06 2.5 t rough idle no codes

MDK · Post by **MDK** » 14 Jan 2023, 18:54

Hey all MDK here, so, more problems. This v70 I bought from a dealership originally started out from Volvo of Tuscon Az. The timing belt was very cracked. It's got the 200,000 mile service on it even though it's only got 177,000 on the odo. No known vacuum leaks, new plugs, fuel filter, air filter, 12quart aisin T5 trans flush , a couple of oil changes, new turbo, new antifreeze and tstat sensor.throttle body cleaned.after all that.. It still has a rough idle. I was in the car wash.. you get the echo , you know and you can hear what sounds like a mechanical tick. Erie Volvo has a known good throttle body for 110$ .. what do you all say?.. sticky valves?

Jonboy74 · Post by **Jonboy74** » 21 Jan 2023, 15:44

Do you have VIDA?

I'm just spitballing...

Are you ABSOLUTELY SURE there are no Vacuum leaks?

Any chance you have a failing plug coil that just hasn't triggered the CEL yet?

Jonboy

MDK · Post by **MDK** » 27 Jan 2023, 03:14

Hey there jonboy, I didn't realize that you could have a bad coil and NOT throw a code. I had a problem with #3coil connector, fixed that. The guys at the shop put the smoker on it and said everything was good. I'll take a look at the coils again. MDK

Post by **jonesg** » 27 Jan 2023, 06:19

MDK wrote: 27 Jan 2023, 03:14 Hey there jonboy, I didn't realize that you could have a bad coil and NOT throw a code. I had a problem with #3coil connector, fixed that. The guys at the shop put the smoker on it and said everything was good. I'll take a look at the coils again. MDK

Vida is the way to go, it can monitor fuel trims,

Jonboy74 · Post by **Jonboy74** » 30 Jan 2023, 20:40

MDK wrote: 27 Jan 2023, 03:14 Hey there jonboy, I didn't realize that you could have a bad coil and NOT throw a code.

Yeah - I've had one start to go bad, but it wasn't missing enough to throw a code...I noticed the car felt different - a little rough, but not too bad....then a week or two later, started getting bad and threw the CEL. I made the assumption it was a coil, and sure enough it was.

Jonboy

Post by **abscate** » 31 Jan 2023, 01:15

The ECU has to detect enough misfires under the right conditions to store the misfire code. It is detecting the acceleration of the crankshaft on. Each firing of each plug, so it’s a subtle measurement that needs validation.

Post by **cn90** » 31 Jan 2023, 09:15

I suggest that you start with the basic...

Get a flash light and physically go over every hose in the engine compartment. Don't forget to check intake boots etc.

If you have Turbo, check the clamps too.

Post by **vtl** » 31 Jan 2023, 21:20

Bosch throttle body rarely fails.

Have you tried disconnecting VVT solenoids? Those do fail. Or their gasket, they have a mesh screen that catches oil debris.

I double what jonesg said: check you fuel trims (short/STFT, long/LTFT), they directly say whether the oxygen sensor sees any excessive oxygen in exhaust. Which usually is directly related to a present vacuum leak.