Im not a first gen guy.. But look into the throttle body issues.

 

A few threads about how the strip in the throttle bodies can lead to surging at idle. An "idle hunt" is hard to internet diagnose but you are tackling the proper things. Vacuum leak somewhere or dripping injectors.

 

Updated post, I don't think its the throttles but we will see. I'd expect to see them moving and "missing" the target position if it was the resistor strip in the TPS.

 

I had a little idle hunting while at idle with my Sprint Booster attached. I contacted Jason B about it and he had me return mine for another updated version with 2nd day air shipping. No idle hunting since installing the new unit. Will follow this thead in case other culprits arise in the future.

 

Lose the booster, it will eff up everything. You're playing with fire and assuming significant exposure.
Updated version!? Lol

 

The guy is a charlatan. Sent you the wrong version? Okay

 

Wrong on both fronts. I reached out to him because of his presence in the exotic car parts space and without hesitation had me send him mine and told me where to send it and sent the second next day air. After we got it all sorted out I found that I had purchased it from another vender and he didn't even blink. He went way above and beyond with no skin in the game nor any culpability. I am not sure what evidence you have for suggesting I am "assuming significant exposure" but that should be a topic of another thread not this one.

 

Update: New Bosch injectors in, no significant change. Car feels like it's running slightly healthier, and at first I thought it was resolved, but I let it sit and idle after a drive for about 5 minutes, and it began to surge significantly, before one bank just died. I turned it off, and re-started it, and the second bank came back, I could hear it start about half a second after the first bank.

Scanned for codes and got a P1106, which checking the shop manual is:
MAP/Barometric pressure - Comparison between ECU bank1 value and ECU bank2 value > 25mmHg for >4s

It's hard to know if this code points the the cause or is just a result of one bank not firing.

I found this thread where another owner had the same code caused by one exhaust valve not opening, but I don't have a valved exhaust. I do however have original cats, and if one is really clogged up I could see that causing issues when warm.

One question I have is: how/where is the ECU measuring barometric pressure? Is it just on the MAP sensor, or do the ECU's have onboard sensors?

 

You have two mass air flow sensors (MAF). With a scan tool view live data to compare MAF readings on the two banks. Be aware they do fail but on occasion just need to be cleaned with MAF spray cleaner.
Also check for vacuum leaks.
I've seen the air tubes between the throttle body and air filter dry rot and get cracked. This introduces air downstream of the MAF sensor that is not being metered and will throw things off.
I'll also urge you to consider my previous suggestion and eliminate that as a culprit.

 

Decat it as a priority imo!

 

Have you tested your intake runner valve? Could be torn, it's the rubber thing down by the oil filter that changes intake length using vacuum.

 

Have not yet tested, I'll do a smoke test which should reveal that. They do suck in and affect the intake runner valves so they can't be too bad.

 

I replaced both of my Throttle Bodies with used units that the seller assured me were 100% functional when removed from the car to go to a Motec twin turbo setup using other TBs. I cleaned both sets and made sure my gaskets were not leaking. I noticed about 50% less idle hunt at that time with all else being unchanged. I have read that others have reported idle hunt resolved after doing the Sacer 100 Contactless Throttle Position Sensor (TPS) via XeModex in Canada. I will likely do the contactless TPS mod to my old Magnetti Mirelli TBs to see if that makes any difference.

 

Check this out.

Xemodex Throttle Body Repair (Pre-LP) -- Review

I thought I would post this thread as something for others to find in the future. Shortly after purchasing my 2005 Gallardo I experienced an MIL with an alternating EPC 1-5 and 6-10 error with the car feeling like it were in LIMP mode with next to zero acceleration under 4k rpms and then perfect pickup above 4k rpms. In addition, with the clutch in at stoplights it did significant idle hunting (bouncing between 1800-2000 rpms over and over again).

I had a feeling it was TPS related given the throttle response symptom, but also thought maybe it was Sprint Booster related or who knows what else. Using my code reader, it pulled up P0227 01 (low input Throttle Position Sensor) and P1227 01 (throttle malfunction, bank 2).

After some time at the shop with the computer hooked up, it was ultimately determined I needed new TBs. I hated the thought of spending $3,600 ($1800/bank) for new Magneti Mareli units from Lamborghini (that are agreed to be a poor design even when new), so I searched out a few options and ultimately landed on the Xemodex website. They get RAVE reviews on Volvo and BMW forums, but I only saw 1 or 2 mentions here and no real review of experience.

Here is how their website describes the service:

Contact-less programmable dual sensor TPS upgrade: Zero wear Hall-Effect dual Throttle Position Sensor, designed and manufactured by XeMODeX. This contact-less TPS design eliminates any friction related TPS failures. XeMODeX TPS sensors are fully programmable unlike the clones out there which are pre-set and locked. Each of the two sensors sends its own throttle angle position to the ETM the closer the angles are to each other the quicker the throttle response will be. This is why we program each sensor on the actual ETM ensuring that the maximum deviation between the two sensors is less than 1.5 degrees (Maximum allowed deviation in the original throttle is 14 degrees before the software triggers the TPS sensor fault codes).
Brand New Stainless Steel Bearings: Steel bearings upgraded to stainless steel to better withstand corrosion
Remanufactured Internal ECU: All fragile aluminum wire bonds inside the ECU are replaced with reliable copper bonds to prevent future joint failures.
Rebuilt Magnet Assembly: The magnets inside the DC motor are completely overhauled and sealed to prevent moisture penetration and subsequent corrosion.
Brand New Inspection Cover: Brand new custom manufactured aluminum inspection cover.
Lifetime Limited Warranty: This module comes with our Lifetime Limited Warranty. Please see here for more information.

I ended up going this route and $2200 later, they sent me shipping labels from me to their shop in Canada. The TBs arrived to Toronto in ~4 days and they were turned around by Xemodex in ~48 hours and shipped back to Virginia in ~3 days -- even using their "non-expedited" shipping option.

The first thing to note is that they arrive returned in anti-static bags and looked WAY better than when they left. Previously the TBs were a dull grey that was chipping a bit, and now they look nicely polished and brand-new. They also returned with a status report indicated that both TBs were tested and found "ok" when cold, but both failed "hot" tests of their functions.

From my reading I understand our TBs are VERY similar to an earlier Volvo XC90 TB....yet the Xemodex rebuild for a Gallardo TB costs 2x as much per TB as for an XC90. They claim its due to additional/different programming which may well be true, but slightly irritating nonetheless. I did see a user somewhere say they purchased an XC90 TB for their gallardo and it threw all sort of lights -- so I imagine there is truth to the need for different programming.

After getting them back on the car, the issues are gone. No more idle hunting. No more MIL/EPC lights and the car rips. I was pleased with the service and glad to save the $1600 while simultaneously benefiting from the Xemodex upgrades.

Caveat Emptor: They have a SUPER aggressive facebook ad campaign, so as soon as you search them or visit their site, odds are good you will see their ads from now until the end of time.

 

Update: went for a ~45 min drive with a fair bit of start stop/sitting at lighs, and the car slowly degraded in performance, I suspect it was pulling timing etc. got home and checked the cats, they were glowing significantly around the thermocou, and even glowing around the O2 sensor and misfire tubes.

This makes me more suspicious of the cats, but it could also be bad coils causing misfires, however it doesn't feel like it's missing.

 

I agree, you'd feel coil misfires.
What fault codes did you retrieve?
Could it be too lean or too rich? Do you have access to a scan tool that can show live data such as fuel trims, fuel pressure etc?
Do you have a bore scope? You may be able to remove a pre cat oxygen sensor to view the media and an exhaust back pressure gauge installed in pre cat O2 bung may give you some direction.

 

We use a Snap On tool however I just saw several BP gauges online for less then $50

 

Had glowing cats on one of my previous SLs. Stopped shifting altogether and had to trailer it to the shop. Double check those cats asap.

 

I assume you replaced them? More info plz!

 

I am now almost completely convinced this is due to a dead evap vent solenoid or blocked vent line, which would also explain my collapsed fuel tanks, and difficulty putting fuel in.

Will investigate as soon as I get a chance.

If anyone else has difficulty fueling and has erratic idle, please have a look at your fuel tanks and check if they have collapsed.

 

Update: Not evap

Fresh air valve replaced, works.
Purge valves working, I unplugged it while the car idles, and I can feel the pulses of the valves opening.

Next theory is coil packs:

Watching trims and lambda via OBDII the trims go hard negative on one bank while O2 reads lean. I imagine this could be happen if it's misfiring (no burn -> still has oxygen) AND detecting the misfire with the 'misfire tubes'

 

Did you already try cleaning the throttle bodies?

 

Yep have done, thought not a thorough job.

 

The TBs have variable resistors that wear out, would make sense that low RPM/idle would have the most wear and contamination... Causing signal hunting..

While higher rpms.. up the resistor are rarely used in comparison.

 

Whelp, I really thought it'd be the coil packs, but after installing 10 brand new NGK 5015s, the issue remains..

I also replaced the MAP sensor after the coils and it also made no difference.

I have noticed that leaving the AC on makes the car idle smoother, maybe due to adding a bit of load to the engine, maybe causing the engine to crack the throttles a little more, maybe suggesting it's throttle related?

I noticed the other day that my bank 1 throttle sits more open than the bank 2 one, bank 2 has less than a mm gap when closed, where as bank1 is probably closer to 2mm. Is there a way to adjust the at-rest position of these throttles? I can't see a set screw or anything on them.

 

From what I recall I don't think there are any adjustments, and the position switches are fixed.
Do you have access to a scan tool? There may be a menu to balance the two banks.

 

Update:

I opened up my throttles, removed the TPS brushes and carbon strips. here's what they looked like:

The brushes were pretty dirty, but the carbon strips are in good condition, with no signs of significant wear. Holding them up to a light, there are no thin spots.

I cleaned the brushes up:

Not perfect, but much better. The brush fingers are absolutely tiny, maybe 1/20th of a mm?

I also noticed that Bank 1 throttle would stick slightly when closed, so I have both of them a good clean.

Re-assembled, all ack in and working, but no significant change to driving.

HOWEVER I believe I've had a breakthrough. I was mulling my engine symptoms in the shower as one does; the car is perfect at full and medium throttle, or when cold - and I realised there's actually an entire mode difference that explains when I have issues:

The car runs great in open loop: Full throttle, medium throttle, when cold.
The car runs ****e in closed loop: At idle once warmed, or at light throttle cruising on the highway.

The fuel trims go nuts during closed loop, with bank 2 being the craziest, and bank 1 doing a more subdued version of the opposite of whatever bank 2 is doing.

Therefore: My Bank 2 upstream O2 sensor is dead.

I have a new O2 sensor on the way, and I will report back after I've installed it, but this explains every symptom.

 

Just by way of comment I am very impressed with your level of problem solving here. I watch with interest as I have followed many of your changes with mine having the same kind of behavior…o2 sensors are next for me…

 

STOP!
Don't you guys have anyone that can access live data and freeze frame data on a scan tool?
Don't burn resources.

 

Labour is substantially more expensive than parts, and everything I've replaced is something that could do with being replaced after nearly 20 years.

I've done some logging via OBD2 and it also suggests an 02 sensor issue.

As you can see, one sensor is moving rapidly as it should, and the other is very lazy.

 

Update:

New cats are here:

So far I've removed the right hand side cat, and the upstream doughnut just fell apart:

This absolutely cannot be good for O2 sensor readings, as this would have been letting oxygen in post-combustion. Also, shaking the old cat, I can hear the core moving around, so probably a good thing I've decided to do this before anything catastrophic happened.

Good news is the new cats seem to fit nicely. They are maybe 5mm longer than the OEM's but that's not too much.

I need to source new doughnuts from somewhere, OEM one's aren't offensively expensive, but they require international postage, and I'm pretty impatient.

 

You can remove the driver side out the top if you remove the cross bar bolts and head shielding on the dry oil sump. Your passenger side gap doesn't look that great. I've found some manufacturers could be using early Gallardo geometry. Hope you have some muffler movement not shown but I had to have my cats corrected.

 

You mean passenger side

Yep I got it out by loosening the cross member and unbolting the back box. I'm guessing it was a lot easier that stock because I've got the tubi exhaust, which came out easily without removing the back bumper.

All that's left now is to put it all back together