I am looking for advice where to start inspecting on my car. I just finished putting another 5.7 tuned port in my 1987 iroc. It didn't run when I bought the car so I am trying to rule out problems caused by me or the cars previous problems. My car seems to start fine when its cold. It seems however to be idling a little high at about 1,100 rpm. The wierd thing is that I can drive it till it gets warmer, and than starts choking out. I can barely keep the rpms up and i can't really drive it. I than put a fuel pressure gauge on the fuel rail and got about 33 psi. I have an afpr so i decided to try to raise it higher since the fuel prssure I bleive is supposed to be like 40-47 psi. however 37 psi was about as much pressure as I coul seem to get after numerous adjusments. I also replaced the fuel filter and no change. My question is where I should start checking> possibly a bad f,p.r. or bad fuel pump? Also on another note It is registering error codes 33 and 36 for maf burnoff and map sensor or high flow maf. I am a college student so I would rather check things before aimlessly replacing stuff, and suggestions would be greatly apreciated!

 

Hello,

The pressure is definitely low, it is normally 42-47 psi. You could pinch off the rubber fuel return line while monitoring the fuel pressure. It should spike to 60-70 psi (don't keep it like this for long).

If it doesn't: the fuel pump may be failing, the pulsator may be leaking, or the fuel filter is plugged, but you already did the filter. I suppose your injectors could be leaking so much that the pressure can never build.
If it does: the fuel pressure regulator may be bad. Your lines could be kinked or blocked internally.

If you have access to a scanner, it would be helpful. If not, do you have a digital multimeter, specifically volts and ohms? Test the resistance (ohms) of the injectors, all injector values should be near eachother (~16 ohms). Measure the volts at the TPS top two wires when connected to the TPS connector, it should be .54v at idle. Measure the resistance of the CTS when cold and hot.

Are all your vacuum lines new?

Hope this helps.

 

Thank you very much for the reply! I forgot to mention that the injectors are alo new(refurbished) but I guess it would be easy enough to check them. When the key is engaged the pressure maintains constant well after the fuel pump turns off, and also I pressure tested the fuel rail with the new injectors before I put them in. Whenever I have time I am going to buy a multimeter(possibly tommorow). The vacuum lines are original so I'm just going to go trough and replace everything because its cheap. Also I had been looking at trouble code flowchart for the 33, and 36 and I need a multimeter no doubt about that. My guess is that the wire inside my maf is not getting proper volts. However I will try what you said and post back with my findings.