Backfire and smoke under the Hood

[J.A.O.]

Lately, the engine is hard to start after it has been running. I am suspecting the FPR (based on previous posts) as the problem only exists when the engine is warm. I have an appointment to take it in Monday.

Last week I tried to start it and it backfired and I noticed smoke coming from under the hood. I popped the hood and noticed that the smoke seemed to be coming from under the vanity cover near the power steering pump. The smoke smelled like fuel. I let it sit for a while and later started it right up. The engine ran fine as it always does but that backfire concerned me. Well, yesterday, right after I got off the phone to make the appointment, it backfired again and the same smoke came out from under the vanity cover. The engine runs fine after it's started and does not seem to have been affected by these 2 incidents. Of course, seeing that smoke concerns me in that I worry that although the car drives and runs the same way it always has, it is possible that there has been any damage under that vanity cover that I am not aware of???? That smoke had to come from somewhere, and I don't have enough knowledge of cars to make any determination. I was hoping that maybe someone might tell me that the smoke was the leaky FPR dropping fuel on the exhaust manifold.

Any help or re-assurance would be greatly appreciated.

Thanks fellas...



Jason

[95Concours]

I believe the FPR can be checked fairly easily, I dont remember how to do it, but if you search Im sure you'll find at least BBOB's instructions on how to. I would certainly remove the engine cover, (its only 4 bolts) and see if anything burned under there, where there's smoke, there's usually fire. Id also leave it off until you get it fixed, that way you can see whats going on the next time the backfire/smoke happens.

[J.A.O.]

Thanks for the response. I'll give a shot if I have time. I've been thinking more and more about this. I believe the intake manifold is made of plastic, I only hope if that's true, that the backfire didnt destroy the ports.

[BeelzeBob]

Sounds like the fuel pressure regulator is leaking while the engine is sitting during a hot soak....or an injector is leaking down during the soak.

Either case puts excess fuel in the intake causing the backfire when you try to start it.

The intake manifold has a built in pop-off valve to vent pressure in the event of a backfire like event so as to not harm the intake itself. If you look at the manifold just behind the power steering pump there is a void down the center of the tubes and at the end of the void is the pop off valve. That is why you see the smoke and smell the fumes from the backfire under the hood. The valve is operating as it is supposed to.

Simply take the silver top cover off, find the fuel pressure regulator and pull the vacuum hose off of it while the engine is idling. Watch for fuel coming out the vacuum nipple on the FPR. There should be none.

[J.A.O.]

Guys,

Thanks for everything. I will check that later today. I hate to brief, but I must head out to work.


Thanks again....

Jason

[jacquelined]

My car did the same exact thing today. I am bringing it to the dealership to have the fuel rail replaced. What should I tell them to look for? I want to give some direction to them so I dont get taken advantage of!

[JimD]

Originally Posted by J.A.O.

Lately, the engine is hard to start after it has been running. I am suspecting the FPR (based on previous posts) as the problem only exists when the engine is warm. I have an appointment to take it in Monday.

Last week I tried to start it and it backfired and I noticed smoke coming from under the hood. I popped the hood and noticed that the smoke seemed to be coming from under the vanity cover near the power steering pump. The smoke smelled like fuel. I let it sit for a while and later started it right up. The engine ran fine as it always does but that backfire concerned me. Well, yesterday, right after I got off the phone to make the appointment, it backfired again and the same smoke came out from under the vanity cover. The engine runs fine after it's started and does not seem to have been affected by these 2 incidents. Of course, seeing that smoke concerns me in that I worry that although the car drives and runs the same way it always has, it is possible that there has been any damage under that vanity cover that I am not aware of???? That smoke had to come from somewhere, and I don't have enough knowledge of cars to make any determination. I was hoping that maybe someone might tell me that the smoke was the leaky FPR dropping fuel on the exhaust manifold.

Any help or re-assurance would be greatly appreciated.

Thanks fellas...



Jason

There was probably no damage to your intake system as a result of the "backfire". There is a pressure relief valve mounted in the front of the intake manifold to relieve any positive air pressure and prevent damage. The smoke was from unburned hydrocarbons.

Identify and correct the fuel or ignition timing problem, and your engine will be back to normal. Sounds like you have zeroed in on a fuel pressure regulator.

My '98 will do what you described several times a year (without the smoke). I just crank it again and drive down the road.

[J.A.O.]

Fellas,

It was indeed the FPR. I had the recall work done for the fuel rail as well. She runs like a top now.

Thanks for the replies

[eldorado1]

Originally Posted by J.A.O.

Fellas,

It was indeed the FPR. I had the recall work done for the fuel rail as well. She runs like a top now.

Thanks for the replies

In my case it was a leaky injector