New Camshaft Idle Issue
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5th Gear
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New Camshaft Idle Issue
I recently installed a new camshaft (Comp Cams 35-512-8), reccomended valve springs, ford performance lifters, and longer pushrods that were needed in my 1993 f150 5.0 4x4 with an aod trans. When I first start it up it idles fine and will idle fine all the way to warming up. However the moment you give it gas and let off of it, it starts to idle rough (surging). It almost dies and then revs up back up. I give it gas and the engine runs fine. Then I let off the gas and get that very rough idle. Temperature and Oil Pressure are good. I set the timing to 12° BTDC and still have the issue. This camshaft is supposed to be speed density friendly. I'm not too knowledgeable with these ford efi systems so any help would be appreciated.
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From: Central Mississippi
I've run the 512 in my 5.8 for quite some time. GT 40 heads, .30 over, flat-top hypers, Cobra rockers, modded intake & factory injectors, etc.
Idle never was an issue nor off idle tip in.
What was the reason for longer push-rods?
You did a good job stabbing the distributor & setting base timing, spout pulled ?
Try going 10*
Idle never was an issue nor off idle tip in.
What was the reason for longer push-rods?
You did a good job stabbing the distributor & setting base timing, spout pulled ?
Try going 10*
Hotshot
Joined: Jun 2015
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I was wondering the same thing. When I put a Comp 35-349-8 camshaft in the ‘89 302 and checked it with a pushrod tool it was the same length as stock.
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5th Gear
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I've run the 512 in my 5.8 for quite some time. GT 40 heads, .30 over, flat-top hypers, Cobra rockers, modded intake & factory injectors, etc.
Idle never was an issue nor off idle tip in.
What was the reason for longer push-rods?
You did a good good stabbing the distributor & setting base timing, spout pulled ?
Try going 10*
Idle never was an issue nor off idle tip in.
What was the reason for longer push-rods?
You did a good good stabbing the distributor & setting base timing, spout pulled ?
Try going 10*
What's the spout? I dont think I had that pulled.
The weird thing is if I let it idle up to temperature there is no problem. However once you give it throttle at temperature it runs fine until you let off the gas. I'm running open headers right now, the o2 sensor is plugged in but not reading exhaust (just dangling there). No check engine light (it's not burned out).
I'm thinking I need to bypass the IAC or something.
Last edited by roliver17; Jun 5, 2024 at 03:14 PM.
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From: Central Mississippi
The spout is a jumper plug over by the diagnostic connector in the drivers side corner under the hood.
You pulll the jumper (stopping the computer from adjusting the timing), set timing to 10* BTDC, tighten down the distributor & re-install the plug.
You pulll the jumper (stopping the computer from adjusting the timing), set timing to 10* BTDC, tighten down the distributor & re-install the plug.
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5th Gear
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Is it possible to leave unplugged until I get it to the muffler shop? Thanks for the help.
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From: Candy Mountain
Make sure you correctly set the base timing with the spout connector removed before you drive it. Too much base timing will result in detonation.
Driving it without exhaust or O2 sensor may be possible but not advisable. I expect the computer would be in "limp" mode and driveablity would be impacted. Never tried it so can't really speak to how it would go.
Driving it without exhaust or O2 sensor may be possible but not advisable. I expect the computer would be in "limp" mode and driveablity would be impacted. Never tried it so can't really speak to how it would go.
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5th Gear
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I figured it something along those lines. I have a y-pipe on it now with the o2 sensor. I also discovered while I was under there I forgot to plug in the knock sensor so that's back on as well. I plan on getting it timed with the spout unplugged tomorrow morning.
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From: Carnation, Wah
If your oxygen sensor can't get an accurate exhaust reading, unplug it.
It will read free air, otherwise, and the computer will try to lean the engine out,
which will make you go very lean, but the oxygen sensor will still be reading lots of oxygen...
Yes, you'll go into a limp strategy, but that's better than an erroneous sensor reading.
t
It will read free air, otherwise, and the computer will try to lean the engine out,
which will make you go very lean, but the oxygen sensor will still be reading lots of oxygen...
Yes, you'll go into a limp strategy, but that's better than an erroneous sensor reading.
t
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