and I know it wont pass with the CEL on. I have thought about resetting the system to get it through the inspection at least. At least then I would have the leisure of time to get it worked out.

 

[KPT]

Wasn't 99 the first year for returnless fuel? Regulator would be at the tank if so.