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Discussion Starter #1
My '99 beetle with AEG. I replaced the spark plugs, wires, coil, fuel pressure regulator, engine speed sensor, MAF sensor, fuel filter, air filter, .....but it's still hard to start. I got the VAG-COM cable a few days ago and read everything seems to be fine. The MAF data at idle 800rpm is between 3.6 and 5.2 grams/second, temperature is OK(I replaced the thermostat and flushed the coolant with the replacement of some hoses and the flange o-ring where they are leaking), also I did a throttle adaption but the problem is still there...

I also checked the vacuum it's around 19 on the gauge(Haynes manual says 17-22) and has a little(within 2) fluctuation. I suppose it's normal.

However it's still hard to start. The symptom is like this:When it's completely cold, I can probably start it with one attempt but the engine speed is not like normally gets to above 800 quickly(like explosion), it increases slowly and the beginning idle is very rough. Also at this time there are a lot of smoke come from the exhaust. After a few seconds it would be all fine. When the car is hot, it usually takes 2-3 attempts to start and I also need to pop gas. But every time I shut off the engine and restart it within 10 minutes it starts very good and engine speed gets to normal very quickly.

The gas mileage is around 21mpg combined. We are in Philadelphia, PA and we are driving approximately 70%local and 30%high way but I feel this gas mileage is still a little bit lower than normal(I used to have a '94 Civic and a '01 Echo they both get over 25mpg on 100%local).

Considering all those I suspect that there might be a fuel injector leaking a little. This can explain why after shut off within a short time fuel has not been leaked too much and is almost same as running. But after a long time the intake manifolds would be full of gas(I also found some liquid likely to be gas in the intake when I take them down) and the mixture would be very rich when trying to start(smoke from exhaust). Is it reasonable? Anyone any ideas?
 

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5/23/10 <3
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Fuel pump problem perhaps?
 

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Discussion Starter #3
Fuel pump problem perhaps?
I guess so too. I don't have a fuel pressure gauge so I have to take to a mechanic to check the fuel pressure. But will a fuel pump problem cause driveability problems also? The bug is really running excellent with no rough idle or power loss. Just hard to start...
 

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Possibly an O2 Sensor, which can cause the fuel to be too rich and also cause white smoke from the exhaust. PULL THE CODES!

MORAV
 

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Discussion Starter #5
Possibly an O2 Sensor, which can cause the fuel to be too rich and also cause white smoke from the exhaust. PULL THE CODES!

MORAV

I replaced the upstream O2 sensor 3000miles ago since I think the downstream O2 sensor only monitors the cat doesn't affect the engine operation I didn't replace it. I think the O2 sensor is giving out good signal. Also when the car is just started in the beginning seconds the O2 sensor is being heated up not giving any signals right? I pulled the codes only fuel trim too rich and the P0420 cat efficiency below threshold.
 

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Neither of which should have anything to do with a failing fuel pump, so I'd be looking elsewhere. Have to give it some thought, and a little research.

After doing a little research on the RossTech Wiki -
16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

Possible Causes

  • Leakage in Intake and/or Exhaust System
  • Catalyst faulty
  • Oxygen Sensor(s) faulty
  • Oxygen Sensor(s) Control faulty
Possible Solutions

  • Check Intake and Exhaust System for Leaks
  • Check Catalyst
  • Check Oxygen Sensor(s)
  • Check Oxygen Sensor(s) Control
    • Perform Oxygen Sensor(s) Aging Check
Special Notes

Retrieved from "http://wiki.ross-tech.com/wiki/index.php/16804/P0420/001056"

I'm sitting firm on a bad O2 sensor, because of the rich running and white smoke you have expressed, although this indicates is could be either the upstream or downstream sensor. Neither of which, to the best of my knowledge, should be a result of an intake or exhaust leak, or a bad cat. If you ran with a bad O2 sensor for any significant length of time (you said you replaced the upstream recently) you could, however, also have done damage to the Cat.

Since you had the codes read with a generic (S.A.E.) scanner, it might be advisable to have it read with a Vag-Com, for possible additional codes which are not read by these generic readers.

It takes a fuel pressure guage to test the fuel injectors and fuel rail for leaks, but I can walk you through the process if you can lay your hands on a fuel pressure guage (0-6 bar, approx 0-100psi required) and want to check those items.

M.
 

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Discussion Starter #7
Neither of which should have anything to do with a failing fuel pump, so I'd be looking elsewhere. Have to give it some thought, and a little research.

After doing a little research on the RossTech Wiki -
16804/P0420/001056 - Catalyst System; Bank 1: Efficiency Below Threshold

Possible Causes

  • Leakage in Intake and/or Exhaust System
  • Catalyst faulty
  • Oxygen Sensor(s) faulty
  • Oxygen Sensor(s) Control faulty
Possible Solutions

  • Check Intake and Exhaust System for Leaks
  • Check Catalyst
  • Check Oxygen Sensor(s)
  • Check Oxygen Sensor(s) Control
    • Perform Oxygen Sensor(s) Aging Check
Special Notes

Retrieved from "16804/P0420/001056 - Ross-Tech Wiki"

I'm sitting firm on a bad O2 sensor, because of the rich running and white smoke you have expressed, although this indicates is could be either the upstream or downstream sensor. Neither of which, to the best of my knowledge, should be a result of an intake or exhaust leak, or a bad cat. If you ran with a bad O2 sensor for any significant length of time (you said you replaced the upstream recently) you could, however, also have done damage to the Cat.

Since you had the codes read with a generic (S.A.E.) scanner, it might be advisable to have it read with a Vag-Com, for possible additional codes which are not read by these generic readers.

It takes a fuel pressure guage to test the fuel injectors and fuel rail for leaks, but I can walk you through the process if you can lay your hands on a fuel pressure guage (0-6 bar, approx 0-100psi required) and want to check those items.

M.

I read the codes with a VAG-COM. BTW, I did a Throttle body alignment with the VCDS-Lite and my VAG-COM cable and now with almost 50miles ran the check engine light still hasn't come on(I haven't read the codes yet so I don't know whether there is actually a fault code). I'll probably take it to my friend shop to check the fuel pressure since I don't wanna spend money on a fuel pressure gauge that I only need once.... BTW, I have a fuel pressure gauge but it only has the connection for a Ford. Is it possible I can buy a fitting or 3-way something like this to make the gauge suitable for this car?
 

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The adapters you need should be available as VW parts. I'll put up some info from the Bentley when I get a chance.

M.
 
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