Rough idle
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New User
Joined: May 2002
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Rough idle
I have am having trouble with my 1991 ford F-150 with a 5 liter engine. It idles rough and sometimes stalls. This happens when it is both warm and cold. The previous owner took off the emission crap but I don't think this is my problem. I scan the computer for codes but all that came up is "insuffient EGR valve flow". And that makes sense because the EGR is unhooked. Please give me some ideas because having to restart it all the time is getting a little old. 
Thanks!
Thanks!
Elder User
Joined: Nov 2001
Posts: 892
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From: Duluth, MN
Rough idle
If it ain't broke.....change stuff till it is!
Only(correct me if it's the wrong year) but i think it's 95' and after need the EGR's to run with the computer, your's doesn't need it. Try taking the IAC off and cleaning it, and removing the throttle body and cleaning that. You may want to ohm fuel injectors to see if they're bad.....
Only(correct me if it's the wrong year) but i think it's 95' and after need the EGR's to run with the computer, your's doesn't need it. Try taking the IAC off and cleaning it, and removing the throttle body and cleaning that. You may want to ohm fuel injectors to see if they're bad.....
Senior User
Joined: Apr 2002
Posts: 467
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From: On the farm near Loveland
Rough idle
I agree, you should start by hooking up the EGR, then take it from there.
Late model computer controlled vehicles absolutely need the EGR connected to run properly. You gain absolutely no full-throttle horsepower by disconnecting it, no benefit to disconnecting it at all, it's disabled at full throttle. EGR only operates at part-throttle.
When you disconnect the EGR on an EFI vehicle you end up with problems like pinging and knock when you step on the gas, then you have to retard the timing to 'correct' it. You also can lose low end torque.
Late model computer controlled vehicles absolutely need the EGR connected to run properly. You gain absolutely no full-throttle horsepower by disconnecting it, no benefit to disconnecting it at all, it's disabled at full throttle. EGR only operates at part-throttle.
When you disconnect the EGR on an EFI vehicle you end up with problems like pinging and knock when you step on the gas, then you have to retard the timing to 'correct' it. You also can lose low end torque.
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New User
Joined: May 2002
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Rough idle
Well I would put on the egr if I had one to hook up. My truck runs fine except for the stalling problem. I beleive that the egr valve isn't supposed to work at idle anyways so that isn't the problem. I will clean the idle control valve and the throttle body and see if that helps.
New User
Joined: Apr 2002
Posts: 12
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From: greenville usa
Rough idle
Well I can't say for sure what your problem with the idle is,but I can say for sure your truck doesn't require recyled exhaust vapors to run properly, or idle smoothly for that matter. However if you live in a emissions state it is illegal to operate a vehicle without factory installed emissions equipment. Enough said for the gov. I think to start cleaning your throttle body and IAC would be a good start. I would check the throttle position sensor, and maybe fuel pressure next. However the map sensor does control how much fuel and timing your getting at idle and all speeds.So if possible forget about the egr crap, because obviously it does't effect real performance , only epa rates. Good Luck, let me know how it turns out!
