Nissan high idle fun and games
A Nissan with the notorious P0507 high idle issue - This is a push button start with electronic throttle body.
I fought with this Nissan for quite awhile before fixing it. I was burned by a new part in the process so I'm posting some throttle body waveforms and other data that might help someone in the future. Also some conflicting service info.
This is a car from a friend who owns a transmission shop. He bought this from a customer who didn't want to fix the bad transmission, so he rebuilt the transmission and was trying to get it setup for his daughter. It had a high idle and would set a P0507. Other than that it ran good. This was a project car that I worked on in between other jobs so after awhile I lost track of the whole sequence of events, but the last time I worked on it, it had a new throttle body already installed.
I tried the usual tricks of disconnecting injectors etc. to get the rpm down but it wouldn't learn. I smoked it and didn't find any leaks. I tried the automatic learn, manual learn and different scan tools and no go. I even re-flashed the ECM with the latest calibration but still no go. I checked wiring and drag tested all the connector pins. No problem found. I even tried a recommendation from a Nissan bulletin that mentions disconnecting the Mass Airflow Sensor with the engine running until the MIL comes on. Then clear the code and do the relearn. This didn't work either.
I replaced a PCV valve that I suspected was flowing to much volume but it made no difference on the idle. One thing I noticed that was odd when performing the relearn is that the idle would initially start to drop but then it would suddenly reverse and increase to … rpms and stay there. I've never seen one act quite like this. I still suspected a possible vacuum leak somewhere so I needed to find a way to rule this in or out.
I decided to try a test I learned in a John Thornton class. I connected a vacuum transducer to the intake. I then plugged the throttle opening and disabled fuel. I cranked the engine for about 12 seconds and the engine pulled 19" of vacuum. At this point I'm confident there are no vacuum leaks. There is no way it could make 19" of vacuum if it was leaking anywhere. So at this point I'm convinced it's some type of electronic issue.
Here's a rabbit hole I went down and maybe someone can explain this. Bad service information maybe? When scoping the throttle sensors I saw that sensor 1 started high with throttle closed and went low as the throttle was opened. Senor 2 did the opposite. Started low and went high when opening the throttle. This is opposite of what service information shows. I went as far as depinning the 2 sensor wires and swapping their locations. The ECM really didn't like this and set a code for the throttle being stuck wide open. I swapped the wires back and moved on.
I went back to the scan tool and this time I tried the function called "Throttle angle assign". It errored out every time I tried it, but then I noticed a new code that wasn't there before. P2119 Electronic throttle actuator has failed (return spring may be damaged)
Ok now I wanted to really scrutinize the throttle body and circuits. I cycled the key on/off and the throttle blade moved through it's normal reset routine. I moved the blade by hand and didn't feel anything obvious. I scoped all the circuits and current ramped the motor. The throttle sensor operation looked good but since I didn't have any know good captures for comparison, I wasn't sure about the motor operation.
At this point I asked my buddy to get me a used throttle body so I could try some experimenting. He said he still had the original TB so he brought that to me. I hung the original TB on the car and low and behold, the throttle relearn completed normally. I was really surprised at this point so I grabbed some captures of the TB again for comparison.
After looking at all my data for awhile one thing stood out. With the good TB there is very little motor current with the throttle closed. On the bad TB there is a fair amount of current with the throttle closed. Almost as if it's struggling to keep it in place. This is starting to make sense when coupled with the code that said there was a potential return spring fault.
When trying the relearn with the bad TB I had noticed that the rpm would initially start to drop but then reverse and start to climb up to … rpms. This seemed strange at the time but now I suspect that the system was fighting the bad return spring and getting confused.
I took a closer look at the New throttle body and noticed a sticker on it that said Reman. This got me curious so I started googling the numbers on it and I finally learned that this New Throttle Body was actually an A1-Cardone rebuilt.
The bottom line is the car is finally fixed and idling properly. I was at a loss as to why the original TB wouldn't learn the first time around but did when it was reinstalled. Maybe the initial problem was the bad PCV valve, but then I went down a rabbit hole because of a faulty "New Throttle Body".
Hopefully some of this data will be helpful if you run into a difficult high idle Nissan. I uploaded Escope files of before and after KOEO shutdown reset and captures of me sweeping the throttle.
In my scope captures the Red channel is TPS 2 and the Green channel is TPS 1 I put my scope leads in the throttle connector in order. Channel 1 to pin 1, channel 2 to pin 2 etc. Throttle body schematic
Bob, Great write up. Thanks for sharing all the info. A-1 Cardone strikes again!
I don't see how Cardone survives as a company. I'm at a 100% failure rate on Cardone parts when I find them installed in my customer's cars.
Ya but they make interesting case studies nothing harder then double proving a fault and then possibly a rabbit hole
Thanks Bob, I have an Altima here that another shop sent me, I have not spent much time on it, but it has similar issues and history. The one I have actually says the Idle did learn, but it is still high. Did yours show it “Learned” in the scan data??
Yes it did but I'm pretty sure that is referring to the closed throttle position being learned.
Ok, thanks. the shop that sent it to me did replace the T/B. It does not have a vacuum leak. It is test book perfect fuel trims. I will see who they bought it from.
Hi Bob, Excellent info and thanks for sharing. Question; is/was there a TAC duty cycle PID and were you able to log it (before and after) by chance?
Scott, Good question but I didn't really focus on that pid. I know I didn't log that specific parameter before and after but I'll look back through my captures and see if that data is in there somewhere. I'll post it if I find it.
Bob, As others have said great job. Love the use of the blocked off cranking vacuum test. Interesting ETB captures as well. I have gotten to the point if shops call me in on Nissan/Infiniti ETB issue I will not go unless an OE unit is installed. Many times I don't get a call from them afterwards. A follow up call to the shop confirms an OE unit fixed the issue. Unfortunately, this is not just…
Yeah John, there are some tests that are pure gold. I kept thinking I must be missing a leak somewhere but after doing that vacuum test I was able to rule that out and focus in other areas. I'm really looking forward to next week also. It will be good therapy as well as good learning. I almost had to cancel but dodged that bullet. Are you going down Friday afternoon?
Bob, I will be there Friday afternoon. Probably with an adult beverage in hand. I will reach out to you when I arrive so we can meet up. Looking forward to seeing you guys.
Good Job buddy. Another interesting thing about some Nissan vehicles showing all signs of having misfire issues but never register on the scanner yet replacing the ignition coils solve the problem. Fuel trims readings great and even mode 6 reports no misfire counts. Sometimes pure instincts play a big role in solving Nissan driveability problems. Cheers
Hi Bob I recently had a Infiniti g35 with a dual throttle body set up that was in for maintenance. An induction cleaning was performed and both throttle bodies were cleaned. After starting the vehicle a high idle and p0507 was observed. Countless attempts with snap on verus, autel, and a older launch unit were used to try and learn the idle with no success. I tried the manual procedures with…
Corey, I can tell you from experience every dual throttle body Infiniti vehicle that I could not do a successful IAVL procedure on was “fixed” by a PCM update and a repeat of IAVL procedure. This was also an issue with … Altima vehicles that will not perform a successful IAVL. An update to the PCM and IAVL procedure is successful. I could never get a straight answer from Nissan on…
They lowered the bottom limit of throttle closed/idle soft-switch because Nissan TBs are ruined if you clean them. Check the voltage after the learned value reset to see what I mean. They have an ablative coating that dissolves in the presence of TB/intake cleaner. Problem is, they were getting a ton of warranty claims for high idle after dealers were performing intake/TB cleaning that was not…
Jeff, thanks for the info I have had mixed luck with Nissan throttle body cleaning and idle learn from that generation. I don't clean them any longer
Jeff, That was one of the rumors I heard as well. However, I have personally cleaned many Nissan throttle bodies responsibly. Furthermore, they have all learned successfully providing they did not have actual mechanical issues. That is just my personal experience.
Not rumor - confirmed by a Nissan technical admin and an engineer from Renault and corroborated by actual airflow before/after measurements I performed on several different chassis that had idle issues after a throttle cleaning and then throttle body replacement. The only “responsible” cleaning on a TB with ablative coating is none at all. Second most responsible would be with denatured…
Jeff, Thanks for that detailed info. I've heard that certain throttle bodies shouldn't be cleaned but never knew specifically what fault that causes. If I understand what you have said, removing the coating effects the closed throttle airflow beyond a point the software can compensate for. A software update was written to give the system more authority over idle airflow.
Jeff, Can you share this info from a Nissan technical admin and engineer? Is there documentation? SAE white papers perhaps. Do you have before after measurements you mentioned. Not doubting just would like to see some affirmation and data. I can only tell you what works for me throughout the years.
Can you share this info from a Nissan technical admin and engineer? Is there documentation? SAE white papers perhaps. No, these were a face-to-face conversation and a text chat, respectively. This is not info anyone at Datsun would ever go “on record” with for obvious reasons. Do you have before after measurements you mentioned. Not doubting just would like to see some affirmation and data. I…
Yes the original throttle was cleaned. I did do a pcm update at one point but I think the update was done when the bad throttle body was on it which is probably why it didn't make any difference.
Thanks for sharing it , interesting case and really enjoyed reading how you find out the problem and fix it , thanks