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Old 10-28-2006, 07:04 AM   #1
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Red face Fluxuating Idle

My 89 5.0 was just upgraded to include heads, a bigger cam, and larger injectors. My idle when the car is completely warm was going up and down like it had a bad mass air sensor. The check engine light is not on though. The mass air meter that is in the car is not the stock setup. it is setup for the stock injectors though. the computer has an aftermarket chip setup for the e303 cam to advance the timing some. The cam I replaced the e303 with is only a little bigger. it is a 498./.510 lift. I did add 1.6 rolllers though as well. I don't think the rollers or the cam has anything to do with the idle though. I am going to tinker with the fuel pressure some and see what happens. If anyone has an ideas let me know. I replaced the calibrated mass air sensor i had for the 19 lbs. injectors with a stock MAS. It evened the idling out. Now the car seems a little lazy till you hit 3500 RPM. I am thinking a newly calibrated MAS and a new computer would help tune it up. If anyone has any ideas let me know.

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Old 11-18-2006, 04:17 PM   #2
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Re: Fluxuating Idle

It needs to be tuned!I had this happen to me when I was EFI and after I put on the bolt-ons.The computer needs to be tuned to your specs otherwise its in a constant loop (rough idle or pulsing) searching for the ideal parameters and cant find it until WOT.

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Old 11-18-2006, 07:11 PM   #3
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Re: Fluxuating Idle

The E-cam is more than just a "little" bigger. People always seem to think that about the E-cam (partially because that's how Ford Racing advertises), but it just isn't true. Lift is not the only important spec of a cam. Duration also isn't. If I'm not mistaken, the E-cam is a 220/220 duration, which isn't too extreme. However, look at the lobe separation angle: 110 degrees. That's a lot different than the stock 115.5 degrees. A cam with 110 LSA is going to lope, and it's also probably going to cause a little rolling idle.

The roller rockers have absolutely no play in this (assuming a proper installation). The 1.6 ratio is the same as stock, which is good.

I'm also confused by your injector/MAF combo. You said the injectors were upgraded to bigger injectors, yet you are still running a MAF configured for 19# injectors??? If so, that's a big part of your problem right there. You are probably running pig rich at idle, and the ECU is trying to compensate by continuously upping and then once again lowering the idle.

Also, what heads and intake are you running?

Scary stuff.
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Old 11-20-2006, 07:04 AM   #4
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Re: Fluxuating Idle

Im running the trickflow track heat heads and intake. I am buying a new mass air meter with the 24 lbs. tube in it next week. I finally found someone who can tune the computer for me who is close. CJ's pony parts in Harrisburg, PA. I already have a custom chip that was tuned to the e cam and the 19 lbs. injectors. Now I have the trickflow cam and the 24 lbs. injectors. The car still has awesome power. I can't wait to see what it will do when tuned properly. The custom chip I have still has 2 open programming slots on it. CJ's in Harrisburg said they can install 2 programs for me in the chip I already have. I going to use one slot for NA and one for 125 horses of nitrous.
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