1987 GN Stall and Backfire

[Georgey0414]

Hello all, new to the forum.

About 8 years ago my father bought a 1987 GN that was in great shape visually. It turned over fine and sounded really nice so he bought it. Mechanically it was a mess, with cracked heads and all sorts of other problems.

Took it to a family friend who is a licensed mechanic and he took it down to the block for the repairs. This car is heavily modified with a turbo that is a bit too big for it. Everything seemed to be fixed and we took it home. Later on that summer we had noticed that some issues started arising with it.

It still sounds great when you turn it over but once the engine is warm it begins to oscillate at idle and will eventually shut off. Once it is warm it just feels like it's dying with a sputter similar to that of running out of gas. Accelerating becomes a problem and it seems to start backfiring with black smoke occasionally.

It also seems to just eat batteries every couple of months and it will die after a few weeks without being started. I think we have bought a few batteries for it since he purchased it and we take the battery out during winter storage.

It also seems to run a bit better once it has a new battery in it but just for a short while.

Last year I took it into storage for him a bit late in the year so it was -20C. It ran great with no backfiring or anything.

Because of all this we are puzzled as to what the problem could be. At times we have thought it was electrical, at other times a heating problem, and from what I've read on here I think it may be something to do with the MAS airflow sensor/tubes. I have attached a picture of the engine and a closeup of the cracked tube I have seen coming from the turbo.

Hopefully someone can give us some input on this.

Thanks!

 

[RmvBfrFlght]

The vacuum line you show is part of the boost control. Replace it and the other two ASAP. If it breaks the turbo will make as much boost as it can. When replacing them note how the Y connector is plumbed. One end has a small orifice in it, that end goes to the turbo bell, which is the hose in your picture.

The intake duct work between the MAF and turbo requires clamps. Any leakage there is un-metered air and will cause issues with how the engine runs. With the engine running lightly tap on the MAF sensor. If that causes the engine to stumble the MAF is suspect.

Battery: typical issue, usually an intermittent trunk light switch, vanity mirror switch, or even the anti-theft system (if equipped). Also, at key-on, engine-off, make sure the dash VOLT light is illuminated. If not odds are the battery isn't being charged.

There is the gnttype.org site and the vortexbuicks-etc.com sites that have a lot of additional information on these cars.

RemoveBeforeFlight

 

[GNVenom]

First thing I would recommend is that you disconnect the fan Delay Relay on the drivers side fender (largest of three). This is a common source of the dead battery syndrome.

After replacing and checking all rubber items as outlined in the previous post, consider bad gasoline as a potential problem, as the car must have been sitting for a while. Running the gas thru and then refilling with good gas can sometimes eliminate the stumble and poor running.

That said, once bad gas has passed thru the system, the fuel injector filters will often clog with residue. Cleaning and back-flushing the injectors would be in order.