High Idle when engine is cold
 

I recently had my engine rebuilt and also installed a PFC. I am having trouble with high idle (a little over 2000 RPM) when the car is cold. It settles down to 900 when the car reaches it's operating temp (around 80 deg C). It just drops instantly when operating temp is reached, it isn't gradual. I turned the idle screw almost all the way closed per the instructions on the forum and gone through the learning cycle multiple times. I notice that the car will start at low/normal idle when I start it up, but will raise a few seconds later. As long as the car is warm, though, things seem to work fine.

I have another FD with a PFC that doesn't have this problem, so I know this is not normal. Is there anything I should be looking for? Could one of the sensors be bad? Is there a setting I might check on the PFC? The only difference between my 2 cars is that the one with the problem has the AWS plugged. My other car has it plumbed. They both have upgraded IC's, Intakes, Exhausts (Downpipes, Hi-Flow Cat, catback) and the PFC. Could plugging the AWS have this effect?

Thanks,

Jim

You need to read up on and understand the ISC, AWS, and hot wax rod which are the three mechanical systems affecting startup.

Most likely AWS which can be eliminated, and the HWR which may need adjusting or replacement.

That's totally normal. The thermowax on the throttle body holds the TB open when the car is cold for a higher idle which slowly comes down as the car warms up. You can adjust it a bit to bring the idle down. The system can also be eliminated as well. I don't mind it personally.

Dale

Starting the car with the clutch in and the shifter in first gear, will bypass the AWS(Accelerated Warming System).

Thanks...I already do that. Putting the shifter in 1st gear when I start it has become second nature to me, even though the AWS is already disabled. I suspect the high idle is either due to the wax rod or the "idle speed vs. water temp" settings on the PFC.

Are the idle speed vs. water temp settings on the PFC the same ones that you can adjust on the commander (fuel correction settings at various temps) or are there specific idle speed settings that can't be accessed without datalogit? I thought people generally didn't mess with the base map's fuel vs temp correction settings.

While I know this isn't a serious problem and I could just try to ingore it, the car is really loud when it idles at 2000 RPM. I guess maybe I could invest in a quieter exhaust...

- J

Try to lower a bit the settings in the "idle speed vs. water temp" screen but not too much or the engine will stall.I had the same symptoms with you,and after lowering the values in the first row(low load),my idle went to 1500 rpm instead of 2000.After 72C the idle goes to a solid 800rpm(ISC and HWR are still installed,AWS is unplugged).

There is no idle speed vs water temp. Datalogit only has INJ vs Water Temp

Bump for an old thread. After having my car tuned here in Portland, OR I have this EXACT same problem and I'm tired of being told this is completely normal, because it doesn't feel normal.

The cold idle is at 2000 RPM even with the car in first gear to avoid the AWS. If I drive the car slowly in first (10mph) and shift to second when the car is cold the RPM jumps up for the brief time in neutral and then goes back down as I shift into second.

Any advice appreciated,
Regards.
Justin Wade

I have the same high idle with the pfc on my FD, my previous fds with pfcs did not do this. What i did was the following:

"Try to lower a bit the settings in the "idle speed vs. water temp" screen but not too much or the engine will stall.I had the same symptoms with you,and after lowering the values in the first row(low load),my idle went to 1500 rpm instead of 2000.After 72C the idle goes to a solid 800rpm(ISC and HWR are still installed,AWS is unplugged)."

I lower the values for both high and low load for the 10C and 30C, the idle went from 2200 to 2000 when cold. Unpluging the AWS did not effect idle at all.

Then i adjusted the thermo wax rod when the engine was running when i first started it. The adjustment is directly ontop of the oil filter. On my car i had to turn in the screw all the way in. You want to tighten the screw to lower the cold fast idle. You will need a short screwdriver, i used a screw driver bit.

No my fast idle is about 1500k and slowlys goes to 800.

I live in San Francisco, so its never too cold. My adjustments have not had any bad effects.

I got my PFC and had installed and working fine for several months on my original motor. Then my motor blew up and I had it rebuilt. I experienced this wierd 2000 rpm high idle condition with the PFC, but not with the stock ecu, after the rebuild. The idle would NOT always return to normal, even after full warm up. With my exhaust mods, 2000 rpm idle in front of my house early in the morning was intolerable to the wife!!

Using Chuck's tuning notes, we adjusted my throttle cable, TAS (throttle adjusting screw), AAS (air adjusting screw), dashpot, and TPS (throttle position sensor). We used the stock ecu for all this except the TPS part which requires you to read the two sensor voltages to adjust - the PFC Commander sensor page lets you monitor this nicely. For now we unplugged the AWS (accelerated warmup system) electrical connector to disable it, but plan to remove it completely and install a block off plate. Chuck says the PFC does not control this anyway, so it is useless with a PFC installed. After all this, we reset the PFC and let it learn ISC (idle speed control). Idle is very good now.

Chuck includes info on the wax rod setup too, but since we bipassed the throttle body warmup circuit on my car, the wax rod would probably not warm up fast enough for me. So for now, we adjusted the wax rod completely out of the way - this results in the fast idle cam not engaging at all. I live in the San Francisco bay area where it rarely gets below 40 degrees F. Now when I fire it up, it immediately drops down to 750 idle. The wife likes it!! Course I have to let it sit there idling for longer to reach appropriate driving temperature, but with down pipe, free fow cat and cat back, it is worth it to avoid the early morning startup fast idle.

I recommend Chuck's PFC / Datalogit tuning notes, he has a lot of good info in there. Contact him here: cewrx7r1@yahoo.com

I also recommend Chuck's notes.

It sounds like all of the people above had issues with the throttle body settings. I was having similar issues as well and after going through the various mechanical settings as laid out in Chuck's notes, I got my car idling *perfectly*. :D

They are pretty inexpensive considering the knowledge he shares in those docs. Best money I've ever spent on my car.