2015 odyssey runs rough when cold.......advice

Joined
Aug 20, 2003
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1,634
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ottawa
Hi Everyone,
We have a 15 odyssey that runs rough when the engine is cold, until warm up 5-10 mins of driving.
It has 145K KMS or 90k miles.
I have replaced the spark plugs 2 months ago - put a VCM blocker on it - did 5 trans drains and refills - new vvt spool valve - right side engine mount. --Cleaned the egr before the winter.
Run 2-3 treatments of SL-1 redline over the last 2-3 months.
Fresh oil change 500 kms ago -0w-20.

After 5-10 mins of driving the engine runs great. Temps here are -10c to -20c on average.
Just started doing it.

No engine codes- no pending codes?
Any help on where to look would be great. Thanks
 
Joined
Jun 28, 2012
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Southern Illinois
I would change the O2 sensor. Had one get "lazy" and did same thing, NO code set either. New sensor, perfect running engine.
 
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I would change the O2 sensor. Had one get "lazy" and did same thing, NO code set either. New sensor, perfect running engine.
Why would an O2 sensor effect the engine in open loop? The ECT sensor is easily checked with even the most basic scan tool.
This could also quite possibly be caused by dirty injectors. In open loop they are running on a fixed table until the ecm goes into closed loop using sensors to control fuel trim, I can simulate this on a machine with sometimes very different readings.
If everything else checks out clean the injectors.

Edit: Many ecm's can compensate for about up to 14cc difference in closed loop although the limit for clean injectors is 3cc or less.
In open loop with all else being equal that would mean one cyl out of a hypothetical 100cc could be 86cc, one at 100cc and others anywhere in between, the greater the difference the rougher the engine will run until it goes into closed loop.
 
Last edited:

nicholas

Thread starter
Joined
Aug 20, 2003
Messages
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ottawa
Thanks everyone- - I think I found my problem.
It was 0celcius today - - - the MAF was reporting the intake temp to be +10c/ +20 celcius.
Went for a drive the air intake temp<MAF> was all over the place. Up down by big swings.

I took it out and gave it a good cleaning with CRC MAF cleaner - let it dry.
The readings were even worse.
New MAF on the way - OEM.

Good news for my valves- - all my fuel trims are in the normal range for my 90k mile engine.
Bank 1 and 2 LTFT -4.5% average -after 30 mins driving - - taken at idle.
Map was in psi - 4.5
 
Joined
Oct 3, 2010
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RI
You want to check your fuel trims when the engine is cold as soon as it goes into closed loop. If it’s fairy deep into the negatives…the valves are too tight.
 

nicholas

Thread starter
Joined
Aug 20, 2003
Messages
1,634
Location
ottawa
You want to check your fuel trims when the engine is cold as soon as it goes into closed loop. If it’s fairy deep into the negatives…the valves are too tight.
Thanks
We talking short term or long term trims?
1 min after start - 5- 10 mins?
 
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