Evo 4g63 Idle conundrum
Discussion
Morning Folks,
I'm looking for some suggestions here please...
So I have an Evo 7 RS model that has always had a poor idle - would idle high and take a while to drop to normal and would often fall off to 2-300 before recovering. But this was a minor annoyance rather than a problem driving it.
So in an attempt fix, the following has been looked at:
1) MAF checked and clean as a whistle and no error codes.
2) No error codes on the 02 sensor.
3) Injectors ultrasonically cleaned and so the flow rate is now balanced - was a tiny bit out but the car now pulls a lot better.
4) Vac leak checked for - no leak.
...and here is the conundrum...
4) Fitted new later model Idle Control Valve - not mitsi part but not a cheap copy either and it's made things better and worse oddly. When it's idling it will set at 900rpm steady as a rock. Blip the throttle and it will rev cleanly and settle quickly back to 900rpm. However, drive it and when you come to a stop with the clutch in or out of gear clutch out, it will fall through the floor to 200-300rpm and often stall. I had thought the ICV had gone bad - not impossible, but sat idle and it will function correctly.
I'm at a bit of a loss TBH, so any suggestions would be helpful.
Thanks
I'm looking for some suggestions here please...
So I have an Evo 7 RS model that has always had a poor idle - would idle high and take a while to drop to normal and would often fall off to 2-300 before recovering. But this was a minor annoyance rather than a problem driving it.
So in an attempt fix, the following has been looked at:
1) MAF checked and clean as a whistle and no error codes.
2) No error codes on the 02 sensor.
3) Injectors ultrasonically cleaned and so the flow rate is now balanced - was a tiny bit out but the car now pulls a lot better.
4) Vac leak checked for - no leak.
...and here is the conundrum...
4) Fitted new later model Idle Control Valve - not mitsi part but not a cheap copy either and it's made things better and worse oddly. When it's idling it will set at 900rpm steady as a rock. Blip the throttle and it will rev cleanly and settle quickly back to 900rpm. However, drive it and when you come to a stop with the clutch in or out of gear clutch out, it will fall through the floor to 200-300rpm and often stall. I had thought the ICV had gone bad - not impossible, but sat idle and it will function correctly.
I'm at a bit of a loss TBH, so any suggestions would be helpful.
Thanks
1. Find a competent mechanic who can diagnose. Don't throw parts at random
2. Has the car ever been tuned, mapped, messed about with, or is it 100% standard ?
3. Has it ever ran correctly ? You seem to suggest not ? Is this weeks, months, years ? more ?
4. Does the speedo work ?
5. Interrogate the ecu to see if it is even trying to control the idle, and if so, does it's operation make sense in terms of what it is doing, and is the engine even responding
2. Has the car ever been tuned, mapped, messed about with, or is it 100% standard ?
3. Has it ever ran correctly ? You seem to suggest not ? Is this weeks, months, years ? more ?
4. Does the speedo work ?
5. Interrogate the ecu to see if it is even trying to control the idle, and if so, does it's operation make sense in terms of what it is doing, and is the engine even responding
stevieturbo said:
1. Find a competent mechanic who can diagnose. Don't throw parts at random
Thanks for replying.
Work has been done by a garage and don't intend to chuck parts at. ICVs are a known weak point on these so it was worth taking a punt on it being a faulty icv - and it has fixed the issue but not all the time.
There is an Evo specialist about an hour away from me which was next port of call.
2. Has the car ever been tuned, mapped, messed about with, or is it 100% standard ?
It's a jap import and yes, running increased boost - peak 1.5 bar.
3. Has it ever ran correctly ? You seem to suggest not ? Is this weeks, months, years ? more ?
It was better previously, but has gotten worse.
4. Does the speedo work ?
Yes
5. Interrogate the ecu to see if it is even trying to control the idle, and if so, does it's operation make sense in terms of what it is doing, and is the engine even responding
Don't have that ability but specialized will.
Answers in line.Thanks for replying.
Work has been done by a garage and don't intend to chuck parts at. ICVs are a known weak point on these so it was worth taking a punt on it being a faulty icv - and it has fixed the issue but not all the time.
There is an Evo specialist about an hour away from me which was next port of call.
2. Has the car ever been tuned, mapped, messed about with, or is it 100% standard ?
It's a jap import and yes, running increased boost - peak 1.5 bar.
3. Has it ever ran correctly ? You seem to suggest not ? Is this weeks, months, years ? more ?
It was better previously, but has gotten worse.
4. Does the speedo work ?
Yes
5. Interrogate the ecu to see if it is even trying to control the idle, and if so, does it's operation make sense in terms of what it is doing, and is the engine even responding
Don't have that ability but specialized will.
Bainbridge said:
Has the throttle body become gunked?
Something to check. Thanks for the suggestion. Thing is it works, then it doesn't and it was better before (not perfect) the new icv.
On the basis of change one thing and test results it points to the icv.
Didn't get chance to idle re-learn over the weekend but will report back.
SO27 said:
Have you got a Vent To Atmosphere dump valve by any chance?
These can often cause idling problems on the Evo. Better to replace it with a recirculating one and lose the loud chuffing when you lift out of the accelerator.
No, it's a standard recirc.These can often cause idling problems on the Evo. Better to replace it with a recirculating one and lose the loud chuffing when you lift out of the accelerator.
Not a fan of atmos DVs as they're generally poorer WRT spool. This is a b road toy, not a big power car.
So an update... of sorts... as I hate a thread left without conclusion.
So I did the idle re-learn without success. On the test drive, I noted that it would idle perfectly with the AC turned on, but not with it off.
So as I was experimenting to try and work out why the the AC load 'sorted' the idle, an odd noise started, which got louder and louder (think bucket full of bolts) so quickly pulled over fearing a turbo that had shat itself (I've had this before and it sounded similar).
Anyway, car recovered to the specialist I was going to send it too anyway, and was AC compressor that had catastrophicly failed.
During investigation, a lot of vac and boost leaks found so most likely those. I did wonder if this was the problem but the new ICV made it worse oddly.
I'll report back when sorted, as it may help another user in the future.
So I did the idle re-learn without success. On the test drive, I noted that it would idle perfectly with the AC turned on, but not with it off.
So as I was experimenting to try and work out why the the AC load 'sorted' the idle, an odd noise started, which got louder and louder (think bucket full of bolts) so quickly pulled over fearing a turbo that had shat itself (I've had this before and it sounded similar).
Anyway, car recovered to the specialist I was going to send it too anyway, and was AC compressor that had catastrophicly failed.
During investigation, a lot of vac and boost leaks found so most likely those. I did wonder if this was the problem but the new ICV made it worse oddly.
I'll report back when sorted, as it may help another user in the future.
Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff