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Author Topic: TBI System Rough Idle  (Read 2783 times)

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Offline Beaverseagle

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TBI System Rough Idle
« on: July 26, 2016, 05:36:11 PM »
Hi All,

Just wanted get some feed back. I installed a TBI system on my 82 eagle 258 six.. She starts and runs wells. Seems to have plenty of power.  But she's idling rough. Not super rough but enough to notice.   Would a bad connection in my fuel return line cause a vacuum leak? That's the only thing I have not checked.  I've ran the PVC valve and the MAP sensor vacuums lines according to the directions everything else I plugged up. I just put a vent on the rear valve cover outlet.  She's timed at 8 degrees BTDC and idles at 650 to 700 rpm per the instructions. The timing is solid and does not jump around.  Does the timing  sound correct for the 258?  Oh and she's an automatic.
82 SX4 258 w/ 2 inch lift 235 tires and TBI kit.

Online mudkicker715

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Re: TBI System Rough Idle
« Reply #1 on: July 26, 2016, 08:02:00 PM »
Fuel return line will not change vacuum. I am a little curious about your plugs,and timing. Not being there hurts, but look at spark delivery. if it doesn't miss at speed could be fuel delivery at idle.

Manitowoc WI

Offline amcfool1

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Re: TBI System Rough Idle
« Reply #2 on: July 26, 2016, 11:46:14 PM »
hi, timing sounds about right, look at your emissions sticker on pass side cowl, it will tell you what it should be. Are you still running the stock distributor? Where is the vac advance hooked up to? good luck, gz

Offline Beaverseagle

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Re: TBI System Rough Idle
« Reply #3 on: July 27, 2016, 12:32:53 PM »
To: mudkicker715

I don't have a fuel pressure gauge out in now...but may hook one up to verify fuel pressure is good.

The plugs have been gaped to .045 per the TFI upgrade which I did before the TBI upgrade. Do you think that could cause the issue?  The kit came with a larger distributor so I figured it wouldn't be an issue.

To: amcfool1

Yes I saw your comment on my other post about the Distro VAC advance. I started wondering if this should be hooked up as well but the instructions say not to use it. I'll reach out to the guy that makes the kits and see what he has to say.  About the emission sticker:  so even with this upgrade you think I should go to the stock advance settings?  I will give that a go.

Thanks comments...this helps. 
82 SX4 258 w/ 2 inch lift 235 tires and TBI kit.

Offline eaglefreek

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Re: TBI System Rough Idle
« Reply #4 on: July 29, 2016, 12:23:19 AM »
Have you verified TDC mark on the damper is TDC is true TDC? The dampers are know to slip. I would always time by ear. Keep advancing until I got pinging while going up a hill and then back it off a hair.
1986 AMC Eagle Wagon 4.2L/4.0L head, AW4,NP242, Chrysler 8.25" rear.
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