2002 backfires & smokes at cold start

Have a 2002 Thunderbird with 40,000 miles...having a odd problem that none cant seem to figure out...
On several recent occasions when I go to start the car I get a loud pop/bang/boom noise and white smoke comes out of the hood and even has come through vents....after awhile you can try again and it starts right up..although it never starts on first ignition turn....2 mechanics haven't been able to find anything....one says could be bad gas...although have put gas in it since it has happen first time.....I am driving it several days a week....it has happen 3-4 times .....seeing if anyone else has had anything like this...thanks
 
Maybe it is firing out of time. I saw something similar on a Jeep vehicle.. Found a bad sensor. Cylinder firing timing on newer engines is computer controlled. When starting,the computer uses a combination of crank sensor and cam sensor to set the correct timing. Once running, the motor can run on either sensor alone..This is a safety feature so that if one sensor failed the other will keep the engine running. Check for codes, check sensors and their plugs and wiring.
 

Frankie the Fink

Well-Known Member
Maybe it is firing out of time. I saw something similar on a Jeep vehicle.. Found a bad sensor. Cylinder firing timing on newer engines is computer controlled. When starting,the computer uses a combination of crank sensor and cam sensor to set the correct timing. Once running, the motor can run on either sensor alone..This is a safety feature so that if one sensor failed the other will keep the engine running. Check for codes, check sensors and their plugs and wiring.
Highly likely
 
Have a 2002 Thunderbird with 40,000 miles...having a odd problem that none cant seem to figure out...
On several recent occasions when I go to start the car I get a loud pop/bang/boom noise and white smoke comes out of the hood and even has come through vents....after awhile you can try again and it starts right up..although it never starts on first ignition turn....2 mechanics haven't been able to find anything....one says could be bad gas...although have put gas in it since it has happen first time.....I am driving it several days a week....it has happen 3-4 times .....seeing if anyone else has had anything like this...thanks
Thanks for all the input. I am attaching a quick video this is me starting it up. You want hear the loud boom because of engine but there is a loud boom when I started it but you will see the smoke suddenly which is when it boomed. The camera jumps because my son jumps when it boomed but you see
where the smoke comes up.

View attachment trim.75D4399D-1F81-43CB-BEF9-25E03F51E7F7.MOV
 
Last edited by a moderator:

biddle

Forum Moderator
Staff member
I would definitely keep a fire extinguisher nearby until this is resolved, better yet, don't start it! I would check out this thread on the COPS-


What is the condition of your spark plugs and coils? You could have more than one issue going on here, but I would check the cowl seal, wiper seal and valve cover gasket too.
 
If you believe it's fuel related? Have you used a fuel pressure gauge to check the fuel pressure? once the gauge is hooked up showing fuel pressure, this pressure should hold after the engine is shut off. If it's not holding? You have a fuel leak most likely at one of your injectors. But........? That doesn't Meagan injector can be the only cause of a fuel leak.

it's concerning you're getting such a violent reaction on initial startup. That can damage other engine components! You want to track this issue down before another problem is caused. Finding one issue os bad enough. Creating another problem while searching for an original problem will make the job much harder plus create a scenario where you start second guessing yourself.

Are there any codes you've pulled up using a scan tool? If so? What are they?
 
I just replaced my valve cover gaskets, plugs, and coil packs on my 2002 3.9L V8. Because I've seen weird things happen after replacing mechanical and electrical parts using new parts. A recent example leads me to write this! I only worked and completed the work on one side of the engine. I check that completed work out before progressing to the other side. That way I keep any malfunctions separate from the other side to avoid getting overwhelmed, not knowing which side has the problem. Although the scan tool will usually indicate where the issue is. It's always nice to know the problem is contained in a known area you just worked on if there is component or electrical connection failure.

I started the engine up knowing immediately there was a problem! I ran the car for a mile or so before I noticed it had set the (CEL) Check Engine Light. Initial thought was a bad coil pack? After using the scan tool it verified cylinder D, number 4 passenger side closest to the firewall misfire. I
again took the access cover off exposing the coil packs and removed the one for D cylinder. I installed one of the FORD marked old coil packs and reassembled. The engine ran great!

So........ Just because you buy and install brand new parts? Never assume they don't have a problem out of the box! Always try to keep your work located in a small area especially if you're replacing, or working on multiple items!!! Then start the engine to see if it's fixed? If not? Was there an issue that was created by working on it's components. This way you minimize troubleshooting area if an issue was created.

Repairing and troubleshooting using this method may not work for everyone? But it's worked for me over the years.
 
The backfires probably have cracked the plastic intake manifold or at the least blown the intake gasket. Plastic intakes are installed to save engine weight, but do not hold up well to repeated backfires. That is the reason for the smoke where you see it. A smoke test of the intake will find any leaks. If when running it idles rough, then it likely has an intake leak, If you are lucky, maybe it only blew of a vacuum line. The only way it can backfire is if spark is introduced to the fuel mixture BEFORE the intake valve has closed. Ignition timing is off, a sensor or computer issue, or a intake valve is not closing properly.
Scan for codes first.
 
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