P0171 Driving me Insane!!!

[four_shot]

The OP really needs to get the live data from the PCM on this one.

If possible, Rent a scan tool from a parts store. Many times it's just a refundable deposit making the rental free. (Make sure it has live data capabilities.)

I don't remember the op mentioning spraying the intake/ injector area with carb cleaner to see if a vacuum leak was noticed. I'd try that just for sh*ts and giggles.

 

[XJSteven]

By the way, the P0171 error code has been much less frequent this week so after only seeing it appear twice on this tank of fuel I filled up today hoping to see a big improvement in fuel consumption. Unfortunately there was no change. Apparently it's still running too rich regardless of whether a P0171 code is thrown.

 

[XJSteven]

The OP really needs to get the live data from the PCM on this one.

If possible, Rent a scan tool from a parts store. Many times it's just a refundable deposit making the rental free. (Make sure it has live data capabilities.)

I don't remember the op mentioning spraying the intake/ injector area with carb cleaner to see if a vacuum leak was noticed. I'd try that just for sh*ts and giggles.

Hi four_shot, I've now ordered a live data scanner for my laptop.

No, I haven't tried spraying carb cleaner but when I unplugged a vacuum hose it started running rough and the voltage from the 02 sensor dropped. When I plugged the vacuum hose back in the idle was smooth again and the 02 voltage went back up. I may be wrong but I thought this test showed it wasn't a vacuum leak?

 

[four_shot]

I'm just throwing ideas out. It's one of the first things I try every time I deal with a lean code at work. It doesn't have to be a change in quality, Sometimes it will only affect idle speed. :dunno:

Carb cleaner's cheap, and doing this test has left me smacking my forehead, going "why didn't I just try that first!":doh:

 

[XJSteven]

Thanks. I have some carb cleaner in the garage so will give it a go.

 

[XJSteven]

Did you replace the IAC actuator. 99.9% of them are missing from JY vehicles, and it's purpose is to lean the mixture. at idle. If bad, it would lean the mixture all the time.

Hmmmm...this might be worth looking at. A new code has appeared tonight - P0505 and it kept stalling (wouldn't idle). Either this is related to my current problem or I've got something else to deal with now.

 

[Ecomike]

Yeah I know exactly what you mean. I've had some very entertaining emails from Chinese Ebay sellers! Last time I complained about an item I bought off Ebay the response I got started with 'Please accept my inconvenience for your life." The rest of the email had me in hysterics too. hahahaha.

"I hope that I am making myself perfectly transparent"

LOL:clap:

 

[XJSteven]

This one is puzzling. I am going to say the computer thinks the engine is running lean, and is adding fuel to compensate, but that the computer is not seeing the rich fuel mix data from the O2 sensor. Sounds like a signal voltage drop between the sensor and the PCM to me, bad wiring or connections between O2 sensor and PCM.

Based on your last post data, the O2 and PCM seems to be working at higher rpms, cruising, but not at idle. The PCM thinks it is lean at idle and is running it rich at idle to compensate, but it seems the PCM is not seeing the data at idle, but you are, which is odd?

Well today I removed the air-box, took off the black cover on the PCM and disconnected the 3 connectors. I tested the continuity of a whole bunch of wires at the PCM including the upstream O2 sensor, MAP sensor, ECT sensor, IAC and TPS - and all had a low resistance reading of approx 0.9 ohms so the wiring appears to be ok between the sensors and the PCM.

I also pulled out the IAC and gave it a clean, then retested the signal at the O2 sensor using my 'imperfect' digital voltmeter. It may have fixed the constant high voltage reading I was getting at idle because it looked to be fluctuating instead but I will have to recheck this when warm. (It's still stalling at idle occasionally, or idling with very low revs, but this is intermittent and the P0505 code hasn't come back on since I cleared it the first time).

The more things I check the more confused I get.

 

[Skreed]

I second the carb cleaner ...spray everywhere air might get in, around the injectors and intake manifold, etc

Does your meter have a min/max function?....the refresh rate it too slow to see a pulse or sweeping signal, but at least you can see if your with in spec.

 

[XJSteven]

Does your meter have a min/max function?....the refresh rate it too slow to see a pulse or sweeping signal, but at least you can see if your with in spec.

No, it doesn't.

I will try the carb cleaner tomorrow.

 

[WB9YZU]

Hmmmm...this might be worth looking at. A new code has appeared tonight - P0505 and it kept stalling (wouldn't idle). Either this is related to my current problem or I've got something else to deal with now.

The reason I suggested it is because I too have been chasing an intermittent 171. When I got the vehicle, it was sound as a pound. Then it would throw a 171 code and idle like crap and stall at lights when warm. The exhaust stunk to high heaven.

I played the "What the hell do these voltage readings mean" game, and got no where. A post to here came back and said "replace the O2 Sensor".

I took a trip to the JY with the intention of replacing every sensor on the TB and manifold, when I found I could not find any IAC actuators, few TPS sensors, but all the MAP sensors were still on the vehicles. Hmmm, a trend?

So I took mine off... and it was broken. The stepper motor and plastic guides are not made of much, and after 190K they gave out. Sometimes the IAC would adjust, but most often it would mess up. So I replaced it. Now it idles normally at all times. The 171 code went away around town.

Presently, I can drive the vehicle for hours without a problem, and unless I crack it open (WOT), the code stays away. When it does occur it is on a very long drive or some decent WOT operation. The code preceding the 171 is a 131, which indicates slow O2 on bank 1 (manifold). The engine runs normally and the exhaust doesn't stink, it just throws a code which goes away after a few starts. I plan on replacing the O2 Sensor when it gets a bit warmer.

 

[XJSteven]

Thanks Zuki-Ron,

WOT is a good point and could explain my own intermittent P0171 problem. I'll have to check that out.

I also have a new IAC valve on order from Rockauto along with a better quality upstream 02 sensor so if they make no difference then worst-case I will have a few spares.

 

[XJSteven]

I second the carb cleaner ...spray everywhere air might get in, around the injectors and intake manifold, etc

Does your meter have a min/max function?....the refresh rate it too slow to see a pulse or sweeping signal, but at least you can see if your with in spec.

I tried the carb cleaner today with no noticeable difference to idle speed. I have a vacuum tester on it's way from Ebay so will confirm vacuum readings with that.

I've rechecked the oxygen sensor with the motor warmed up and its definitely fluctuating at both idle and higher revs now,which I wasn't getting at idle before I cleaned the IAC. Although my voltmeter doesn't have a min/max function I can clearly see it dropping below 0.2 and above 0.8 on the digital display so appears to be within spec.

Sitting in my driveway in neutral with my foot flat on the accelerator (at WOT) didn't throw up a code.

 

[Skreed]

Seems like you have done a lot of testing and haven't come up with anything out of the ordinary.

You said you are getting OBD2 software with live data stream right? I would hook that up, clear the codes, then drive around until it pops up again. It should "freeze" the data when the code pops up and record it. Take a look at that and report back, it might give us some more ideas.

 

[XJSteven]

Seems like you have done a lot of testing and haven't come up with anything out of the ordinary.

Yes I have and is why the title of this thread says I'm going insane!

I tested the vacuum today and got a normal vacuum reading. The vacuum gauge showed a reading of 15 initially but after a few minutes crept up to a steady 17 (which apparently is within the healthy 15-22 range). When I gave it some throttle it dropped below 5, shot up over 22 and then came back down to a steady 17 - so all looks good there.

I was going to test the fuel pressure but none of the connections that came with the vacuum/fuel pressure tester fit the screw on test port at the fuel rail. Do I need to order a special 'Jeep' connector for this?

You said you are getting OBD2 software with live data stream right? I would hook that up, clear the codes, then drive around until it pops up again. It should "freeze" the data when the code pops up and record it. Take a look at that and report back, it might give us some more ideas.

Sounds good, just waiting on the software to arrive from China. I will also swap out the IAC, O2 sensor and TPS when the spare parts I ordered arrive (one thing at a time of course).

 

[four_shot]

The vacuum/fuel tester is a carbuertor only fuel pressure tester. It is designed to test old mechanical fuel pumps that generated less than around 10 psi. Your fuel system should generate 47-51 psi Key on Engine off.

If you have a guage like I'm thinking, testing fuel pressure with it is a bad idea.

the fuel injection guages at the parts stores don't require a special adapter though and run around (yet another) $30.

 

[joe_peters]

Yeah, you don't want to be using that vacuum/pressure gauge combo on a fuel injected system.

 

[XJSteven]

The Ebay seller had incorrectly described the vacuum/pressure gauge as suitable for all vehicles. They've fixed the ad now (to exclude fuel injected systems) but I decided to keep the gauge for vacuum testing.

Four days ago I cleaned the IAC valve again and the P0171 hasn't returned since. Prior to that it was coming back on whenever I cleared it so I'm fairly certain the IAC is the culprit. I have a brand new one ready to install but I will wait and see if the error code returns first.

When I had the IAC removed from the throttle body with the plug still connected I turned the ignition on and the IAC suddenly sprung apart into two pieces. I gave it a clean and pushed it back together. Is it normal for it to shoot apart like that or is it faulty?

 

[Ecomike]

Yes it is normal, but not good!!!!! It can (usually does) damage the IAC letting it do that!!!!!

 

[four_shot]

The IAC really shouldn't be powered up when not installed. I'd say replace it with the new one.