Idle Quality
10-08-2009, 03:58 PM
#1
Registered User
Thread Starter
Join Date: Apr 2009
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
Idle Quality
Problem: Erratic (cyclical) Idle and Stalling When Cold
Car:
2003 Honda S2000 315whp
Comptech SC with AC
7.0psi (To be Confirmed)
AEM EMS w/ UEGO Gage
Comptech Header
RSR Exhaust Magic Exhaust
K&N Filter (No Airbox)
AEM 3.5bar MAP Sensor (T'd In to small vacuum line, OEM MAP Remaining)
Oil Catch Can
Car Tuned by AEM on street and dyno'd later for numbers. (Per Prev Owner)
Fuel Pressure Gage Installed in Fuel Rail
Siemens Deka 630cc injectos. 12 ohm
VAFC For Monitoring
I recently acquired a Comptech S/C'd S2000 earlier this summer. Currently, it idles fairly well but will cycle between 700 and 1100 rpms at startup. During this time, the UEGO shows the engine cycling between rich and lean. It will also dip down to around 500rpm and run rich until the computer leans it back out and the rpms rise. This condition was present before I acquired it. Also, if driving while cold, it is at risk to stall when rpms drop quickly during coasting. The amplitude of the rpm cycling decreases when it warms up to ~800 +/- 75. or 900 +/- 75 depending on how it feels that day. Fuel Pressure at Idle is ~45psi
I did fix one vacuum leak on the intake manifold and that helped the situation but didn't completely fix the problem. The leak was on the intake manifold at a port (PCV?) that is capped off. The hose had split.
Once warm, the surging persists a little bit but not as badly. When applying throttle slowly in neutral, the idle will surge up until around 1500 rpms where it immediately smooths out. (No more IAC activity??) The car generallly runs rich with AF ratios around 11.5-12.5 during WOT before VTEC and 10.0 to 10.5 during VTEC. Seems awfully rich to me.
AF raitio is about 14.5 during crusing.
I've taken a few logs with my laptop while idling and driving. The O2 sensor output seems very different from what the UEGO is reading. Also, the MAP is reading 1.96 volts at peak during WOT runs which equate to ~4psi. I think it may currently only be running stock boost. Or the vacuum from the engine is causing the pressure at the connected location to be lower than the pressure closer to the throttle body, AC, SC.)
Winter time is coming. I'm planning to evaluate.
Vacuum Leaks
Spark Plugs
A/F & O2 Sensor
IAC Valve, Thb valve cleanliness.
Compare AEM EMS MAPS loaded to Base Maps
Can anyone provide some guidance?
Car:
2003 Honda S2000 315whp
Comptech SC with AC
7.0psi (To be Confirmed)
AEM EMS w/ UEGO Gage
Comptech Header
RSR Exhaust Magic Exhaust
K&N Filter (No Airbox)
AEM 3.5bar MAP Sensor (T'd In to small vacuum line, OEM MAP Remaining)
Oil Catch Can
Car Tuned by AEM on street and dyno'd later for numbers. (Per Prev Owner)
Fuel Pressure Gage Installed in Fuel Rail
Siemens Deka 630cc injectos. 12 ohm
VAFC For Monitoring
I recently acquired a Comptech S/C'd S2000 earlier this summer. Currently, it idles fairly well but will cycle between 700 and 1100 rpms at startup. During this time, the UEGO shows the engine cycling between rich and lean. It will also dip down to around 500rpm and run rich until the computer leans it back out and the rpms rise. This condition was present before I acquired it. Also, if driving while cold, it is at risk to stall when rpms drop quickly during coasting. The amplitude of the rpm cycling decreases when it warms up to ~800 +/- 75. or 900 +/- 75 depending on how it feels that day. Fuel Pressure at Idle is ~45psi
I did fix one vacuum leak on the intake manifold and that helped the situation but didn't completely fix the problem. The leak was on the intake manifold at a port (PCV?) that is capped off. The hose had split.
Once warm, the surging persists a little bit but not as badly. When applying throttle slowly in neutral, the idle will surge up until around 1500 rpms where it immediately smooths out. (No more IAC activity??) The car generallly runs rich with AF ratios around 11.5-12.5 during WOT before VTEC and 10.0 to 10.5 during VTEC. Seems awfully rich to me.
AF raitio is about 14.5 during crusing. I've taken a few logs with my laptop while idling and driving. The O2 sensor output seems very different from what the UEGO is reading. Also, the MAP is reading 1.96 volts at peak during WOT runs which equate to ~4psi. I think it may currently only be running stock boost. Or the vacuum from the engine is causing the pressure at the connected location to be lower than the pressure closer to the throttle body, AC, SC.)
Winter time is coming. I'm planning to evaluate.
Vacuum Leaks
Spark Plugs
A/F & O2 Sensor
IAC Valve, Thb valve cleanliness.
Compare AEM EMS MAPS loaded to Base Maps
Can anyone provide some guidance?
10-08-2009, 04:17 PM
#2
10-08-2009, 05:18 PM
#3
I don't think the MAP whack is necessarily the solution.
AEM EMS can be tricky in changing weather for the cold start tables.
That being said, why do you have the OEM and the 3-bar MAP sensors both attached?!
AEM EMS can be tricky in changing weather for the cold start tables.
That being said, why do you have the OEM and the 3-bar MAP sensors both attached?!
10-09-2009, 06:59 AM
#5
The map sensors were also my 
moment.
Your current issue aside, 14.5 is good at cruising and for idle, but your WOT is super rich. I'd prefer to see 12 -12.5 top end at your boost level and kit, and a little leaner yet pre vtec couldnt hurt. Your not even producing enough boost to change the stock timing map on the car yet so your no where near needing to run 10.5afr anywhere in your rpm range for "safety". Classic paranoid tuner for you at the expense of your power and fuel economy, possibly even fuel washing your motor given the right conditions, 10afr is rich enough to cause deposits and possible pre ignition which is not good either.
Not that I’m suggesting you do this, but knowing the Comptech kit rather well and the fact that you have a wideband, id say you could throw on the next size pulley without a tune and have your afrs sitting much closer to where they should be, I would experiment with that myself, but I’m also very accustomed to street tuning my car and know what to expect.
moment. Your current issue aside, 14.5 is good at cruising and for idle, but your WOT is super rich. I'd prefer to see 12 -12.5 top end at your boost level and kit, and a little leaner yet pre vtec couldnt hurt. Your not even producing enough boost to change the stock timing map on the car yet so your no where near needing to run 10.5afr anywhere in your rpm range for "safety". Classic paranoid tuner for you at the expense of your power and fuel economy, possibly even fuel washing your motor given the right conditions, 10afr is rich enough to cause deposits and possible pre ignition which is not good either.
Not that I’m suggesting you do this, but knowing the Comptech kit rather well and the fact that you have a wideband, id say you could throw on the next size pulley without a tune and have your afrs sitting much closer to where they should be, I would experiment with that myself, but I’m also very accustomed to street tuning my car and know what to expect.
10-09-2009, 07:12 AM
#6
few things.
1st, its in possible to use both map sensors with aem. you choose one or the other in aem software. most likely, your using the aem 35 bar. i mean, who installs it and doesnt recalc the map for it.
2. your problems are very similar to what i was having. aem needs to be calibrated for coldstrart. there are many trims, settings, what nots to tweak to get a real nice cold start and idle. i spent many moons getting mine friggin perfect. and even at its current point, i dont start driving the car until i hit 140 water temps.
aem settings allow for enrichement, of course, and o2 feedback doesnt start until a set water temp. mine is 140. your idle jumping up and down can be a few things. iac bad. clean it and see if things change. also, there are ignition and fuel trims for idle offset. if your idle gets to far +/- then iac valve will open or close to help, and trim tables will start to add/subratct either fuel or timing. if it takes/adds to much, then your too far off the other way and it compensates the opposite, and you get this bouncing effect. blipping the throttle sometimes fixes it.
on top of this, you have o2 feedback. whcih is trimming fuel at idle. if it trims to much, idle changes then idle feedback tries to fix it. well you get the point.
anywho, first things first. turn off idle feedback. tune fuel at idle. make sure o2 feedback is trimming as little as possible. also make sure timing at idle is 5 degrees. then turn on idle feedback and adjust iac on idle setttings. also adjust trims fuel/ignition for timing.
you should be able to get it normal. will just take time
1st, its in possible to use both map sensors with aem. you choose one or the other in aem software. most likely, your using the aem 35 bar. i mean, who installs it and doesnt recalc the map for it.
2. your problems are very similar to what i was having. aem needs to be calibrated for coldstrart. there are many trims, settings, what nots to tweak to get a real nice cold start and idle. i spent many moons getting mine friggin perfect. and even at its current point, i dont start driving the car until i hit 140 water temps.
aem settings allow for enrichement, of course, and o2 feedback doesnt start until a set water temp. mine is 140. your idle jumping up and down can be a few things. iac bad. clean it and see if things change. also, there are ignition and fuel trims for idle offset. if your idle gets to far +/- then iac valve will open or close to help, and trim tables will start to add/subratct either fuel or timing. if it takes/adds to much, then your too far off the other way and it compensates the opposite, and you get this bouncing effect. blipping the throttle sometimes fixes it.
on top of this, you have o2 feedback. whcih is trimming fuel at idle. if it trims to much, idle changes then idle feedback tries to fix it. well you get the point.
anywho, first things first. turn off idle feedback. tune fuel at idle. make sure o2 feedback is trimming as little as possible. also make sure timing at idle is 5 degrees. then turn on idle feedback and adjust iac on idle setttings. also adjust trims fuel/ignition for timing.
you should be able to get it normal. will just take time
10-09-2009, 09:08 AM
#7
^^^ There is some experience talking for you, always refreshing to see some insight and good suggestions to a problem on s2ki 
After you resolve this, then deal with your rich open loop afr's
After you resolve this, then deal with your rich open loop afr's
Trending Topics
10-10-2009, 05:34 AM
#8
Registered User
Thread Starter
Join Date: Apr 2009
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
So the story on the map sensor is that the factory MAP is still physically there but not connected. The wire harness coupler that would normally connect there is now connected to a MAP sensor (cylinder style) that is teed into a small vacuum line shared with the Intake manifold and the fuel rail damper regulator??).
Active AEM MAP sensor P/N is: 30-3130-50
http://www.aempower.com/ViewProduct.aspx?ProductID=462
I'll do a MAP whack and IAC Valve cleaning to start.
AFter that, I'll work on setting the idle as camuman said.
Active AEM MAP sensor P/N is: 30-3130-50
http://www.aempower.com/ViewProduct.aspx?ProductID=462
I'll do a MAP whack and IAC Valve cleaning to start.
AFter that, I'll work on setting the idle as camuman said.
10-10-2009, 06:56 PM
#9
Registered User
Thread Starter
Join Date: Apr 2009
Posts: 50
Likes: 0
Received 0 Likes
on
0 Posts
Interesting results:
MAP Whack and IAC cleaning showed no improvement. (But it was surging so improvement is difficult to gage)
I started to tune the idle. The idle target was set at 825. However, there was no fuel trimming/richening or ignition advancing/retarding vs. idle rpm error programmed in. Therefore, it was as if it had no control feedback system in place. (Basemap maybe?) In any case, I had it retard timing when it was over target and advance it if it falls below idle target. It now idles smoothly at 850 rpms with an afr of 13.5 to one. I may play around with the fuel control but it should be ok. I also found that the warmup enrichment was still active up until 210 deg F for coolant temperature. I cut it so no enrichment was present after 180. Should I turn the O2 feedback back on?
Afterwards, I compared my MAPs to a 9psi vortech kit running larger injectors and found them to be adding far less less fuel (even with the bigger injectors and running more advanced timing all around.) I think I may have a basemap . I'm wondering if it'll be easier to retune it to be more lean or try to test out my 10psi pulley carefully and see where the afrs fall. Also, my understanding is that WOT runs in open loop mode so does that mean it will ignore the MAP sensor? I'll admit I don't quite fully understand where the MAP is coming into play. I can see where the MAP characteristics are loaded into the setup in the EMS. But I'm not seeing any pressure vs. fuel tables or anything like that. Please forgive my ignorance. 
MAP Whack and IAC cleaning showed no improvement. (But it was surging so improvement is difficult to gage)
I started to tune the idle. The idle target was set at 825. However, there was no fuel trimming/richening or ignition advancing/retarding vs. idle rpm error programmed in. Therefore, it was as if it had no control feedback system in place. (Basemap maybe?) In any case, I had it retard timing when it was over target and advance it if it falls below idle target. It now idles smoothly at 850 rpms with an afr of 13.5 to one. I may play around with the fuel control but it should be ok. I also found that the warmup enrichment was still active up until 210 deg F for coolant temperature. I cut it so no enrichment was present after 180. Should I turn the O2 feedback back on?
Afterwards, I compared my MAPs to a 9psi vortech kit running larger injectors and found them to be adding far less less fuel (even with the bigger injectors and running more advanced timing all around.) I think I may have a basemap
. I'm wondering if it'll be easier to retune it to be more lean or try to test out my 10psi pulley carefully and see where the afrs fall. Also, my understanding is that WOT runs in open loop mode so does that mean it will ignore the MAP sensor? I'll admit I don't quite fully understand where the MAP is coming into play. I can see where the MAP characteristics are loaded into the setup in the EMS. But I'm not seeing any pressure vs. fuel tables or anything like that. Please forgive my ignorance.