89BlueTA

hey guys,

According to TECH1 my car is staying in closed loop at WOT, it is going into BLM cell 15, but it still reads closed loop. The fuel integrator is locking at 128, the BLM at 141. I was just wondering if anyt one had any ideas.


Also on a side note at any other throttle setting my BLM's are at 160, with a fuel integrator at 160-168. This is in every cell it tries to go into. If any one has any ideas let me know. I thought that maybe I had a vacuum leak, but could not find one.

Car is an 89 L98 MAF.

thanks guys
nick

Brent

iTrader: (1)

Look at the "Learn Control" value. This is what turns off during WOT. Even thought Closed Loop stays active the learn proccess is off and the ECM is ignoring the O2 sensor during WOT.

The numbers indicate a lean condition. I'd look at fuel pressure and for leaks between the MAF and throttlebody for starters.

89BlueTA

Fuel pressure is rock solid at 47 psi, and I cannot find any airleaks. The integrators are locking and it appears to be functioning like it is in open loop. It just says closed loop still.

nick

Craig Moates

The BLMs max out at 160 right?

Have you diddled with your MAF sensor like cutting out the fins or removing the screens? If so, your MAF will read lower than the actual value, so the ECM will compensate by adding more fuel than that which is appropriate for the erroneous MAF reading. This'll give you lean conditions and force your BLMs high.

If this is the case, you can diddle your FI constants lower and that'll take care of things. You could also diddle your MAF tables, but that would be more troublesome although more accurate.

So? Any fancy ductwork around the MAF or missing material which would allow gases to bypass the sensor wire within the housing? Doesn't take much methinks.

89BlueTA

Yes I have gutted the MAF, I will look again for air leaks.

My main concern is why it is not switching to open loop at WOT,
the TPS is reading 4.40v, is that high enough?

thanks nick

Craig Moates

Just to restate, if you've gutted the MAF, you'll need to plug in a lower number for your FI size on the EPROM.

Ski89Z28

So this is standard practice for a gutted MAF??
Hence I have 22# injectors then I need to set it to 19#????
Or I should monitor the BLMs to see first, I guess.

Craig Moates

It's my experience, and it makes sense. Held true even when I changed out injectors and went with 24#ers. I'd bet it holds true for others like yourself.

GregWestphal

iTrader: (1)

As Brent tried to explain, the Closed Loop flag will still remain on since all of the conditions for being in C/L are still being met while WOT. It's just that the computer used the Power Enrichment tables for the additional fuel being injected. 4.4 volts is definitely high enough for WOT, especially since PE can be engaged at a lower TPS value (it's based off of %TPS, not the voltage).

AFA having to change the injector constant due to modified MAF sensor, you probably won't have to change it more than 1 lb/hr. My injector constant is set at 25 lbs/hr for the SVO 24# injectors that actually flow more like 26 lbs/hr.

89BlueTA

Thanks for clearing that up for me everybody, the learn values due seem to lock, I just thought it was strange that it was staying in closed loop. I will not worry about it anymore and consider it normal.

Thanks for all the reply's it was very helpful!

nick

89BlueTA

Ok guys, please due not get mad at me for bringing this up again, I am just trying to understand a little better.

But after thinking about this for a little longer, I was under the impression that one of the conditions for the car to be in closed loop. Was that the car not be at WOT. So if that was one of the conditions it should send the car to open loop at WOT.

Please correct me again if I am wrong, any input is greatly appreciated.

Nick

GregWestphal

iTrader: (1)

There are 3 conditions to be met before the computer goes into closed loop: minimum coolant temp, minimum engine run time, and O2 sensor hysterisis (swing). The coolant temp is usually a little over 100 degrees F for most 350 TPI's. The run time varies depending on the start-up coolant temp, varying from 30-50 seconds for a hot engine to 300 seconds (5 minutes) for a cold engine (start-up temp less than 59 degrees F). The O2 swing is that the O2 sensor reading must drop below 200 mv or climb above 700 mv. Once these 3 conditions are met, the computer will go into closed loop. Technically, it won't be in closed loop at WOT since it isn't using the O2 sensor, but these 3 conditions are still being met.

89BlueTA

Thanks for the additional info Greg, it is really appreciated!

nick