Just a general note:
The Bentley Corrado Factory Repair Manual is as valuable a tool for the DIY G60 mechanic as anything.
The parts I will refer to are plainly illustrated in diagrams in that manual if you're not sure what they are.
Basic info on Digifant fuel injection
Advanced info on Digifant fuel injection
mrkrad's basic explanation of warm-up and such, related to the blue coolant temp sensor.
|Quote, originally posted by mrkrad »|
|1. A car requires more fuel when dead cold.|
1a. The blue CTS tells the car its dead cold.
1aa. The black cts is a good way to test the blue cts, swap harnesses.
2. The car needs less fuel to idle when it has reached optimal temps (AKA WARMED UP).
2a. faulty blue cts will dump cold start fueling when warm - aka poor mpg, no sweeping action on a/f gauge, car will bog and die.
3. Closed loop emissions control mode is engaged when a valid signal, or BLUE CTS temperature range is met see #2a.)
3a. the heating element in the o2 sensor warms it up in 30-60 seconds so it can accurately feed data to the ecu
3b. the o2 wiring is usually both flex stressed and heat stressed (brittle).
3c. failure for the ecu to see an o2 signal will assume the car is very lean, thus the car will keep adding fuel.
3d. shorting of the o2 heating element 12V wires to the ECU INPUT 0-1V, will permanently damage the ecu and make the car run like butt.
if you swap the blue and black cts harness, and its great, go buy a $14 blue cts, its safe to drive on the black cts, be gentle on hot days, monitor MFA OIL TEMPS for cooling system malfunction.
if the blue cts is good, warm the car up, find the wot switch (See sig), and tape it shut. Go for a drive? Feels good? If so you have bad o2 system: wires, o2 sensor, ecu, anything in between... welcome to vw viring
This lesson assumes you have gone to the real forum AKA G60 and done all the basics, including tune-up.
We are capable of testing ecu's but honestly its not worth my time. My car works, and if you believe you've fried the ecu circuitry, it is possible to just drive with wot switch plugged in or chipping the ecu to not participate in emissions control, for off road purposes. race car folks dont need emissions/catalysts.
The bucking and such is REALLY bad, especially for the tranny, motor, and motor mounts, don't drive it like that man, show some respect.
The Idle Switch, and its relation to the ISV:
|Quote, originally posted by mrkrad »|
|it tells the isv to engage and also tells the ecu to cut fuel when you let off the gas (decel fuel cut).|
The isv does two things:
1. holds the idle at desired idle minimum 840~'ish
2. Engages an air leak when you clutch out so the engine rpm won't drop too fast (!!) and stall.
at least in the states, that is all it does.
also i think it prevents a runaway motor, if you are at idle it cuts fuel at 2500rpm or somewhere bout there, badly tuned cars will surge from 1500-2500(cut) and back and forth.
Setting the idle:
|Quote, originally posted by jwatts »|
|leave blue coolant temp sensor connected.|
The procedureis: set to 1000rpm with ISV disconnected
Then fine tune afterwards, if needed.
If it stalls, or dips and revs, then you need to open the idle screw up until it smooths out.
If the revs hang high, then you need to close it until they settle to your target idle speed.
Air/Fuel Gauge Behavior
|Quote, originally posted by mrkrad »|
|basically once warm or acceptable signal (varies on chip)->|
1. goes to close loop which is a sweep lean to rich
2. except when you go wot (rich lights)
3. except when you go idle decel (no lights)
4. there's a few other times when the car decides to hold it lean or rich for emissions purposes, shortly.
some of the chips will go very fast based on detection of valid signal (1 minute on sub freezing day, less than 30 seconds on warm day). Other chips rely more on the blue CTS.
|Quote, originally posted by TBT-PassatG60 »|
|For timing you should be seeing around 15-18[hg -vacuum] at idle with a stock cam. If you're seeing less either your timing is retarded or you have a vacuum leak.|
Basic Steps to Troubleshooting Bad Idle on a Corrado G60, for Beginners(What I've Done In This Situation That Has Worked For Me)
First, do this basics to eliminate some variables:
DEGUNK THE Idle Stabilizer Valve (ISV) - Pull it off, spray it full of brake/parts/carb cleaner. Shake it around with the cleaner inside, empty it out, repeat until the cleaner comes out clear. Remember, do not unplug the ISV with the key in the accessory or on position. THis is bad for the ECU.
Check for vacuum leaks. There are a load of vacuum lines on the G60. The stock lines are rubber wrapped in a braided cloth, and can dry-rot and crack. I replaced all of mine, from the dealer, for less than $40. Just ask for the diameters and lengths, and they should be able to cut them for you.
Here are the sizes, courtesy of the G60 Forum FAQ:
3.5 mm size line: 34" (brake booster line) + 39.5" (1 meter ECU line) + 6" (FPR) + 55"(charcoal mainifold) + 30" (air box to brake booster line) = 14.3 feet
9 mm size line: 40" (throttle body to charcoal)
5 mm size line: = 23" (brake booster to charcoal) + 28" (fuel tank breather line to charcoal) = 4 feet 3 inches.
That one-meter throttle-body to ECU line is important. There are two vacuum lines that go to the throttle body, and the ECU line connects to the nipple closest to the passenger side.
Second, Look at the electrical stuff.
Make sure there is no interruption in the spark: spark plugs/wires...make sure they are in good shape.
There's an electrical switch on the throttle body called the "idle switch" that should click on when the throttle is closed. Not surpisingly, the car will not idle right if this switch is fouled. It actually might not even start. It shares its connection to the harness with the wide-open throttle (WOT) switch, and the plug is on the back of the throttle body.
The fuel injector harness is in a pretty crappy place, between the head and intake manifold, where there certainly is significant heat. The insulation gets very brittle over time and there is the potential for electrical shorts. Check it.
Look for corrosion at grounding points. Particularly the ground on the coolant flange on the (transmission) side of the cylinder head.
Third, determine under what conditions idle is poor.
>Is it bad when the car is cold but better when the car warms up?
>Or is it good when the car is cold and worsens when the car gets warmed up?
>Or is it just crappy all the time?
>Idle Is Bad When The Car Is Cold:
If you disconnect the blue coolant temp sensor while the engine is running and it idles better, you probably need a new blue coolant temp sensor.
If that doesn't do it, then check the O2 sensor, check your timing and reset your idle*
>Idle Is Bad When The Car Is Warm.
If you disconnect the o2 sensor before or while the engine is running, and the car idles better, you probably need a new o2 sensor.
If that doesn't do it, then check the blue cts, check your timing and reset your idle.* If the idle is set too low, then the ISV will attempt to compensate for it once the car is out of cold-start mode, and the idle will be bonkers.
>Idle Just Sucks All The Time. Either the timing is way, way off, or you didn't set the idle right (too low).*
*Remember, the idle won't set correctly using the idle screw if you don't have the ISV unplugged.
And remember the method for setting the timing: The car must be warm, with the blue CTS unplugged, and the motor must be at ~2500 rpm. Set it for 6-8 degrees BTDC.
If idle is still bad, ask the experts in the G60 tech forum and read through the G60 tech forum FAQ if you haven't already and be sure to tell them you've done the basics.
Modified by cbgthor at 5:56 PM 3-17-2006