car has a slight backfire

**basballny2** · 09-12-2010, 01:30 PM

last night i took my car out and noticed it was idling a little funny, it would have the same idle the whole time then for a second or two would back fire a little bit. then when i took off my buddy was behind me and noticed when i got on it a little i had a puff back of a little smoke. ive only put about 200 miles on it this year. car has brand new plugs/wires only 200 miles on them and was just tuned 2 months ago. any ideas? could it be from just sitting? bad gas?

**98TransAmWs-6** · 09-12-2010, 01:47 PM

Originally Posted by basballny2

last night i took my car out and noticed it was idling a little funny, it would have the same idle the whole time then for a second or two would back fire a little bit. then when i took off my buddy was behind me and noticed when i got on it a little i had a puff back of a little smoke. ive only put about 200 miles on it this year. car has brand new plugs/wires only 200 miles on them and was just tuned 2 months ago. any ideas? could it be from just sitting? bad gas?

What gas do you run? Also how long does it sit without running? I know on my 85 corvette if I don't start it for a couple of weeks it would do that for a little bit until the carbon was kicked out of the pipes.

**basballny2** · 09-12-2010, 02:03 PM

i run 93.....i took the car out about 2 weeks ago nd DROVE it.....didnt have any problems

**98TransAmWs-6** · 09-12-2010, 07:52 PM

Originally Posted by basballny2

i run 93.....i took the car out about 2 weeks ago nd DROVE it.....didnt have any problems

Have you changed your fuel filter recently? If you haven't it is possible however unlikely that the contaminants that are getting past the fuel filter have damaged the fuel pump which in turn is causing the fuel to air ratio to become out of wack. Which may cause the unburned fuel to ignite or backfire. The other thing to check would be your cats if you have any. But you'd probably be throwing codes if this was happening. It would be kinda strange for this to happen in a two week time period. You might want to try getting gas from a different gas station to see if it is really bad gas or some sort of fuel cleaner or octane boost or something.

**0rion** · 09-12-2010, 08:38 PM

also check your pcv line on the passenger side where it bends going into the intake....sounds like you might have a vacuum leak and those are known to crack on the backside of that bend.

**basballny2** · 09-12-2010, 08:57 PM

changed the fuel filter last summer and it only has prob 700 miles on it and ill check out that line and see whats goin on

**thechad125** · 09-14-2010, 11:13 PM

Originally Posted by basballny2

changed the fuel filter last summer and it only has prob 700 miles on it and ill check out that line and see whats goin on

Did u recently have headers installed or a new exhaust? Check the O2 sensors, I had this problem every day for a while. Had a leak in the headers from some "proffessional installation" and the O2 sensors were shot...Replaced them and fixed the leak and shes fine now...also had a tune.

***SMWS6TA*** · 09-15-2010, 07:23 AM

Originally Posted by 0rion

also check your pcv line on the passenger side where it bends going into the intake....sounds like you might have a vacuum leak and those are known to crack on the backside of that bend.

THIS^^

I have to say that for a long time now I've had an annoying backfire every time I let off the gas, especially under high rpms. Last Saturday I changed my PCV and had to do a fix because the rubber garment that holds it fell apart. Then because of another reason, last night I needed to go back under and found another failure further down the same part. If you follow the pcv line towards the back of the manifold you will see that it connects to another line. At the connection spot I had another failure.

Here's the line I'm talking about.

This is where it failed

this is the line that connects the pcv to the 1st pic. The garment that holds the pcv failed here to.

Here is where it sits across the back (the arrow). In the pic I was swapping my intake (last Sat), But last night I was able to get my bear claws back there. BE ADVISE WHEN MOVING HOSES BACK THERE! You have a oil pressure sender that breaks like a twig. So be careful. In case your wondering where it is at in the below pic it is missing, because yes I broke mine. It is where the head meets the valley tray on the back side. It would be to the right of the circle.

Now here is the scary part. If you need to fix this pcv line, the part is sold as a whole unit. Meaning from the manifold, including the pcv, all the way to where it connects to the valve cover drivers side rear. It costs $130 at the dealer or with gmpartsdirect $60 - $80. I check twice and 1st time it said $60 and the 2nd time said $80. Email them for a confirmation.

Now I have made a fix for the pcv for about $6 including the pcv and another for the one in the second pic ($10). I plan on taking some pics later today, it was to dark to take them last night. I'll post later, if you want PM and I'll sent them direct to you.

My point in all of this and agreeing with Orion is:

1) he told me the exact same thing yesterday, thus the reason for me going back under my hood to fix it.
2) On my way into work I did everything I could to make it back fire and all is fixed.

I still have the header pop because I have LTs and deleted CATS but no huge backfire like before.

**basballny2** · 09-15-2010, 10:44 PM

thanks for the pics! im not guna have time to check it until the weekend, big week at work this week im putting in 12 hour days so the car has to wait, but ill check it all out and let you guys know whats goin on, thanks for the help!

**Too Fast** · 09-16-2010, 02:35 AM

Originally Posted by basballny2

last night i took my car out and noticed it was idling a little funny, it would have the same idle the whole time then for a second or two would back fire a little bit. then when i took off my buddy was behind me and noticed when i got on it a little i had a puff back of a little smoke. ive only put about 200 miles on it this year. car has brand new plugs/wires only 200 miles on them and was just tuned 2 months ago. any ideas? could it be from just sitting? bad gas?

We've seen a lot of people here who think the plugs/wires connection is good, but to find out they really are not. 200 miles is really like they were just put on yesterday. I'd take the plug wire off the coil and spark plug, and reinstall them. Be certain about a click/double click when it goes together.

It could also be gas going bad, supposedly it only has a 3 month shelf life once it is in a car's gas tank, but I've never had problems with gas 2x that age.

Is your MAF clean? Have you cleaned it lately?

I really don't think it's a vacuum connection/vacuum line issue, that mostly causes idle problems.

And the puff of smoke? It'll probably go away when the little misfire is fixed, but these cars do have normal smoke when you get on it. Lots of fuel being burned....