To make a long story short I have an exhaust leak at the drivers side y-pipe at the donut and was curious if this could be causing a p0171 and p0174 code. The only other thing I have done so far is look for vacuum leaks and I found none. Thanks for the info

 

P0171 and P0174 - OBD-II Trouble Codes

 

The engine was just repaired and put back in. I know I have to find access to a scanner which would probably tell alot. I just started with the easy things and fond the exhaust donuts leaking and have to replace them anyways.

 

Those DTC's tell us it is a late 1995 or newer. Knowing exactly what year the vehicle is would help.

They indicate a lean condition on both banks, and if both DTC's set simultaneously, chances are it is not the "Y" pipe or a vacuum leak. Most likely something that is common to both banks. Start with checking fuel pressure and leakdown.

 

Im sorry I forgot my info. I have a 99 blazer 4wd. The engine was just put back in after some repairs and the codes popped up after this. I did have a p1345 (I think this is right) and I moved the distributor back 1 tooth. I also just changed the fuel filter thinking this might be it. I need to test the fuel pressure and get a scanner, just dont know anyone that has one.

 

Its now fixed. I changed the fuel filter and cleaned the MAF sensor and the light went out. Im just happy it didnt turn into something big.

 

good news, thanx for posting the results

 

I haven't had time to post back but it came back with the same codes. I did the fuel pressure test and everything is fine except when the gauge is hooked up to the test port the pressure immediately drops to zero when the pump shuts off. Looks like a bad regulator or injectors.

 

Follow the steps in this link, and it will tell you where the leak is, (in the plenum or in the tank). Post all 4 readings and we can analyze them. https://blazerforum.com/forum/2nd-ge...eakdown-88305/

 

I had the service manual with me and did get all the pressures but didnt write them down. All were within limits except when I use the service port and this is when I had the immediate drop to zero.