Hesitation when Motor is Cold. 99 OB with 2.5 motor.

[roadsubiedog]

have had this 99 outback for 11 years and never had this problem before. when motor is cold the car hesitates when accelerating going down the road. seems to bog down a little and then goes.

 

when warmed up it is fine.

 

it acts exactly like a car that has a choke that is not fully opened.

 

i have a feeling that this problem is going to get worse if i dont find the problem and fix. it does have a clean air filter and recent oil change. could it be a fuel filter? or the MAF? or something with the fuel injection?

[porcupine73]

Any codes? What's the mileage / when was the last time it had a tune up i.e. new plugs, wires, etc? You mentioned fuel filter, when was it last replaced?

[wtdash]

Last tune-up w/NGK plugs and wires?

 

Not in order:

1. CTS - coolant temp sensor 

2. MAF

3. Catalytic converters

4. Fuel filter

5. etc?

6. valve adjustment due @ 105K miles, too

 

For curiosity's  sake, when were the HG replaced?

Edited December 28, 2015 by wtdash

[roadsubiedog]

las tune-up was about 15k ago. hg was replaced 90k ago. no codes. 

[Rooster2]

I would suspect the coolant temperature sensor.

[roadsubiedog]

I would suspect the coolant temperature sensor.

im curious why this would make the motor bog down for a few seconds and then go or fine when motor is completely warmed up?

 

the best way to describe problem is that the motor acts like my 84gl with carb acted before it it was warmed up and the choke was not open all the way. after my outback is completely warmed up it runs fine.

 

only has happened the last 2 times . both mornings it was around 0-5 degrees out but i have had many days like this over the last 11 winters without this happening..

 

thanks for the replies.

[wtdash]

Hi,

Are you asking because you don't understand what the CTS does? Or some other reason?

 

If the sensor is bad, it's mis-reading the engine temperature and supply the ECU w/mis-information. The ECU then gives the engine too much/not enough fuel which causes it to run poorly when cold. Once the car warms up the CTS may be 'accurate' enough that engine runs normally.

 

There's also the open vs. closed loop ECU function, but I barely understand that myself so won't bother explaining!

 

The CTS is a cheap part (no need for OEM from what I've read), but kind a of PITA to replace. After 11 years it's a good thing to replace regardless.

 

GL,

TD