Random hesitation and lots of greyish smoke

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
Hey guys i'm new here. I've spent a lot of time reasearching my issue, and replacing random parts . I have a 2000 mk4 jetta with a 2.0l 5 speed . The issue i have is very intermitin 50% of the time my car seams to run good , but the other half the time , when I'm at a stop sign / light . And take off my car hesitates big time then exspells a lot of whitish smoke . And at idle it sounds like it has a miss and the engine is shaking the car / running rough. I sometimes can smell that the car is running rich. Also has irratic idle sometimes . But like i said, it only does those things some of the times. Other times it runs great . I'm pretty sure my milage is not as good as it should be either.The check engine light is not on BTW and I've scanned it , theres 0 errors or codes
I've replaced both O2 sensors, MAF sensor, plugs and wires , coil, fuel filter ,cleaned throttle body , sea foamed it checked for vacuam leaks.
To me it seams like its a sensor starting to fail , but i'm not sure , any ideas ??
Thanks in advance
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Are you certain you have the correct plugs? The AEG engine does not use the same plugs as the later ones.

The AEG is a well known oil-burner, and they can be pretty bad. It will need rings to fix that. Have you noticed a loss of oil or coolant? Is the dipstick and dipstick tube intact and correct? Again, these are engine-specific, and if it has a wrong one, the oil level could read incorrectly, which could result in an overfilled crankcase which could cause oil to be drawn into the vent tube.
 

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
thanks for the reply , I've tried 2 different sets of plugs , ran the same , i'm using the ngk iridiums atm .they all look fine , not oil soaked .what plugs do you recommend ? the only time it smokes is when it hesitates off the line ( and not that often. car does burn some oil but not too bad ,it has almost 389k on it .Coolant level hasn't changed . and like I said there's no CEL . seams like it should be getting better mileage also , so it kinda seams like a sensor , but i'm not sure

any other ideas ?

thanks in advance
 

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
Hey guys

thought I would scan just for the heck of it , sure enough there was a error code , p0422 (Main Catalyst,Bank1 Below Threshold ) , but for some reason the CEL was not on though
Could my cat be plugged ? the rest of the exhaust has been changed to a full stainless catback system, was done just before I bought the car. The cat looks really old .

Any ideas ?
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Does the MIL even work?

Catalyst faults are pretty common on those. I doubt that has anything to do with your issue though.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Malfunction Indicator Lamp. Should come on when you turn the key on, then go out once the engine is started.

All the 2.slo engines have catalyst issues, very common, many got a warranty extension up to 120k miles. Do them all the time.
 

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
Malfunction Indicator Lamp. Should come on when you turn the key on, then go out once the engine is started.
All the 2.slo engines have catalyst issues, very common, many got a warranty extension up to 120k miles. Do them all the time.
What are usually the causes of the catalyst issues ? I thought it was strange that the CEL wasn't on but yet there was a error
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
Normal use. And compounded by oil use. Most AEGs are using massive amounts of oil by 80k miles.
 

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
Normal use. And compounded by oil use. Most AEGs are using massive amounts of oil by 80k miles.
Thanks , what usually fixes the issue, I'm sure there's several things that can cause that error , what are the most common things ? My CEL came on today, got the same code p0144
Thanks for your time
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
What fixes a bad catalyst? A new catalyst. What keeps it from happening again? An ALH swap.

The AEG was riddled with oil consumption problems, air/fuel ratio management problems, and catalyst problems. They were the first sold here with both a fragile hot film MAF and a sensitive planar wide band lambda sensor AND VAG/Bosch use the post catalyst sensor for lambda correction under certain circumstances. The 1998 New Beetle self study guide would probably explain a lot of this better than I have the time or ability to. That engine was all new for 1998 (as was the chassis).

Mid-2001 the AEG was replaced with the much improved AVH/AZG engines. Better pistons, better valves, better valve cover, better injectors, better ignition system, better throttle body, better catalyst and manifold (although those still fail, at least it is usually from normal decay and not massive oil use), and a descendant of that engine was still sold here right up until 2016 and is still being sold in other parts of the world today. :)
 

mk4steveo

Member
Joined
Sep 3, 2018
Location
campbell river
TDI
2000 mk4 jetta
What fixes a bad catalyst? A new catalyst. What keeps it from happening again? An ALH swap.
The AEG was riddled with oil consumption problems, air/fuel ratio management problems, and catalyst problems. They were the first sold here with both a fragile hot film MAF and a sensitive planar wide band lambda sensor AND VAG/Bosch use the post catalyst sensor for lambda correction under certain circumstances. The 1998 New Beetle self study guide would probably explain a lot of this better than I have the time or ability to. That engine was all new for 1998 (as was the chassis).
Mid-2001 the AEG was replaced with the much improved AVH/AZG engines. Better pistons, better valves, better valve cover, better injectors, better ignition system, better throttle body, better catalyst and manifold (although those still fail, at least it is usually from normal decay and not massive oil use), and a descendant of that engine was still sold here right up until 2016 and is still being sold in other parts of the world today. :)
A new catalyst as in a new catalytic converter ? Is there something else I should check first ? Or is that the issue for sure? I cleared the code and it hasn't came back yet ! Is that normal ?
 
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