5.0L idle oscillating then dies

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5.0L idle oscillating then dies

June 14, 2009, 09:57:09 PM

Hey guys, any thoughts? I have an 85 T-Bird with 5.0L 5-speed. I just swapped in a new Holley Systemax kit with heads, upper intake, lower intake, throttle body and a C&L mass air meter. I've gone though adjusting the idle and TPS. Here's how the car behaves... warm or cold it will hold a nice 900RPM idle for 5 minutes sitting right in my driveway, then it starts oscillatting slowly until the motor begins swinging from 500RPM to 1500 RPM, eventually it dies. Start it up, and immediately I have a smooth idle again.... 5 minutes later the oscillation starts again lasting for about 30 seconds until it dies. Otherwise everything is cool. Any ideas? Thanks in advance.

5.0L idle oscillating then dies

Reply #1 – June 14, 2009, 10:02:52 PM

Quote from: Mikelonis;277762

Any ideas?

Don't let it idle... LOL

What cam???

5.0L idle oscillating then dies

Reply #2 – June 14, 2009, 10:18:32 PM

Funny

... It's got the Ford Motorsport E303. That's the same cam that was in it before the swap.

5.0L idle oscillating then dies

Reply #3 – June 14, 2009, 11:14:44 PM

Probably doesn't have enough base idle speed...

With motor warm, disconnect the IAB and set it for the RPMs you want(do not adj the idle with the IAB connected)... Then set the TPS to .9 -.95v, reconnect IAB... Would be a good idea to disconnect the battery for a few minutes after the voltage adjustment, so the EEC will start a fresh learning cycle...... If you still have problems, try rotating the MAF slightly, often this helps...

Another trick that works, is create a vacuum leak after the MAF meter... If you're looking for 900 RPM, use the above method to set idle about 750 and "leak in" the difference...

5.0L idle oscillating then dies

Reply #4 – June 14, 2009, 11:56:35 PM

Thanks TC50. Yeah, been through that process a few times with no luck. I have no problem getting any idle speed I want and my TPS is set to .95. It just keeps foolin me. I take it for a drive, idles great, accelerates great... then suddenly it starts the oscillation, I feather the throttle to keep it alive for about 30 seconds, then the issue passes and it's back to normal driving.

I did notice the idle oscillation can be induced by heavy accelleration. Whatever, thanks... I know it's a weird one but it's keepin me from taking the car out of my neighborhood!

5.0L idle oscillating then dies

Reply #5 – June 15, 2009, 12:00:46 AM

Check your vacspooge lines and try cleaning out your IAC.

5.0L idle oscillating then dies

Reply #6 – June 15, 2009, 06:45:09 PM

Does it throw any codes? Sounds like an IAC issue to me.

5.0L idle oscillating then dies

Reply #7 – June 15, 2009, 08:05:15 PM

didn't notice you were in nevada. If you ever feel like going for a really long road trip, let me know. My birds nothing to look at though.

5.0L idle oscillating then dies

Reply #8 – June 15, 2009, 09:33:25 PM

Big time shot in the dark put your original mass air meter back

5.0L idle oscillating then dies

Reply #9 – June 16, 2009, 01:22:16 PM

Thanks guys for the suggestions. I haven't had time to get back in the garage but will in the next day or two to try some out some of these possible solutions.

I did notice that if I unplug the MAF, the car just idles rough but there is no oscillation. When I plug the MAF in, it starts oscillating and I hear a noticeable whistle in sync with the oscillation.

5.0L idle oscillating then dies

Reply #10 – June 16, 2009, 03:22:04 PM

Quote from: thunderjet302;277902

Does it throw any codes?

5.0L idle oscillating then dies

Reply #11 – June 16, 2009, 03:44:13 PM

Like said try the old mass air if you can. Try codes to.

5.0L idle oscillating then dies

Reply #12 – June 16, 2009, 04:32:37 PM

My 3.8 did this when it was cold out. I know your is substantially more built than mine. I dumped 4 cans of fuel injector cleaner in it, and it did it once more, then never again. I'm not saying it was the injectors, but it was something. I don't recomend that, it says 1 can for 20 gallons, I was just frustrated.

5.0L idle oscillating then dies

Reply #13 – June 16, 2009, 06:00:23 PM

Thanks. Ok, I got the hint guys :)... hold on for an update.

5.0L idle oscillating then dies

Reply #14 – June 20, 2009, 01:21:48 AM

Update. I put the 19lb injectors back in (had 24's) and also put the stock MAF in as well. Problem went away.