Idle/Surge Help???

[T-royB]

I have a 93 Full Size with 180k, I just had installed an ATK rebuilt 351w, after install truck ran fine, but engine light was on, returned and diagnostic indicated oxg sensor, sensor replaced engine light off, but engine surges around 1500 to 2000 rpms and lopes at idle??? everything on motor checked, replaced and rechecked except injectors(no fault on computer) and fuel tank. Two ASE mechanics could not diagnose a fault in engine....or correct problem... /emoticons/[email protected] 2x" width="20" height="20" /> Many $1000's invested including new soft top....PLEASE HELP...any suggestions would be appreciated!!!

 

[wrachet]

I have a 93 Full Size with 180k, I just had installed an ATK rebuilt 351w, after install truck ran fine, but engine light was on, returned and diagnostic indicated oxg sensor, sensor replaced engine light off, but engine surges around 1500 to 2000 rpms and lopes at idle??? everything on motor checked, replaced and rechecked except injectors(no fault on computer) and fuel tank. Two ASE mechanics could not diagnose a fault in engine....or correct problem... /emoticons/[email protected] 2x" width="20" height="20" /> Many $1000's invested including new soft top....PLEASE HELP...any suggestions would be appreciated!!!

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Is it possible that you could have gotten some bad gas?

Colleen

 

[T-royB]

Is it possible that you could have gotten some bad gas? 
Colleen

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I don't think so, as I have run several tanks through...I only get about 10mpg and have put 700 miles on new motor, the mechanics also installed new fuel filter?

thanks

 

[Broncoholics]

Not sur if this is it but...

Do you have an automatic trans? If so you can disconnect the wire connector on the side of the trans and see if that helped. I've heard its an idle/torque converter problem sending wrong info and will cause the truck to surge forwards from a top to rolling (go gas) along. If its faulty it will not respond correctly. There was something else but a trans shop can answer it for you.

 

[T-royB]

Not sur if this is it but...Do you have an automatic trans?  If so you can disconnect the wire connector on the side of the trans and see if that helped. I've heard its an idle/torque converter problem sending wrong info and will cause the truck to surge forwards from a top to rolling (go gas) along. If its faulty it will not respond correctly.  There was something else but a trans shop can answer it for you.

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Thanks, I have the e40d auto tranny, I'll check this out!

 

[gump_black]

do you think it could be the mass air sensor?? mine used to surge at idle, in gear and parked. luckly it was just a sticky butterfly valve but my mechanic told me it could have also been a faulty air sensor

 

[T-royB]

do you think it could be the mass air sensor??  mine used to surge at idle, in gear and parked.  luckly it was just a sticky butterfly valve but my mechanic told me it could have also been a faulty air sensor

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the 93 I have is a speed density efi system, not mass air, thanks

 

[gump_black]

the 93 I have is a speed density efi system, not mass air, thanks

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what is the differ between the two?? and what does a 92 have?? :huh:

 

[American Rebel]

It's neither of those... It's the TPS (Throttle Position Sensor)..... That happened to my bronco before I bought it...but I could be wrong, the TPS is my guess

 

[Thadoggma]

do you have a/c on your bronco? if you do it could be a bad a/c compressor and/or clutch.... i have an 89 that doesnt like to idle when the ac compressor is running.

 

[dicain]

I have a 90 351 and I had a simaller problem and it turned out to be the idle control valve and its a spendy part.

 

[T-royB]

FYI, I had two plug wires that were bad!!!!!! so far so good......

 

[Broncoholics]

Are you kiddin me?

 

[T-royB]

Are you kiddin me?

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No, I even put the wires (which were relatively new oem motorcraft) on the meter to confirm, although the arc burns on the insulation gave the fault away? The surging when accelerating is gone totally, the idle is improved although it's no lexus....I'm going to change the injectors next time I get some cash, hopefully that will make it purr... any idea as to what would cause the plug wires to fail?

 

[Broncoholics]

They can fail by pulling on the wire instead of the plug area and the wire pulls away inside. #7,#8 wires needs to be routed away from each other, don't let them cross each other. Can cause cross fire problems and mess up the wires. Which ones where they? What kind of ohms did you get on the good vs bad wires?

 

[gungho]

They can fail by pulling on the wire instead of the plug area and the wire pulls away inside. #7,#8 wires needs to be routed away from each other, don't let them cross each other.  Can cause cross fire problems and mess up the wires.  Which ones where they?  What kind of ohms did you get on the good vs bad wires?

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Are you talking about if they are just crossed over each other? My truck has been surging for a long time, throughout the rpm range. When i first got it back in october the first thing i did was a full tune up which included new wires plugs cap and rotor. It ran smooth for a week, then i made an 1800 mile trip and it was running rough and surged. #7 and #8 have been crossed the hole time, maybe my wires are bad. What do you think? What ohms are the wires supposed to be?

 

[T-royB]

Are you talking about if they are just crossed over each other? My truck has been surging for a long time, throughout the rpm range. When i first got it back in october the first thing i did was a full tune up which included new wires plugs cap and rotor. It ran smooth for a week, then i made an 1800 mile trip and it was running rough and surged. #7 and #8 have been crossed the hole time, maybe my wires are bad. What do you think? What ohms are the wires supposed to be?

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I'm clueless as to which wires they were? which cylinders are 7 and 8? as far as the resistance the 2 bad wires had twice the resistance as the good wires.... If you are interested in the exact reading, I will recheck with the meter

 

[brizzy351]

I'm clueless as to which wires they were? which cylinders are 7 and 8? as far as the resistance the 2 bad wires had twice the resistance as the good wires.... If you are interested in the exact reading, I will recheck with the meter

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[/quote If your engine is still idling rough you could have a bad (I.A.C. valve) Idle Air Control valve. This valve has been problem for me in the past. Sounds like you have some of the same symptoms I had. It is located on the throttle valve. Its a little silver canister with two wires going into it and its held on by two screws. You can take it off and clean out the carbon that builds up in it that might get you by for awile but ultimately it will have to be changed. Another reason your engine will idle rough is if the throttle valve is caked up with carbon. I use a tooth brush and some carb. cleaner with the engine not running open the throttle valve by hand wet the tooth brush and scrub the black film off the walls of the valve. When you are done doing that start the engine and spray carb cleaner in while reving the engine by hand. Just make sure when you buy the carb cleaner it compadable with fuel injection systems.

 

[Broncoholics]

#7, #8 are the last two cylinders on the driverside. This might not be the problem, just something I've come across. Just route the wires away from each other the best you can. Wonder if you have a bad wire? Try ohming to see they are all close to each other.

When this happened to my 89 it was the valve seats were bad. Seems some jack ass put an old motor without case hardened valve seats and they wore into the head 1/4" and caused leaks. Pulled the head, had them fixed at a auto machine shop and it ran perfect. A compression test did not find it. Only an air leak down test will find it.