What causes open loop FS operation at higher RPM?
09-24-2013, 12:27 PM
#1
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What causes open loop FS operation at higher RPM?
Recently, I started noticing my car pinging and misfiring at WOT above 4k RPM. Reading the codes revealed ( freeze-frame ) that the car was running in open loop fuel system operation when the codes were thrown. Multiple misfires detected. Fuel trim appeared normal. What is my next step? The car has 137K miles, fuel filter changed this summer, all the ignition equipment is original. Air filter changed recently, spark-plugs changed around 100k...
09-24-2013, 02:28 PM
#2
Gentleman's Relish
Join Date: Feb 2005
Location: AZ
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What are the exact codes? Do they include misfire codes?
Pinging at high rpm is typically incorrect A/F (lean) or timing too advanced. Does your CEL blink or just come on when the 'misfires' are detected. If it blinks, those are misfires, if it doesn't then that is most likely not a misfire.
With Severe misfiring the CEL will blink for several seconds or drop the car into limp mode...you'll know if you're in limp mode.
Pinging at high rpm is typically incorrect A/F (lean) or timing too advanced. Does your CEL blink or just come on when the 'misfires' are detected. If it blinks, those are misfires, if it doesn't then that is most likely not a misfire.
With Severe misfiring the CEL will blink for several seconds or drop the car into limp mode...you'll know if you're in limp mode.
09-24-2013, 07:53 PM
#4
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At WOT the car is supposed to be in open loop. In open loop there is no fuel trim, the car reverts to the AFR set in the tune. Most of your sensors shouldn't influence the AFR at WOT/open loop.
Stock air filter or aftermarket CAI? Tuned? You're way lean for some reason. Clean your MAF and look for a post-MAF air leak. Fuel pump could be going too, check the pressure/pump duty cycle.
Lots of really crappy gas out there too
Stock air filter or aftermarket CAI? Tuned? You're way lean for some reason. Clean your MAF and look for a post-MAF air leak. Fuel pump could be going too, check the pressure/pump duty cycle.
Lots of really crappy gas out there too
Last edited by jpplaw; 09-24-2013 at 07:58 PM.
09-24-2013, 09:09 PM
#5
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Wow, I did not know realize the car is "supposed" to run in open loop at WOT!!! Cool thing to know. Thanks for help! About an air leak - I might have a small leak because a while ago I stupidly broke off a plastic feed/connect part from the intake manifold where the vacuum hose connects to it and had to jury-rig it with a ductape - there might be a small leak there... Gonna get a used take off manifold from ebay for a hundred bucks...
09-25-2013, 11:01 AM
#6
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Wow, I did not know realize the car is "supposed" to run in open loop at WOT!!! Cool thing to know. Thanks for help! About an air leak - I might have a small leak because a while ago I stupidly broke off a plastic feed/connect part from the intake manifold where the vacuum hose connects to it and had to jury-rig it with a ductape - there might be a small leak there... Gonna get a used take off manifold from ebay for a hundred bucks...
09-25-2013, 12:06 PM
#7
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Yes, that's exactly what I was thinking last night. For years, I had an itch to upgrade to Edelbrock E-force, but since my convertible is a daily driver, I have been somewhat hesitant about it. What would my MPG become? How much more maintenance heavy will the car become? With the supercharger in place, would it be much more difficult to do the usual maintenance like alternator replacements, sparkplugs, etc, etc? The car has almost 140k miles and soon things will start going, I am sure... Also, these days I really do not have time for DIY work so I have to figure in install, and perhaps tuning? Can jpplaw chime in on this? I see you have an Edelbrock too?
09-25-2013, 04:02 PM
#8
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Join Date: Feb 2005
Location: AZ
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Wow, I did not know realize the car is "supposed" to run in open loop at WOT!!! Cool thing to know. Thanks for help! About an air leak - I might have a small leak because a while ago I stupidly broke off a plastic feed/connect part from the intake manifold where the vacuum hose connects to it and had to jury-rig it with a ductape - there might be a small leak there... Gonna get a used take off manifold from ebay for a hundred bucks...
You can burn out your motor like that.
Get the leak fixed.
09-26-2013, 05:21 AM
#9
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As far as the E-Force:
Install - I originally put mine on during a 3-day July 4th weekend. Not a hard job. I upgraded to GT500 fuel pumps at the same time. Motor was up and running by the Monday. Only thing I needed help with was lifting and placing the blower on the car.
MPG - just putting the blower on won't change the mileage. How often you go into boost will. You don't get into boost unless you get to 0 vacuum, meaning you hammer the gas. If you hammer it, it will pull like a freight train, otherwise the car will drive perfectly normal. Until I did cams and headers, I got 20 city/ 23 highway and that was with occasional "spirited" driving. I used a 3.50" pulley. She had 475 rwhp/434 rwtq with that pulley.
Maintenance - It doesn't interfere with maintenance items. Everything is just as accessible as it was stock. Maintenance requirements are the same as stock, nothing special because of the blower. I have been daily driving this blower for 3 yrs and around 70,000 miles. Zero problems.
Tune - You would definitely need a tune from someone. It normally comes with one from Edelbrock but I bought my kit from Brenspeed and I already had a SCT tuner, so they just did an email tune for me. A Brenspeed, JDM or dyno tune is a must, I have heard the edelbrock tune is really conservative. Since I turned up the wick, I got a dynotune at Brenspeed.
Install - I originally put mine on during a 3-day July 4th weekend. Not a hard job. I upgraded to GT500 fuel pumps at the same time. Motor was up and running by the Monday. Only thing I needed help with was lifting and placing the blower on the car.
MPG - just putting the blower on won't change the mileage. How often you go into boost will. You don't get into boost unless you get to 0 vacuum, meaning you hammer the gas. If you hammer it, it will pull like a freight train, otherwise the car will drive perfectly normal. Until I did cams and headers, I got 20 city/ 23 highway and that was with occasional "spirited" driving. I used a 3.50" pulley. She had 475 rwhp/434 rwtq with that pulley.
Maintenance - It doesn't interfere with maintenance items. Everything is just as accessible as it was stock. Maintenance requirements are the same as stock, nothing special because of the blower. I have been daily driving this blower for 3 yrs and around 70,000 miles. Zero problems.
Tune - You would definitely need a tune from someone. It normally comes with one from Edelbrock but I bought my kit from Brenspeed and I already had a SCT tuner, so they just did an email tune for me. A Brenspeed, JDM or dyno tune is a must, I have heard the edelbrock tune is really conservative. Since I turned up the wick, I got a dynotune at Brenspeed.
10-02-2013, 09:49 PM
#10
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Sounds awesome! I have just been trying to decide if I should mod my car or just get a faster newer 5.0 where everything is better to begin with and also going to last longer being a new car. But I will really miss the color, which is Lime Green I have now.
Now, the state of things with my pinging and misfires.
Hooked up the laptop to the OBD port, checked the fuel pressure - steady between 30-40 save to occasional ( rare ) trips to 60 after a few sudden lift offs ( did not cause any problems ).
Fixed the broken hose connector, glued the plastic part with Permatex plastic Epoxy that people mentioned on-line. Worked well. However, the pinging and misfire is still there.
Further observations. Things go smooth in 1st gear and 2nd gear, but in third, when the car gets to about 4K, it starts choking, pinging and throws the misfire code. Moreover, if I quickly stop, I can still hear the engine missing one cylinder, which quickly gets back to normal. Under normal driving, there are no issues. Only happens at WOT at acceleration.
I have been thinking of a faulty spark-plug, but I have changed them about 50k ago, and was driving highway mostly. I was also thinking of it having something to do with either motion-charge plates ( sticking?? ), or MAF sensor somehow. The car otherwise drives great, and the only thing I can think of is light surging with light throttle and low RPM, or occasional misfire that does not last more than one cycle, a kind of short bucking that occasionally happens on low RPM ( <1400 ) at WOT.
When looking at data logs, the only thing I cant stop noticing is how the airflow and RPM go smoothly up hand in hand in first, then AF becomes not so smooth in 2nd, and in third, around the time when bad things start happening, the airflow looks very erratic on the datalog. I could not verify what is the normal airflow rate at WOT at RPMs, but I think my max was something like 160 g/s or whatever units it is being measured. I wonder if something is interrupting it, or its just a consequence of a misfires, or motion charge plates getting in a way, or faulty MAF. But I think something is up...
I am thinking to start with a set of new plugs, cleaning the motion charge control butterflies, and replacing the MAF sensor ( or cleaning it somehow...? )...
Now, the state of things with my pinging and misfires.
Hooked up the laptop to the OBD port, checked the fuel pressure - steady between 30-40 save to occasional ( rare ) trips to 60 after a few sudden lift offs ( did not cause any problems ).
Fixed the broken hose connector, glued the plastic part with Permatex plastic Epoxy that people mentioned on-line. Worked well. However, the pinging and misfire is still there.
Further observations. Things go smooth in 1st gear and 2nd gear, but in third, when the car gets to about 4K, it starts choking, pinging and throws the misfire code. Moreover, if I quickly stop, I can still hear the engine missing one cylinder, which quickly gets back to normal. Under normal driving, there are no issues. Only happens at WOT at acceleration.
I have been thinking of a faulty spark-plug, but I have changed them about 50k ago, and was driving highway mostly. I was also thinking of it having something to do with either motion-charge plates ( sticking?? ), or MAF sensor somehow. The car otherwise drives great, and the only thing I can think of is light surging with light throttle and low RPM, or occasional misfire that does not last more than one cycle, a kind of short bucking that occasionally happens on low RPM ( <1400 ) at WOT.
When looking at data logs, the only thing I cant stop noticing is how the airflow and RPM go smoothly up hand in hand in first, then AF becomes not so smooth in 2nd, and in third, around the time when bad things start happening, the airflow looks very erratic on the datalog. I could not verify what is the normal airflow rate at WOT at RPMs, but I think my max was something like 160 g/s or whatever units it is being measured. I wonder if something is interrupting it, or its just a consequence of a misfires, or motion charge plates getting in a way, or faulty MAF. But I think something is up...
I am thinking to start with a set of new plugs, cleaning the motion charge control butterflies, and replacing the MAF sensor ( or cleaning it somehow...? )...
