500 RPM idle & hesitations

[Ecomike]

mattbred,

I am not sure about part of what you said below. You said itdropped from 15 ohms to less than 1 ohm with the battery cable disconected, but which battery cable was disconnected? Was it only the possitive, or was when either battery cable was disconnected. Also did you have the ignition turned off?

What you might do is disconnect the negative battery cable, with the ignition key out (everthing off, and pull the hood light bulb for a minute, then check the negative battery post to the negative battery cable connector while disconnected to see if there is any voltage present. IF there is voltage pressent then something is still powered up on its own, and it will affect the ground ohm measurement when the negative cable is connected to the battery.

In which case you need to disconnect the positive cable to get an accurate negative battery post to engine/firewall ground reading. Then you might want to chase down what is still running (I do not have a hood light bulb, nor does anything else that I know of run when my hood is up and doors are open on mine (no courtesy light bulbs anywhere in my jeep, so most others might need to disconect that positive cable if they have dome and hood lights working, security systems, clocks, etc that run all the time!!!!!

Probably just a coincidence that mine are all off, disconected, not powered up so I did not need to disconnect the positive cable on mine.

 

[mattbred]

Ahh okay. When I disconnect the positive cable, then from the negative battery post to the engine block right where the cable connects to, I get under 1 ohms.

When I reconnect the cable, I get 13-15 ohms.

If I disconnect the negative cable and check the CABLE to the engine block, I get under 1 ohm.

I will try powering EVERYTHING down and testing. Thanks.

 

[Ecomike]

Sounds to me like you have a very good ground now. Time to move on to the other possible causes.

 

[mattbred]

Alright. I did some diagnostic tests.

At warmed up temperature, my Manifold Air Temperature sensor gives a reading of
380-400 Ohms of resistance

My Coolant Temperature Sensor gives a reading of
340-360 Ohms of resistance

Idling at 900 RPM's, my MAP Sensor from Terminal A to Terminal B gives a reading of
1.2-1.3 volts.

My output TPS voltage with engine hot & off, ignition on, is at
.820 volts.

My output TPS voltage with engine hot & on, is at
.832 volts

My Input TPS voltage stays constant around
4.93 volts

Are these all to spec?

I also tried moving the TPS lever (not the throttle lever, just the TPS) with the engine idling, probably down at least a volt or so with no noticable change in idle speed. What's that mean?

 

[Ecomike]

That all sounds pretty normal. Let's go to back to square one on the decel hesitation problem.

What problem(s) are you still having at this point and when are they happening.

 

[mattbred]

Seems the only problems now are:

When it's cold, if you press on the gas, it hesitates.
When it's cold, if you rev it up a bit, then let off the gas, RPM's dip way below idle. (Almost stalled on me at a stop sign! Rpm's were below 500 for a few seconds and it was sputtering)

When it's warming up, idle RPM's go up as well.
When it's hot, idle RPM's will be at 900-950.


That seems about it for now that I can tell.

 

[89xj]

have you tested the MAP sensor and checked the vacuum line from MAP to TB?

 

[mattbred]

have you tested the MAP sensor and checked the vacuum line from MAP to TB?

Idling at 900 RPM's, my MAP Sensor from Terminal A to Terminal B gives a reading of
1.2-1.3 volts.

How do I check the vacuum line? I don't have a hand pump or vacuum gauge.