2001 Pathfinder - Dies when idling, rides rough when accelerating

[MClark00]

My 2001 Pathfinder has been having trouble over the past year with idling. Here's the timeline: - Around 9 months ago, was dying or shuddering at stop lights. Took it into a local mechanic twice, no change. ECU throwing codes P0505 and P1110, both related to IACV. - Around 6 months ago, took apart the throttle body and completely cleaned it and the openings leading into the IACV. Problem solved, although the codes didn't go away, and came back after resetting ECU. - Around 1 week ago, car has been driving fine, but codes prevent inspection, so I've got to get them fixed. I take it to a mechanic to ask them to do the idle relearn procedure, but they tell me the IAC motor is bad and there is a vacuum leak in the throttle body. I decline their repairs, but when I leave the gentle shuddering at idle has returned. - I ordered a replacement throttle body and IAC (used), and replaced it. After getting everything reassembled, the car now behaves like this: - Cold start, idles fine - Rev up the engine to 2-3K rpm, and most of the time it will fall down to 500 RPM or less and then die. - When driving it's extremely rough at 1800 RPM and what feels like the transition between gears. It surges up and down until I power through it, and then it drives smoothly. - When the car is warm, it will die at idle (such as at a stop light).

I've gone back and forth between the two throttle bodies, and the behavior is consistent now.

After reading about bad MAFs on another thread I disconnected the MAF and drove around. It idles perfectly like this, but still drives very rough when accelerating. After reconnecting the MAF the idle problem returns, and I now have code P0100 (MAF circuit) in addition to P0505 and P1110.

I really want to try and avoid the $750 for a completely new throttle body and all of the labor at a mechanic. Any suggestions?

Thanks for your help!

I've cross-posted this over at nissanhelp, hopefully that's not spamming anyone.

[sixty4]

I have the same issues, including a power loss when accelerating heavily such as out into traffic. Feels like a power loss or gear slippage.

I was pointed toward the MAF but hope you get a solid answer I can use.

I have a 2001 QX4.
Modified by sixty4 at 7:25 AM 2/2/2010

[MClark00]

Here's some more data - any help would be *greatly* appreciated. I'm not sure what to test next.

I cleared codes and drove for a while, and got P1135. Then I cleared again, and haven't gotten any codes since.

I warmed the car up for 10 minutes, then ran a few datalogging sessions each time just turning the car on and letting it idle until it died.

Using a mix of OBD-II and Consult-II logging, I see this pattern:STARTUP - Ignition, RPMs up to 1800, dip to 450, then settle around 825

INITIAL IDLE - RPM: ~825 - Injectors B1 and B2 settle around 7 - A/F Corr B1/B2 both at 100 - STFT B1/B2 both at 0

20 SECONDS IN - RPMs dip to 450 - Injectors run up to 10 to compensate - RPMs run back up to 825, injectors back to 7 - STFT B1/B2 still at 0

SECOND IDLE PERIOD - Immediatley after recovery, A/F Corr B1 and B2 (with B1 leading by 1 second) start a gradual decline to 75, which takes 11 seconds - Injectors slowly decline from 7 to 4.5, stop declining when the A/F Corr B1/B2 stop declining, and stay at 4.5 - STFT B1/B2 drop slowly to -25 (I believe this starts after A/F Corr and Injectors have finished their decline, but data is from different sessions so they could be declining together)

ENGINE DIES - 15 seconds after A/F Corr and Injectors have declined, RPMs drop in 1 second to 275 - A/F Corr B1/B2 immediately jump to 100 - Injectors jump to ~13.5 - STFT B1/B2 jump back to 0 - Engine dies

[josephdmartin8]

I just ordered a new MAF sensor to replace mine, which has been slowly going bad. I used the Maxima sensor instead of paying 600 bucks for the Pathfinder one, the specs are supposed to be identical and it has worked fantastic for lots of people on another Pathy forum. My truck just today started doing the same thing as yours, and I've done a tuneup but have been dealing with a lean bank 1 & 2 codes for months.

[MClark00]

Please let me know if it fixes the problem for you. I'll try again tonight disconnecting the MAF to see if the default values let it drive without stalling or jumping during acceleration.

Question to anyone: Would a bad/dirty MAF cause the problem where once it enters closed loop, it slowly decreases the short-term fuel trim until it stalls, at which point it ramps it back up?

[Pwnin O'Brien]

Quick question, after you replaced the throttle body and the IACV-AAC valve, did you complete the Idle Air Volume Learning procedure again (after resetting the ECM to clear all of the codes)?

[MClark00]

I tried to do it using the non-Consult-II procedure, but it never would take. Sometimes it would die before I let it run 30 seconds, other times it didn't seem to have any effect. I haven't asked a mechanic to use the Consult-II to do the relearn yet.

[Pwnin O'Brien]

I tried to do it using the non-Consult-II procedure, but it never would take. Sometimes it would die before I let it run 30 seconds, other times it didn't seem to have any effect. I haven't asked a mechanic to use the Consult-II to do the relearn yet.

Did you check the preparation checklist for the Idle Air Volume Learning procedure? If any of those items in the checklist fall out of specification during the learning procedure then it will automatically exit learning and default to the previous specs. Are you currently getting any DTC codes?

[MClark00]

I did check the checklist, but I'll try again tonight to make sure. The only thing I couldn't check was the coolant temperature, but I did drive it for 10 minutes beforehand.

The idle volume relearn wouldn't solve the problem where it jumps during acceleration though, would it? Neither problem started until disassembling the throttle body.

A new code just came on today after a few days of driving, but I haven't checked it yet. The only ones I've received so far (outside of the time I disconnected the MAF) are P0505, P1110, and P1135.

[Pwnin O'Brien]

You need to troubleshoot the P1110 and P1135 codes, both codes are for the IVT (intake valve timing) system (not related to IACV). Below are a couple of threads which discuss those two codes in-depth. These codes are EXTREMELY common on 2001's and are quite difficult to diagnose.

zer...ensor

zerothread/358345