Figured I'd document my saga of resolving the hunting idle issue my 06 Gallardo gets when the car is warm, usually when in start-stop traffic. I've had this issue since I got the car a few months ago. Lots of others seem to have this issue so it'd be amazing to figure out what's going on and resolve it for everyone.
The car performs perfectly under throttle, I recently did a track day, and did 3 sessions out on track, with a lot of WOT, and it never missed a beat.
On the way home I hit traffic, and the idle started hunting. After about 20 mins of traffic I got onto the highway, but after a few minutes the car shut down 1 bank, and then the second. I pulled over for about 1-2 minutes, restarted the car, and it drove fine, if a bit sluggish, the rest of the way home (~15mins). I'm guessing the idle threw out trims, and caused issues under partial throttle on the highway.
I've also monitored fuel trims via OBDII when this happens, and they go all over the place.
Things it isn't:
1. Fuel pumps, both replaced.
2. Spark plugs, all replaced.
3. FPR (at least not Bank 1), replaced, and swapped back.
4. O2 Sensors - both replaced.
5. Intake heat-soak: Intake wrapped in gold heatwrap, IAT's observed to be ~40deg, down from ~60deg observed via OBDII
6. Injectors - Replaced with brand new Bosch, no change.
7. Evap purge/fresh air issue - Tested working
8. Coil packs - Replaced with brand new NGKs
9. MAP sensor - Replaced with brand new Bosch
10. Vacuum leak - Sprayed ether all around the engine bay, no change to idle.
11. Throttle bodys/TPS - Thoroughly cleaned, including teardown of TPS/clean/check not worn out
Things I'm now 99% it was:
- Bad Cats/Doughnut gaskets
- Both cat cores had detached from the walls, were moving around, and had bits missing:
![Image]()
![Image]()
- Both header -> cat gaskets were either in very bad condition or completely broken:
![Image]()
![Image]()
New cats + moved the better condition rear gaskets to the front, and idle is much improved.
Original post:
I'm currently replacing all injectors, removed them all last night, and am waiting for the new ones to arrive.
For the most part, the injectors look in very good condition, no gunk, very clean, all O-rings are still very compliant.
This was the worst one and the one I think is most likely to have been causing issues, it looks like grime has been able to get past the O-ring, which would imply a vacuum leak, which could definitely cause idle issues.
![Image]()
If the new injectors fix this, I suspect this will have been the cause, and all I really needed was to replace this one O-ring, but new injectors wont hurt after nearly 20 years.
The car performs perfectly under throttle, I recently did a track day, and did 3 sessions out on track, with a lot of WOT, and it never missed a beat.
On the way home I hit traffic, and the idle started hunting. After about 20 mins of traffic I got onto the highway, but after a few minutes the car shut down 1 bank, and then the second. I pulled over for about 1-2 minutes, restarted the car, and it drove fine, if a bit sluggish, the rest of the way home (~15mins). I'm guessing the idle threw out trims, and caused issues under partial throttle on the highway.
I've also monitored fuel trims via OBDII when this happens, and they go all over the place.
Things it isn't:
1. Fuel pumps, both replaced.
2. Spark plugs, all replaced.
3. FPR (at least not Bank 1), replaced, and swapped back.
4. O2 Sensors - both replaced.
5. Intake heat-soak: Intake wrapped in gold heatwrap, IAT's observed to be ~40deg, down from ~60deg observed via OBDII
6. Injectors - Replaced with brand new Bosch, no change.
7. Evap purge/fresh air issue - Tested working
8. Coil packs - Replaced with brand new NGKs
9. MAP sensor - Replaced with brand new Bosch
10. Vacuum leak - Sprayed ether all around the engine bay, no change to idle.
11. Throttle bodys/TPS - Thoroughly cleaned, including teardown of TPS/clean/check not worn out
Things I'm now 99% it was:
- Bad Cats/Doughnut gaskets
- Both cat cores had detached from the walls, were moving around, and had bits missing:
- Both header -> cat gaskets were either in very bad condition or completely broken:
New cats + moved the better condition rear gaskets to the front, and idle is much improved.
Original post:
I'm currently replacing all injectors, removed them all last night, and am waiting for the new ones to arrive.
For the most part, the injectors look in very good condition, no gunk, very clean, all O-rings are still very compliant.
This was the worst one and the one I think is most likely to have been causing issues, it looks like grime has been able to get past the O-ring, which would imply a vacuum leak, which could definitely cause idle issues.
If the new injectors fix this, I suspect this will have been the cause, and all I really needed was to replace this one O-ring, but new injectors wont hurt after nearly 20 years.
