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Discussion Starter #1
Been fighting this idle issue the last few days :cussing:. Current symptoms, during cold start, idle bounces between ~900rpm and ~1300rpm until it warms up. Once at operating temp the idle settles at around 850-900rpm. Once I am driving, the other problem is the car stalls often on deceleration. Say I'm coming to a stop sign/light and I push in clutch and brake to stop. Well, instead of the rpms dropping down to 850rpm and idle'ing, the rpms drop low, under 500rpm. Sometimes it stalls, sometimes it catches itself and gets back up to 850/900rpm idle. I can sometimes reproduce this just sitting here in my garage at idle, and blip the throttle, it will drop real low then come back up. I took some datalogs of this is anyone wants to look.

Relevant info:
d16y8 block/z6 head, low compression ~8.8:1, new engine, ~350 miles on it.
y8 intake mani with b16 tbody
40 micron fuel filter, fuel pressure set to 38psi with pinched off fpr vacuum
Hondata s300 loaded with stock p28 calibration (min idle 850rpm)

What we've done:
-fixed bad vacuum leak, don't think there are anymore vac' leaks cause I can plug the tbody up with my hand and engine will immediately stall
-clean out iacv with carb cleaner
-calibrated tps sensor per helms, ~.4v closed ~4.6v fully open I believe were the recommended.
-adjusted idle screw with iacv plug still connected. If I tried to set the idle like the helms says, by unplugging iacv connector, the car just stalls. I cannot keep an idle at all with the iacv plug disconnected.
-reset timing after that
-re-adjusted throttle cable
-swapped in my Hondata 4bar MAP sensor to try, same problems (I also uploaded new calibration to the hondata to reflect MAP sensor change).

A few other things I cannot remember off top of my head but basically anything related to idle problems.

Really not sure what is causing this. I have taken everything apart again and re-cleaned iacv and tbody one more time. I noticed my tbody plate sticks a little, so tried to fix that. The throttle stop screw was not touching the throttle link arm, so I screwed it in a bit more enough so the throttle plate wouldn't stick but still appeared fully closed. I have yet to test after these changes.

Hondata datalog:
http://jackmoves.com/~justin/warm-idle-decel-drops.s3d

Justin
 

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when your car warms up it will idle fine for the most part...when you turn on your lights or heater or wipers does the idle start to mess up? i have that problem now after replacing everything but the iacv(in the mail) and tps sensor. id bet the tps needs to be adjusted
 

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Discussion Starter #5
when your car warms up it will idle fine for the most part...when you turn on your lights or heater or wipers does the idle start to mess up? i have that problem now after replacing everything but the iacv(in the mail) and tps sensor. id bet the tps needs to be adjusted
Don't remember what it did if I turned lights/heater on. I had to put the TPS sensor on this tbody from my old engine, so it was originally out of wack. We tried to set it yesterday but the problems continued. So, I will reset it again here in a minute, almost have it all back together. Also, need to correct the timing, we messed that up yesterday too. :/

Justin
 

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Discussion Starter #6 (Edited)
:cussing::cussing::cussing::cussing:

Everything back together, same exact problems...wtf. Here is what I did this time:

-cleaned iacv again
-cleaned out tbody, idle adjust screw and hole
-set throttle stop screw
-new air filter (old one broke)
-verified resistances were correct on TPS sensor
-verified voltages were correct on ecu harness plug for TPS fully closed and fully open (.509v closed and 4.6v open)
-set timing in hondata using "set timing" feature (to 16 btdc) and then set dizzy timing to the center mark on the 3 mark set on pulley.
-set base idle successfully this time w/out iacv plugged in, it chugged along at 500/550rpm idle
-plugged iacv back in, checked timing again to make sure it was good

Let car sit for 20 mins to settle/cool a little. Start it up, idle bounces up and down and up and down between 600rpm and 1200rpm. After couple minutes it stabilizes at 850/900rpm according to hondata. Every other minute or so the idle will just drop to 200/300rpms and bog down, then idle back up normally, seemingly for no reason???

Blip throttle up to 3k rpms, the rpms come down and car nearly stalls, one time it DID stall doing this. Just sitting there in my garage.

Took it for a drive. Anytime I decelerate and push in clutch the car almost stalls, battery light flickers on/off and engine drops to 200/300rpm before catching back up to 800/900rpm. Other then this car is running strong and pulling hard (for stock low compression), I am at least happy about this.

That is where it sits...I'm friggin pissed. Oh, and turning on lights and heater full blast does nothing to idle, it stays normal @ 850/900rpm.

What could it be? These are remaining things I can think of to check/replace:
iacv
throttle body (one with stock positioned TPS)
fuel filter?? (I have one of those little "Trick" black filters, 40 micron metal cheese grater type filter)

Justin
 

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Discussion Starter #7
Bonus, found this info in hondata help:

7. Increase the engine speed to 2500 - 3000 rpm and abruptly let off the throttle. If the engine speed dips below 850 rpm, move the duty cycle slider to the right. If the engine speed hangs above 850rpm for some time, move the duty cycle slider to left.
Also, got a tip from local tuner to try checking the "invert purge valve" box in hondata settings as well. Supposed to help hot idle stall problems.

I'll try this in the morning and report back with, hopefully positive, results.

Help me :jesus: !

Justin
 

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Discussion Starter #8
FIXED! Thank you :jesus::jesus::jesus: :bravo:

Fix cold start idle bouncing = checked "invert purge valve" box in hondata under Misc. tab. Idle'd fine on cold start then.

Fix stall issue when bringing rpms up then letting off = adjusting iacv duty cycle in hondata to the right. Blip throttle up to 3k and it holds idle rpm when it comes down now just fine!

I still need to road test but this is much much better so far.

Justin
 
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