ROND this one's for you

[broncobuckinaround]

Tested the map sensor. With a Hz meter. You posted once about what the specs are. You said 155Hz koeo and 80Hz engine warmed and idle. Well mine was 141.5Hz koeo and 106.4 engine running warmed up and at idle.

With these readings is it ok to assume my map is giving false info to the pcm. And should Ingo ahead and replace it

 

[RonD]

Yes those readings are fine, MAP is OK
Lower Hz = higher vacuum
At 20" of vacuum, engine idling, 106Hz would be correct
It would only go down to 80's when decelerating and intake manifold vacuum peaked in the high 20's" of vacuum, so my bad if I posted that 88Hz was expected at idle, oops.

0" vacuum, engine off, should be above 150Hz but I don't think your 141Hz is an issue.
Computer "learns" the range of some sensors, like MAP and TPS.
When you turn on the key the computer use the MAP Hz as 0" vacuum, and this is also an altitude compensation method, driving at 4,000ft elevation the oxygen levels are lower so less fuel can be added, MAP baseline Hz compensates for that.

Air pressure at sea level is 14psi at 4,000ft it is 12psi, in inches Hg it is 29" and 25" respectively, MAP measures air pressure, so at 4,000ft the MAP is reading in essence -4" of air pressure, so a "vacuum" with engine off.
If you are not located at sea level then your 141Hz could be completely normal

But in the end the O2 sensor data will also override MAP data once engine is running, if MAP was reporting slightly incorrect baseline, exhaust would be a bit lean or rich, O2 data would correct it.

Good read here with vacuum/Hz table for Ford MAPs: http://www.aa1car.com/library/map_sensors.htm

 

[broncobuckinaround]

I live in cedar city ut. it nearly 6000 ft in elevation me and a friend checked kpa and my map reading don't come close to the ones shown on the chart you provided in the link. kpa is 83 and the Hz should be in the 90's koeo with knowing that. I'm guessing the map is shot. I'll test another known good one to be sure

 

[RonD]

??

You are looking at the Ford graph, 2nd one down, correct?


Your vacuum at idle is 83kpa or 25" of vacuum?

Previous post said 106Hz at idle which would be 19" of vacuum and normal

At 6,000ft the 141Hz with engine off would also be very close to normal

 

[broncobuckinaround]

it just doesn't make sense. if you were to Google the atmospheric pressure for cedar city ut. it would say between 24 and 27 hg which would mean my map should read 88 to 95 hz. maybe I'm looking at it wrong. but to me and a friend who's an engineer and smart as hell when it comes to pressures. idk tho. it still seems like the sensor would be reading wrong for my altitude

 

[broncobuckinaround]

well i had a local mechanic come over and take a look he said it very well could be the solenoid in my trans. i dont understand how the solenoid can cause the pcm to ground the circuit. unless it grounds itself. which i can prove it doesnt. idk that guy wasnt much help.

 

[RonD]

I think I see your confusion, you are dealing with "-" Hg on the graph, and MAP calibration.

So 0 Hg for the MAP is actually 30Hg, Sea level air pressure in Hg
3 is -3
6 is -6
ect........it is a vacuum level, so a negative number from 0(30Hg)

24Hg at 5,800ft is a positive number, like 30Hg at sea level, so wouldn't correspond to negative 24Hg on graph.

At 5,800ft elevation and 24Hg outside air pressure with engine off MAP sees -6Hg(30Hg - 24Hg = 6Hg)
-6hg on graph = 141Hz, so bang on for your original reading.

 

[broncobuckinaround]

ok so yes than map is ok. where im at. ok tps and map are both fine.

that mechanic said it could be the solenoid. how could that be

 

[RonD]

Don't recall what the problem is?

Shift solenoid on '86 should just be the TCC(torque converter lock/unlock), not sure when the 3-4 shift solenoid was added?

If TCC is staying locked engine can stall when coming to a stop
Or if it isn't locking up then it can take a while to get up to speed, similar to bands slipping

TCC solenoid gets 12volts with key on
Computer Grounds the other wire to activate lockup
As far as I know there is no external connection between MAP and TCC

 

[broncobuckinaround]

pcm grounding lock up solenoid in all gears, park reverse neutral drive. when leaving from a stop the pcm will ground the lock up for no reason found yet.

 

[broncobuckinaround]

me and you have covered just about everything. tps was replaced map was tested and confirmed good. engine wiring harness was replaced, pcm is replaced. all grounds have been checked. new distributor. speed sensor.

seriously what else could be missing. unless its in the transmission, can a bad valve body cause an issue.

 

[RonD]

I don't recall the "issue"?

 

[broncobuckinaround]

ron ive told you the issue. OVERDRIVE ENGAUGES LEAVING FROM A STOP. DOESNT MATTER WHAT GEAR IT IS IN. P,N,R,D PCM IS GROUNDING THE GROUND WIRE

big letters so you dont forget again. not yelling.

 

[alwaysFlOoReD]

^^^ that wasn't in the original post. Perhaps you should be a little more polite if you want help.

 

[RonD]

OK, I remember now.

Then I guess you are down to the shift solenoid and the trans as the problem.