Idle problems/Coolant Temp Sensor Swap - Subaru WRX Forum
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post #1 of 4 Old 01-09-2017, 05:31 PM Thread Starter
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Idle problems/Coolant Temp Sensor Swap

Morning all

After changing the head gasket, timing belt and water pump I've nearly got the car sorted and driveable... The remaining issue is once the car starts to warm up the idle bounces from 1k - 0 Rpm repeatedly.... I've searched for a leak to no avail and when I unplug the MAF it improves short term only to start lurching again. Spark plugs and leads were changed when everything else was done.. I've been reading and reading and I think the coolant temp sensor may be contributing to this. I changed the temp sensor to a 3 pin and wired in the gauge wire to it in addition to the ecu wires. The temp gauge appears to work and slowly moves up to half way but I cant help thinking that possibly the ecu isn't enjoying the 3 pin approach and not giving the right coolant temp. Anyone got any info on the 3 pins being used on a my98 or earlier? or any other suggestions are much appreciated.
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post #2 of 4 Old 01-10-2017, 05:20 PM
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Common issues with timing belts on Subarus, because the valves are so thin if you don't secure the cams while you change belts you'll bend the valves. Good news is it causes no issue at all other than rough idle. Bad news if you want to get it fixed you have to take it to the dealer for new valves or a valve adjustment depending on how bad it is. I see alot of Subarus come into my shop, we even stopped doing timing belts on Subarus because it's almost inevitable. A good friend of mine at Carter Subaru is a Master Tech and he says they get an average of about 8 or 9 Subarus a week for valve adjustment. Good luck, I did my own timing belt at home but luckily I knew the risk and made sure thoes puppies stayed still.

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post #3 of 4 Old 01-11-2017, 06:18 AM
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clean your IACV. make sure to use a new oem gasket.

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post #4 of 4 Old 01-12-2017, 10:20 AM
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We don't know what car you're referring to? And why the hell are you cutting wires without knowing what you're doing or about the vehicle? Stop creating more issues than you had.

Try a new IACV, cleaning it. Try going to a parts store and using the CEL scanner to see what the Coolant Temp is and how it changes with load. If you don't have the emissions purge solenoid plumbed and a tune for it, this will cause issues similar, so will fueling issues.

Again if you don't know what you're doing, get a diag done at Subaru!
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