Diagnosing common problems in the MKIV

**Kirk** · 07-30-2007, 03:56 PM

Symptom:
Rear Hatch Rattles
Problem:
Weak rubber hatch bumpers
Fix:
Replace rubber hatch bumpers with stronger updated part

Symptom:
Engine won’t turn over when first turning key, it just click the first few tries
Problem:
Starter is dieing
Fix:
Replace starter

Symptom:
Engine makes no or little boost on second turbo, it also makes a bad noise
Problem:
2nd turbo is dead
Fix:
Replace turbo

Symptom:
“Thunk” when coming to a stop, and then starting off again, and sometimes when making a tight turn, especially down a hill
Problem:
Drivers side engine mount
Fix:
Replace the mount with new updated part. Or TRD engine/trans mounts

Symptom:
Light grey smoke with a blueish tint when first starting the car. Also leaves a puff of smoke when leaving a stop light, or blipping the throttle after idling
Problem:
Leaking valve stem seals
Fix:
Replace seals (not a cheap or easy repair)

Symptom:
The car was a full throttle and at high boost, then the engine just died all the sudden, now it runs but has almost no power
Problem:
An intercooler hose popped off.
Fix:
Clean hose connections, and reinstall using T-Bolt hose clamps. Tighten clamps firmly, but do not crush the hose

Symptom:
Rapid ticking sound when accelerating, even light acceleration, and also when letting off the gas. Sound does not change with speed (sounds the same at 2mph, and 70mph)
Problem:
Worn rear upper control arm bushings
Fix:
Either replace, or try lubricating

Symptom:
Noise coming from rear wheel
Problem:
Possibly rear wheel bearing
Fix:
Jack up that side, rotate wheel by hand, and try to wiggle back and forth. If you feel roughness when turning, or movement when wiggling, replace bearings and seals as soon as possible

Symptom:
Transmission seems clunky when applying and letting of throttle abruptly, or shifting gears
Problem:
Normal behavior for the very beefy Getrag transmission
Fix:
Try matching revs with engine speed when shifting, and drive more smoothly. The noise will go away, and your transmission will last longer

Symptom:
Transmission sounds like ball-bearings in a can when idling or at slow speeds
Problem:
Normal behavior of the stock sprung flywheel
Fix:
Get used to it

Symptom:
Smoke (grey/blue) comes out of exhaust when letting off the throttle after being on boost, or while on boost
Problem:
Could be turbo seals
Fix:
Rebuild or replace turbos (check for oil in the intercooler hoses)

Symptom:
Excessive oil consumption
Problem:
Either PCV valve (cheapest and easiest to fix), Valve Stem Seals, Turbo Seals, Piston Rings/Cylinder Wall, or oil leak
Fix:
Track down which one it is

Symptom:
Engine misses at high boost
Problem:
Miss firing spark plugs
Fix:
Switch to NGK 6097s gapped at .031-to-.035

Symptom:
Second turbo doesn’t kick-in immediately after down shifting
Problem:
Probably the pressure tank is bad
Fix:
Replace pressure tank (also check lines)

Symptom:
When my (6spd) car hits high boost, the car seems sluggish, and the tach instantly jumps to high rpms and stays there, even though the car is still accelerating
Problem:
Clutch is slipping
Fix:
Replace clutch, pressure plate and flywheel (along with flywheel bolts, and snap rings)

Symptom:
High pitched squeal from engine compartment
Problem:
Accessory belt tensioner pulley bearing bad (usually happens as a result of getting it wet when washing engine compartment
Fix:
Replace tensioner pulley

Symptom:
Took dash apart, now the airbag light stays on
Problem:
The Odometer/Malfunction Lights panel was disconnected when the ignition key was in the on position
Fix:
(From MKIV.com) Go under the hood and open the diagnostic cap located on the passenger-side near the firewall, look for AB & TC. Make two plugs with wire to fit into these connectors. With the ignition key turned to the ON position alternate the two wires to the negative terminal of the battery. They need to be done in a consistent rhythm, about one second apart. TC,AB,TC,AB,TC,AB... This needs to be done several times. If you can't get it to work, try adjusting the speed. It is helpful to have someone look at the airbag light while performing this to let you know when the light goes out/blink.