Question regarding high/fluctuating idle when cold

Hybrid96EK · Post by **Hybrid96EK** » Wed Sep 09, 2009 12:01 am

B18B1, stock other then a 3 bar map sensor. Correct map selected (Xenocron 3 bar). Everything seems to work fine except a problem I haven't been able to solve. When the car is cold the idle is VERY high... 1,800rpms or so. I have noticed what sounds like the IACV working extra hard durring this time as the intake note is changed at idle. The idle will sometimes bounce on its own up and down slowly, sometimes settling around the target cold idle of 1,200rpms. I have tried everything I can think of but I can't seem to get the idle down to a \"normal\" level... Any ideas? Also, when the temps were very warm outside... 100+, after driving the car a good distance it would no longer start. Holding the throttle all the way open would get the car started again. It would take a few seconds of rough running before things cleared up and seemed normal. Everything worked fine on the stock OBD2 LS ecu, if that helps.

Post by **Gaskleppie** » Wed Sep 09, 2009 1:12 am

What rpm runs the car at idle with the iacv unplugged? It should be around 500rpm, if it does not run about 500rpm's take care it does do that!

Hybrid96EK · Post by **Hybrid96EK** » Wed Sep 09, 2009 9:43 am

Gaskleppie wrote:What rpm runs the car at idle with the iacv unplugged? It should be around 500rpm, if it does not run about 500rpm's take care it does do that!

IACV disconnected the RPMS stabilize. I didn't check what RPM it was at since the car wasn't up to normal operating temperature. I am assuming it needs to be in order to do this check, no?

marshall.hagen · Post by **marshall.hagen** » Wed Sep 09, 2009 10:38 am

Did you adjust the Moving Idle Correction table and ECT vs Idle Speed table in addition to the Target Idle entry? Without touching all three, it is likely that your idle will not be completely tuned.

Post by **Gaskleppie** » Wed Sep 09, 2009 1:17 pm

If the engine was cold and you pulled the plug from the eacv and the engine didnt stop running, I guess the base idle is too high. Take care it runs about 500rpm when hot with the eacv unplugged. If its higher than 600rpm, lower it with the idle screw!

Post by **calvin** » Wed Sep 09, 2009 2:02 pm

that it go from there

Hybrid96EK · Post by **Hybrid96EK** » Thu Sep 10, 2009 12:38 am

Car warm, IACV unplugged = 500rpms like it should. I have adjusted the other two items as well, not just the \"Target idle\". I didn't seem to have these issues with my single cam setup. Idle was solid as a rock.. Something else I noticed that seems odd. I re-enabled the stock O2 in order to seek mileage. The car is now periodically bucking under light/moderate throttle like its running very very lean. Almost like the fuel cut routine is engagging. Anything -9-0 on the vac gauge works perfect... but more vac then -9 and it bucks and jerks. I would think it was simply the fuel cut setting for the map sensor, but it won't always do it. In fact, on the ride home tonight it worked perfectly after about 20 miles of driving. Strangest thing. I started thinking it was temperature related, but I had the problem this morning when it was 50 outside also...

marshall.hagen · Post by **marshall.hagen** » Thu Sep 10, 2009 1:12 am

Could be a throttle position issue. If under high vacuum (low throttle position) it could be prematurely engaging fuel-cut (deccel injector cut). If the TPS was not scaled correctly, this could lend itself to idle issues as well. Just an idea.

98vtec · Post by **98vtec** » Thu Sep 10, 2009 1:04 pm

Hybrid96EK wrote:Car warm, IACV unplugged = 500rpms like it should. I have adjusted the other two items as well, not just the "Target idle". I didn't seem to have these issues with my single cam setup. Idle was solid as a rock.. Something else I noticed that seems odd. I re-enabled the stock O2 in order to seek mileage. The car is now periodically bucking under light/moderate throttle like its running very very lean. Almost like the fuel cut routine is engagging. Anything -9-0 on the vac gauge works perfect... but more vac then -9 and it bucks and jerks. I would think it was simply the fuel cut setting for the map sensor, but it won't always do it. In fact, on the ride home tonight it worked perfectly after about 20 miles of driving. Strangest thing. I started thinking it was temperature related, but I had the problem this morning when it was 50 outside also...

if your closed loop parameters are too lean, the o2 sensor will freak out.

Bindegal · Post by **Bindegal** » Fri Sep 11, 2009 6:32 pm

Is there an FITV (mechanical fast-idle thermo valve) on that throttle body? I have seen very similar problems on a couple of cars where the FITV was broken. This can happen if the IACV is broken, too. If FITV or IACV is opened too much, RPMs at 0% TPS will be too high, alitnd the ECU will fuelcut, causing RPM to go up/down. A broken FITV will/can cause a number of very weird problems that can be hard to diagnose, as we somehow usually start with the complicated things first

/Allan

Hybrid96EK · Post by **Hybrid96EK** » Sun Sep 13, 2009 2:15 am

Bindegal wrote:Is there an FITV (mechanical fast-idle thermo valve) on that throttle body? I have seen very similar problems on a couple of cars where the FITV was broken. This can happen if the IACV is broken, too. If FITV or IACV is opened too much, RPMs at 0% TPS will be too high, alitnd the ECU will fuelcut, causing RPM to go up/down. A broken FITV will/can cause a number of very weird problems that can be hard to diagnose, as we somehow usually start with the complicated things first /Allan

There is no FITV on this engine. It is an OBD2 engine, they aren't equipped with FITV's... at least in the U.S.... anyways, here is a new find.. I used the calibrate TPS feature and it changed nothing. The voltages remained the same and the idle was once again very very high at cold.. I've noticed in the last few days that now it pops twice while idling high and when it does, it goes down about 500rpms rapidly, then back to 2,100rpms. Very strange. I made a completely new basemap and used the stock P75 B18A rom and fired up the car and everything worked perfect. Idle was like it should have been. If I add my slightly revised (widebanded) fuel maps with 0 other changes, its back to the same old crap.

Hybrid96EK · Post by **Hybrid96EK** » Mon Sep 14, 2009 11:56 pm

Just an update. It seems I solved the whole O2 issue. I first tried changing the closedloop settings to only allow it to pull a max of -10... It was -30. That seems to have mostly fixed the issue. I then noticed while driving the O2 showing readings of like 10.0:1.. Strange. So anyways, I changed the O2 with a known good one. The readings seems more correct now... more like 14.7:1 at idle, etc. Before they were kind of random. I also adjusted the fuel cut setting and lowered the mbar to 200. Nice and smooth now with no jerking coming on/off the throttle. I'll find out in the morning if the cold idle is still hosed, but so far things seem good.