Question: Back Firing though Intake Manifold

[DonBatt]

I have a 1994 Coupe with an automatic trans. with an LT1 Gen 2.
Runs good, idles smooth, lots of power, but if you press down on the throttle just right it pop's though the intake and bogs down. I have to release the throttle and hit it again to get the car to respond. Any idea's ??

 

[Hib Halverson]

I'm a little confused.
If the car runs good, why is it popping back though the intake? That's, actually, a pretty major drivability problem.

When does this happen, during light throttle acceleration?
During a quick opening of the throttle?
From idle?

How many miles on the engine? What's its recent maintenance history?

 

[KANE]

I have a 1994 Coupe with an automatic trans. with an LT1 Gen 2.
Runs good, idles smooth, lots of power, but if you press down on the throttle just right it pop's though the intake and bogs down. I have to release the throttle and hit it again to get the car to respond. Any idea's ??

Welcome to the !


Yeah- we have some really smart folks here that can help. Hib started off with some great questions.

So... to be helpful... you'll need to describe everything you can think of that is going on when when the pop happens. You can copy & paste and then respond right after each question.

1.) Is the check engine light on?
2.) Is this intermittent? As in... does it happen some of the time but not all the time?
3.) When does this happen- is the engine warm or cold?
4.) Does this happen only at an idle or coming off an idle and rolling in drive?
5.) Does this happen at low speeds or high speeds (rpm)?

 

[Wegone]

Did this just start happening? or was it after some maintenance?

 

[DonBatt]

Back firing though intake

OK it doesn't happen all the time. But it has been happening on and off every so often since I bought it. Usually not at a good time.
Yesterday I was out on the highway, the car has plenty of power and good throttle response. I got off an exit stopped at the light and when I went to pull away real easy it started to pop and sputter, I released the peddle and hit it again a little harder and it took off, no sputter. Got to the next light and the same problem, and at the next light no problem all was ok.

The engine has 75,000 miles on it, the distributor and wires were replaced at 68,000 miles by a dealer before I bought it. I replaced the plugs at 70,000 miles, I change the oil every 2500 mile Mobil One with a Fram filter. I rebuilt the throttle body Last summer. When I bought the car it was in storage for a couple of years. It happens when the car has been running and is warm or when cold it doesn't matter, the idle seems a little low about 600 RPM but its smooth and no check engine light. It seems to only happen coming off and idle, if you just punch it it might light up and go or it might pop and sputter.

So... to be helpful... you'll need to describe everything you can think of that is going on when when the pop happens. You can copy & paste and then respond right after each question.

1.) Is the check engine light on? NO
2.) Is this intermittent? As in... does it happen some of the time but not all the time? Intermittant
3.) When does this happen- is the engine warm or cold? Both
4.) Does this happen only at an idle or coming off an idle and rolling in drive? Coming off an idle
5.) Does this happen at low speeds or high speeds (rpm)? Once your rolling it's ok

 

[DonBatt]

Welcome to the !


Yeah- we have some really smart folks here that can help. Hib started off with some great questions.

So... to be helpful... you'll need to describe everything you can think of that is going on when when the pop happens. You can copy & paste and then respond right after each question.

1.) Is the check engine light on? NO
2.) Is this intermittent? As in... does it happen some of the time but not all the time? Intermittent
3.) When does this happen- is the engine warm or cold? Warm, Usually after coming from Highway Speed to a stop then coming off an Idle
4.) Does this happen only at an idle or coming off an idle and rolling in drive?
5.) Does this happen at low speeds or high speeds (rpm)?

Low Speeds

 

[1cooldaddyo]

I'm assuming it's just a kind of sneeze and not an actual, flame spitting, blast into the intake.
First off, I would be highly suspect of the quality of any parts the dealer put on before you bought it. New cap and wires would be my first stop, or at least look at them real close.
If you're 100% sure of the ignition, the next thing I would look at is the fuel.
I'm not really a fuel injection pro, but if you had a carb on it I'd say you were going lean when you jumped on it and look at the accelerator pump. The engine has to have an extra dose of fuel when you quickly open the throttle or it'll do just what you're describing.
I'm still betting ignition, but I suppose could also be fuel pressure or an injector not up to snuff.