As a technician at ND for the last ten years or so. Over the years, I've had the great pleasure of encountering some great technical mind bogglers as well as repair a lot of problems that other people had trouble with. When you see the same cars come in the door day after day, you start to see patterns.

I read a lot of your postings when I get home from work and often think I can help out with the solution, except I never have time to write. So, I wanted to dump a whole lotta stuff I accumulated over the years in hopes it can solve some drivability problems for you.

1) Drivability- on Corrado g60 the TSB concerning the flat ground strap that goes from the coil to the right rear nut on the valve cover-move the vc end to the top of the throttle body because it acts like a knife and abrades into the two hot wires of the fuel rail power supply wires (no thermal protection) and causes fire up to the fuse box.

Most of the G60s ECM grounds terminate at stud above left coolant flange on cyl head (4 wires-brown, brn with black tracer). I usually remove ring term ends, solder on four longer wires and run directly to battery neg post. One large ground for ECM is also at bolt on clamp-clean it shiny bright and tighten. Any undue resistance or corrosion from the wires causes overly rich mixture and problematic idle.

Overly rich mixture (black smoke, no power) also usually caused by these three things: broken signal wire on harness side of o2 sensor plug behind engine on right rear mount, bad nt. sensor (blue front of engine), or bad o2 sensor. You need a four gas analyzer to determine if co.% is problem and also to see if what you are repairing fixes the problem. The signal wire is purple and goes to the black wire from the probe. It breaks from bad front mounts causing undue strain on harness or old age and heat.

NTC sensor can fail from an overheated car or just no reason at all. O2 sensor failure isn't that common but contamination from using too much K & N oil and not letting it dry thoroughly, silicone spray or goop, or letting the car run with a bad miss or too rich too long can do it. Also check the two vac hoses behind the throttle body. One goes back to the firewall and the the ecm-it is the signal for the map sensor (it controls fuel delivery for load). A gaping hole in this hose causes rich mixture because ecm thinks atmosphere pressure is manifold pressure. Incidentally, don't replace your o2 sensor unless you are sure it has a problem- its really expensive and they normally last at least 75-100k miles for the heated variety. Also, this component is covered (as well as your cat) under your federal emissions warranty for 6yrs or 60k and 7yr and 70k miles!

Idle problems are usually related to incorrect mixture and idle screw adjustments and it really does help to have it on the scope to set these properly. However, some quick checks: replace small o-ring on the idle screw-they almost always leak and allow false air to enter the engine unmetered, never disconnect idle stabilizer two wire connector with the car running or the key on-reason-you can short the driver end stage of the ECM and ruin it. To quick check, disconnect ntc and see if idle changes- usually, if it does, it is working. The idle can go up or down depending on where mixture is and a whole lot of other things, but generally it should go up. Also, the unit should hum when held in your hand with the key on and the engine off. I never had much luck cleaning them-usually replacing them is best.

When your car feels like it is only as fast as a rabbit-look down by the battery at the intercooler pipe-if you press your finger into the plastic you will find a hole where boost can escape. Check the vac hose to fuel press regulator and on cars with microswitches instead of tps at throttle-remove plug and check resistance of switches. I usually change them if the resistance is higher than one ohm closed and anything other than "open" when pulled off throttle. Too much resistances here causes the ECM to think the car is off throttle and changes the timing and signal to the stabilizer, thus affecting idle.

VR6's--very few drivability problems overall but here's some tasty stuff: idle problem #1 is caused from vac hose (7mm smooth rubber one on right side of engine by #1 plug) that purges the fuel vapor canister. It is formed like an "s" and melts on manifold. I highly recommend using no other spark plug except the ngk or Bosch dual electrode ( cant remember the #). I have seen it clear up slight idle problems in a jiffy. Always use the factory tool to remove plugwires- ANY cuts or rips on the boots will cause a short to ground from your high energy ignition system. You can feel it when you are pushing hard on acceleration as a "buck", or at idle as a "tick". Look at the car running in the dark down at the plug holes to see it jump, especially in damp weather or spray misted. Be really careful if you have Ram Air or K&N filters and you clean them. After you oil them, let them dry thoroughly! I have seen two cars that got excessive oil on the Mass Air Flow Sensor and made the car run too rich. There is absolutely no way to clean the hot wires of the unit, so if it happens to you, remove the offending filter until it is dry and drive car a bit, starting and stopping engine so the inherent burn off cycle can clean the wires off itself. Throttle position sensors can also cause idle fluctuations but it is rare. You really need the VAG 1551 to check the live readings. The dvom wont do.

Last tip for the cooling system-VR6s run HOT. Change your coolant and install a low temp fanswitch(remove the battery to make it easy). The thermostat is also a good idea-but I only recommend it if you have over 60k and you replace all three pcs of the plastic thermostat housing. These things leak like crazy! replace all the seals and don't use goop on any of it except at the mount to the head( I prefer aviation sealer - the brown stuff in the little can) Anyway, the fanswitch cycles the fan sooner and longer and end result is that your gauge which normal reads about 230 can drop as much as 10-15 degrees. It seems that all the car's gauges read a little different.

O.K., now my opinion about this G11 to G12 changeover. In order to understand this better, I'll tell you what I know about coolant. Buy only high quality antifreeze-cheap brands can be straight ethylene glycol minus important corrosion inhibitors and lubricants. ALWAYS mix 50/50 with water(preferably distilled) or follow ratio recommend for your climate. Never top off coolant tank with straight coolant-preferably small amount of distilled water or your 50/50 mixture. Use common sense, large amount missing means that if you refill, you are going to throw off the glycol to water ratio, and it is very important. Antifreeze should never exceed 65%. Exceeding 85% will cause the silicates to drop out of suspension and goo up to clog the radiator and reduce heat transfer.

VW recommends the water and compressed air treatment to upgrade to G12 because up to a third of the coolant is still trapped in the heater core and the engine after you pull a hose or the drain cock. This flush ensures that you are removing all accumulated rust, scale, silicate buildup and old coolant as best as possible. By the way, the blue and red coolant will foam up and turn brown in your expansion tank if you mix them or don't get all the G11 out. The degree of corrosion that takes place in your VW depends upon the type of minerals and alloys in the engine and radiator, and the acidity or alkalinity of the coolant. So long as your coolant remains alkaline, corrosion will be held to a minimum.

Conversely, acidic coolant hastens the corrosion process that occurs between the cast iron and the aluminum present in the engine and radiator. The corrosion inhibiting chemicals that are added to you coolant is what keeps the alkalinity on the high side of the Ph scale. That's why adding aftermarket wetters and boosters is not smart because you are altering the already unknown alkalinity of your coolant(no matter how new, it varies depending on mix ratio, mineral content, additive content) More important, this alkalinity ratio doesn't have to be bigger to be better-it just needs staying power. This is measured as alkalinity reserve(how long your coolant can resist corrosion).

The enemies of your coolant are heat, dissolved oxygen and minerals which react with the metal surfaces in your engine depleting the capacity of the coolant to resist becoming acidic. Therefore, changing the coolant annually or at least bi-annually guarantees that you never exceed the coolants ability to resist corrosion. European car makers like VW specify coolant additives lacking in phosphates and including borates and low silicates because their water is harder and it reacts with phosphates to create calcium and magnesium deposits. The Japanese disagree and specify high in phosphates and low in borates and silicates because they fear lack of maintenance will cause borate corrosion. This is the reason you see the little "phosphate free coolant " only from vw under the expansion tank cap-or it will void mf's warranty. It seems that in my opinion, the original G11 coolant must have been a poor acidic retardant-either from the reaction to the water installed from the factory and/or an additive package that was insufficient to go more than a couple of years on North American water. Mixing the two coolants causes problems because you get saturation of the silicates and gelling inside the engine, thus the specific ritual flush with water and compressed air. I firmly believe that no matter what proportion VW used for an additives package with the G12 coolant, it too should be flushed out and refilled every year or two. Considering that it isn't that much work and it beats playing with litmus paper and rebuilding your cylinder head. By the way, the corrosion we usually see on VR6s is surface etching that rubs away to leave pits-almost always around any flange that attaches to the head, or on the water jack inlets comprising the head gasket. They're usually good to go because they are far enough away from critical sealing areas, but we do replace heads when they are questionable. I really doubt that the new metal gasket is the reason for the G12. There is actually no bare metal on the gasket and all the passages have sealer from the factory around them. I think the reason was simply that G11 didn't provide long enough reserve capacity and coupled with poor maintenance, they were getting too many warranty problems.

Go Back to the page you came from HERE