• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

Oil pressure


miller time

Member
Joined
Jan 27, 2011
Messages
237
Reaction score
3
Points
18
Location
rockfalls IL
Vehicle Year
2000 1999
Make / Model
FORD
Engine Size
3.0 duals out the back 4.0
Transmission
Automatic
My dad and I was changing out a 4.0 to a 4.0 no big deal. He got it running and it ran fine blew a rad hose that we forgot to tighten. Well we got home and I watched it a it idle 800 toms or so and then it drops to 500 and then the oil pressure shows nothing for 5-15 sec and idle back at 800 and reads again
 


Spott

Member
TRS Banner 2012-2015
Joined
Nov 28, 2010
Messages
925
Reaction score
21
Points
18
Location
SE Idaho
Vehicle Year
2000
Make / Model
Ford
Engine Type
4.0 V6
Transmission
Automatic
2WD / 4WD
4WD
And then what? If the rpm's dropped once, ever, you just keep am eye on it.

If it does it regularly, then be concerned. If that's the case, try and figure out if it corresponds to anything else going on.
 

miller time

Member
Joined
Jan 27, 2011
Messages
237
Reaction score
3
Points
18
Location
rockfalls IL
Vehicle Year
2000 1999
Make / Model
FORD
Engine Size
3.0 duals out the back 4.0
Transmission
Automatic
It does it every time I rev it up
 

Earl43P

Well-Known Member
U.S. Military - Veteran
Joined
Aug 7, 2007
Messages
3,159
Reaction score
38
Points
48
Location
Farmington, Pa
Vehicle Year
2019
Make / Model
Ford F250 4WD
Engine Size
3.0
Transmission
Manual
Low rpm like that does make the oil pressure gage drop to zero because the oil pressure pressure switch is about 8 psi. Low idle will trip it to a zero psi indication = NORMAL at THAT low of an idle.

Focus on the low idle problem.
The IAC controls idle.
A simple test is to disconnect the IAC and see if idle drops. If it does, the IAC is at least working. That doesn't mean it isn't STICKING.

With your newly installed engine, you may also need to let it relearn its idle strategy.
Let it idle for 4 minutes in each of the following conditions:
Engine must be at operating temperature:

Park
Drive, foot on brake pedal the whole time.
Park with AC on
Drive, foot on the brake pedal the whole time, AC on.

If it has a clutch, you only have to let it idle with foot on the brake and again with the AC on.
It's best to do this after resetting the PCM (Disconnect battery, touch the removed Negative cable to the Pos Battery post still connected to the battery. Or simply turn on the headlamps with the battery disconnected. Either method works).

Another possibility is that you have a vacuum leak and the PCM is trying to compensate for it. Make sure the tube from the air filter box to the throttle body is tight and has no holes in it!

You can clean the IAC shaft with a solvent and then whack it against your palm so the plunger thwocks as it slides along the shaft. Again, the IAC contols idle by metering a certain amount of air to maintain idle. Another thing to check is that the throttle body plate is fully closing and clean. Do not adjust that unless you are going to probe the TPS center wire for proper voltage with the plate closed, less than 1 volt. I think .96v is optimum, but you should look up the TPS test and do that.
 

miller time

Member
Joined
Jan 27, 2011
Messages
237
Reaction score
3
Points
18
Location
rockfalls IL
Vehicle Year
2000 1999
Make / Model
FORD
Engine Size
3.0 duals out the back 4.0
Transmission
Automatic
Ok we changed the iac from the donor truck that ran fine before pulled and unhooked the battery and did the steps
It now high idles more that it low idles and drops oil pressure shifts crazy like you have to let your foot off to shift and it over heats but we are going to change thrumstat and clutch fan
 

scotts90ranger

Well-Known Member
RBV's on Boost
Joined
Feb 28, 2001
Messages
7,925
Reaction score
4,227
Points
113
Location
Dayton Oregon
Vehicle Year
1990, 1997
Make / Model
Ford
Engine Type
2.3 (4 Cylinder)
Engine Size
2.3 Turbo
Transmission
Manual
2WD / 4WD
4WD
Total Lift
6
Tire Size
35"
I would check for missed grounds too.
 

JackDW

Member
Joined
Jul 9, 2012
Messages
33
Reaction score
0
Points
6
Location
North Carolina
Vehicle Year
2003
Make / Model
Ford
Engine Size
4.0
Transmission
Automatic
I would check for missed grounds too.
+1 and hopefully you didn't make the same mistake I made. Painted the frame and under the hood and then connected a ground. Paint made a nice insulator. All kinds of funny electrical issues. Removed the ground and scraped down to the metal and reattached which fixed a lot of funny little issues.
 

Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top