Need advice on 1989 ford F150 302
Per previous posts completely rebuilt 302 from ground up. After startup engine run well but would not have stable idle/ fluctuation and then stall. After all below still run great on road but coming to a stop and stalls. Engine starts right up even when hot or cold. I am at a loss here. Below is what has been done to this engine

New Pistons
New Rods
Crank
Roller Cam 35-351-8
Springs 986-16
Bearings
Seals
Timing Chain
Shorty headers
All new sensors, water and air
New PVC
New map sensor
New Idle control valve
New TPS
New Eng. control module
EGR checked for proper operation
New O2 sensor
New fuel regulator
Cleaned and rebuilt injectors.
Replace all plastic vacuum lines with new lines verified proper routine and termination
Gaskets
Rebuilt GT 40 heads, new valves guides seals springs
New Rockers
New push rods. Stock was 6.2 slightly noisy, measured for correct size. Engine quiet and smooth running.
New upper intake gaskets after removal of upper intake
New distributor cap, rotor, wires, motor craft plugs Times properly 10 degrees with shorting clip removed
No Codes registered or engine light on
Checked for vacuum leaks around intake manifolds

 

sounds like a vacum leak have you tried carb cleaner spay it a round the intake meets the heads around the carb or throtle body i had one that did that turned out the inside bolt on the upper intake was a hair to long and was allowing it to suck air

 

Thanks
I checked both the upper and lower manifolds with carb cleaner while Eng was running, no change in Eng speed.

Just checked the fuel rail pressure = 35lbs +or minus 2.
Disconnected all vacuum lines from intake manifold tree and plugged. I ran a separate vac line from intake vacuum tree to fuel reg on fuel rail and to Map sensor.

No change, scratching my head now.

Thanks for response, Art

 

That's your problem right there... WAAAAAAAAAAAAAAAAY to much cam for an SD EFI truck motor. I got a friend with that cam in a MAF Mustang that does the same thing.

 

Conanski.
Thanks for the reply, Now I am really confused

The cam I used was recommended by Comp cams and my machinist the info form the Comp site is:

View Specs

35-351-8

XE270HR

Hydraulic Roller Lifter

Hydraulic Roller-Best when used with better heads, Intake, Exhaust and 3.55-3.73 Gears. Works with O.B.D.1

Ford 5.0L 8 cyl. 1982-2001

Xtreme Energy™ Hydraulic Roller Camshafts, Computer compatible (E.F.I.) with O.E. hydraulic roller cams 1985-95

This Cam gives a little more Torque

Thanks

 

Yeah.. but for what vehicle/EFI system?

The simple fact is the stock truck EFI system needs a steady and high vacuum signal or it loses all control, so not only do you need at least 114deg LSA but it's also got to have no more than about 210deg intake duration at 0.050" lift. You can improve things a little by advancing the cam a couple degrees and also advancing the ignition timing 2-4deg, but you're still going to have stalling problems.

 

Is it an auto-matic truck?

 

Oh no! My Machinist recommended this cam! I hope I can do something without pulling the eng all apart. I contacted Comp cams again and they said you are right!!. It is also an automatic AOD. Is there anything I can do??

 

Automatics are worse here since the torque converter is always applying some load to the engine. My buds Mustang with this cam is a manual so he's able to get by with it because you can bring the rpms up a little before loading the motor, and besides that the car only gets occasional use so it's not a daily problem. You could install a higher stall TC but I'm not sure even that would totally eliminate the stalling, and of course that will make the truck even less suitable as a daily driver though the fact you selected this cam in the first place suggest this isn't one anyway. I'd say start with the cam and igniting timing advances and see where that gets you, the motor shoud handle 2-4 deg more ignition anyway and that will boost idle vacuum a little.

 

Thanks for the reply. Looks like the only way to make this a daily driver is to change the cam. Lot of work! What would you recommend for a replacement cam?
It is a roller set up. I hope I do not have to redo my push rods again.

1989 F150 EFI 302 AOD, GT40 heads with headers,

Man I wish there was something I could do!

 

For a daily driver you'll want the Comp 35-512-8 or similar.

 

Thanks Conanski.

One last question if I go with the 35-512-8 cam will I be able to keep my GT40 heads and
Springs 986-16? I had to buy new push rods 6.3 in, stock was 6.25 and they were noisy. I am just afraid of dumping more money into this eng. I got 2k in already. And still not running correctly.
Thanks
Art

 

That cam is a direct swap with no other changes necessary, you needed custom pushrods because the heads are different from stock but that won't change this time around.

 

Thanks for the help! I checked all technical resources I could think of. Called Comp Cams and everyone confirmed my fears. Ordered new Cam #35-512-8. Comp tech confirmed proper cam for truck. I will post when I install cam.
Thanks for everyones input!!
Art

 

Bad news replaced cam with 35-512-8 timing perfect, no vacuum leaks, blocked off EGR valve, all vacuum lines disconnected and plugged, except map an fuel Reg, truck will not idle. Same as above. Runs great down the road, trans shift right but stalls at light when coming to a stop, and starts right back up. I have replaced everything related to Idle and EFI. No computer codes, both eng off and eng on tests, 35 to 40 psi fuel pressure. Plugs clean no injectors stuck. I am at a loss!