Idle issues and oil pressure gauge not working! (1 Viewer)

[ThePatient1]

Hello forum, I haven't been on here for quite some time, but have been doing research into the issues in the thread title on the forum, and downloaded a FSM.

Firstly, my LC was sitting for over a month and I took the battery out to recharge it and put it in the other day. It idled really low when I started it (Sits around 200 rpm) I read in another thread it could be caused by the throttle position sensor being out of wack due to the battery being disconnected and the ECU being reset. I did what was mentioned, which is leave the ignition on and press the gas pedal down a couple times and then started it but that did not fix the issue.

Is the only option now to get the sensor tested for proper voltage/resistance readings? Or should I take it to a dealer so they can use an OBD scan tool? Where is the sensor located exactly? I couldn't find a diagram in the manual for its location, just a section on how to test it. Could I maybe just adjust the throttle cable to increase the idle speed?

The oil pressure gauge also gives no reading, even when revved up. I checked the oil level and it was at the max level. I read it could be as simple as the oil pressure sensor being disconnected or corroded which I'll check on soon. If its connected and not corroded what can be a possible cause for no oil pressure reading at the gauge?

Thanks for any advice or help!

 

[Kernal]

What year and model/engine do you have? Was the oil pressure normal before the vehicle sat for a month? Any recent work under the hood?

 

[ThePatient1]

Whoops, how newbish of me. It's a '94, all stock. I do recall the oil pressure gauge working before it sat. There has been no mechanical work on it in awhile.

Just thought I would add that it has 248k miles on it, and it is quite rusted underneath. She definitely needs some TLC.

 

[neal0124]

Is the crank pulley bolt tight?

 

[cruiserdan]

It takes up to a dozen start cycles to get the IAC motor to adjust the hot idle. Pressing the accelerator pedal does nothing. Start the engine and let it run for ~30 seconds and then shut it down. Repeat the process and the idle will slowly bump up. Do first sort out the oil pressure issue.

If the vehicle had good oil pressure when it was last run then I would suspect an electrical issue. Check under the hood for rodent-damaged wires.

 

[Epic Ed]

I'm having a similar issue with my oil pressure gauge suddenly not working. Where is the sensor located?

 

[Kernal]

Front right side of the block, small round can looking thingy with a wire going to it, below the exhaust manifolds, slightly above and behind the AC compressor. Look from underneath the front of the truck, near the lower radiator hose extensions.

 

[Epic Ed]

Found it. Found two plugs - a gray one and a black one. Black one is disconnected. There's only one prong on the sensor. No dangling wire anywhere that I can find. I have no idea where to plug in this black plug.

*sorry for the thread hijack.

*Found some good pics in this thread. Looks like my second connector has broken off.

https://forum.ih8mud.com/threads/94-lc-oil-pressure-sensor.622165/

*UPDATE* The black connector (+) does not connect to a prong/blade coming off the sensor like the gray connector does. The connector is a "button" dead center of the sensor and the black connector slides onto it.

 

[ThePatient1]

No worries about thread hijack, if its on topic and helpful I don't mind.

So Cruiserdan you are correct and I did what you suggested and it bumped up to a steady 600rpm or so. I started it up let it idle, shut it down about 7-8 times.

I got underneath the truck and located the oil pressure sensor, all the wires appear to be connected and I did not see any sign of foul play from rodents. Although the entire sensor seems quite rusted. I'd like to remove it and clean it up. What's the proper procedure for removal? Do the electrical connectors slide right off (I just want to be sure I don't force or break anything)? When I unscrew it will oil start draining out? If so do I need to drain the oil before I remove it?

Regarding the crankshaft pulley bolt, I am unsure of it's tightness, I'll reference the FSM for its location and try and check it. I do not think any mechanical work was ever done to it, so I assume its still at its factory torque rating.

 

[Epic Ed]

I can tell you the black connector slides in an up/down orientation. Not push/pull like the gray/white connector. The "button" style contact in the center of the sensor matches with the flat back of the black connector.

 

[ThePatient1]

Okay, thanks for the info. I'll get under the truck again and try and pry off the connectors and take it out and clean it up.

 

[hh65flyer]

My sensor was so rusty that there were holes all the way through it. You may not be able to see them from your position on the ground. Likely why yours isn't working. I replaced mine with a unit from RockAuto as the OE sensor was pretty spendy IIRC. The gauge barely reads anything at all now. So perhaps the RA unit isn't calibrated properly for our engine. That, or I actually have no oil pressure!

If you look at the picture above note the threaded portion at the lower right of the picture. That's what threads into the block. There are flats just above the threads that will accept your wrench (sorry, not sure size at the moment...14?). The oil will not drain out assuming your not doing this with the engine running. Once you see the tiny orifice that actually measures the pressure you will understand.

The wire that attaches to the 'button' in the center slides off. Pull in the direction of the wire (not too hard). The other is a simple blade connector.

Good luck!

 

[ThePatient1]

Well I was not very successful with removing the connectors to the switch. I got one off just fine, but ended up breaking the larger tab off after trying to force it. Now I got a rusted part of the blade connector stuck in the wiring connector. After much frustration I just gave up on it. Maybe I'll try some penetrating oil and try to pry it out with a pliers. Or perhaps use a de-rusting solvent on it might free it up.

Just called my local dealership, they said $64 for a new one. Just checked Autohausaz.com and they have a non oem brand for $23.

 

[MoeGasim]

im in the process of re-wiring my whole cruiser.....because everything was a mess. question.... where does the black wire originate from..i mean what fuse does it take power from?

 

[ThePatient1]

Update:

I installed a new OEM oil pressure switch, hooked up the wiring, and STILL no oil pressure reading. Now I'm concerned. Oil level is still fine. The truck warms up just fine and doesn't overheat, nor does it have any irregular sounds from the engine. I'm hoping its just a connection issue on the wiring harness of the oil switch. Not sure how to do electrical trouble shooting of it. Maybe I'll just order an entire new harness.

I'm going to take it to a local shop and have them test the oil pressure to find out if it truly is a no oil pressure issue.

 

[FnLexus]

I was under the impression that the OE oil pressure gauge was next to useless....

 

[Squash]

If it makes you feel better get a "T" fitting installed where the sensor was. Now hook up a mechanical gauge and your brand new sensor in the hopes that your sensor will eventually work or you will delve into the dash to remedy the problem sometime in the future.



Unless you rip into the dash your sensor will most often remain useless!

To make you feel better:
Check oil on a regular basis such as filling with fuel
Last line of defense is the low oil level sensor...our diesel 1HZ fleet only has the low oil sensor.
Carry one extra qt of engine oil with you in case. Store the oil in the engine bay to the front of your battery.