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Old 08-15-2013, 01:26 AM   #1
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High idle carb wont adjust!!!

Ok so when I start my jeep it up an fires right up and will idle at about 850-900. As soon as you give it gas it will idle at around 1200-1300 and stay there no matter how warm it gets. Upon inspection under the hood I notice a few things. 1) when cold the choke is not engaging not a big deal SoCal is pretty warm. 2) when first started the idle screw is in contact with the carb thus adjusting the idle speed to 850ish. 3) once some gas is applied the screw does not go into contact with the carb and stays out setting the idle speed to 1200-1300 and will not go back down until you manually depress it. I have replaced the return springs figuring they had lost their springyness but still nothing. My next guess is that a sensor is bad somewhere and the stupid steper motor is trying to adjust it for some random condition it perceives. I'm thinking maybe O2 sensor? Any ideas?

87' 4.2L

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Old 08-15-2013, 03:46 AM   #2
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Timing? Pictures of the carb throttle assembly would be helpful too

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Old 08-15-2013, 08:17 AM   #3
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sounds like the choke might not be fully opening
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Old 08-15-2013, 11:43 AM   #4
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Will post pics once I get home from work
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Old 08-15-2013, 06:16 PM   #5
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Two pics one is when first started idle screw us just touching after giving it gas throttle will not return all the way
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Old 08-15-2013, 07:15 PM   #6
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well,no doubt that the choke plate is open..check to see if you can tell what is keeping the throttle from returning all the way..could still be the choke linkage..just fiddle with the throttle and see if you can find whats holding it
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Old 08-15-2013, 07:49 PM   #7
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Ya I saw that it was wide open I checked the linkage and every thing is moving with no binds.
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Old 08-15-2013, 07:51 PM   #8
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When I shut the engine off linkage returns to normal and stays there until you get the rpm to 1200 then it won't return
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Old 08-15-2013, 07:56 PM   #9
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can you tell what is moving that lets the linkage return to normal
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Old 08-15-2013, 07:59 PM   #10
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if you have a fast idle solenoid,see if that's what is causing it
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Old 08-15-2013, 08:02 PM   #11
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Solenoid, loosen up the screw on the solenoid to what it needs to be to return to idle.
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Old 08-15-2013, 10:59 PM   #12
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High Idle

sounds like my 2.5 when the throttle position sensor went out.

careful when you change it, the spring needs to be set right.

part will probably run $20 - 25
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Old 08-15-2013, 11:03 PM   #13
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I have loosened pretty much all the screws its like something inside is not allowing the throttle to return all the way unless the engine is shut off
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Old 08-15-2013, 11:15 PM   #14
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Quote:
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sounds like my 2.5 when the throttle position sensor went out.

careful when you change it, the spring needs to be set right.

part will probably run $20 - 25
Your 2.5l is fuel injected, flyngtwg's rig is carbureted and doesn't have a TPS

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I have loosened pretty much all the screws its like something inside is not allowing the throttle to return all the way unless the engine is shut off
Are you sure you have all the springs, and that they are in the right places. From the pictures, it looks like you have both in the same spot when the short one goes where they are in the pictures, and the longer one goes to a lower point on the egr valve bracket but runs under the egr valve to the lower hole on the throttle linkage. If thats not the problem and if you are mechanically savey, then I'd say get a gallon can of berrymans carb and parts cleaner (about $20 but has many other uses till it goes bad) and a rebuild kit (about $20, somewhat difficult but well worth it)
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Old 08-15-2013, 11:31 PM   #15
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like these pictures, sorry but it's night time. Your problem could also be the stepper motor which would be the 1st thing I'd have checked if the springs aren't the problem.
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Old 08-16-2013, 12:22 AM   #16
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Ok c5wagner ill try hooking them up like that tomorrow and see what happens I'm just waiting to get a holley 390 cfm and ditch the stock system
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Old 08-16-2013, 12:32 AM   #17
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The Holly isn't smog legal in CA if you've got it registered here
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Old 08-16-2013, 12:52 AM   #18
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I know I only have a little over a year left here and it will be registered somewhere else
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Old 08-16-2013, 12:53 AM   #19
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To upgrade and stay smog legal here is near imposible on a budget
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Old 08-16-2013, 01:02 AM   #20
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To upgrade and stay smog legal here is near imposible on a budget
I know. I was lucky enough to find a guy who is a wiz with carbs, and he adjusted mine and got it to pass. Runs great now, I'm getting between 11-12 mpg with a 4" lift and 33s. I just ran a can of Seafoam through the gas and now I'm driving in the fast lane, lol
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Old 08-16-2013, 01:47 AM   #21
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I did the same when I got it first got it smoged but the carb is so tempermental. I can't aford to pay him to keep it in tune for me.
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Old 08-16-2013, 01:49 AM   #22
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I have worked with holleys and others my whole life but this one has got me stumped.
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Old 08-16-2013, 07:51 AM   #23
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Are you sure you have all the springs, and that they are in the right places. From the pictures, it looks like you have both in the same spot when the short one goes where they are in the pictures, and the longer one goes to a lower point on the egr valve bracket but runs under the egr valve to the lower hole on the throttle linkage. If thats not the problem and if you are mechanically savey, then I'd say get a gallon can of berrymans carb and parts cleaner (about $20 but has many other uses till it goes bad) and a rebuild kit (about $20, somewhat difficult but well worth it)[/QUOTE]
many throttle return springs,especially original equipment ones were one inside the other
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Old 08-16-2013, 10:11 PM   #24
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I know. I was lucky enough to find a guy who is a wiz with carbs, and he adjusted mine and got it to pass. Runs great now, I'm getting between 11-12 mpg with a 4" lift and 33s. I just ran a can of Seafoam through the gas and now I'm driving in the fast lane, lol
Thanks for telling me about that guy, he got my car to pass smog no problem too
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Old 08-16-2013, 10:26 PM   #25
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Thanks for telling me about that guy, he got my car to pass smog no problem too
That's great! It helps that he smogs too, so he knows what to do to make them pass. I just wish his shop was in a better area, I have a 1968 Triumph TR 250 with twin Stromberg carbs that need to be rebuilt and I don't want to leave it there.
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Old 08-17-2013, 04:44 PM   #26
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That's great! It helps that he smogs too, so he knows what to do to make them pass. I just wish his shop was in a better area, I have a 1968 Triumph TR 250 with twin Stromberg carbs that need to be rebuilt and I don't want to leave it there.
I wouldn't worry about it, my grandfather just gave me his 1969 firebird with a chevy 454 and holly 4160 4 barrel, I took it to the shop dropped it off and he rebuilt the carb for me and there were no problems, the beast is running great. I just wish my YJ could get up to 70mph as fast as the firebird!
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Old 08-17-2013, 06:37 PM   #27
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I wouldn't worry about it, my grandfather just gave me his 1969 firebird with a chevy 454 and holly 4160 4 barrel, I took it to the shop dropped it off and he rebuilt the carb for me and there were no problems, the beast is running great. I just wish my YJ could get up to 70mph as fast as the firebird!
Well that's good to know. Congrats on the Firebird, I used to have a 69 Mustang with a 351, so I know that 454 will fly. I know what you mean about the YJ, but I get my speed fix from my 06 Mustang GT. But I have a tendency to get road rage when I drive it, and turn into one of those maniacs who has to be in front of the line. My Jeep grounds me, kinda takes me to a different place, so I drive it when I need to regain my sanity. It's nice to have the best of both worlds.
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Old 08-18-2013, 12:03 AM   #28
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Well that's good to know. Congrats on the Firebird, I used to have a 69 Mustang with a 351, so I know that 454 will fly. I know what you mean about the YJ, but I get my speed fix from my 06 Mustang GT. But I have a tendency to get road rage when I drive it, and turn into one of those maniacs who has to be in front of the line. My Jeep grounds me, kinda takes me to a different place, so I drive it when I need to regain my sanity. It's nice to have the best of both worlds.
Hopefully I will get around to swapping my dodge v8 into my yj soon, then I can at least keep up on the freeway. Just dreading the electrical work that I'll have to do.
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Old 08-19-2013, 08:56 AM   #29
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Currently putting a 4.3 vortec in mine. wiring is the only part I really need to figure out.

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