stalling issue w/new build
Apr 13, 2008, 11:47 AM
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stalling issue w/new build
I have a stalling issue with my new build. I think it's most likey due to the valvetrain...I have GSC S2 cams with 1mm oversize valves. Also, I have a Buschur intake. For sure those 3 things have to due with idle...and I am still on the stock ECU. The injectors are 750cc but are dialed in already. I've searched and found some threads but they didn't help at all. I've tried advancing the timing, increasing the RPMs but it just doesn't work. I found a MAF scaling for an HKS RS intake and put that in hoping it would at least help just a little bit but NOPE. Any help would be appreciated. It runs really rich before it stalls out. On cold starts, it stays idling until it fully warms up, then starts to surge the RPM up and down until it finally dies. Again, any help and input would be greatly appreciated.
Apr 13, 2008, 05:54 PM
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When it's cold, it idles just fine. It'll die when it warms up. I can still drive it but whenever I come to a stop and in neutral, it stalls. Sometimes it can idle ok until I touch the gas pedal, then it stalls.
I have tried advancing timing in the 10-30 load cells to about 12 and tried all the way to 22. Vacuum readins are around 9-11 in hg.
Because in cold idle, it goes into open loop fuel control and idles fine, I raised the min temp for the ecu to go into closed loop to 120 degrees celsius. That makes it never go into closed loop fuel control...and it still doesn't want to stay running. What next?
I have tried advancing timing in the 10-30 load cells to about 12 and tried all the way to 22. Vacuum readins are around 9-11 in hg.
Because in cold idle, it goes into open loop fuel control and idles fine, I raised the min temp for the ecu to go into closed loop to 120 degrees celsius. That makes it never go into closed loop fuel control...and it still doesn't want to stay running. What next?
Apr 13, 2008, 06:13 PM
#5
Maybe start tuning the ISC tables. You might need higher values to maintain the idle properly and I think, IIRC, that one or more of those tables are based on coolant temp. So, as the car warms up, the values drop. You can probably concentrate on the higher coolant temp values.
Apr 13, 2008, 06:27 PM
#7
I think there are a few good threads in here. If you search for idle stepper or ISCV you should find some good threads.
The ISCV and idle stepper tables contol the idle speed control valve. The ECU uses the values in these tables to know what position to set the ISC at in order to maintain a certain idle RPM. If the value is too low, then the idle drops too far, like you are experiencing. The ECU will then try to increase the steps to catch and raise the idle, but if the ISC values are too far off, then it's difficult for the ECU to control the idle.
I think there are better explanations than I can give in some of the other threads, but I would suggest to start with these tables to try to solve your issue. You can also log ISC steps via EvoScan or any of the loggers to see what the ECU is trying to do in different situations to get an idea of where the values should be set.
Eric
The ISCV and idle stepper tables contol the idle speed control valve. The ECU uses the values in these tables to know what position to set the ISC at in order to maintain a certain idle RPM. If the value is too low, then the idle drops too far, like you are experiencing. The ECU will then try to increase the steps to catch and raise the idle, but if the ISC values are too far off, then it's difficult for the ECU to control the idle.
I think there are better explanations than I can give in some of the other threads, but I would suggest to start with these tables to try to solve your issue. You can also log ISC steps via EvoScan or any of the loggers to see what the ECU is trying to do in different situations to get an idea of where the values should be set.
Eric
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Apr 13, 2008, 06:39 PM
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Oh, AFR's are in the 11's and 10's when it starts to bog down. The AEM can only read down to 10:1 so you can say the car runs even richer and then stalls out...even in open loop idle. It doesn't even look close to my fuel maps but the timing is close to the maps.
Apr 13, 2008, 09:35 PM
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Many things you have to play with before you dial it in for your situation:
1: accel enrichiment -> this thing is often gets ignored but I found playing with this sometimes gives the solution for all.
2: injector latency -> very important to set it where it should be. Usually, higher value than stock works good with big injectors.
3: fuel trim -> It better be +- 5% range
4: Maf scailing -> big cams and all sometimes fool Maf readings at low load. Also, this could be the only way to have the perferct fuel trim with big injectors and big cams.
5:ISCV -> stock settings are usually fine but adjust it for your taste
1: accel enrichiment -> this thing is often gets ignored but I found playing with this sometimes gives the solution for all.
2: injector latency -> very important to set it where it should be. Usually, higher value than stock works good with big injectors.
3: fuel trim -> It better be +- 5% range
4: Maf scailing -> big cams and all sometimes fool Maf readings at low load. Also, this could be the only way to have the perferct fuel trim with big injectors and big cams.
5:ISCV -> stock settings are usually fine but adjust it for your taste
Apr 13, 2008, 10:05 PM
#12
12-22* is way high for idle IMO. The higher you advance the timing at idle with bgger cams, the harder it seems to be for the ECU to 'catch' the car from stalling out during deceleration. I usually get the best results between 5-9* at idle usually.
You dont want the car to NEVER go into closed loop (by doing your coolant temp mod), you just want to bypass it temporarily at low loads until you find the cause. To do this, go into your open loop load tables and set the lowest rpm ranges to a load value of 20 for now. You dont want to be cruising down the highway using your open loop tables, god knows they're probably all over the place with your mods.
So when it goes into closed loop, it should read how RICh you are running and literally PEG the front O2 sensor signal at .9volts. This should tell the ECU to pull as much fuel as possible. I'd guess your your LOW fuel trims are pegged in the negative range but its still not enough to keep the car from flooding itself with fuel. Definitely check your fuel trims, check that the Front O2 sensor is indeed going into closed loop and what its readings are. Then adjust your Injector Scaling is needed. What is your injector scaling set to now?
You dont want the car to NEVER go into closed loop (by doing your coolant temp mod), you just want to bypass it temporarily at low loads until you find the cause. To do this, go into your open loop load tables and set the lowest rpm ranges to a load value of 20 for now. You dont want to be cruising down the highway using your open loop tables, god knows they're probably all over the place with your mods.
So when it goes into closed loop, it should read how RICh you are running and literally PEG the front O2 sensor signal at .9volts. This should tell the ECU to pull as much fuel as possible. I'd guess your your LOW fuel trims are pegged in the negative range but its still not enough to keep the car from flooding itself with fuel. Definitely check your fuel trims, check that the Front O2 sensor is indeed going into closed loop and what its readings are. Then adjust your Injector Scaling is needed. What is your injector scaling set to now?
Apr 14, 2008, 06:31 AM
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Ok so now, I got the idle almost perfect...but I started to drive it and then the ecu started to dump a whole lot of fuel in. My AEM wouldn't read below 10:1 so it stayed at 10 and I'm pretty sure the car was running richer than that. I couldn't even get up past 1500 rpms because it was too rich. Now I gotta find out what I did wrong.
Apr 14, 2008, 06:39 AM
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I changed the last 3 slots of the ISCV settings for A/C neutral, A/C drive, no A/C neutral to 70. I turned closed loop back on. I changed injector scaling to 835. I also quickly put in a temporary maf scaling of an HKS RS intake on there. This brought my fuel trims to about 7% on a 0 scale (scan tool)...so it was pretty close. I got my idle almost perfect. I drove it and then it started dumping a whole lotta fuel in. Now when I go to start it, it won't even idle with all that fuel being dumped in. Can anyone tell me why? What did I do wrong?