91 F150 Does the 02 sensor affect idle?
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From: Lexington Park, MD
91 F150 Does the 02 sensor affect idle?
I have a 91 F150 with a 302. A while back I had a dual exhaust system put on it. It doesnt have any catalytic converters. It has dynomax super turbo mufflers on it. Whenever the truck sits overnight and I go to start it the next day, it will start, idle lower and lower until it cuts off.I start it again and its fine. I havent got underneath it and checked for the sensors yet, but I dont think think they were installed. Would these things affect that initial fuel flow or idle through the computer? Any input would help and would be greatly appreciated.
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91 F150 Does the 02 sensor affect idle?
Well if the 02 sensor isnt there, then the fuel injector computer will not know how much gas to give the engine. If there are no 02 sensors, then the engine shouldnt even run i dont think. But if they are gummed up or something, then the engine could be recieving too much gas, almost like a choke on a carb. That sounds like the problem. Either way, replace the 02 sensors. Hopefully that would help the problem. It cant hurt anything either.
Jonathan
Jonathan
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From: Lexington Park, MD
91 F150 Does the 02 sensor affect idle?
Thanks a lot. I really appreciate the info. I have never known much about those things, but I will definitely look into it much deeper now. About the offer, yes I love my truck. In fact, it just took it to get a brand new paint job today. It sounds tempting, but I think Ill stay with my ol 2wd. Thanks again for the advice.
Chris
Chris
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91 F150 Does the 02 sensor affect idle?
Your O2 sensor shouldn't affect Idle too bad. Is the check engine light on? Did the problems start right after the exhaust mods? From what you describe, I would suspect the idle air bypass. This solenoid valve is located near the throttle body and lets air go around the closed throttle body during idle.
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From: Virginia
91 F150 Does the 02 sensor affect idle?
On an initial cold start-up, the computer doesn't look at the O2 sensor. It goes through a warm up cycle and is in what they call "open loop". When the truck warms up, it will go into "closed loop" where the computer will look to the O2 sensor for important info about fuel/air mixtures. On your truck it's going "hey I am not receiveing a valid O2 signal" and will tell the "check engine" light to come on. You are really crippling your engine managment system with no O2 sensor.
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From: Lexington Park, MD
91 F150 Does the 02 sensor affect idle?
Hmm. I had no idea about that. Franklin2, do you agree with Frenchie about the idle air bypass? Do yall think that would be a more likely culprit? Yes, the problem pretty much started around the same time frame as my mod, but no, Im not getting a check engine light. Should I investigate this valve more, or go straight to the 02 sensor? Unfortunately, I just took my truck to the paint shop, so I cant go look at it, but I definitely know what I will be doing when I get it back. Any more of you guys' opinions would be greatly appreciated. I cant begin to tell you how much they are now. Thanks.
Chris
Chris
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91 F150 Does the 02 sensor affect idle?
With no O2's it will cause your truck to run rich.
John
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From: Coon Rapids, MN
91 F150 Does the 02 sensor affect idle?
my truck is doing the same thing. It just happened withing the last month and I havn't done anything to the truck except change the air filter and oil but it started happening before that. It will idle on startup and gradualy decrease but I have never let it die. I will hit the gas about the time it drops to 400 rpm and then it will start to idle like normal. But the difference is it only happens part of the time. It seems to be a little cooler when it does though. If this condition is affected by temperature I would really like to get it fixed by winter as we see temps in excess of -30 without windshield. Thanks for any help.
'90 1/2 ton 4x4 XLT Lariat
RC LB w/5.0 EFI M50D 3.73gear
true duals w/glasspacks
'90 1/2 ton 4x4 XLT Lariat
RC LB w/5.0 EFI M50D 3.73gear
true duals w/glasspacks
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From: Lexington Park, MD
91 F150 Does the 02 sensor affect idle?
Yep, thats what mine is doing, but only it does everytime it sits for an extended period of time. I havent noticed a difference when the temperature changes, though. Its pretty much a regular occurence. I appreciate all of you guys opinions and help. I certainly know what I will be doing when my truck is done getting painted. Ill just have to be more careful now! Thanks again,
Chris
Chris
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91 F150 Does the 02 sensor affect idle?
IAC can affect idle if it is sticking and cannot respond to commands from engine computer. Also, you may have carbon build up on the valves. The carbon absorbs the fuel that is sprayed by the fuel injector, and then the fuel is not ingested into the cylinder correctly. The carbon also affects airflow. My 1988 was doing same thing, only when cold started, it would not want to stay running, and had extended cranking time. When warm, the fuel vaporizes more readily because of the heat of the engine, but when cold the fuel remains liquid, and is easily absorbed by the carbon deposits. I used BG Products 3 pack that included 44K in the gas tank, throttle body cleaner, and intake manifold cleaner. I used a vacuum hose to suck the intake cleaner into the engine while it was running (do this a bit at a time or it stalls). I sprayed the throttle body cleaner into throttle body with a spray bottle. This has so far resolved the concern, but I suspect it will reoccur over time. My truck had over 200K miles at the time I did this (last summer). The throttle body cleaner spray will help clean IAC passages and reduce tendency of IAC to stick.
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