I need some advice on a tuning problem I am seeing with a high powered engine combination in a 1990 corvette. The combination and problem definition:

-434 SBC
-248/252 @.050 .600 lift cam
-Idle KPA of 70 KPA at 800 RPM
-Cruising at 1900 RPM vacuum of 50 KPA
-Idles and drives well at light throttle <20%
-7730 ECM

Problem statement:
-Start to roll on the throttle in overdrive at 1900 RPM without a downshift and as soon as the intake vacuum hits 80 KPA, it sets a check engine light for code 33 MAP sensor too high and goes into some sort of limp mode. I can turn off the code so no light comes up but the car acts the same and still goes into a limp mode until I lift on the throttle. (FYI even at idle if a shift from drive to reverse and the intake vacuum hits 80 KPA it will throw the code and go into limp mode)
-I am scanning the car and all sensors are reading correctly and nothing appears out of wack except for this code.

Any ideas on how to solve this, so far I have discussed this with Tunercat who makes my tuning program and they are at a loss on what could be causing this. It appears to me to be some sort of hard code in the bin file that I cannot adjust that assumes a 80 KPA reading at light throttle is a failure of the MAP and I cannot get it tuned out.

Any ideas?

 

OK, it isn't in limp mode, the ECM is creating a default MAP value via N-Alpha mode. Which as you discovered will do it even with the malfunction code disabled.

The entries are likely not in Tuner Cat, but you need to adjust the code 33 MAP high malfunction parameters.

RBob.

 

Thanks for the reply, now how do I do this? I am willing to learn but I am not a computer programmer so I need some specific instructions on where to find this and eliminate it.

 

Sorry to hijack the thread, but what kind of power numbers are you putting down with that engine?

My future long term plans may have a 400+ cid engine in them... probably a less radical cam though...

 

It is not fully tuned yet but it should be close to 500 RWHP when complete.

 

I see this allot on my test bench when starting off and the MAP is not high (like >98%) to enable a good Baro read.
I have to keep the MAP high, start the RPM simulation and then drop the MAP signal to a running level.

As something to try...
Turn the key on and wait for a second before cranking it up. The little delay to stabilize the MAP reading may help.
My thinking on that is that you are immediately cranking when the key is put in and the ratio may not be good for your combo. Not sure on that but was a thought.

Anywho...
There are several parameters relating to Code 33.
There is an "Idle" parameter and "In Gear" parameter for a MAP/Baro value ratio.

0x8283 = ERROR QUAL 33, PK/NEUT HI MAP/BARO Ratio Thresh
(value of 88.1 Kpa in AUJP)
0x8284 = ERROR QUAL 33, In Gear HI MAP/BARO Ratio Thresh
(value of 218.0 Kpa in AUJP)

The conversion to obtain the engineering units is uncertain due to being a ratio from Baro/Vacuum readings.
You may want to tweak the values to max and see if they solve it, then go back and find a threshold value that suits your setup so you can have indication when MAP sensor fails.
Use hex values and disregard the "Units" as a starting point.

Other factors in setting the code are:
0x8285 = Minimum TPS% to set the code 33 (1.92% in AUJP)
0x8286 = Minimum RPM to increment the Error timer (500 RPM in AUJP)
0x8287 = Error time delay (0.31 seconds in AUJP but unsure if that conversion is correct)
All the above variables are 8 bit.

These are defined in the S_AUJP V4 or V5 definition but you would need to use TunerPro to take advantage of them.
HTH

 

Thanks for the reply, I have tunerpro and I can open the bin editor but I am unsure how to find these locations and what I need to modify. When I look for Ox8285 for example I do not see anything that resembles that. Can you explain how I find and modify these locations in the bin?

 

The definition "XDF" in TunerPro already has the offset of $8000 set into it.
Create the new "value" item using just the "285" for example.
Jp