ecal533

I have an 03 Cobra with the following Mods: Kenne Bell SC, Big air Mass Air, Cold air intake, Boost a pump, stock Cobra Fuel Pumps,SCT CustomTune and Bussani Header back exaust.

Here are my problems.

On a cold start car will not idle with out holding throttle just a bit. After a minute or so I can let off and it will idle decent. I don't get normal idle until fully warmed up. IAC in brand new. Is this a tuning issue?

Second, with car at idle fuel press reads 25 to 30 psi. When I snap the throttle the pressure climbs and then drops down to almost zero before stablizing back to the 25 to 30 psi mark. Is this normal? I don't think it is. ( I haven't had the car long)

Last, on a hard acceleration in say second or third when I let completly off the throttle and coast down to a slower speed the engine will stall. Could this be the tune as well?

Other than these issues this car is ridiculously fast and has no signs of fuel starvation on top end. I'm told it has close to 600hp.

Any help would be great.

Blownsvt

sounds like it could be some tuning issues, the fuel pressure issue could be a PPRV valve problem. has your been removed yet?

ecal533

You may have to elaborate on the PPRV valve and what I need to do to check it, remove it, or test to see if it had been removed.

Here's where I am now. I replaced the Fuel Rail pressure sensor and got no change. Then I disconnected the Fuel Press line to the dash gauge and hooked up an actual Fuel Pressure Gauge. The good news it that the test gauge shows about 31 to 33 PSI at Idle. The Auto Meter dash gauge must need some calibration adjustments. This leads me to believe that the fuels pumps are delivering adequate fuel press at idle and since I have no problems at higher RPMs under load the fuel pumps just arent the issue.
Then I pulled the vacuum line off the rail sensor and the pressure increased to 40 PSI or so. When I crack the throttle under this condition the fuel pressure doesn't drop but maybe 5 or 6 PSI. Far less than falling to "0" and then rebounding.

Is this more than likely a simple tunning issue?

Some one also suggested that Kenne Bell Blowers have to different inlet plenums. One for a stock Throttle Body and one for a single blade as he called it. My Throttle body says Kenny Bell on it. I have to assume that the thing came in the complete kit so it should be matched. How can I tell on the blower? This he said may relate to my cold start issue where the car wont idle until warm. Different Idle speed effects vacuum and the fuel pressure electronics also use a vacuum measurement to pulse the injectors. This could be playing a part as well?

ecal533

Update.. Got the cold start idle resolved. I decided to pull off the throttle body from the plenum and right away I see where some yahoo had the gasket flipped upside down. The cut out for the IAC was face down so the thing wasn't getting air to regulate.

I'm going to take it out and see if that effects the stalling issue on coast after hard excel.

Blownsvt

see if that helps for sure, the only way i know of to check for the pprv valve is to drop the tank and remove the " hat" from the tank. there is a vlave int eh pump assembly that people had issues with generally occuring once power levels over 500 hp were reached. it genrally occurs right after shifts. as an example when data loggin you would be cruising under throttle go to make a shift and immedaitly after shifting and getting back on the gas the fuel pressure would drop to close to 0 the car would fall on its face and then rebound after a second or 2. theres is a write up on how to remove it floating around if you think that might be the problem.