Just two days ago my truck out of the blue started to idle roughly. This happended no matter if the vehicle was in park or drive with the brake on. A/C didn't affect the idle. Yesterday the CEL came on. I went to Autozone who said it was a P0171 which equated to the O2 Sensor on Bank #1 which "they" said was on the drivers side forward of the Catalytic Converter. With that said I bought two sensors for the forward group (driver and passenger side). I replaced the driver side first since Autozone said that was the bad one. I never got a chance to replace the forward passenger one (ran out of day light). What a pain to work on, had a hard time just trying to reach the wiring harness to disconnect. Anyways replaced PCV valve while I was at it (elbow looked good - no cracks). Was going to replace fuel filter but first sensor took too long (was pretty well seized). Reconnected battery started up idle great for a few seconds then started idling rough again. When stepped on gas at WOT then releasing pedal truck would idle back down to around 700 rpms then slowly creap up to around 1200 rpms idling great then all of a sudden drop to 500 rpms almost acting like she wanted to stall then idle rough again. Truck just got 100,000 rpms (1997). I'm hoping replacing passenger side fixes the issue but not counting on it. One thing I did notice was I did not hear the air sucking noise from my K&N that I normally hear (just the filter not FIPK). I tapped on the IAC valve and heard a fair amount of vacuum for a few seconds so don't know if this is my next project. Anyways any help would be greatly appreciated. I can't stand seeing my truck sick. The GMC/Chevy fans at work are enjoying their Fix or Repair Daily Jokes. Oh yeah, truck drives fine no problems there, just idle problems.

Regards,
Tom in Connecticut
U.S. Navy - Retired

 

You said you checked the PCV elbow, did you check the elbow on the other end of pcv tube this is on the back of the intake manifold? That is the one that rots off.. The elbow that hooks to the valve doesnt give any trouble..

My wifes 97 expy 5.4 had the same symptoms at 120k and the elbow was rotten.

 

No, forgot to check that one. Thanks, will check when I change out the other O2 Sensor tonight. Anyone with a 97 have a trick to changing out the forward passenger O2 sensor. I can touch the wiring harness but have trouble trying to coordinate pressing the release on it and pulling (sort of like trying to walk and chew gum at same time)

 

P0171=System too lean (Bank 1)

Not necessarily the O2 sensor.

Is it worse when the engine has been run for a while or does it do it even when cold? Sounds a lot like the same problem I am trying to fiqure out on my truck, I haven't had the CEL come on yet.

If you get it figured out let us all know what it was. Thanks

Rob

 

When cold idle is normal. Give it a minute to two and it's rocking and rolling (it you stand back by exhaust pipe you hear it putting)

 

Tom,

Take your 2nd HO2 sensor back to them and get your money back. P0171 is system too lean Bank 1.

The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit.

Check;
Fuel system, excessive fuel pressure, leaking/contaminated fuel injectors, leaking fuel pressure regulator, low fuel pressure or running out of fuel,

Vapor recovery system.

Induction system, leaks after MAF, vacuum leaks, PVC system, improperly seated oil dip stick.

EGR system, leaking gasket, stuck EGR valve, leaking diaphram or EVR.

BASE Engine, Oil overfill, cam timing, cylinder compression, exhaust leaks near or before the HO2 sensor.

Regards

Jean Marc Chartier

 

Jean,

Thanks for your help! Should the IAC Valve still be considered a possible culprit?

Regards,
Tom
U.S. NAVY - RETIRED

 

IAC bypasses air around the throttle body to control idle speed. I doubt it would effect mixture.

 

Just FYI, Bank 1 is on the passenger side, not the drivers side. however I doubt the o2 sensor is the problem. You need to find out why it is running lean.

 

Tom,

What was done to the truck prior to this happening? Oil change, spark plug change, power wash engine, anything? When was the last service done?

JMC

 

Oil change done @ 3000 miles ago. When rough idle started happening did check the oil which was a little low (not normal from my experience with the truck at 3000 miles). Am doing oil change this weekend. Plugs change at 65,000 miles. No other work performed. Did notice last night when I bought the truck in the garage that it had a slight exhaust odor. Didn't get a chance to find that PCV elbow (frustration hit me last night along with 95 degree weather, decided to take night off working on truck and hit the pool). I did try following the hose to back of engine (what a pain, couldn't reach far enough into engine compartment - engine still hot, didn't feel like climbing on engine). Getting up at 6 a.m. before heat hits to finish working on truck. Autozone told me Bank #1 was on forward drivers side so that is the O2 Sensor I changed. Now I see by post that Bank #1 is on passenger side which I haven't changed yet. Could this be an issue?

This weekends to do list:

- Check PCV hose connection on back on engine (if I can reach it)

- Change out Fuel Filter (Was last change a little over 15,000
miles ago)

- If Bank #1 is on passenger side, change that sensor out

- Check IAC valve and clean

- Get totally frustration, have a few beers and probably end up going to repair shop on Monday when all else fails.

Did I forget anything?

Regards,
Tom in Connecticut
United States Navy - Retired

 

JMC,

Truck serviced around 65K mark (new plugs etc.) Oil was changed a little over 3K ago so am about 200 miles past due. I did notice oil was a little lower then I though it should be comparing to previous oil changes. Will be changing oil this weekend.

I based which side Bank #1 was on by what Autozone told me. Seems like I changed the wrong side. (Autozone said Bank #1 was on drivers side not passenger side). Either way I had bought two new Oxygen sensors for the forward of the Cat. Will change the passenger side one tomorrow. Been too hot to feel like crawling under truck the last two days. Starting to get frustrated with working on truck so took last night off and hit the pool with kids instead.

Plan on doing the following tomorrow:

- Oil change
- Replace Fuel Filter (last changed @ 15K miles ago)
- Change out passenger side O2 Sensor (forward of Cat)
- Check PCV elbow on back side of engine (was too hot to crawl in engine last night. Is this one easy for will I have to climb in engine to find?
- Maybe clean IAC.

- If all else fails, open beer and sulk.

Regards,
Tom in CT
U.S. NAVY - Retired

 

Solved it. The PCV elbow (the one on the back of the manifold) had a large dimple in it. When I started the truck up and touched the elbow my figure was getting sucked into the elbow. How hard is it to remove that connection from the back of the engine? Will be visited the parts department today for a new PCV line. Also was going to change out the O2 Sensor on the passenger side (forward of CAT). Unplugged it then realized I could get any of my wrenches or tools up in the area of the sensor to remove it. Now I can get the wire connection to snap into place (keeps pulling apart). The harness is in good shapes just can reach high enough to push both connection together. Always something.

Thanks to everyone for the input.

Regards,
Tom

 

To replace my pass' side 02 sensor I ended up having to take out the fender liner. It really wasn't that bad of a job, except I have aftermarket flares on the truck. It really opens that area up. Good luck!,,,,98

 

Another question. I went to the local Ford dealer for the PCV hose assembly. My 1997 5.4 has a hose going directly from PCV to back of TB. The new one they sold me for 25.00 has a "Y" by the actual PCV valve. I explained that my truck did not have the extra hose in that area and all they did was pull off the extra hose and vacuum plug it. I inquired if there was another model assembly for the 1997 and they admitted there was but didn't carry it, that they were using the one they sold me for all year models and simply vacuum plugged the extra hose if it wasn't needed. Any foreseeable complications with that idea. Anyways putting it on tonight after work. Will be glad to have my truck back from the binacle list.

Regards,
Tom
U.S. Navy - Retired