V6 passat pops when warm and turning over. I'm stumped.
Discussion
1998 V6 Passat Syncro.
Sorry if I already sound boring.
Cold starts are fine. Fires up every time.
The issue arises when the engine is warm/hot and I try to start it again.
It sounds like a balloon being popped under the bonnet and there is a slight amount of faint smoke from the grill. If the pop occurs, I have to turn off the ignition and restart to be successful.
Vagcom used on different occasions and no faults stored. Connections, wires and other bits all checked.
I hope someone has some light to shed on this. Thank you in advance.
Sorry if I already sound boring.
Cold starts are fine. Fires up every time.
The issue arises when the engine is warm/hot and I try to start it again.
It sounds like a balloon being popped under the bonnet and there is a slight amount of faint smoke from the grill. If the pop occurs, I have to turn off the ignition and restart to be successful.
Vagcom used on different occasions and no faults stored. Connections, wires and other bits all checked.
I hope someone has some light to shed on this. Thank you in advance.
Edited by read5458 on Sunday 25th September 02:45
Sounds as though you are getting a flashback through the air intake. Can damage airflow meters &/or air filter housings so needs sorting
As it only happens when hot I wonder if you have an intermittent fault with a sensor which isn't showing up or a fault on a lead or plug?
We had a cutting out when hot fault on a Pug 306 1.6 which didn't show up at all on diagnostic - engine would occasionally cut out when at idle, but would start immediately & then be fine for days - but turned out to be a coolant temp sensor on the way out. Finally appeared on diagnostic when the engine wouldn't restart & the car had to be recovered. Was telling the ECU the engine was cold when it was actually hot & overfuelled.
As it only happens when hot I wonder if you have an intermittent fault with a sensor which isn't showing up or a fault on a lead or plug?
We had a cutting out when hot fault on a Pug 306 1.6 which didn't show up at all on diagnostic - engine would occasionally cut out when at idle, but would start immediately & then be fine for days - but turned out to be a coolant temp sensor on the way out. Finally appeared on diagnostic when the engine wouldn't restart & the car had to be recovered. Was telling the ECU the engine was cold when it was actually hot & overfuelled.
Edited by paintman on Sunday 25th September 09:44
That could be a faulty air temp sensor over reading causing an excessively lean mixture when cranking hot causing the motor to spit back up the intake 
may not show up on VAGCOM as its out of range rather than broken for example open circuit/short circuited,worth monitoring on the live readings 
or as above seeing as VAG seem to struggle to make a reliable ECU coolant sensor at the moment 
may not show up on VAGCOM as its out of range rather than broken for example open circuit/short circuited,worth monitoring on the live readings or as above seeing as VAG seem to struggle to make a reliable ECU coolant sensor at the moment Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff