hey guys anybody run into a cold rough idle that runs high and low until she warms then runs fine, changed out a couple of throttle bodys and thats not it, checked for vacum leaks, all good, no check engine light , runs rough until it warms then its fine, HELP????? :dontknow:
rough cold idle
- Thread starter beastly1
- Start date
FATJACK
Full Access Member
Could it be the Throttle Positioning Sensor??
Cheap and easy to replace,
Cheap and easy to replace,
chuck tator,local viper tech, told me that the tps has nothing to do with idle, it's when it's in a closed loop when cold, the computer is not compensating, i cleared the computer and i still have the same problem, only when cold.
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JeffBoyette
Full Access Member
The throttle position sensor is used when it is in closed loop or open loop. That's how the computer know you just gave it gas. If the tps thinks you have for example 15% throttle at idle it will spray extra fuel, run rich, see is, compensate, and you will get irratic or rough idle. Chuck Gayle should have put a multimeter on the sensor, or plugged in a diagnostic scanner to read the signal being sent to the computer.
I also believe it is most likely the tps, even tho you change the tb, the sensor is a common denominator.
I also believe it is most likely the tps, even tho you change the tb, the sensor is a common denominator.
JeffBoyette
Full Access Member
It's a really cheap fix, a lot of us have had the issue, including me. Grab a sensor at your local autoparts store.
local parts center ??, i think this a dealer part, i checked it's about 45 bux at the dealer, hey jeff, how can i check to see if my sensor is no good, and did you get a check engine light, i have no light. thx jeff i have an multi meter here, may be i have no power going to the plug
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rare03srt10
Full Access Member
You can also buy at autozone/o riley / pepboys for about half that price bud. You can check the ohms with a volt meter also though. Should read 4.0 at WOT and like .5ish for idle if i remember correctly
TheMoparConnection
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i believe it may be your tps as well. its happened to me before. typically will not through a check engine light for an irratic reading.
JeffBoyette
Full Access Member
Half that at a parts store. Like rare said, autozone, advanced, etc. I think I paid under 25. No difference in the sensor, probably made at same plant.
I believe those voltages listed seem familiar. You will have voltage going to the sensor or you would have a cel. There are these tiny contact plates inside the sensor. Each contact is connected to a resistor that modifies the voltage that returns to the ecu. This is how the ecu knows how much throttle you apply.
These contacts wear and cause dead spots, moisture gets inside and screws with the voltages. Sometimes when you are at idle its suposed to be sending .5 volts but either the moisture, corrosion or worn contact inside the sensor will reduce the resistance, increasing the voltage sent to ecu. The ecu interprets that as you requesting power, and it tries to give it to you but doesn't get enough air.
The idle air control valve does a fair job of supplementing and correcting the air requirement to sustain idle. But it operates when the ecu thinks you have are not pressing the gas. The idle air control valve is a stepper motor. It opens and closes to correct the idle and this causes the surge. One a side note, it also works during decel to reduce excessive vacuum, engine braking, and lean condition, also contributing to the popping we have on decel.
Carbon also builds up on the pintle of the iac valve that fills the hole. Unbolt it with the torx screws and using carb cleaner scrub the carbon off it. And make sure the hose that connects to your intake tube is not kinked.
I'm sure these low cost low labor solutions will help eliminate the problem or at least reduce possibilites. Pm me anytime if you have questions.
MY guess is the IAC. Idle Air Controller. dohicky just behind the TPS . 2 screws remove it and pull the plunger out squirt some penatrating oil in there and wash it around wipe it clean and work the plunger in and out a few times to loosen it up. disconnect the battery so it can relearn the idle parameters . reinstall it while the battery is disconnected . reconnect battery and start it up and see if that fixes it. they seem to seeze up alittle over time
thx jeff, and slitherbeast, just got back from autozone 19 bux what a deal, thx again, will pop that in tomorrow and clean up the iac, will post up tomorrow with results thx again guys great help..:rock: hope this works
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VENOMOUS1 RACING
Has Left the Room - Banned from VTCOA!
You can check the voltage on your multimeter by probing one of the three wires on the TPS while connected to throttle body. It (as Jeff said) be around .5 volts with Key On/Engine Off and slowly open the throttle blade via linkage on Throttle Body and make sure there are no bad/dead spots thru the sweep. The voltage should cleanly sweep from about .68 with closed throttle to around 4.5 volts which is wide open throttle.
It is cheap to replace at around $18 at any parts store.
It is cheap to replace at around $18 at any parts store.
ok that did not work
ok posting my results and changed out the tps and cleaned up the iac and i still have a **** cold idle,the idl still runs up and down for a bout 30 seconds then smooths out once it warms up, not giving up but can't figure this out, very frustrated, disconnected the positive side of the battery and same ****, so i don't know.
ok posting my results and changed out the tps and cleaned up the iac and i still have a **** cold idle,the idl still runs up and down for a bout 30 seconds then smooths out once it warms up, not giving up but can't figure this out, very frustrated, disconnected the positive side of the battery and same ****, so i don't know.
JeffBoyette
Full Access Member
Post a video and list all mods, also any changes you may have done before this happened. Did it sit parked for a while and do it as soon as you started it. Or did you drive to work one morning and that evening when you started it to go home you get the symptoms.
yeh thx jeff, can do will do a video, when it is ice cold and post it, my mods are sct tune by torrie, headers high flow cats , tony's tb, k&n, demon coils and wires, chuck tator told me to throw the stock tune in and see if it does the same thing, will try that ,if not he has to put a drb scanner and see what it tell him when it first starts, i tried everything,it started out of nowwhere, started it one morning and it's been doing it ever since, can't figure this one out, only when cold it flucuates almost to to where it stalls,and then when it warms it smooths out , and the exhaust smells like it is running real rich.
JeffBoyette
Full Access Member
x2 on back to stock tune for diagnostic purpose. How long ago did you install the coils wires and tb?
coils and wires about a week throttle body yesterday, had the bbk went over to tony's tb. runs the same, no diff between the cold starts. i sent a pm to torrie for a possible solution, i'm all out on this one, you guys are a great help. but this one is tough.
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