EFI Troubleshooting help? Code 22

[bronko69er]

So heres the deal:
'69 302 running '89 mass air stang EFI with an A9L
No problems for over a year now after the swap.

Last week I started to notice that the throttle was a little slow to return to idle, nothing terrible, but noticable.
Yesterday on my way home my check engine light came on.
Got home, counted flashes, code 22.

Code 22: MAP/BP sensor out of self test range.

I had no light on the way to work today and also didn't notice any slow throttle return (though I wasn't paying attention to it, a little sleepy this morning)

Upon leaving work tonight I noticed the light was on again.
The throttle return was normal when the light was on.
After a little while the light went out and the throttle was quite sticky (took 8 sec or so to return to idle from 2k).
Later the light came back on and the throttle returned to normal function.

Any idea how to troubleshoot this issue?
TIA.

 

[Viperwolf1]

The BP sensor outputs a frequency inversely proportional to barometric pressure. You'd need a frequency counter or o'scope to check the output. A junkyard BP sensor would be the cheap/easy test/fix.

 

[bronko69er]

Does the throttle response seem like a likely result of a failing baro?
Do the symptoms make sence given that code?
I do have access to a scope and a power supply at work, do you know what voltage (assuming 5Vdc) to apply to what pins and what frequencey to expect for a normal range?

 

[Landho]

My '69 has a Speed density EFI from 90 Lincoln Mark VII - a while back I was getting code 22, turned out to be a vacuum leak (many, actually).

 

[Viperwolf1]

Does the throttle response seem like a likely result of a failing baro?
Do the symptoms make sence given that code?
I do have access to a scope and a power supply at work, do you know what voltage (assuming 5Vdc) to apply to what pins and what frequencey to expect for a normal range?

The BP sensor controls spark advance so it would have some effect on response. Everything is spelled out here: http://fordfuelinjection.com/index.php?p=32

 

[73Russell]

my book says to connect the map/baro tester to the sensor connector and sensor harness connector. With ignition on engine off, use DVOM to measure voltage across tester terminals. If the tester's 4-6V indicatior is on, the reference voltage input to the sensor is okay.

If the DVOM voltage reading is as indicated in the table, the sensor is okay

Table I believe is
Altitude Voltage + - .04V
0 1.59
1000 1.56
2000 1.53

 

[73Russell]

You are welcome to come look at my manual if you want

 

[bronko69er]

Thanks for all the help guys.
Update: On the way to work today, no light and perfect operation for the first 10min or so, then light came on with no change in operation for the rest of the drive.

I think I'll pull it today and hook'r up to the scope.

 

[Viperwolf1]

Don't forget to take pics.

 

[bronko69er]

Don't forget to take pics.

Well there wasn't much to take pics of...
Just me sitting at the scope.
118Hz is no where near the atmospheric pressure of today (~160Hz) so I guess its off to the u-pull.
Can't choke down the $80 price tag that the parts stores want for a new one.

Thanks again guys.

 

[Landho]

I got mine at AutoZone for $63, if that helps you any. It was $18 more at Napa and I think $26 more at Oreilly.

http://www.autozone.com/autozone/ca...+Sensor&searchText=Barometric+Pressure+Sensor