Howdy everyone. I have a 98 Ranger, 4x4 extended cab, about 170K miles on her.

Short version of a long story, the temperatures are now cooler, and I started getting P0171 & P0174 codes. Had the same issue last year, problem goes away when spring/summer returns.

Looking through earlier posts, most folks suggest cleaning the MAF, which I will do this weekend. However, failing that, another suggestion is checking for vacuum leaks. What is the best way to check for one? How might you find its location?

Thanks for any help and advice

 

do you have a repair manual for the ranger because there is a vacuum gauge that you can get and i am pretty sure it explains how to hook it up and test it, but as far as finding a leak i have no idea except to spray soapy water over every hose. hope this helps.

 

Thanks seth1 for the info.

I do have the Chilton guide for my truck, but the vacuum diagram doesn't seem to match what I have - a 4.0L engine.

There isn't really much of a discussion on the vacuum system at all.

 

in my haynes manual it talked about how to do it and what the vacuum pressure would be because i tested my old 92 before. you might be able to find somethin on the net on how to test it but i always have a hard time looking stuff up with pop up ads and always getting led to totally wrong sites.

 

Welcome to FTE!!!

I have used carb cleaner to find them, spray it in the location you suspect a leak and the rpms will change if there's a leak.

Do this on a cold engine and use common sense, carb cleaner is VERY flamable.

 

Welcome!

Try re-torquing the upper and lower manifold bolts. You can find the torque specs and some other useful information HERE.

 

I have the same issue with my 99 4.0L. PO171 and PO174. I am reasonably sure both O2 sensors did not go out at the same time so I also suspect a vacuum leak. If you find the problem, let me know so I can solve my issue also.

 

Thanks guys, I will keep posting on my progress to resolve this problem. Need to stop and pick up some carb cleaner on the way home tonight.

 

Yes you can find them with the carb cleaner or wd-40 ect ect. I also have had good luck listening for them. I took one of my old engine stehoscopes and put a piece of 1/4" copper tubing in place of the rod and then I start probing with this when you get close to the leak you will definitely hear it.

 

The stethoscope thing is a neat idea, I have one I can give this idea a try. Thanks

 

This may also help you out. If you smoke, pull the big vaccuum line off of the brake booster (truck running) and blow smoke into the line - then just look for the smoke.

 

The rain and wind finally stopped.

Started poking around for vacuum leaks. Squirting carb cleaner around vacuum line connections didn't do a thing.

Looked at the 3/8 fuel line that runs from the throttle body to some sort of modulator (EVAP part I think). The outer coating of the tubing would just crumble as you bent the tubing. Replaced it.

Also found that the throttle cable was rubbing against a plastic vacuum line. Can't find a replacement for that - have a seperate post for that issue.

Will just keep watching to see what happens next.