# throttle/deceleration problems



## jessebruffett (Apr 16, 2015)

2003 altima 2.5l se 5spd, 135k miles

when i drive the car and I'm coming to a stop i put my foot on the clutch pedal the rams drop to ~1200rpms then surge back up to 2000rpms then back and forth slowly several times for 3-10 seconds but generally 5. if i blip the throttle when stationary and in neutral the rpms will come down very slowly from 2000 and do the above surging thing for several seconds and then drop to 750. its been doing something similar to this for the 6 months I've owned the car but it would hold at 1k rpms with the clutch pedal depressed until i came to a stop then immediately drop to idle. i assumed that was normal, I'm beginning to think not. I have been unable to find a definitive procedure on resetting my ECU. i can get my hands on an obd2 scanner from a friend, can i reset the edu with that or will that even help? it does not surge or lag under power and in gear just with the clutch depressed. it does seem to get worse and the time of the surging gets longer after a longer driving session, but i have not been able to definitively confirm this. there are no codes. any ideas or am i in for a trip to the stealership?


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## jessebruffett (Apr 16, 2015)

No ideas at all?


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## SPEEDO (Jun 9, 2003)

you may have a issue with the throttle chamber, check to see if its dirty, check the air intake(air cleaner to throttle chamber) for any leaks, any codes??


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## jessebruffett (Apr 16, 2015)

No codes. As far as I can tell no leaks in the piping. I don't have a bathtub in my dorm room so I can submerge it and see. Would a simple vac leak cause this? Are are you thinking major obstruction?


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## SPEEDO (Jun 9, 2003)

I am thinking check the simple stuff 1st, like air leaks, the hose that goes from the air cleaner to the engine etc, make sure the electrical connections to the throttle chamber & air flow meter are good etc, I think its Auto Zone that will check for codes (free). what you describe sounds like its "hunting" (rpms up/down) thats why I am bringing up the throttle chamber..


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## jessebruffett (Apr 16, 2015)

the codes have been checked and there are none. i used carb cleaner all around the intake piping form the filter to the TB, i also checked all the hose clamps and they are good. the connections on the AFM and TB are solid and no corroded, i did a visual check of the TB and there are no chunks of crap in it but its also not "clean" either. i won't clean it, i have cleaned 2 on other vehicles that had no issues there were just dirty and i ended up having to replace the TBs so messing around with an electronic throttle body is something i just don't do.


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## SPEEDO (Jun 9, 2003)

"messing around with an electronic throttle body is something i just don't do." Dont blame you!! if it is the throttle chamber (which I think it is) if you let it go too long it will get out of spec and you will have to preform a re-learn when you install the new one, I have a oem pt# 1611K-AE01BRE (re-man & has a $40 core) think it runs about $180 but that is oem, probably find something cheaper online


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## jessebruffett (Apr 16, 2015)

What exactly do you mean by throttle chamber? just to clarify, to me that means the entire inside where the valve is. do you think the throttle body itself is just dying?


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## SPEEDO (Jun 9, 2003)

its mounted on the engine, has a big butterfly in it, the air intake hose from the air cleaner feeds it..


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## jessebruffett (Apr 16, 2015)

yes, thats what i call the throttle body. there is nothing in it gross, i can still see silver all the way around the inlet and the butter fly valve does not have crap on it. when i say it wouldn't eat off it means that there is a slight amount of material in it but not a lot. if its dying is there a definitive way to tell other than throwing a part at it and seeing if it goes away? like i said, there are no codes at all as per an obd2 tool.


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## SPEEDO (Jun 9, 2003)

it may not throw a code until its too far out of spec...


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## jessebruffett (Apr 16, 2015)

so there is no way to tell its going bad till it throughs a code? how does it go out of spec(just curious)? i really can't afford to just through parts at it without knowing thats the definitive issue.


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## rogoman (Dec 16, 2004)

jessebruffett said:


> 2003 altima 2.5l se 5spd, 135k miles
> 
> when i drive the car and I'm coming to a stop i put my foot on the clutch pedal the rams drop to ~1200rpms then surge back up to 2000rpms then back and forth slowly several times for 3-10 seconds but generally 5. if i blip the throttle when stationary and in neutral the rpms will come down very slowly from 2000 and do the above surging thing for several seconds and then drop to 750. its been doing something similar to this for the 6 months I've owned the car but it would hold at 1k rpms with the clutch pedal depressed until i came to a stop then immediately drop to idle. i assumed that was normal, I'm beginning to think not. I have been unable to find a definitive procedure on resetting my ECU. i can get my hands on an obd2 scanner from a friend, can i reset the edu with that or will that even help? it does not surge or lag under power and in gear just with the clutch depressed. it does seem to get worse and the time of the surging gets longer after a longer driving session, but i have not been able to definitively confirm this. there are no codes. any ideas or am i in for a trip to the stealership?


An OBD2 portable scan code reader will only reset any fault codes that may be set. It doesn't reset any learned parameters. The problem you're having may be due to a dirty IACV valve that's sticking.


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## jessebruffett (Apr 16, 2015)

there is an iac? i figured the idle speed would be controlled by the throttle since its electronic. i know the obd2 tool wont reset the parameters only codes, there are however no codes to even reset. where is the iac located? again its something i hare cleaning because I've cleaned ones on other cars and they usually fail very shortly after the cleaning or it makes no improvement. in addition would a dirty iac cause the surge? i could see it not allowing the rpms to drop fast enough since many iac's open to release back pressure when the throttle it let off suddenly. I'm not doubting the possibility, if i know what the problem was i wouldn't me here, I'm just trying to work it out in my head and gain the wisdom for future issues.


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## rogoman (Dec 16, 2004)

Sorry about the misinformation. I'll modify my previous post in that there's no actual IACV valve. Instead the IACV function is integrated into the throttle body electronics. Try the following procedure for resetting the idle speed:
Clear Self-Learn Settings:
Disconnect the battery cables, first the negative (black), then the positive. Touch the cable ends together for ten seconds. Reconnect the cables to the battery. This should clear all of the self-learn settings.

Reset the Idle Air Volume Learn Function:
Turn the key on (but do not start the engine) for one second and off for ten seconds. Repeat three times. Time the intervals as accurately as possible. This should reset the idle air volume learn function.

Reset Throttle Valve Closed Position Learn:
The engine and transmission must be at normal operating temperature for this procedure. Drive the car around--don't just warm it up in the driveway. Turn the ignition off and wait ten seconds. Verify that the accelerator is fully released, then turn the ignition back on and wait for three seconds. Push the pedal in and release it fully five times within five seconds. Wait for seven seconds, then push the pedal in and hold it for twenty seconds. The MIL (Malfunction Indicator Lamp) will stop blinking and come on steady. Hold the pedal in until the MIL goes out. When it goes out, release the pedal and start the engine within 3 seconds.


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## jessebruffett (Apr 16, 2015)

Has anyone had any experience positive or negative when using an ELM wifi obd2 adaptor to the dash commander app for an iPhone/ipad? i took it to the dealership, they said the TB is in great shape and they reset the ECU. the problem went away for a few days now its back, i have heard the ECU can take between 40 minutes and 400 miles to start causing a stable normal idle after a relearn but i can't find a definitive on this either way. it has been suggested a MAF or MAP sensor problems causing fuel trim issues but not being bad enough to through a code. I've read mixed reviews on these adaptors going from they are fantastic to toasting ECU's. so I'm wondering how they do on these cars. any thoughts?


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## jessebruffett (Apr 16, 2015)

I should clarify, after the ECU reset the surge is better, much better, its now just surging up to 1100ish rpms and not as constantly but its still happening.


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