ALFAGTV6.COM

Yesterday, I decided to take my GTV6 for a ride. I started the engine, and almost imedietly I heard the engine turn over and loud bang. Then the car lost power. I tried to start again, I could hear the engine for couple of seconds (5 seconds) then it lost power again. I smelled a burning rubber, and i also saw some smoke coming out from under the hood. Leter that evening I inspected the engine, I did not see any visiblie signs of damage. All the belts seems in place...

I have no idea what could that be. I checked the oil level it was above minmum. To things that are important to know is that the car needed a new timing belt it has 72000 miles. And I noticed an oil leak right after the oil was changed 10 days ago. Does anyone have any idea in how much trouble am I right now ?

Thank you

badger77 it sounds as if you experienced "plenum pop".Run a search on this site and you'll see that it is fairly common.What happens is you get a backfire and the explosive force travels back up through the air intake path.The most common result is that the air plenum pops off the six runner hoses that attach it to the intake tubes.After that the engine will run very poorly or not at all.Check to see if that is what happened.
This backfiring can occur due to poor ignition timing (check your distributor cap and rotor) or because the gas pedal is partially depressed during starting.A properly tuned L-Jet Alfa requires that you leave the pedal alone during starting or push it to the floor if the engine is flooded.

Murray wrote:A properly tuned L-Jet Alfa requires that you leave the pedal alone during starting or push it to the floor if the engine is flooded.

I can confirm this with my own little ancedote. My GTV-6 was running perfectly (and still is) when I found myself at 7,000 feet in New Mexico on a very cold, clear, morning, coming out of a Ramada Inn where I slept very uncomfortably the night before in a poorly heated room.

This was my first experience with the GTV-6 in this type of climate - I was on my way home to Oakland from Oklahoma, where the GTV-6 had received "Special" treatment from Greg Gordon.

Sidebar: My '72 Saab 99E (my first car) had the same starting requirements relative to regular starting - no gas pedal - so that part I have always attributed to fuel injected autos (rightly or wrongly).

When I went to start the GTV-6 on this bitterly cold and windy morning, I did what I normally do and it fired the second it engaged, but then quit. Feeling like it must be close, I gave it 4 or 5 good tries in succession.

At this point, I proceeded to worry about the plenum (why worry about a battery when you can worry about a plenum?), having read all the stories about what happens when one held down the pedal on ignition. I didn't feel like I had many starts left, it was oppressively cold, and so I did what any dumb-ass former Saab owner would do - I said "Fuhgetaboutit!" and hit the ignition and lowered the boom! Actually, I timidly tried the pedal at first (nothing), then finally all the way down. Voila! She fired right up.

Dumb luck (helps when the "luck" is based on good science)

Thanks (sorry for the mini h-j).

David

Hi guys. . . Yes it was indeed a plenum pop. 4 out of the 6 runner hoses got disconnected. It took me 20 minutes to get it back in place. . . The only problem is that I was unable to tighten the bottom part of the hoses, they are abstracted by a metal pipe. Any ideas how I can get to it ?

The good news is that the car started again... Thank you for the help.

This had happened to me a few times, and you get better with practice.

If i have time i usually attach the all lowers first then the upper clamps last.

One time when this happened i was in my suit without tools so i had to jump up and down on the plenum to get me home. got some weird looks and comments that day!!

Karl

That is a funny story. I actually did the same thing at one point, I stood on the top of the plenum. Then I found an easier way to do the same thing, grabbed two ends of it and gently but firmly pushed it down on one end pulled it up on the other end, and vice versa did that movement couple of times until the plenum was in its place.

Had a classic plenum pop "sound" on my '86 GTV6 ... without even touching the accelerator. But the plenum didn't actually "pop" off ... instead, it blew off the large "air hose" which then needed replacing (US$167.50) to make things work again.

i intentionaly leave my intake hose "slightly" loose on both the AFM and the TB..so it will blow the hose easyer than the plenum...and have never had the plenum pop or any damage to the hose...but its been a long time since i had a "pop"

In all my time with my alfa this has never happed to me. Mind you the timing is set slightly behind. Still runs great.

May be it won't make a difference but I always disconnect the cold start injector.

Sounds kind of strange. Its likely running rich if you have to disconnect the cold start valve.