02 4.2L

Check engine light has been on for some time. I finally have the $ to start fixing. Went to Autozone and pulled the codes.

P0174 and PO171

P1151 and P1131

I grouped them like that because the guy at AZ said they were the same.

I pulled the plugs and the front 2 on the passenger side were in bad shape and needed to be replace. The others looked worn but in ok shape. I replaced all 6 plugs and wires. I did not replace the coil pack.
I also cleaned the MAF and replace the PCV Valve Hose. part number 1L3Z6758BA 33.65 + tax
Its the only hose that appeares to be in bad shape.

I drove it quite a bit today and the check engine light has not returned.

The issue I was having is while at a stop and in drive with the AC on the RPM will go up and down from 7k to 6k until I started to drive.

It is still doing that after the tune up just not nearly as bad, the RPM will go up and down 2 or 3 times before leveling out. Do I still have an issue, maybe with an 02 sensor or another possible vacuum hose leaking?

Also a question about oil. I check my oil every week and always have to add some. I have not found any evidence of leaks. just wondering why this happens.

Thanks for the help!

 

Remove the IAC (intake air controller) and spray clean it to make sure the pintle moves freely.
The trottle body and plate should be cleaned as well.
The IAC controls idle.
I'm sure you don't mean 6 to 7000 rpm. More like 600 to 700 rpm.
Normal idle is at 750 +/- 50.
Most motors as they age will begin to use oil from ring wear , intake valve stem guide seal wear and small leaks.
Good luck.

 

Thanks Bluegrass!

Yea I meant 600 -700 rpm

Should I use the MAF cleaner or my TB cleaner on the IAC?
Is there a IAC or TB gasket that will need to be replaced?

Thanks again!

 

Use wd-40 on the IAC, and work the plunger back and forth to loosen it up.
The IAC and throttle body both have gaskets, but can be reused if they are in good shape.

 

The po171 and po174 codes refer to banks 1 and 2 being lean. My sons 03 4.2l was popping those codes, did all the things that you are doing and codes kept coming back. Found thru some conversations with others and a couple Ford mechanics that the gaskets under the plastic intakes are the problem. The material used to make the gaskets in combination with the hold down bolts used will let the gaskets shrink causeing air to enter the intake stream and throwing the codes. Ford ( only place you can get them ) has a new gasket material and new bolts that should fix the problem. Its about 500 parts and labor to have someone do it or 250 parts if you do it yourself. Good luck.

 

Thanks for all the help and useful information on this site! My truck is running a lot better!

She still stutters a little while waiting at the light with the AC on and in drive. Its very rhythmatic. Its not as bad as it was before but she is still doing it. Hell its not happening 100% of the time anymore, more like 85% of the time and she is still throwing codes 171 and 174.

Does anyone have a picture of the vacuum hoses for a 4.2L engine? There is a diagram under the hood but I cant make heads or tails of it. I could use something that looks more like the real thing.

Ive replaced the PVC and have checked all the other hoses but honestly I am not sure which ones are vacuum hoses. Ive ruled out the AC lines and Radiator hoses. Are the rest vacuum hoses? How many vacuum hoses are there?

I also removed and cleaned the IAC, TB and plate. Might take this apart and clean again.

What are these 2 hoses?

Here are some pictures and a video.

Thanks for looking!!

 

i think those two hoses are heater core hoses.

 

Yes 1&2 are heater hoses.

 

This is the problem. I fixed mine in December and haven't popped a code since.

 

Thanks Mike and Str8t six!


despain85 and c.frank
Yea, I have been doing a little research on the subject. Looking more and more like that the route I will end up taking. Did you replace your O2 sensors, MAF or EGR before doing the Plenum gaskets and isolator bolts?

I found a detailed write up on this, it does not look too difficult.
http://sites.google.com/site/fordf15...P0171P0174-Fix

How well did your repair go, any issues? How long did it repair take? I am no mechanic, Im definitely more of the shade tree fix it type. Its my daily driver and weighing doing it myself or paying to have it done. Just not sure if I want to tackle this one.

 

Ford will charge you about 600 bucks to do the plenum gaskets and isolator bolts. It may be worthwhile just to take it in and pay for a diagnosis - go from there.

 

I didn't have the time or space to fix it myself. My mechanic had it done in about 4 hours time. I never replaced anything as I ruled all of it out by checking everything. Mine only pulled the code when the engine was cold, it warmed up and everything would seal and it never ran fine. I did notice that my milage had went down the drain and that's when I knew it needed to be fixed. It seems like a fairly easy task that can be done in a days time.. as long as it all rolls right.

 

Had a mechanic do mine also. No time or space. The only issue I had was the 550.00 price tag....

 

Finally made the repair! All for around 100 bucks. Replaced the Isolator bolts and gaskets, also replaced the IMRC bushings. In the past, the check engine light would show up around 40 miles after reset. More than 700 miles later and still no check engine light.

The repair was pretty easy, took me around 6 hours. All the trouble shooting I did from cleaning IAC and TB to checking vacuum lines etc I was pretty familiar with taking everything off the plenum. The most time consuming part was cleaning off all the gummed up oil off the inside of the plenum. Went through 4 or 5 cans of carb cleaner. And the bushing were a pain in the @$$.

 

Thanks for updating the thread. Glad you got it worked out