How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Matt Your Own Question
Matt
Matt, Engineer
Category: VW
Satisfied Customers: 21849
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
12772297
Type Your VW Question Here...
Matt is online now
A new question is answered every 9 seconds

1999 beetle having intermittent problem, when starting from

Customer Question

Customer: 1999 beetle having intermittent problem, when starting from a stop light, or sometimes upon initial startup, engine will idle fine, but around 2000 rpm will surge up and down, or chug and sputter if trying to accelerate. upon restart, will usually behave correctly
JA: Thanks. Can you give me any more details about your issue?
Customer: i have replaced plugs and wires, maf sensor, on a side note it also has an exhaust leak, the cat converter was cut out when i got it, but has not been an issue in the past
JA: OK got it. Last thing — JustAnswer charges a fee (generally around $18) to post your type of question to VW Experts (you only pay if satisfied). There are a couple customers ahead of you. Are you willing to wait a bit?
Customer: if it solves my problem, sure.
JA: OK. Now I'm going to take you to a page to place a secure deposit with JustAnswer. Don't worry, this chat is saved. After that, we will finish helping you.
Submitted: 1 year ago.
Category: VW
Expert:  Matt replied 1 year ago.

Hello

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and can lean the engine out and can also allowthe engine to rev up when not desired causing rough running.

As its amechanical fault it tends not to turn on the fault light and you can sometimes hear a 'hissing' noise with the engine running.

Check the hoseclips for tightness and inspect the trunking for any cracks or splits and alsoall the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas/propane around each joint in turn. If the engine rev's up you've found yourleak.

Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or sparkto set it off and I’ve used this method for many years without incident.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can oflighter gas to provide a spraying 'wand' and allow a direct blast of gas intoeach area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Might also be worthcleaning out the throttle body as these get clogged up withcarbon and some brake cleaner washed through helps free things off.

Might also be worth checking the wiring and connector to the airflow meter for any signs ofcorrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

Air leaks are very temperature dependent as gaps can open or close up as things expand with heat,so the weather and engine temperature can effect them.

This leads them to be quite intermittent in the case of mild leaks

its also worthcleaning the airflow meter by removing it from the car and spraying the exposedsensor wires inside the tube with a brake or switch cleaner - ensure that thecleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Expert:  Matt replied 1 year ago.

Hi

do you still need help?

Bear in mind that the site takes a deposit from you at the beginning and this is held by the site until you rate my answer at which point the cash is split between the site and the expert. so if my answers have been helpful please rate my answer.