Idle surge issues


masanders

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2000 Ranger XLT RWD 2.5L

My engine will raise the rpms while driving to 2000 and generally get stuck there for a few seconds until the rpms go back down or I dang near stall it on purpose to get rpms down. I’ve tested the IAC, IAT, TPS, and MAF. Every sensor changes the idle when unplugged except for the IAT. Nothing changes when I unplug it.

I even took the sensor out of the intake tube while it registered 120 degrees at 94 degrees ambient temp (Bluetooth OBD 2 reader) in order to spray an electronics cleaner which brought the temp reading to 34 degrees. As it warmed up outside of the tube it went back to around 118 degrees. The point was to see if air temp changed anything about the idle. Nothing changed.

Any help is appreciated helping me figure out this idle issue.
 


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Bill

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I had that problem. It was the TPS. Idle would stay high between shifts, sometimes rising when I pressed in the clutch while driving. It would maintain a high idle while I was moving. When I came to a complete stop it would finally go back down to normal due to the speed sensor signaling the computer that I was no longer moving, then the computer tells the IAC to reduce idle. This also indicated the IAC was working. I can't remember the steps I took that led me to the TPS, but after unplugging the TPS the computer went into fail safe mode and the problem mostly went away. It turned out that the TPS was worn and acting erratically. It never threw a code until I unplugged the IAC.

Also, make sure nothing is sticking in the throttle plate and holding it open. A leaf fell in the air cleaner box when I changed the air cleaner. The leaf managed to stay in there for several months before getting sucked through the intake tube and lodged in between the throttle place and the throttle body and held it open resulting in a high idle. The computer then signaled the IAC to reduce the idle, but since the throttle plate was being held open the IAC was unable to reduce the idle to 800 rpm and started varying idle speeds as a test before it finally threw a code that said something like, "Idle speed out of range" or something like that.
 

masanders

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Sorry for the late reply Bill. I’ve been doing some remodeling in the house and haven’t thought twice about the truck.
I took some OBDII readings with my BlueDriver scan tool and wanted to show you the readings. The first picture marked 1 shows a five minute live reading without the TPS plugged in. The second picture marked 2 shows a five minute live reading WITH the TPS plugged in.
I think it’s the TPS as well. When the TPS plugged in, the computer adjusted this and that with the values fluctuating during the whole five minute time frame, more than what should happen when an unplugged sensor is plugged in.
If you could let me know what you think about the readings I’d appreciate it! Have a great day!
 

masanders

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masanders

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Any possibility this could be an O2 sensor? The B1S2 is reading N/A, but has voltage.
 

Dirtman

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Sensor 2 does nothing to effect the engine. It's there just to make sure the cat is functioning.

B1S1 should constantly switch from 0 to around .9 volts. B1S2 should show a steady voltage. The only thing B1S2 can do is throw a CEL if your cat malfunctions, has no control over the way the engine runs.
 
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masanders

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Sensor 2 does nothing to effect the engine. It's there just to make sure the cat is functioning.
Then why does it have voltage but no reading? Every O2 data stream I’ve seen has the downstream sensor readings, not just voltage. I’m just not sure what it means by n/a. It had plenty of time to heat up
 

Dirtman

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It probably says NA because it doesn't have percentage reading or temp reading available, only voltage. If it has steady voltage, its functioning. Voltage is how you read a o2 sensor. You could literally unplug the downstream sensor and the only thing that will happen is the cel will come on...
 

Dirtman

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Blue driver is nice but it lacks advanced data and can only tell you what the manufacturer decided to put through the obd2. Non obd2 info requires a more advanced tool.
 

masanders

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Blue driver is nice but it lacks advanced data and can only tell you what the manufacturer decided to put through the obd2. Non obd2 info requires a more advanced tool.
Agreed. Blue Driver has served it's purpose so far, but it would be nice to have access to more data.
 


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