Rpm Drop And Intermittent Jerky Feeling Of Engine At Idle And Low Cruising Rpm

[Charith H Jayasinghe]

About one month back I was fool enough to do high pressure wash in my car engine bay.

Soon after that I felt rough idling and sense of engine was going to stall. Then my mechanic and I removed most of the sensors and connectors including MAF, ECU, Throttle body, coil packs, applied air and contact cleaner (Wurth).

Problem was solved at that time but end up with a high RPM of 900-1000. (It was used to be at 700).
Then did idle air volume learn from a place but it wasn’t operated by usual technician but it came down. But after driving for about 50 km ( after 2 days ) some kind of a jerky feeling started to feel while idle with specially AC on or while gear in D or R without AC. It also occur when cruising around 60kmph when OD engaged, torque converter locked and cruising RPM comes near 1400-1500 area. It doesn’t occur in RPM like 2000. Battery voltage didn’t dropped when this happened.

After driving about 250km (I came back to work) I did a clean and removed MAF connector while engine was running (I just wanted to check MAF) and removed battery terminals for a while (2days) and allowed ECU to reset. Surprisingly it improved for few km and started again.

After coming back (another 250km) did a sensor clean again and did a re-learn from a different scanner (x431) things got solved significantly and frequency of occurring went down and happened only at idle with lesser frequency.

Later, in the scan report I saw load indicator was on while doing that even though everything was turn off (may be cabin light was on or car stereo panel lights stays on though it is turned off). I went over internet for read regarding this and saw “ Accelerator paddle release position learn and Throttle close position learn” should be performed prior to idle air volume learn.

I changed MAF and O2 sensor later. Even though fuel figures came close to factory figures (16.2/16.6 kmpl) those symptoms didn’t improve. My next plan is to check fuel pump and AC (clutch or something)

So,
1 What may be issue?
2 Is idle air volume learn is highly sensitive thing that need to follow exact procedure?
3 Is this condition relate to above thing or any other isolated condition?

http://forum.autolanka.com/topic/15462-fb-15-idle-drop-issue/ this thread somewhat similar but not exactly similar

[The Don]

I guess a few things could be a potential issue

1. Some component is incorrectly indicating load causing the ECU to instruct the rpms to be increased. Load in this case is mostly electrical load like headlights coming on etc

2. There is a mechanism to keep the idle up when the engine is cold to help it warm up. In the older engines a hot water line was directed towards the throttle body to control this. I'm not 100% sure how it works in your car but you should check it out as this normally allows the idle air adjustment to be bypassed.

3. The ECU is faulty. Best place to check this out is the agents.....

[Charith H Jayasinghe]

Thanks Don.

Do I need to remove power from car security system to set the load sensor OFF when doing idle air volume learn?

Thing also settled with removal of battery terminal to reset the computer (is it?), and re-cur after some times later. My gut feeling says( and I'm praying) ECU may be ok.

As you suggested its time to take it to agents.

[Charith H Jayasinghe]

I did this to give a re learn yesterday http://www.nissanclub.com/forums/f-q-2002-2006/121664-idle-air-volume-learning-procedure.html

1) Drive the car to "warm up" temperature. Make sure your idle is close to 700 rpm.
2) Ensure any battery draining devices are off. Ie. headlights, interior dome lights, HVAC, stereo.
3) Turn the car ignition key to "OFF"
4) Wait ten seconds
5) Turn the key to "ON" (not start)
6) Wait three seconds.
7) Perform the following five times in five seconds or less. Fully press the gas pedal and release.
8) Wait seven seconds from last of the five releases.
9) Fully press the gas pedal and hold down. Within ten seconds the "Service Engine Soon" light should begin to blink.
10) Wait another ten seconds (while still holding the gas pedal) and the "Service Engine Soon" light should stop blinking.
11) As soon as it stops blinking, release the pedal, start the car and check the idle (should still be around 700 rpm)
12) Let the car idle at 700 rpm or so for about 25 seconds, rev the engine a few times and then let it return to idle.
13) Shut the car down.

Seems it didn't solve the issue

[Charith H Jayasinghe]

OK I came back home again.

On the way to home it disappeared after driving about 50km.

This time did a Injector clean up with ultrasound (??).

Cleaned the IAC Valve (there was a carbon built up) (can that be a time to time carbon dislodged and block it? ).

Car was running smoothly but it is too early to tell.

Agent's diagnostic run for ECU I've planned on next week.

Thank you Don for suggestions and Thank you Rumesh for helping me since the problem began.

Edited March 16, 2014 by Charith H Jayasinghe

[Charith H Jayasinghe]

Issue didn't came back . so I think it was due to IAC valve block with carbon.

[The Don]

Great to hear you resolved the problem. Depending on the design of the ICV valve carbon build up can cause jerky operation meaning you experience idle hunting at times. Seems this was probably the issue.

[Charith H Jayasinghe]

This problem was keep coming back but ultimately found the cause. It was a leaking coil pack. issue was completely solved following coil pack replace. 

[NRX]

Glad that you found the root cause of the issue Charith, and thank you for updating the original thread

And I myself did an idle air relearn which was successful. But the procedure was different, it involved disconnecting and reconnecting the TPS within 5 seconds while the engine is running. Hope you came across that

Edited January 19, 2017 by NRX

[Charith H Jayasinghe]

Yes  did that too :-) . This issue found when I check coil packs closely. There was a rainbow color discoloration at the body of a coil pack. Then I lifted it partially when engine was running and I saw their is a side spark to the engine block. After that no issues at all. 

[NRX]

9 minutes ago, Charith H Jayasinghe said:

Yes  did that too :-) . This issue found when I check coil packs closely. There was a rainbow color discoloration at the body of a coil pack. Then I lifted it partially when engine was running and I saw their is a side spark to the engine block. After that no issues at all. 

Great. did you replace it with a recon one ? How much did it cost you ?

[Charith H Jayasinghe]

Yes... I found one for Rs 4000 .