This is a little on the long side so please bear with me.

As you can see from the picture below I have a 88 F250 with a 5.0. I recently installed Mass Air because I was expecting to do a roller swap. Truck was running great then..

I just installed a new 5.0 block from Central Coast Mustang with a roller cam and gt40P heads. I installed the block and also installed a new MSD distributer. Everything went ok except there was no knock sensor in the new block. I left it unplugged and installed everything else. I started the rig up and it felt like it was missing on a few cylinders I used the roller firing order (which is 13726548) and left the injectors as they were. I moved adjusted the dist. and it seems to run best at 20 degrees. I move it back and forth and it seems to stumble at 10 degrees and 30 degrees. At 20 degrees it seems to run ok at 1500 rpm but at idle it is very rough.

I have several questions. I used the stock balancer from my 88 F250 and installed it onto the new block. Are the balancer's different and is this the cause of an improper reading? The old speed density system was a bank fire system. The new system is sequential. Due to the firing order change does it matter if the injectors are not installed to the new order ( I was told by the ford tech hotline that I didn't need to).

What could be my problem. Is there an easy way to check to make sure each injector if firing properly? Is there something else that I am missing?

THANK YOU!!!!

 

Maybe someone else can verify for sure, but I believe since you switched to the sequential fuel injection you need to switch the injector harness according to the cylinder. In a bank fire application - I dont think switching the harness would be necessary - maybe the Ford hotline is talking about the bank fire.


Good luck

 

according to the ford tech hotline when the injectors do not need to be changed. They stated that the bank fire system has 6 miss timed injectors (which I now can see what he is talking about) so if you just have 4 miss timed injectors it will not cause any performance problems.....

thank you greatly for your input!!!!!!!!!!!!!!

 

Ok, a little more info. I found a semi bad plug wire and it is now replaced. I continued my check and all of the spark plugs look the same. They are just a shade brown from new. I checked the vacuum and I have 9-10 inches at idle. The engine still runs real rough. I decided to do a smoke test and Smoke came billowing out the EGR valve. I also had a little comming out the TPS sensor as well as the canister which the gas line vapor return hooks to. Tomarrow I will install a new EGR to see if that helps.

I am still wondering why the heck it would run decent (still rough) at 20 degrees and run poorly on either side of 20 (meaning 30 to 10 degrees). Why does it take so much advance?

 

Are you sure your valves are closing properly - rockers too tight? Do you have an adjustable valvetrain or the bolt down pedestal type? Where are you injecting the smoke during your smoke test??

 

I checked the valves twice and they were all fine. I injected smoke into the intake through one of the exhaust ports. So if there was an intake leak this test should of told me where. I checked all of the plugs again today and still all are very clean. I continued to move the distributer around on all notches and found only one that it runs right on (top dead center). I called ford tech hotline and central coast mustang and apparently everything is compatable. I am now in the process of switching the injector leads to see if that helps. Other than that I am stumped??????