Here's the key trick and the code's. Right here on good ole DF in the FAQ section https://dodgeforum.com/forum/2nd-gen...code-list.html

 

Ugh, I really didn't wanna make a thing out of this, but I also can't stand seeing misinformation provided in a tech forum. Once again, the MAP sensor doesn't control ANYTHING. It's just a vacuum sensor, little more than a diaphram attached to a variable resistor. The only controller is the (P)owertrain (C)ontrol (M)odule. The MAP is used to determine engine load by comparing vacuum to vehicle speed, engine RPM and throttle position. The logic circuit calculates a fuel curve based on these inputs, then adjusts it further using the O2 inputs.

Unlike a MAF sensor, the MAP sensor cannot be used to calculate airflow by itself.

So is it an important sensor in the system? Yup. Is the PCM able to calculate timing and fuel delivery with only the MAP input? Absolutely not. The PCM can substitute approximate values to a certain degree when a sensor fails by using inputs from the others that are still online, but the system isn't working right unless it has all of them.

Also, gotta curb the redundancy, man. Timing and spark advance are one and the same, is are A/F ratio and injector pulse width.

once again, I apologize for being argumentative here, but bad information is never helpful, and that's what people are seeking here; Help.

 

ok ive done the key trick on a few of my cummins trucks but on this old 94 there is no digital read out? Is there anyway to check those sensors or just replace them.

 

For the model years before the digital readout, the CEL will flash a certain number of times, followed by a pause, flash a certain number of times, followed by a pause, etc.

Example: Flashes three times, short pause, flashes four times, longer pause, flashes five times, short pause, flashes eight times. This translates to trouble codes 34 and 58.

As far as actually testing the sensors, yes. Grab yourself a Haynes manual from your nearest auto parts store, it contains detailed testing procedures (that work most of the time) for the sensors.

 

ok i did the key thing. its a little different than i was used to on the cummins motors. i got map sensor vacuumsystem, coolant sensor, cam position sensor signal from distributor, no distributor reference signal detected during engine cranking... What the heck do i do or try.

 

I'm not arguing here but, the fact is, I stated that in conjunction with the PCM, it is used to control the timing. Having made III and IV devices myself, I am aware of what's inside a MAP sensor and how it functions but, I thank you anyway for your basic explanation.

Again, the fact is, The PCM uses the MAP sensor input to aid in calculating the following:

-Manifold pressure
-Barometric pressure
-Engine load
-Injector pulse-width
-Spark-advance programs
-Shift-point strategies (certain automatic transmissions
only)
-Idle speed
-Decel fuel shutoff

That is far more than just just functioning as a vacuum sensor and, if the vehicle is running rough, the MAP can induce a rough running condition along with various other sensors as well. This was my point. I may have been redundant and, it may have not been worded the best either and, again, my apologies for the "bad" information.

CM

 

Those two words make all the difference, turning an erroneous statement into a factual one. Thank you

 

I had similar problems with my truck, really rough idle, really sputter-y when i put the pedal to the metal.

Emptied my gas tank, filled it with a different tank of gas, all was good.

 

sixtsixduce, You seem to have some advanced knowledge of MAP sensors. I've recently put on a CAI and all of the sudden my mileage went from 14-16 to 5-8. I reset the PCM and the mileage was still low. I've run about a tank through the rig with no change. So I put the stock air hat on and the mileage is still the same. Could a faulty MAP sensor cause this drastic of drop in fule mileage? Can MAP sensors on this engine be ruined by over oiled air filters?

 

There is a thread from a while back about the MAP being replaced and gaining some MPG (not that much though). But somehow I don't think that is your problem. How is oil consumption?