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Old 06-06-2014, 01:11 PM   #1
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Default New goodies, now bad idle

I have a 1993 E-150, 351w. But in a comp cam, #35-349-8 eldebrock heads #60379, hyd roller lifters, roller tip rockers new timing set, stock EFI, MSD coil, cap and rotor. New 2.5" duals w/ H-pipe, resonators and Flomaster 40 series mufflers. It ran fine before all the mods. Just wanted to get some extra power for hauling 5 kids, boat or camper. Not a daily driver, but my main vehicle (wife has a honda pilot for around town stuff).
Now when it's cold, runs fine. When it warms up, in park, the idle fluctuates, same in gear, just more so. If I give it just a small amount of throttle, all is good, WOT it goes like a bat out of H***. Timing is at 10 BTDC as per the ford spec. I haven't messed with the timing yet, wanted to get input from some of you guys. Do I need a performance tune done to my ECU, or are there adjustments that need to be done? Any and all help is much appreciated!!!!
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Old 06-06-2014, 09:35 PM   #2
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Hookup a vacuum gauge and see if the vacuum is moving around a lot. That cam is a pretty high lift and could be messing with the vacuum a little when at idle. Comp says that cam is fine for the stock OBD1 tune. You could also unhook the connector to the IAC and see how it acts.

One other thing I'll mention. Listen for a noisy valve train with that cam. When you're up over a .500 lift the stock springs have a chance of binding and they don't have the pressure to deal with that much lift. You said you put roller rockers on, what kind are they? Were you able to get the right preload on the push rods?

The reason I ask these questions is because I just put a new 302 in my 95 F150 with a 35-308-8 Comp cam. It's a .533 lift. At high rpm that valves will float with the stock springs and the valve train is noisy. Also, most aftermarket cams have a smaller base circle than the stock cam does, so even if you torqued the stock rockers down correctly the preload won't be right. Just this week I had to buy the Trickflow Kit with new springs, retainers, keepers, shims, and valve seals. Also had to buy some adjustable roller rockers. It's the only way to get the valvetrain up to snuff for the cam and the Trickflow springs are the only upgraded springs that will work with the stock heads.
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Old 06-07-2014, 07:28 PM   #3
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I have new edlebrock heads that came loaded with upgraded springs. I have edlebrock roller rockers, pushrods and hyd roller lifters. I did all the valves per the instructions and verified with edlebrock. I'll hook the vacuum up tomorrow and see what that reveals.
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Old 06-07-2014, 11:20 PM   #4
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Very nice setup. Is that on a stock shortblock or did you do the bottom end also? I bet it runs great besides the idle. Check the MAP sensor and the vacuum line for it. I have a '91 E150 that's used for hauling a PA system and when the MAP sensor went out the idle was all jacked up. Also, Since you said it is fine when it's cold then this would tell me the problem is most likely only happening when the computer is in closed loop operation.


I told myself when I was at the shop to have the longblock built for the F150 that I wasn't going to go nuts because it's a daily driver. Otherwise it would probably be a built 347 with a blower on it. I only put this cam in it because the stock one was scarred and a new stock cam was the same or more than the comp cam. However,, I didn't even think about the lift being too high so now I'm putting in parts to rectify that situation.
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Old 06-08-2014, 11:02 AM   #5
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Stock short block. Not enough mods to really constitute a rebuild It only has 73k on it.
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Old 06-13-2014, 02:30 PM   #6
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Ok, so my vacuum is all good. I did throw some new parts at it. IAC valve, fuel pressure regulator, and new map sensor. I went thru the valve train again just to be sure. I've called comp and edlebrock to get seat and lift pressure. All within specs. The idle is better, but I still get fluctuation at idle when warm. Noticeably worse when in reverse. Fuel pressure is 34# at idle, unhook the vac and it goes to 40# as per spec. I know o2 sensors aren't suppose to affect drivability, but I'm getting to the point that it can be anything else. I've adjusted timing up and down, no change to idle. Super frustrated!!!
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Old 06-13-2014, 10:53 PM   #7
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Well, after all this crap, it dawned on me. "Why not try resetting the computer". And guess what!?!? Idling issue went away. YAY!!
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Old 06-13-2014, 10:53 PM
 
 
 
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