Jump to content

High Idle Rpm On Start Up


Recommended Posts

So the car has started doing something weird where the first six seconds or so the engine revs really high on cold start with no throttle input for the first six seconds or so. I would be grateful if someone could look over the log and map to check I haven't done something wrong please. Other than that I'm presuming something must be wrong with the idle control valve






Link to comment
Share on other sites

There is not really enough parameters logged to get a full picture of what is going on, but I dont see anything that the ECU is doing that would cause the high idle at start up.  The Idle valve position is sitting pretty constant at 40% when the RPM drops from 3700 to 1200RPM - in fact the valve is opening further when the RPM drops.

Has anyone had anything apart?  Any chance the open/close wires have been swapped on the valve?  What happens if you start the engine with the valve unplugged?

Link to comment
Share on other sites

it seems like you are relying pretty heavily on ignition idle control to keep idle RPM at cold temps.

try dropping the ignition 1 table value for the 20 kpa row from 1500 up to ~3k rpm by 10 points - ie keep it below 20*. You'll only hit this on overrun & at idle anyway so it should just mean a bit more engine braking if you notice it at all while driving.

It might be worth running the open loop idle tuning process to set your base idle numbers a bit closer to "correct" then switch back to closed loop. You havent logged closed loop correction percentages but your idle actual % is quite a lot different from your target table, and I dont see that many fixed corrections that would account for it, so its likely closed loop correction.

All of that being said, it looks like either your throttle is a bit gummed up at cold temps or your idle valve sticks. The MAP value drops away real slowly after startup, and comparing 0:08-0:09 (where it drops rpm happily) vs a few seconds earlier, the MAP value can clearly hit 10kpa when the engine "wants" to drop rpm, but at what it says are the same idle, TPS, and ignition angle, its only showing 25-30kpa, suggesting air is getting in somewhere.

Try re-running your TPS calibration once the engine is hot too. You havent logged enough parameters to be sure, but for the sticking throttle theory to be correct, you would have had to run the calibration when it was cold/sticking so it reads "0%" when its actually 1% or below - ie your tps% doesnt reflect the real throttle opening.

the reason it bounces around like that at 3k is because fuel cut is coming in and out because you are so far above idle that it thinks you are in overrun / rolling to a stop so it cuts fuel completely.

your lamba sensor goes full lean for about 10 seconds right after startup too. I assume this is just something the controller does when starting itself up but it could be worth looking into as well as its not lining up with the fuel inputs at the time so I dont think its a real value.

Link to comment
Share on other sites

Thanks for the help chaps, I did all of the above to end up annoyingly with the same result. Ended up getting another idle control valve and that seems to have sorted it, even though it check out electrically ok so very strange. Now with the ignition more retarded on the overrun it does make quite a few more pops 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...