Confused 4.0

[BrokenVet]

I may see some light.

When the engine is idling I seem to hear a vacuum leak but can't seem to find it.

I will try the WD-40 Trick for vacuum leaks and get back to you.

I think I will look at the temp sensor also just as a rule out.

Mike

 

[MAKG]

You can try removing and capping all the vacuum lines except for the fuel pressure regulator (which you really need) and see if the hissing goes away. If it does, start reconnecting lines until you find the culprit. If it doesn't, get a few feet of flexible tube and put one end in your ear and use the other as a probe.

You can't get WD-40 or brake cleaner or carb cleaner or whatever everywhere you might have a vacuum leak.

If the hissing is more audible in the cab than the engine compartment, it's probably the power brake booster. You can confirm by squeezing the booster line with pliers while idling -- if idle quality changes noticeably, the booster is definitely leaking.

 

[BrokenVet]

Confused-Enlightened and Lost

The scenarios to check the vacuum leads will be done this weekend as soon as I have time. I do have a question however. Regarding the fuel pressure regulator WHICH I NEED??
I know that I need it but what happens if the vacuum line comes off. I found the nipple off one time and had to replace the nipple but, the vehicle still ran.
Could the regulator be the problem?

 

[MAKG]

If you know you need a fuel pressure regulator, replace it. But I thought there was significant doubt.

When the vacuum line comes off, you make a vacuum leak and the fuel pressure is too high at idle (40 PSI vs. 32 PSI spec).

 

[AllanD]

I take all complaints about injectors with a wheelbarrow of salt.

They are just solenoid valves. They will usually outlast the vehicle. They are not AT ALL temperamental.

You might go there after you rule out everything else.

When installing my 4.0 I discovered a serious "bug"

when the engine was pulled from the donor and placed on the engine stand the fuel in the injector manifold and injectors dried in place, so the injectors were basically varnished shut.

I had to pull the injectors and hand clean the feed side inlet screen with solvent and even then they didn't want to spray.

I had to FILL the injector rail with techron and pressurize it while
generating an injector pulse to get them to clear out.
I spent several hours getting them cleaned to the point where I was happy with the spray pattern.

AD