Will not accelerate?

CHRIS CARMEAN

MEMBER
2002 CHEVROLET IMPALA
3.8L
6 CYL
2WD
AUTOMATIC
146,000 MILES

The computer is has no fault codes, the live data on scanner shows' almost everything normal except the timing which restarts to 7 btdc when you try to accelerate. The engine is running warmer than normal but not over heating. I just replaced the intake manifold gaskets, thermostat, plugs, wires and one bad coil. The engine ran great for about 200 miles. I was sitting on the side of the road on the phone when the car backfired and shut off. It started back up but ran very poorly and only intermittently bucked and shut off several times. After it cooled down some I did start again and ran the same long enough to get it home. The next morning the fluid levels are fine and it started fine but trying to accelerate it just bogs down and the timing retards when you try to accelerate.

1 Reply

KASEKENNY

MECHANIC
18,907 POSTS

You are correct that the backfire would point to a timing issue but it could be a couple other things.

Here is a guide that will help with this:

https://www.2carpros.com/articles/engine-backfires-while-running

The fact that you recently did a repair to the manifold gaskets means I would start with checking for vacuum leaks.

Here is a guide that will help with doing that:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If this checks out then we need to move onto the fuel pressure.

Again, here is a guide that will help with this as well:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Once we confirm this is ok we can move on but I suspect we will turn something up. Let's make sure we check the system really well for vacuum leaks.

We will then need to make sure we check the engine vacuum as well. Below is a chart that will help with figuring out if the intake valves are an issue.

Let us know what you find with this and we can go from there. Thanks

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