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Old 05-01-2014, 08:04 PM   #1
Join Date: Jun 2011
Posts: 54
idling issue

I have a pretty stout vibration at idle that smooth up if I press the gas or raise the rpm above 900. It's driving me nuts, especially since it wasn't doing it before. It runs fine otherwise.

It's a used engine I dropped in, it has brand new
Rotor Cap and Finger
Main and rod bearing
Fuel,air,oil filter
Clutch kit
Motor/tranny mounts

I can take the serpentine belt out, doesn't change, no codes stored, balancer doesn't shake at all. Compression are fine, cam is alright.
No loose bolts/nuts, no vacuum leaks. I hooked up my timing light and it showed about 18* of advance at idle, though light hasn't been used in years and once I took it out, it wouldn't work until I popped it open, so I don't want to rely on what it says until I double check with another one.

If you guys can point something I forgot, that would be great.

/l , [____],
()_) ()_)--o--)_)
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Old 05-01-2014, 09:34 PM   #2

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Join Date: Apr 2012
Location: North Las Vegas
Posts: 9,663
Year and engine??? Carb, EFI or throttle body?

The tach is not exactly accurate

18 degrees at idle is a little much thought it should be about 8.

89 2.5 TBI, 4" RC lift, 1" Booms, SYE, Adams Driveshafts front and rear, Ford 8.8 with 4:88s, BFG 33X12.50X15, and a ton of other stuff.

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Old 05-01-2014, 09:36 PM   #3
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Join Date: Apr 2014
Location: Virginia
Posts: 10
see if your throttle bore and blade are coked up(black carbon deposits on edge of blade and bore walls) you could also check the pintle on the IAC motor
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Old 05-01-2014, 11:21 PM   #4
Join Date: Aug 2011
Location: north of St.Franisville La.
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If that don't do it clean the injectors.
The Government can not give anything to anybody that it does not first take from someone else !
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Old 05-02-2014, 06:06 AM   #5
Join Date: Jun 2011
Posts: 54
It's a 95 2.5L, mpfi. I cleaned the throttle body about a 150 miles ago and swapped in new injectors. I'm gonna clean the IAC and MAP today, hope it helps.

/l , [____],
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Old 05-03-2014, 02:00 PM   #6
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Location: SoCal
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I swapped in new injectors and the connectors on the wiring were so brittle. I ended up needing to push on the connectors and then super glue them in place so they made a good connection.
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Old 05-03-2014, 02:27 PM   #7
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Join Date: Mar 2012
Location: Ridgway, Pa.
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Did you use the flywheel from the donor motor, or the original flywheel?

2.5L are externally balanced. Harmonic balancer on the front and the flywheel on the rear.

Or possibly the flywheel has come loose and is causing the vibration. Everything has to be "clocked" correctly when setting up a 2.5L because of the external balancing.
'87 YJ, 4.2L built and bored, 8.5" of lift, 8.8 rear, AX15/NP 231, Tom Woods drive shafts, Flat fenders, 12,000LB winch, Custom bumpers, Rattle can paint job. Never completed...
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Old 05-03-2014, 03:03 PM   #8
Join Date: Jun 2011
Posts: 54
Injectors are all spraying fine, I check the connections twice.
I kept the original flywheel, but I took it out to clean it up while replacing the tranny. It is on torque and I still have the same vibration. I just cleaned up a spare throttle body from the old engine and will swap it out monday.
I need to get somebody else timing light to double check my result. If it is my problem, I guess I can only get a new ECM.
/l , [____],
()_) ()_)--o--)_)
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Old 05-04-2014, 05:00 PM   #9
Join Date: Jun 2011
Posts: 54
Well, I checked the MAP sensor and it is on specs, tried a new one for the heck of it, same result. I also swapped the throttle body, TPS and IAC for a different unit and still the same.
I'm going to get a different timing light to double check the advance.
When I pay attention, I can tell the idle wave up and down slightly. Also, it takes a few engine revolutions to start it, but it may be the way all 2.5L starts.
/l , [____],
()_) ()_)--o--)_)
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Old 05-08-2014, 10:14 AM   #10
Join Date: Jun 2011
Posts: 54
I just checked the timing with another light, It shows 14 to 16 of advance. It hoovers between the 2 aa the idle goes up and down. I also find I have a partially clogged cat, thanks to that sweet whistle and smell of rotten eggs in the cap when I take the rear window down.

At 8* of advance on the harmonic balancer, the dizzy gear is past number 1 plugs, but not by much. I'm trying to take the dizzy out but the nut won't budge.

/l , [____],
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