Speed density bug
Jul 16, 2013, 03:46 PM
#1
Speed density odd issue
Here is what happen:
I'm cruising full time open loop. Car is tuned for about 15.5 AFR.
All goes normal 99% of the time and suddenly car starts to run really rich. It cruises rich and it idles pig rich (low 10s). WOT isn't any richer. I go to WOT a few time and the issue disappears.
The more and more the car runs richer. IT was 1% of the time at beginning but now it's more 50% of the time. What an odd issue.
Theories for testing:
Update: Tonight I opened the synapse BOV. Altough it looked like new and not dry at all, I still applied synthetic grease and retried the car. Same issue.
Update: no boost leak. I will wait the new wideband o2 sensor before messsing with fuel rail pressure and injectors
Update: The issue doesn't disappear anymore, it runs rich all the time now
Update: Tonight I filled the fuel tank and instead of running low 10s AFR, I'm running much more close to 15.5AFR. But you can see the issue is still there, only less drastic. It may be overheating fuel pump, but I don't think it would cause higher fuel pressure.
Update: August 1st, installed new wbo2 sensor. August 7th, no issue yet
Update: Issue started back by august 20. By Boosted tuning experience with sound deadened trunks, fuel temps can vary a lot more. I started to hold a minimum of 1/2 tank of fuel in the car and issue hasn't came back since then.
Update: Issue has started again last week, cold outside temperature. Ordered a GM MAT sensor and bung, I'll retune the car for it and see how it goes
The problem isn't really there in high load because fuel variance from MAT isn't high enough to see a drastic AFR change. The problem is more accentued from running open loop idle and cruising because actual IDC is very low, so temp correction shift it a lot more than when IDC are high on boost.
Any ideas?
I'm cruising full time open loop. Car is tuned for about 15.5 AFR.
All goes normal 99% of the time and suddenly car starts to run really rich. It cruises rich and it idles pig rich (low 10s). WOT isn't any richer. I go to WOT a few time and the issue disappears.
The more and more the car runs richer. IT was 1% of the time at beginning but now it's more 50% of the time. What an odd issue.
Theories for testing:
- Stuck open BOV,Boost leak
- Fuel pressure raise (bad FPR)
- bad wideband O2 sensor
- Injector leaking into combustion chamber
- Fuel temperature variation, has to convert to GM MAT
Update: Tonight I opened the synapse BOV. Altough it looked like new and not dry at all, I still applied synthetic grease and retried the car. Same issue.
Update: no boost leak. I will wait the new wideband o2 sensor before messsing with fuel rail pressure and injectors
Update: The issue doesn't disappear anymore, it runs rich all the time now
Update: Tonight I filled the fuel tank and instead of running low 10s AFR, I'm running much more close to 15.5AFR. But you can see the issue is still there, only less drastic. It may be overheating fuel pump, but I don't think it would cause higher fuel pressure.
Update: August 1st, installed new wbo2 sensor. August 7th, no issue yet
Update: Issue started back by august 20. By Boosted tuning experience with sound deadened trunks, fuel temps can vary a lot more. I started to hold a minimum of 1/2 tank of fuel in the car and issue hasn't came back since then.
Update: Issue has started again last week, cold outside temperature. Ordered a GM MAT sensor and bung, I'll retune the car for it and see how it goes
The problem isn't really there in high load because fuel variance from MAT isn't high enough to see a drastic AFR change. The problem is more accentued from running open loop idle and cruising because actual IDC is very low, so temp correction shift it a lot more than when IDC are high on boost.
Any ideas?
Last edited by domyz; Sep 11, 2013 at 06:22 AM.
Jul 16, 2013, 06:56 PM
#2
Am I the only one to have this bug. I haven't logged it yet, but here is what happen:
I'm cruising full time open loop. Car is tuned for about 15.5 AFR.
All goes normal 99% of the time and suddenly car starts to run really rich. It cruises rich and it idles pig rich (low 10s). WOT isn't any richer. I go to WOT a few time and the issue disappears.
My theory for now would be a stuck open BOV, I will get into that in the next days. If it's not the BOV, I honestly have no other ideas except a SD ROM bug...
I'm cruising full time open loop. Car is tuned for about 15.5 AFR.
All goes normal 99% of the time and suddenly car starts to run really rich. It cruises rich and it idles pig rich (low 10s). WOT isn't any richer. I go to WOT a few time and the issue disappears.
My theory for now would be a stuck open BOV, I will get into that in the next days. If it's not the BOV, I honestly have no other ideas except a SD ROM bug...
That's the good thing about speed density...as long as you arent at WOT, air leaks like that shouldnt make you go crazy rich as the ECU is making it's calcs based on inlet temp and density at the manifold.
Jul 16, 2013, 07:01 PM
#3
Update: Tonight I opened the synapse BOV. Although it looked like new and non dry, I applied synthetic grease and retried the car. Same issue.
My next guess would be a FPR failure raising fuel pressure. Any ideas?
My next guess would be a FPR failure raising fuel pressure. Any ideas?
Last edited by domyz; Jul 16, 2013 at 08:18 PM.
Jul 18, 2013, 12:08 AM
#4
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I had some strange intermittent fueling issues when I forced open loop with the periphery bits on 88580714. Went away if I forced open loop by changing the load tables instead and leaving the periphery bit enabled.
Worth a try depending on how you are forcing open loop?
Worth a try depending on how you are forcing open loop?
Jul 18, 2013, 03:49 AM
#5
I also ordered a new o2 sensor for my wideband, it might be starting to act.
Last edited by WestSideBilly; Jul 18, 2013 at 08:48 AM. Reason: removed spam bot links
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Aug 6, 2013, 11:15 PM
#9
Fuel temp sensor. It seems temperature related, but I'm not sure yet. Last week I installed a new o2 sensor. I'll wait for a really warm day, to see if fuel starts to get too hot from exhaust and engine bay recirc. It's cold here and I haven't had the issue since 2 weeks or so, but can't confirm it's temp related.. Maybe it was just the old o2 sensor.
Did you happen to encounter something like this Jay?
Did you happen to encounter something like this Jay?
Last edited by domyz; Aug 6, 2013 at 11:17 PM.
Aug 6, 2013, 11:56 PM
#10
Fuel temp sensor. It seems temperature related, but I'm not sure yet. Last week I installed a new o2 sensor. I'll wait for a really warm day, to see if fuel starts to get too hot from exhaust and engine bay recirc. It's cold here and I haven't had the issue since 2 weeks or so, but can't confirm it's temp related.. Maybe it was just the old o2 sensor.
Did you happen to encounter something like this Jay?
Did you happen to encounter something like this Jay?
I had issues in one car while using the fuel temp sensor for SD. The AFR would drastically change based on how much fuel the car had ie tune the car at 1/4 tank to desired AFRs, then filled up to full tank and the AFR would be way off. Going to a GM AIT solved this issue. This car did have Dynamat (sound deadening) all over the trunk and rear seat area though, basically "insulating" the fuel tank and fuel temp sensor.
Had another car that while his fuel temp sensor SD tune was decently solid, moving to the GM AIT made the tune more solid and better overall. Now Im a fan of running a GM AIT for SD.
Aug 7, 2013, 09:57 AM
#11
Yeah.
I had issues in one car while using the fuel temp sensor for SD. The AFR would drastically change based on how much fuel the car had ie tune the car at 1/4 tank to desired AFRs, then filled up to full tank and the AFR would be way off. Going to a GM AIT solved this issue. This car did have Dynamat (sound deadening) all over the trunk and rear seat area though, basically "insulating" the fuel tank and fuel temp sensor.
Had another car that while his fuel temp sensor SD tune was decently solid, moving to the GM AIT made the tune more solid and better overall. Now Im a fan of running a GM AIT for SD.
I had issues in one car while using the fuel temp sensor for SD. The AFR would drastically change based on how much fuel the car had ie tune the car at 1/4 tank to desired AFRs, then filled up to full tank and the AFR would be way off. Going to a GM AIT solved this issue. This car did have Dynamat (sound deadening) all over the trunk and rear seat area though, basically "insulating" the fuel tank and fuel temp sensor.
Had another car that while his fuel temp sensor SD tune was decently solid, moving to the GM AIT made the tune more solid and better overall. Now Im a fan of running a GM AIT for SD.
I'll convert to GM AIT on lower UICP soon. Many, many thanks for sharing your experience.
Last edited by domyz; Aug 7, 2013 at 03:50 PM.
Sep 6, 2013, 02:59 PM
#14
