Bouncing Rev Counter

[JMan69]

Symptoms: Bouncing Rev Counter when I start the engine. The revs over shoot the regular idle mark then under shoots and repeats this process while getting closer to the regular idle mark until it finally stops at the idle mark.

Any suggestion on why this is happening?

Thx,

Jay

P.S. What is the recommended idle for a 1993 SVX?

[SoCal LS-L]

Listed in order from the flow chart (you can download the service manual from the link in my signature).

1. Bypass air control solenoid valve

2. Throttle position sensor

3. Coolant temperature sensor

The manual also provides testing information for # 2 and 3.

[JMan69]

Thank you very much, I didn't know about that manual... I will try some of the error checking methods to identify this problem and also to check why I occasionally get an intermittent check engine light.

[JMan69]

Indentified error codes stored in ECU:
12- Starter switch
21- Coolant temp sensor
37- Oxygen sensor No.2

All these errors have symptoms relating to failures to start, rough driving and rough idling

Any suggestions on how to fix any of these?

[1986nate]

Originally Posted by JMan69

Indentified error codes stored in ECU:
12- Starter switch
21- Coolant temp sensor
37- Oxygen sensor No.2

All these errors have symptoms relating to failures to start, rough driving and rough idling

Any suggestions on how to fix any of these?

Start with the coolant temp sensor. Should be relatively cheap even in Australia.

[JMan69]

Where would the Coolant sensor physical be in the car? Is there a replacement tutorial for this component of the car?

[JMan69]

In the recent days starting up my engine first thing in the morning (cold) is becoming harder and harder to do. It's just keeps cranking and then if the engine start it conks out very quickly. Is this also a symptom of the coolant temp sensor being stuffed?

[SoCal LS-L]

Yes, a prime symptom. Your ECU uses the signal to implement the correct ignition timing and injector pulse width, among other things. It also opens a valve that allows extra air in to idle faster when its cold. The sensor is located right under the intake, rear of engine, on the drivers side (if LHD)... its the one that has TWO wires going into it, should be brass colored. Simply unplug, unscrew, and replace. Make sure the engine is cool before you do this obviously.

[JMan69]

Thank you, it's releaving to know it's only one part that is majorly causing all this trouble. I got the part ordered in for tomorrow for $45. There is only 2 in stock in Australia haha

[JMan69]

Another thing, was just looking in the engine bay and oil dipstick had popped out. Replaced PCV maybe 3 months ago for that reason, could this be another symptom of the coolant temp sensor

[1986nate]

Originally Posted by JMan69

Another thing, was just looking in the engine bay and oil dipstick had popped out. Replaced PCV maybe 3 months ago for that reason, could this be another symptom of the coolant temp sensor

Probably just need to replace the o-ring on the dipstick itself if you didn't do it when you did the PCV

[JMan69]

I got the part today and have located the old sensor too. How would I go about the procedure of replacing it? The Subaru guy said I HAD to bleed out all the old coolant replace it once it's cold and then refill it the coolant. Is this essential? What would you recommend to do?

Cheers,
Jay

[SoCal LS-L]

Originally Posted by JMan69

I got the part today and have located the old sensor too. How would I go about the procedure of replacing it? The Subaru guy said I HAD to bleed out all the old coolant replace it once it's cold and then refill it the coolant. Is this essential? What would you recommend to do?

Cheers,
Jay

Thats the "proper" way, albeit far too unnecessary way to switch it out. Just wait till it's cool, unplug and unscrew the sensor, and install in reverse order. You will lose very little coolant, and a couple shop rags underneath will absorb it ok.

From 1 - 10 on the PITA scale, the temp sensor is about a .00001, compared to the valve cover gaskets at 11,009

Oh and you should do a hard clear of the codes by disconnecting the battery for about 60 minutes.

[JMan69]

Thanks will do. I'm looking forward to my engine purring as it shud again haha

[JMan69]

Outta curiosity wat is the small looking sensor right next to the coolant temp sensor? And what does it do? Cheers