Rough Idle

[dazcoates]

Hi all,

I bought the SSV wagon about a year ago and every since then I'm of the opinion that i have been having a rough idle/running lean issue. It's a 6.0 L77, so when i first got it the idle was smooth then it started to develop a little hiccup every now and then, it just kept getting slowly worse right up to the point 12 months on that yesterday as you pulled up to a set of lights it seems it wants to stall, really bad idle, but in a matter of seconds from being stopped it comes good and idles fine. It's like it's starving for fuel or the spark is breaking down. It doesn't seem catastrophic though, so I'm not panicking. I bought it second hand and have had it back to the dealer early days, nothing wrong with it was the response, I took it to see if it was a previous tune or it needed a tune, they tuned it, still had the intermittent idle issue after but nothing wrong with it I got told again!!?? It has always had the permanent PO240 & PO230 codes and was told it was to do with the tune and addon's. It has a 3" X-Force exhaust, Headers, CAI and it's tuned to use 98, I use Shell. Not sure about the Cats. Another code has come in a little more recently, a PO174 code, yep it's lean on bank 2. It's got 130,000 on it so I replaced the plugs about 6 months ago, made no difference. The only other thing is it runs fine on acceleration so there is no breakdown under load, plenty of power. I will take it back to the tuner/mechanic when I have the cash but........

Anyone got any ideas.

 

[blackve76]

Sounds really odd with those codes, maybe maf clean and fuel injector check up.

 

[dazcoates]

Sounds really odd with those codes, maybe maf clean and fuel injector check up.

Maf Sensor clean seems to be a popular remedy.... might just search for the procedure to clean them and give that a try. Thanks for your input.

 

[Skylarking]

@dazcoates what sort of tune as a MAF clean won’t help on a MAFless tune

I’d look at throttle plate/sensor and air bypass systems and ensure they are clean and working as expected... also check if the intake is at all clagged up with oil film and if so consider a catch can

 

[dazcoates]

@dazcoates what sort of tune as a MAF clean won’t help on a MAFless tune

I’d look at throttle plate/sensor and air bypass systems and ensure they are clean and working as expected... also check if the intake is at all clagged up with oil film and if so consider a catch can

I wouldn't know if it was Maf or Mafless, I know the sensor is there and wired up so I assume tuned with the Maf?

Yeah see, the throttle plate/sensor and bypass system is probably beyond me and more for a technician. But thanks for the input.

 

[dazcoates]

Had a look at some data tonight and this might tell a story?

Fuel Trim
At idle
Bank 1 st and lt sits at 0.8
Bank 2 st 1.6 and lt 12.5

 

[Skylarking]

Also have a look at o2 sensor readings.... bank2 sensor may be a little lethargic impacting st & lt trim. Even so, in essence the system is doing what it should do which is adjust for a/f so it averages ok (or so it thinks it’s ok).

But it may be that the true a/f ratio is actually wrong due to a bung o2 sensor or there is some air leak on that side of the motor forcing lean mixtures which the system is trying to sort out.

It’s a bit out of my wheelhouse as I haven’t had to delved into such problems as I haven’t had those sorts of issues.

 

[Anthony121]

Had a look at some data tonight and this might tell a story?

Fuel Trim
At idle
Bank 1 st and lt sits at 0.8
Bank 2 st 1.6 and lt 12.5

How did you find this info?

 

[dazcoates]

How did you find this info?

Hi, via the ODB2 Scan

Cheers.

 

[Anthony121]

Hi, via the ODB2 Scan

Cheers.

Thanks. I will need to check mine