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Idle randomly dipping #4498704
08/26/17 01:31 PM
08/26/17 01:31 PM
Joined: Apr 2013
Posts: 2,333
The Northeast
mclasser Offline OP
mclasser  Offline OP
Joined: Apr 2013
Posts: 2,333
The Northeast
This is in my Pilot.

90% of the time, the car idles at a solid 750 RPM at a traffic light with all accessories off. But the other 10%, the idle dips to like 600-650. When this happens, the engine makes a rumbling noise and you can feel the center console shake a little. BUT...turn on the headlights or A/C, the idle rises and everything smooths out again. It's strange that this happens intermittently. Car drives great otherwise.

Any ideas what could be going on?


2018 Hyundai Elantra VE -- 4K
2013 Honda Pilot EX-L 4WD -- 56K
2002 Honda Accord EX-L -- 211K

Re: Idle randomly dipping [Re: mclasser] #4498794
08/26/17 03:57 PM
08/26/17 03:57 PM
Joined: Sep 2016
Posts: 1,418
Minnesota
bioburner Offline
bioburner  Offline
Joined: Sep 2016
Posts: 1,418
Minnesota
Maybe the 5 year old battery is starting to fail and the alternator is having to engage more to keep the system at 13 or so volts.
Many cars the AC system still exercises to keep seals good even with the switches off.



97 Ford E350 D,99 F350 dually D
13 Scion Xb
12 Ford Transit Connect
06 Nissan Xterra
03 K1200 BMW
07 Kawasaki KLR650
13 Madass
Re: Idle randomly dipping [Re: bioburner] #4498800
08/26/17 04:06 PM
08/26/17 04:06 PM
Joined: Apr 2013
Posts: 2,333
The Northeast
mclasser Offline OP
mclasser  Offline OP
Joined: Apr 2013
Posts: 2,333
The Northeast
Battery was replaced earlier this year; connections are all clean & tight.

In addition:

- All fluids are clean & full.
- I mainly use BJ's gas but fill up at Top Tier stations every 3rd tank or so to keep things clean.
- Inspected the air filter. It's 25k miles old but light still shines through; manual says to change every 30k.

I'm thinking about cleaning the MAF sensor & TB. I don't expect them to be dirty at only 45k miles but maybe it'll make a difference.


2018 Hyundai Elantra VE -- 4K
2013 Honda Pilot EX-L 4WD -- 56K
2002 Honda Accord EX-L -- 211K

Re: Idle randomly dipping [Re: mclasser] #4498840
08/26/17 05:19 PM
08/26/17 05:19 PM
Joined: Jan 2009
Posts: 6,204
New England
gathermewool Offline
gathermewool  Offline
Joined: Jan 2009
Posts: 6,204
New England
My Civic will idle rough (haven't heckled RPM) after being fully warmed up and at higher ambient temps. This seems to coincide with the ELD sensing low electrical load and lowering supply voltage to 12.6 or so.

Turning even just the running lights on (all but headlights on) will raise the voltage to normal. The vibration doesn't go away completely (likely something else is the root cause of that) but the the vibrations do lessen.


'14 Forester XT FA20DIT (Cobb Stage 1)
Edge 0W-40 + FU filter
'15 Legacy FB25 (OEM Stage, uh, neg. 7?)
Edge 0W-20 + FU filter
Re: Idle randomly dipping [Re: mclasser] #4498855
08/26/17 05:39 PM
08/26/17 05:39 PM
Joined: Dec 2006
Posts: 917
midwest
JamesBond Online content
JamesBond  Online Content
Joined: Dec 2006
Posts: 917
midwest
Maybe it's the cooling fans or ac kicking on. Try cleaning the throttle body.

Re: Idle randomly dipping [Re: mclasser] #4498965
08/26/17 08:49 PM
08/26/17 08:49 PM
Joined: Apr 2016
Posts: 845
KS
FordBroncoVWJeta Offline
FordBroncoVWJeta  Offline
Joined: Apr 2016
Posts: 845
KS
Might be time for a new intake sensor.


17 Volkswagen Jetta 1.4T
15 Honda CRV 2.4
12 Volkswagen Jetta 2.0
01 Pontiac Sunfire 2.2
Re: Idle randomly dipping [Re: mclasser] #4498990
08/26/17 09:33 PM
08/26/17 09:33 PM
Joined: Jan 2017
Posts: 331
Texas,USA
ATex7239 Offline
ATex7239  Offline
Joined: Jan 2017
Posts: 331
Texas,USA
Go get the battery, alternator, voltage reg, etc. checked anyways. Sometimes you get a bad battery. Autozone with do it for free.

I've had bad or fouling plugs give me a rough idle, as well. Might be good idea to check those out and test the coil packs.


'12 Buick Enclave 139,xxx
Valvoline ML SynBlend 5w30
ACDelco PF63E

'17 Ford Fusion (Company Lease) 42,xxx
Oil Don't know
Filter Don't care
Re: Idle randomly dipping [Re: mclasser] #4501727
08/29/17 08:42 PM
08/29/17 08:42 PM
Joined: Jan 2010
Posts: 954
North Carolina
4ever4d Offline
4ever4d  Offline
Joined: Jan 2010
Posts: 954
North Carolina
Check the IAC valve. They will get dirty and cause idle issues. Throttle body cleaning will sometimes cause this problem also.


04 Chevy Colorado 3.5 I5 5w-30 OEF
07 Honda Element 2.4 I4 5w-20 OEM
10 Nissan Rogue AWD 2.5 I4 5w-30 OEF
Amsoil Products & Fram or Wix Filters





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