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Discussion Starter · #1 ·
Hello,

I've been trying to chase this idle Issue with 2002 V70 2.4 non-turbo M56 and cant figure it out, so wanted to see if anyone had any similar symptoms.

Since owning the car I replaced the engine with a used low mileage one (old one was down a cylidner), sorted out so many issues, so many new parts, but the idle just isn't acting right when the car is hot.

On cold start it idles completely fine, drops down to around 900 smoothly when it drops initially, the problem is after about 10-15 minutes of driving, when everything in the bay starts to get a bit more heat soaked, as I'm coming to a stop, I release the clutch, the idle drops to around 1200, hangs there for a while, then as I approach 5-0 MPH stopping, the idle will dip to about 500RPM before it bounces back up, then hunts between 800rpm to 1000 for a while.

No codes in vida.

Car has an aftermarket manifold with a cat, other than that its stock.

The thing thats throwing me off is that it only happens after 15min of driving. Sensor going wonky after heating up? Throttle body issues? Vacuum leak? I dont know.

Very similar symptoms here: Volvo V70 2.4T Engine struggling at idle

Any clues or hints as to how to diagnose this would be greatly appreciated.
 

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Check and clean the throttle plate. It is easy to access on a non-turbo. Just pull the rubber intake hose off at the t-plate, inspect and clean. It is OK to manually move the t-plate disc while cleaning it. Oil vapors go past the t-plate to be re-burnt into the engine. The hot oil vapors build up on a colder t-plate. The oil vapor build gunk can soften after engine running and restrict the t-plate movement. The t-plate may not look very dirty, but it can affect idle issues. Clean it and retest. After cleaning, touch the battery cables together to erase any stored ECM adaptive memory.
 

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Discussion Starter · #3 ·
Check and clean the throttle plate. It is easy to access on a non-turbo. Just pull the rubber intake hose off at the t-plate, inspect and clean. It is OK to manually move the t-plate disc while cleaning it. Oil vapors go past the t-plate to be re-burnt into the engine. The hot oil vapors build up on a colder t-plate. The oil vapor build gunk can soften after engine running and restrict the t-plate movement. The t-plate may not look very dirty, but it can affect idle issues. Clean it and retest. After cleaning, touch the battery cables together to erase any stored ECM adaptive memory.
I thoroughly cleaned the throttle when I replaced the engine, will inspect it again though, thanks for the tip.

I also ran the throttle test on Vida and it came back with something like .8% difference.
 

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Hello,

I've been trying to chase this idle Issue with 2002 V70 2.4 non-turbo M56 and cant figure it out, so wanted to see if anyone had any similar symptoms.

Since owning the car I replaced the engine with a used low mileage one (old one was down a cylidner), sorted out so many issues, so many new parts, but the idle just isn't acting right when the car is hot.

On cold start it idles completely fine, drops down to around 900 smoothly when it drops initially, the problem is after about 10-15 minutes of driving, when everything in the bay starts to get a bit more heat soaked, as I'm coming to a stop, I release the clutch, the idle drops to around 1200, hangs there for a while, then as I approach 5-0 MPH stopping, the idle will dip to about 500RPM before it bounces back up, then hunts between 800rpm to 1000 for a while.

No codes in vida.

Car has an aftermarket manifold with a cat, other than that its stock.

The thing thats throwing me off is that it only happens after 15min of driving. Sensor going wonky after heating up? Throttle body issues? Vacuum leak? I dont know.

Very similar symptoms here: Volvo V70 2.4T Engine struggling at idle

Any clues or hints as to how to diagnose this would be greatly appreciated.
Which throttle body do you have on your 2002, Magneti Marelli or Bosch? I believe some 2002 still had the MM throttle body.
Have you looked at the short and long term fuel trim levels, which can help determine a vacuum leak. I do know from experience the throttle body to intake manifold gasket is a one use only or it will leak, at least that's the case on the turbo models with an all metal gasket with a crush to fit seal.
 

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Discussion Starter · #5 ·
Which throttle body do you have on your 2002, Magneti Marelli or Bosch? I believe some 2002 still had the MM throttle body.
Have you looked at the short and long term fuel trim levels, which can help determine a vacuum leak. I do know from experience the throttle body to intake manifold gasket is a one use only or it will leak, at least that's the case on the turbo models with an all metal gasket with a crush to fit seal.
Thanks for your reply! Greatly appreciated.
It’s got the MM throttle body, I used a fresh gasket when I swapped it onto the new motor. I also vaguely recall checking fuel trims and saw nothing alarming, but I will look into that again!

I do have an extra gaskets laying around. I’m thinking of trying a junkyard throttle body from another NA car. Someone recently told me you do not need to reprogram a used throttle body?

will update the thread once I get one.
 

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Thanks for your reply! Greatly appreciated.
It’s got the MM throttle body, I used a fresh gasket when I swapped it onto the new motor. I also vaguely recall checking fuel trims and saw nothing alarming, but I will look into that again!

I do have an extra gaskets laying around. I’m thinking of trying a junkyard throttle body from another NA car. Someone recently told me you do not need to reprogram a used throttle body?

will update the thread once I get one.
From what I've read you won't need to reprogram the throttle body if you get one from a NA car or a newer throttle body from Volvo, which the software works for both NA and turbo cars but I don't know the year the compatible software started. .
 

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Thanks for your reply! Greatly appreciated.
It’s got the MM throttle body, I used a fresh gasket when I swapped it onto the new motor. I also vaguely recall checking fuel trims and saw nothing alarming, but I will look into that again!

I do have an extra gaskets laying around. I’m thinking of trying a junkyard throttle body from another NA car. Someone recently told me you do not need to reprogram a used throttle body?

will update the thread once I get one.
Did you swap the throttle body from your old motor to the replacement motor? If so did you have any idle problems with the throttle body on the previous motor? I know you did the throttle body test but with this throttle body(MM) I'd still be suspicious of worn throttle position sensors although this should show up on the Vida sweep test.
 

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Discussion Starter · #8 ·
Did you swap the throttle body from your old motor to the replacement motor? If so did you have any idle problems with the throttle body on the previous motor? I know you did the throttle body test but with this throttle body(MM) I'd still be suspicious of worn throttle position sensors although this should show up on the Vida sweep test.
The throttle body did indeed come off the old motor, I couldn’t tell you if the car had the problem before the swap unfortunately. I bought it with a blown engine so I didn’t really put any miles on with the old motor myself. Hopefully gonna head to the junkyard soon and give it shot. Thanks for your help/advice!
 

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from your description it sounds like the idle is good while the car is running in open-loop, and then once it goes closed-loop, you have issues.

I would be leaning towards vacuum leak somewhere, especially since you say it’s hunting. I read that as ECM hunting for a stable idle given imbalanced air/fuel.

Smoke test would be good if you have any way to do so.
 

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Which throttle body do you have on your 2002, Magneti Marelli or Bosch? I believe some 2002 still had the MM throttle body.
Have you looked at the short and long term fuel trim levels, which can help determine a vacuum leak. I do know from experience the throttle body to intake manifold gasket is a one use only or it will leak, at least that's the case on the turbo models with an all metal gasket with a crush to fit seal.
I have read that all non-turbo models have a MM throttle, Bosch only for turbo.
 
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