mr3dman

ok I will start off with what has been done. new longblock this year. 7.4 mpi gen6 roller setup all stock. has slight "idle seek" problem and is real rich at idle and wants to to die if u bump the throttle and go back to idle. grey/ blue smoke seen from exh at idle. Runs awesome at all other settings. following have been replaced and values currently next to each:
- new fuel pump/cooler
-injectors rebuilt. took back out to see if any were leaking down. all ok
- new upper fuel rail and regulator runs at 41psi
-checked the return line from pump to filter
-map sensor new
-coolant temp sensor new
-intake air sensor checked out
- tps new .65v at idle
-iac new
I have a Rinda scanner and all looks good no codes. reset the iac, sensors all sending good signal, temp vaccume etc. The computer is mefi2. running 2.4gph at idle. hooked up to a buds and he is mefi3 and running 1.0gph at idle. any ideas what I can try next? is my mefi2 messed up? help!! the exhaust at idle burns my eyes. not good

firehawkcat

If your buddys is at 1.0 gph you may not be burning all fuel at idle wander if that is the grey and blue smoke your seeing

FIXX

Ruptured diaphram on the fuel pressure regulator?? may be dumping fuel in the intake..

Blueabyss

Cam is degree is off.. Most rebuilders just stick the cam in at preset marks and never use a degree wheel. every so often this does not work..IE mark on cam is slightly off. Have the cam set with a cam degree wheel.. From a 1-10 likeley hood I would put this at 4-6 out of 10... Worth looking at...

Chris

mr3dman

I can rule out the regulator because the pressure at idle and running is fine. As far as the cam goes, i did check the timing before assembling the front of the motor but did not degree it since it is a stock setup. One more thing i forgot to mention, at idle the injectors are firing at 33ms my friends that i checked with the mefi3 was 55ms at idle. What am i missing? I have a hard time believing that not degreeing a stock cam will give me the problem i'm seeing on a 7.4mpi stock. Any other ideas?

FIXX

if your regulator is under the upper plenum you wont be able to see it leaking and it dont take much for it to run rich Pull the dipstick and check it and smell the oil for fuel in the oil,if theirs a leak in the regulator it wont hold pressure when you turn the engine off, it will bleede down and fill the intake with fuel..

also did you replace all the injector o rings when you replaced the motor? they will leak also once you crack the seal..

mr3dman

I will check the regulator with a hand vaccume pump on friday and let you know what I find.

mr3dman

ok update, I put a clear piece of hose inline with the intake side of the regulators and no fuel was detected while running. also checked with a vaccume pump while the rail had pressure. Still have rich idle. any other ideas?

maddad

I thought if it was burning your eyes, it meant the mixture was to lean for a complete burn at idle.

Pliant

- new upper fuel rail and regulator runs at 41psi

Is your fuel pressure running at 41psi at idle...I believe 35 is recomnened @ idle...40's @ wot..mefi is a rich burn system if that is a stock tune and high pressure at idle wont help