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Old 10-31-2007, 08:17 PM   #1
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Default Bad Idle????

My idle likes to bounce up and down all the time. The weird thing is that is drops really fast and slowly climbs back up?? Any suggestions?

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Old 10-31-2007, 11:19 PM   #2
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When it's idling like that, open your spark and VE tables and see if it's jumping between two cells that are drastically different. Mine did that at first; and it was hitting one cell, dropping down to the other, and then the other cell would throw it back up to the first. Vicious cycle. Make both cells the same, and the car will stop hunting and just settle down.
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Old 10-31-2007, 11:46 PM   #3
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I'm having idle issues as well. Similar to yours, though I have my cells all the same so that there is no "hunting" taking place. I'm running 550 cc injectors and can't get them to idle for ****. I now have a good steady idle but only because of how rich it is. It bounces like crazy like yours unless i tune it to idle at 11.8-12:1 AFR. I have my ve table set to 64 in the idle cells, if i decrease them to 63 my idle instantly goes to hell and i'm back to bouncing like crazy.
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Old 10-31-2007, 11:56 PM   #4
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tune your VE table.
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Old 11-01-2007, 12:06 AM   #5
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For example, here's my fuel and spark tables. I put rows in for my idle MAP values for both no load idle and with the A/C on.

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Old 11-01-2007, 12:10 AM   #6
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mmmmm, idle!

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Old 11-01-2007, 12:13 AM   #7
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Mine looks like that, just alot richer.
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Old 11-01-2007, 02:30 AM   #8
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I will tune my VE table...and way to rub it into the less fortunate...jk
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Old 11-01-2007, 02:34 AM   #9
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Cjernigan or other 1.8l w/ 550cc people....could you post your cranking settings? We have a similar setup and I have yet to get mine right.

I will update what happens with the VE tune.
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Old 11-01-2007, 01:25 PM   #10
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Tuning the VE table is key, and a bit more ignition advance may help as well, maybe 17 degrees ballpark at idle-- some car idle stock at 20 FYI. It also might help to look and see if your closed loop idle is playing a role, check the 'idleDC' reading in the logs and see what's up. The reaction times in the idle settings may need to be slowed a bit if it's idle valve oscillation, probably just the slow time, not the fast, but I'd have to know what your current settings are to know...
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Old 11-01-2007, 03:20 PM   #11
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The idleDC only jumps from 9 to 10 when the idle drops really quick and brings it back up. The spark and VE tables also seem to stay in the same cell during oscillation. Except if the cells near it are averaged in??

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Old 11-01-2007, 03:23 PM   #12
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Old 11-01-2007, 03:33 PM   #13
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i can see a problem by glancing at your fuel map.

try this, make all the cells around the one cell highlighted in that post 59%. see what that does.

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Old 11-01-2007, 04:00 PM   #14
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Yeah, the pulswidth is calculated by taking a weighted average of the cells that your current params fall into.

looking at your map and datalog, you're oscillating averages between the 6 cells that span the 26 - 34kpa and 500 - 1800rpm axes. when you're at the low rpm, you're averaging out the two 60's, the 59 and the 58 made by the 26, 24, and 500 - 900 bins. and then when it adjusts, you're averaging out another set of bins.

since they all have different values, it's hunting as it does those averages, even though it might not wander from that one cell, visually.

see if you can change them all to be the same values and see if you get better results.
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Old 11-04-2007, 10:48 AM   #15
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^^ What these last two posts said

And if 59 is too rich/lean, move all 6 cells up or down as a unit (all up to 60 or 61, or down to 58 or 57, whatever is needed). Shoot for 13.3:1 AFR at idle. That may not be perfectly attainable depending on the injectors you're running, the larger they are, the smaller your idle PW will be, meaning big steps will have to be taken when adjustments are made, and this will result in bigger steps in AFR....

Also-- if you want to take closed loop idle out of the picture entirely while you work this out, change 'When to use PWM Idle' to 'Warmup Only'. This will disable it's compensation for changes in engine load (such as AC activation) though.
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Old 11-06-2007, 08:01 PM   #16
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I changed all 6 cells to 60 and it did not seem to work. Even if I rev the engine to 2500rpm with no load it still goes up and down?? I have not tried turning off closed loop idle yet but will soon.

My idle is also high at around 1400 unless I have been driving for a long time. I know that it should stay at 1400 for like 30 seconds at startup but not for a long time?
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Old 11-06-2007, 08:46 PM   #17
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I don't have any help for Kyle, but...

cjernigan: My 2000 motor likes 20 degrees timing and stoich at idle.... I think your 13 degrees may be WAY too low. Unless you've got an offset in there due to the CAS. Also, be aware that reading timing on a 99+ motor is different from reading it on an older one. On the 99+, you want the two marks on the crank pulley at 0 and 10 when the timing is 10 degrees.

-Mike
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Old 11-06-2007, 09:26 PM   #18
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Quote:
Originally Posted by kylelind View Post
My idle is also high at around 1400 unless I have been driving for a long time. I know that it should stay at 1400 for like 30 seconds at startup but not for a long time?
Depending on settings. Your car should stay under high idle until it reaches somewhere around 80-160*. If it's really cold it could take quite a bit more than 30 seconds. All depends on your settings though.


Grippa- I'll look into it. Need to borrow a timing light again i suppose to double check my work. I'll let you know what i find.
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Old 11-06-2007, 09:28 PM   #19
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Quote:
Originally Posted by kylelind View Post
I changed all 6 cells to 60 and it did not seem to work. Even if I rev the engine to 2500rpm with no load it still goes up and down?? I have not tried turning off closed loop idle yet but will soon.

My idle is also high at around 1400 unless I have been driving for a long time. I know that it should stay at 1400 for like 30 seconds at startup but not for a long time?

What AFR did putting all 6 cells at 60 give you? Was it at or near 13.3:1? That's what I'd use as a target on these cars at idle with batch injection.

If you're idling at 1400 when it's fully warmed up to around 195-203 degreesF, and the idleDC is at the minimum idleDC setting when it's idling at that speed fully warm, then you've probably got a vacuum leak.
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Old 11-07-2007, 02:13 AM   #20
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what is the minimum idleDC?
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