I recently purchased a 97 F150 with a lot of mods. It has Ported PI heads, PI intake, BBK Mass air, TB, custom Crane cams, headers, etc and a Dyno tuned DiabloSports chip to make it all work together. This truck had been working well for the last 20k, but then had problems. Thats how I bought it.
The previous owner told me that it was running good, then it started to stumble when you accellerated, it got worse till it was undrivable. He had cranked up the fuel pressure till he had lifted an injector, so that was leaking when I got it (the custom/hacked fuel rails arn't perfect).
I reseated the fuel injector and got the fuel rail to sit better and then it started. It sounds good except it idles HIGH! Around 2k. the Fuel pressure seems to be fine and according to the A/F gauge it is running lean.
I ran the codes and the only code was a P1506 (IAC, engine speed to high). I swapped that out of my 02 GT and no change. I disconnected and plugged all vacuum lines off the upper intake, cleaned the Mass air, still no change. I pinched the line going to the IAC and no change, so I know that isn't it. I put a bag over the K&N filter to prevent any air from getting in, still no significant change.
At this point everything sounds like a vacuum leak to me.
I pulled the upper intake and inspected it allong with the throttle body. I saw no issues (but did clean the TB a little). I inspected the lower intake and didn't see anything with it on the vehicle (this is the plastic PI intake with the aluminum coolant lines in the front). I tried to pressurize the intake and look for any leaks around the fuel injectors. I put some carb cleaner around them and looked for bubbles. I saw one that looked like it bubbled a little bit so I loosened everything up and reseated it. I couldn't get it to bubble again after that. I put it all back together and it is doing the exact same thing.
Any ideas? It seems wierd that it could be the intake because it seemed like I could pressurize it at least a little bit (I was using an air supply into where the upper intake goes "sealed" with a damp chamois. I could get enough pressure that it was bubbling up around that chamois, so it seems like it is sealed somehow.
The only other thing I can think of doing at this point is pulling the intake and inspecting that and the intake runners. Anything else I should be looking at? Most of my stuff is older so I only have one other Mod motor, and that is a nearly stock 02 GT (exhaust and a different Mass Air, thats it).
thanks in advance.
-MrCarlson
The previous owner told me that it was running good, then it started to stumble when you accellerated, it got worse till it was undrivable. He had cranked up the fuel pressure till he had lifted an injector, so that was leaking when I got it (the custom/hacked fuel rails arn't perfect).
I reseated the fuel injector and got the fuel rail to sit better and then it started. It sounds good except it idles HIGH! Around 2k. the Fuel pressure seems to be fine and according to the A/F gauge it is running lean.
I ran the codes and the only code was a P1506 (IAC, engine speed to high). I swapped that out of my 02 GT and no change. I disconnected and plugged all vacuum lines off the upper intake, cleaned the Mass air, still no change. I pinched the line going to the IAC and no change, so I know that isn't it. I put a bag over the K&N filter to prevent any air from getting in, still no significant change.
At this point everything sounds like a vacuum leak to me.
I pulled the upper intake and inspected it allong with the throttle body. I saw no issues (but did clean the TB a little). I inspected the lower intake and didn't see anything with it on the vehicle (this is the plastic PI intake with the aluminum coolant lines in the front). I tried to pressurize the intake and look for any leaks around the fuel injectors. I put some carb cleaner around them and looked for bubbles. I saw one that looked like it bubbled a little bit so I loosened everything up and reseated it. I couldn't get it to bubble again after that. I put it all back together and it is doing the exact same thing.
Any ideas? It seems wierd that it could be the intake because it seemed like I could pressurize it at least a little bit (I was using an air supply into where the upper intake goes "sealed" with a damp chamois. I could get enough pressure that it was bubbling up around that chamois, so it seems like it is sealed somehow.
The only other thing I can think of doing at this point is pulling the intake and inspecting that and the intake runners. Anything else I should be looking at? Most of my stuff is older so I only have one other Mod motor, and that is a nearly stock 02 GT (exhaust and a different Mass Air, thats it).
thanks in advance.
-MrCarlson
