Vacuum leak?

[sauldlt]

Hey all!
I've got a 99 Ranger 4.0L with a high idle. With the A/C on It takes 5-6 seconds to come down to normal idle when coming to a stop, sometimes the "check gage" light will come on and then go away. I have already replaced IAC valve, also looked at most if not all hoses for tears. Im not sure where else there could be a leak. Or is something pulling in air? Any help would be appreciated!

 

[franklin2]

I thought certain year 4.0 engines had a problem with leaking intake gaskets?

 

[franklin2]

I did some searching, there was a TSB 98-6-8. Don't know if this expanded out to others. Here is a copy of it.


Article No. 98-6-8

LIGHT TRUCK: 1997 RANGER, AEROSTAR

4.0L ENGINES ONLY

This TSB article is being republished in its entirety to correct the part number listed, revise the Service Procedure, and add Aerostar.

ISSUE:
A rough idle, stalling at an idle and/or Diagnostic Trouble Codes (DTCs) P0171, P0174, P1131, and/or P1151 may be stored in memory on some vehicles with a 4.0L engine. This may be caused by the gasket located between the fuel rail and lower intake manifold losing its compressive loading and becoming drawn into the intake manifold runners resulting in a vacuum leak.

ACTION:
Replace the fuel rail-to-intake manifold paper gasket with a revised gasket.

SERVICE PROCEDURE
1. Remove the upper intake manifold and inspect the O-ring style gaskets on the mounting surface of the upper intake manifold. If the gasket bead is above the intake surface and is not torn, do not disturb the gasket. If any of the O-ring gaskets are torn or do not protrude beyond the mounting surface of the upper intake manifold, the gasket should be replaced.
2. Remove six (6) studs and lift off fuel rail manifold and paper gasket.
3. Inspect all holes in the lower intake manifold to make sure there is no debris.
4. Replace the Gasket (F8PZ-9E436-AA) (bright green paper and blue bead) and set the fuel rail manifold on the gasket. No paper gasket is needed on the top side of the fuel rail manifold.
5. Lubricate the lower portion of the stud bolts with a light grade oil such as 5W30 and torque the bolts to 14 ±2 Nm (10 ±1.5 lb-ft)
6. The upper intake manifold should be installed and the nuts torqued to 25 Nm (18.5 lb-ft)
7.Start and warm the engine.
8. Allow the engine to cool and retorque all of the nuts to 25 Nm (18.5 lb-ft).

PART NUMBER / PART NAME
F8PZ-9E436-AA / Fuel Rail-To-Intake Manifold Gasket

OTHER APPLICABLE ARTICLES:
NONE

SUPERSEDES:
97-20-10

WARRANTY STATUS:
Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage And Emissions Warranty Coverage

 

[fastpakr]

The 'check gauge' light is a little curious since that is separate from the CEL. But Franklin2's suggestion of the intake vacuum leak is a strong possibility. You can also look for a leak with starter fluid or a smoke machine. Any codes?

 

[sauldlt]

I haven't pulled codes yet since I have no CEL, I am going to smoke it later today and pull codes, so I can let y'all know what comes of it. For TSB I haven't had any stalling issues

 

[Angie]

With the A/C on It takes 5-6 seconds to come down to normal idle when coming to a stop,

Does this happen with the a/c off? or just on? any chance your brake booster is leaking air in the vacuum process?

 

[sauldlt]

With the A/C on It takes 5-6 seconds to come down to normal idle when coming to a stop,

Does this happen with the a/c off? or just on? any chance your brake booster is leaking air in the vacuum process?

Not as high of an idle, just more noticeable with A/C on. On start up its has an unusually high idle as well. Would that show up on the smoke test?