Idle problems on a 5.0 EFI
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New User
Joined: Apr 2014
Posts: 7
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From: Portland
Idle problems on a 5.0 EFI
I have a 1986 Bronco I bought for my son to drive in High School. We finally got the darn thing tuned enough to get it to pass emissions in the state of Oregon (real pain) and it took a while! it runs good at all speeds but what I have noticed is that when I go from Park to reverse or drive the idle increases and then drops down low. sometimes it goes low enough to kill the engine. I haven't worked around a lot of fuel injection engines so I am not sure how to even go about troubleshooting this. I did think it might be a vacuum issue so I used starter fluid to spray around to see if there was a leak somewhere around the intake area but didn't get anything. I have not messed with the timing after the shop got it tuned to pass DEQ but I know it was not set to 10 degrees as the manual says.
any ideas on what could be causing this?
any ideas on what could be causing this?
Former Vendor
Joined: Apr 2019
Posts: 279
Likes: 3
From: Shawnee KS
Advancing or retarding timing is done to effect emissions but it may have downsides like it not being enough timing at idle to keep it running. Since you know it's not at 10 degrees, you (we) need to know where it's at. So I'd check timing to see where it's at first. Then you can move on to checking/cleaning the IAC, resetting base idle, etc. if necessary.
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
Check the timing like mentioned. you can safely bump the timing up to 11 or 12* btdc with the spout connector unplugged. since its a 5.0 look into the 6litre tune up.
the TPS could also be the culprit or a dirty IAC. Do you notice this when its cold or all the time? Perhaps its a voltage issue, im still rocking an old 95amp alternator and if the headlights and blower fan are on high my volts drop pretty good and the rpms can drop. if this is the case look into the 3G alt upgrade, its inexpensive and pretty easy. the stock 2g Alt on that year is prone to failure and fire.
passing emissions there in the Portland area can be a pain for sure. I used to live in Clackamas county so it was just a sniffer. but i have heard in other areas its more involved.
the TPS could also be the culprit or a dirty IAC. Do you notice this when its cold or all the time? Perhaps its a voltage issue, im still rocking an old 95amp alternator and if the headlights and blower fan are on high my volts drop pretty good and the rpms can drop. if this is the case look into the 3G alt upgrade, its inexpensive and pretty easy. the stock 2g Alt on that year is prone to failure and fire.
passing emissions there in the Portland area can be a pain for sure. I used to live in Clackamas county so it was just a sniffer. but i have heard in other areas its more involved.
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