Sr20det "weak" fluctuating idle. Haltech Sprint 500 ECU **VIDEO**

[KingSpence]

Alright, where should I start. It's a 1998 s13 blacktop sr20det. It's running a Haltech Sprint 500 ECU, so it's MAP sensored. I drove the car for about 100km before seeing the dyno, light driving, it idled perfect.

Dyno day came. The car starts and idles like a champ, we check timing and he starts the tune. After about 3-4 pulls on the dyno close to redline I see a cloud of steam/coolant from under my hood. We turn the car off, investigate. The coolant AN fitting's threads had somehow snapped loose, odd as fuck. Tightened up the fitting and fired up the car to continue the tune (I may have lost 50ml of coolant, tops). This is when the issue started, it was fine up until the car was shut off to fix the coolant.

Other than the idle and driving in slow gridlock traffic the car drives fine. AFRs are good through the range in every gear. We managed to put down good numbers on the dyno at the end of the day.

The car starts horribly on cold mornings (5c*), it chokes hard for the first ten seconds. I don't know whether is choking of air or overfueling. When it's warm, it lugs and chugs in traffic, anything under 2000rpm load or not cannot be held steady.

DOES THE IACV NEED TO SEE THE ECU TO FUNCTION? I ask this because my tuner said there was no DPO designated for an idle control, nor is there a wire tied into the DPO's on the harness. Does it seem IACV related?

Idle vacuum is 20psi.

I'm lost. Let brainstorm.


EtlZtdSP_2k

[jdm-specs]

the video is set to private dude....cant play it

[KingSpence]

the video is set to private dude....cant play it

Thanks, should be public now.

[zombiewolf513]

Mine was doing that before i got a retune and it was corrected, same setup but a ps1000 ecu. I think it may have had to do with iacv settings.

[mihellokeirt]

i think so,Mine was doing that before i got a retune and it was corrected, same setup but a ps1000 ecu.http://goo.gl/E0iu44

[derass]

Does the car idle like this when cold, at operating temp or hot? Or always? I see in the video you are at operating temp.

I have an S13 SR engine with PS1000. The engine would hunt for idle, with a lean AFR similar to your video. This would happen when the Intake Air Temp Sensor, installed in the Intake Manifold, would become heat soaked. I fixed the problem by adding fuel at higher IATs at vacuum in the Air Temp Fuel Correction Map.

Since the Sprint 500 does not have idle control, perhaps you could open the screw on the IACV further, or adjust the throttle plate open further with the stop screw, or both. This would likely hold a steady idle, then just verify/adjust your AFR at the new idle RPM.

[KingSpence]

This issue is the same whether the car is warm or cold. Also, until the thermostat opens, the car will lug under load. It's almost like the tune isn't compensating for the coolant below operating temperature.

[derass]

There is a Coolant Temperature Fuel Correction map in Haltech ECU Manager, however this is only used to enrich the AFRs when cold to bring the engine up to temp faster.

The lugging (hesitation) is likely caused by the Transient Throttle Enrichment settings/map. There are settings for both cold and warm conditions. This can be difficult to tune, mine is not perfect either, I have a slight hesitation at low RPM when cold.

If you haven't already, I would suggest you install ECU Manager on your PC and mess around. Haltech includes excellent documentation as to what everything does and how to adjust.

[KingSpence]

I backed the IACV screw out a few turns and it catches itself nicely when the clutch goes in and the rpms drop. It does however fluctuate between 900-1150 rpm, and the afr's tend to be leaner for the most part at idle. 16ish.

What can cause fluxuating idle on these engines? TPS? Coolant temp sensor?

I can also hear a quick "sucking" from under the hood somewhere (vague I know) when I blip the throttle from an idle.

[Def]

If you don't have an IACV you need to cleverly tune the fuel and ignition around your idle target to make it at least somewhat stable there. It lugging at low RPM is probably a really off timing setting - post up your timing map, doesn't sound like it'll look that good.


Blipping the throttle and hearing a sucking sound is normal - it's the TB.