Computer constantly in Closed Loop Mode?

[2FastTSiAWD]

Ok, here goes with my problem, I ve searched and couldnt find anything. 2 Days ago, I was messing under the hood, doing some routine checking and the such, and decided while I was in there, to remove the fuel pressure solenoid. I have an afpr, and after reading on here so much about removing it, I figured why not. well, I did it correctly, except I unplugged the solenoid, and fired the car up(didnt kow to keep it plugged in). At partial throttle, the engine sputters, and seems to be missing, also smelling insanely rich. So I put everything back to stock, and it s still the same, then I disconnect the battery to clear the ecu, because i had ;left the solenoid unpluged. Still the same problem. Now I ve noticed that based on 02 volts, at anythign other than idle, my ecu stays in closed loop mode? I tried changing the 02 sensor to no avail, I ve played with the fuel pressure, I ve checked the plugs, everything is exactly how it was before I removed the solenoid, yet the car is still staying in closed loop?! WTF? Anyone have any idea whats going on? Or why this suddenly occured? incase of needed info, I have a walbro 255 with an aeromotive afpr. Stock Boost, rest of my mods are in profile, please help, and thank you for any suggestions! I m jsut sick of fixing things on this damn car, but I love her so much.

 

[DiabloRT]

Disconnect the battery again and step on the brake pedal.

Maybe....even disconnect the plugs at the ECM.

Then reconnect everything and see what it does.

 

[leakyfaucet]

It stays in closed loop in everything but idle? So you're running in open loop at idle?

 

[2FastTSiAWD]

Well, reited the brake pedal thing, didnt do anything, I also just noticed yesterday that I got a CEL. SO I checked that out and it was the TPS, I swapped a different TPS in, and it s still the same. About the constant closed loop: When I got my DSM chips eprom, I had the factory boost gauge changed to a 02 volt gauge, he told me that for the most part it is to tell wether or not the computer is running in closed, or open loop. It s kinda weird, before all of this, the 02 volts were constantly cycling as normal, and going to right under 1 volt at WOT, now, it is always at under 1 volt, sometimes even during idle, but it seems that as the car warms up, it cycles normally at idle, but pegs once I even touch the gas pedal? Any other suggestions? Thanks

 

[Oreopride18]

Subsribed.

People don't believe this to be a problem when you tell them your air-fuel gauge is pegged to the green side at all times (since Air Fuel gauges are "highly" inaccurate)

So when I got a logger I look at them and that "worthless gauge" was right: The O2's NEVER cycle. I've had this problem for 4 months and still dont know what it is. Things that have been changed:

Thermostat; working order.
Coolant Temp sensor
Bumped down the feul pressure (more on this in a second)
O2 sensor itself!

I'm at a total friggin loss and haven't gotten on my car in months because of this problem. Here is what I'm betting happens to you:

- Until warm up it pegs as far to the right as possible.
- At idle your O2's cycle properly.
- Whenever you feather the pedal it pegs all the way to the right. When driving on the highway at 22% throttle on my logger my O2's were not cycling.

So the fuel pressure was a temporary fix I deemed unsafe. I pumped it down to 32 psi and.....low and behold! Great gas mileage! The O2's would cycle from .01 to .6 volts if I kept throttle under the 25% range. But it was an obvious bandaid masking a very real problem; and at idle the car would be damn near unsafe to drive with fuel trims at 140.

So, basically, I would have 140 at low trim, and 81 at mid, then 81 at high.

This isn't a tuning problem; there is seriously some sensor or something not right in the car. Since I can get the car to cycle the O2 volts with uber low fuel pressure I can tell the O2 sensor works. The temperature is logged properly so the coolant temp sensor works. I can get idle to change with my MAF adjustments but MID and WOT won't do anything; I doubt it's the program itself.

If I figure it out I'll put it back on here. I hope you do the same man and all the luck.

 

[2FastTSiAWD]

thanks for all the info OREO, sounds EXACTLY like my problem. But, my car is finally moving on to bigger and better things, I jsut bought a 94 beretta with a 3.1 that needs headgaskets. So, the talon is getting parked in a few days, and getting stripped and prepped to be drag only. I will figure out what this problem is, and I ll let you know when I do.

Keep Tuning

Fred

 

[johnk]

Could be your TPS went bad that will get you in closed loop fast.

 

[Oreopride18]

Thanks, john. Im buying a TPS off of Ebay and will try it; its starting to throw a code (last 2 days) so Im going to go get that checked out.

 

[2FastTSiAWD]

I ve already changed my TPS to no avail, any other suggestions?

 

[2.4 turbo Hyped]

All of your symptoms are pointing me to think you have a boost leak. Do a boost leak test and dont just reply with ok I did it. Get out there with a spray bottle of soapy water and pump up that intake tract and start spraying. Chances are you have a throttle body gasket on the way out. This was my problem that drove me insane a couple of months ago. Ultra crappy gas mileage too.

 

[johnk]

Do you have a datalogger? You should really check your TPS readout on one. From what you said in post 4 I would say your TPS is dead. When your throttle is closed all the way there is a switch that closes that sends the ECU in a set idle mode(you said your O2 cycles at idle this helps point to TPS). If the TPS is reading anything but 10% (that's as low as it goes atleast on dataloggers) you get a CEL. So you TPS could be reading anything. In my case the TPS would send out 76%-99% wasn't particular just settled on a random number when the car warmed up. I don't know what trigger% the TPS has to read before it goes to closed loop but 76% is in the range. The rest you know when ever you crack the throttle it's in closed loop so it runs rich as hell pegging out the O2s at the ceiling.

You can also use the datalogger to set the TPS at the right position when you install it. Your profile listed a larger fuel pump but no other fuel mods. If your plan is to tune your fuel later you'll need a datalogger eventually and it could help you to diagnose this problem better. You can get real O2 readouts on it too.

If your convinced it's not the TPS you could also try checking the Coolant temp sensor for the ECU. There's a seperate one for the gauge so even if that reads ok it doesn't mean the ECU sees it.

 

[2FastTSiAWD]

I will do the boost leak test soon. Also, like I said, I changed the TPS, and it didnt change anything. I do have a datalogger, the TMO software, but my laptop is crashed, so I have no way of using it until I can find a laptop to borrow. Also, I ve already changed both of the coolant sensors maybe 3 weeks ago, so I know thats not it. Thanks