P0171 CEL after Timing Belt replacement (1 Viewer)

[BnvS]

Ok folks, here's a thread that I am gonna start that will update as I go. But I did my 180k timing belt change. It took me a good 3.5 days of work but I got it done. I also have a radiator leak which I fixed as well by replacing the radiator (symptoms of this initially was engine running hotter around 215 F). Anyways after I replaced the timing belt. The engine runs great. No water leaks, engine hot goes max to 195F so I assume Timing belt job was success which it is. Engine runs smoothly, No idle issues, no surging, sputtering, lose of power..

BUT BUT.. when I ran some Torque Pro. I notice the Fuel Trims are sky rocketing. BTW the engine condition at this time is - Engine runs smoothly, No idle issues, no surging, sputtering, no lose of power..after about 2-3 power cycles I get a Pending fault code of P0171 - Bank 1 System to Lean.

BTW LTFT's are at 21.1% on both 1 & 2 banks, STFT's are at 19.5% on Bank 1 and 2. When I do hit the throttle the STFT's & LTFT's do come down to zero but when I Idle it climbs back up again. So all indications are it is a vacuum leak.

Troubleshooting steps already done/taken are
1. Replaced PCV valve and grommet. No change in FT's
2. Cleaned MAF sensor but no change in FT's either
3. Cleaned Air filter area and box
4. Reseated Air intake hose going from Airfilter box to Intake
5. Verified if I left of any connection.

Next steps
1. Blip the throttle and see if my O2 Sensory follow to rich condition and come back down
2. Monitor the MAF input and see what voltage I get and different RPM
2. Do a do a vacuum test with propane or similar and see if I can pin point a leak.

Will let you know what I find out. Thanks

 

[JunkCrzr89]

Diagnostic procedures: https://lc100e.github.io/manual/rm/rm630e/m_di_0061.pdf

 

[BnvS]

Ok so I made myself a DIY Smoke machine.. it was easy for around $15 bucks but I used tupperware lol... I pulled out the Evap plug (left one) after looking at the vacuum diagram and blew smoke but did not find anything major (there was very minor smoke from air box which is expected). So nothing major that I found in terms of a air leak.

Now I am going to find a fuel pressure gauge and make myself a DIY fuel adapter using this video here Fuel Adapter for Fuel Pump. So this will confirm if its not a fuel pump issue. Although I suspect its a fuel issue. I will follow up and let you all know.

BTW I'll get some pics of the Smoke machine when I get a chance. It worked great.

 

[abuck99]

Overthinking it- you’ve either crossed a vacuum line or left a line loose or off somewhere. Fuel trims are off due to it sucking air from somewhere. Retrace all connections for correct placement/connection

 

[2001LC]

Did you check the 2 vacuum lines and niples on vane pump idle up controller! Those plastic nipples get old and brittle, broke a few just touching them.
Did you happen to scan for DTC, before beginning T-belt service?
What are LTFT, cruises steady on HWY?

Fuel pump & filter issue (starvation) will usually set off both BK1 & BK2 lean DTC.

Tip: Control FI output in tech stream, watching o2's as you do.

 

[BnvS]

@2001LC

1) Did I check the vacuum lines and niples on the vane pump???? Is the nipples on the Idle air controller valve? circled in Red in the diagram below? Do I just need to check that to see if they are going bad?

As mentioned I did a smoke test and found no air gaps, so nothing major was leaking air or taking in air Afaik.

Now when I did the Timing belt I had to take out the whole air box and take the 3 (iirc) hoses that from that circled in Yellow. I know I put them back on correctly. But I will just take the whole thing out again and put it back on and insure I did not pinch any hoses or anything.

2) I did not scan the DTC for a before and after look. But the LTFT's on both banks (1&2) are going all the way to 21% & STFT (1&2) goes to 19%.

When I do drive the LTFT does go down while driving at normal/highway speeds and both the LTFT and STFT come down. LTFT both 1&2 come down to 10% ish, STFT both 1&2 comes down to -7% ish while cruising. But right when I come down to Idle the LTFT and STFT directly back up to 21%. So both times it effects both Banks...

So because it is happening on both banks I am thinking its the Fuel Pump. But I'll first redo the air box again and see.

3) In regards to the FI and monitor the O2 sensors - what test should I be using to monitor the O2 with FI variation on Techstream?

Thanks

 

[2001LC]

Yes you've circle in red. Here's picture of idle up circle in red.

@JunkCrzr89 posted a link for you. You'll see some of the 02 test there, with voltage specs. Basically I watch to see each side )bk1 & BK2 a/f & O2s) reacting the same or near same. As I adjust fuel trim to full rich than full lean. But highly unlike both bK 's a/f or o2 suddenly went bad. So it's more likely you've vacuum issue or mixed something up, as @abuck99.

Diagnostic procedures: https://lc100e.github.io/manual/rm/rm630e/m_di_0061.pdf

Also make sure MAF wire block locked in MAF sensor. Which is best to disconnect battery before disconnect MAF, reconnect battery after MAF connected.

VVT have a bad fuel pump. But they act differently when bad. Typically after pull up a long hill with RPM at or above 3K. Then as throttle let off as hill created, RPMS drop. Engine dies. Lean BK1 & BK2, fuel starvation.

 

[jerryb]

propane will be your friend. I wouldn't do anything else.

 

[BnvS]

Ok so update to what I found..

I must be crazy.. i didnt see the Idle up tube that was just hanging there and not connected.. so much thanks to @2001LC and others. I plugged that monitoring my fuel trims and immediately noticed my fuel trims drop and the idea by a little bit..

The tube was hanging there and b/c of the angle I thought it was plugged in...and I countless times were tugging other tubes around the area.. so morel of the story.. check all and I mean ALL your daam tubes hookup dummy.. . hehe anyways thanks for helping me out.

BTW after plugging this in my LTFT dropped to 4.7% and STFT's where between -5 to -20% due to trying to correct the lean condition...

The good thing I got out of this is how to check for any leaks by making a DIY smoke machine (pic below).. BTW here are the pics album of the DIY tupperware smoke machine.

Come in handy when troubleshooting EVAP, O2 sensor, System too lean or rich (p0171, P0174 codes) issues quiet a bit. Here's the video I used to get the idea and components and adopted it for my own DIY tupperwhere smoke machine..lol

 

[AlpineAccess]

Ok so update to what I found..

I must be crazy.. i didnt see the Idle up tube that was just hanging there and not connected.. so much thanks to @2001LC and others. I plugged that monitoring my fuel trims and immediately noticed my fuel trims drop and the idea by a little bit..

The tube was hanging there and b/c of the angle I thought it was plugged in...and I countless times were tugging other tubes around the area.. so morel of the story.. check all and I mean ALL your daam tubes hookup dummy.. . hehe anyways thanks for helping me out.

BTW after plugging this in my LTFT dropped to 4.7% and STFT's where between -5 to -20% due to trying to correct the lean condition...

The good thing I got out of this is how to check for any leaks by making a DIY smoke machine (pic below).. BTW here are the pics album of the DIY tupperware smoke machine.

Come in handy when troubleshooting EVAP, O2 sensor, System too lean or rich (p0171, P0174 codes) issues quiet a bit. Here's the video I used to get the idea and components and adopted it for my own DIY tupperwhere smoke machine..lol
View attachment 2847000

 

[BnvS]

@AlpineAccess ooh dont give people any ideas...especially in clean states. lol

 

[jerryb]

i erased my a****** comment about checking unmeasured air and you should be able to just look at it and fix that. Maybe use your thumb on a hole.
jesus would only say that south atlanta has free shipping again. This is a big deal for big items. I swear they're competing big with mcgeorge. I dropped my monthly budget yesterday. Megazip has 20%off but their prices aren't great lately.