Backfire followed by a stalled car.......

[elevario]

Hello, I am a long time member but more of a lurker. Today on my way into work I was driving and the car lurched as if to backfire and then finally backfired when I hit the gas again. I've experienced a fair share of backfires in my life but the thing that made this one different is that my car stalled. What the heck causes that? My car is a 1998 Campari z28 t56 with 139k on the clock.

I'm a little worried and my car just restarted and drove to work no problems. But I drive the remainder 3 miles like a grandpa. No codes were thrown so I don't have that. Any insight would be greatly appreciated.

[SMWS6TA]

Backfire could be from several things.


Did you fill up recently? Bad gas...
Check plugs & wires, see if any are loose.
When's the last time you cleaned you MAF?


Without a code I'm just throwing out the most common issues. May be a clogged CAT (if you still have them)

[elevario]

Backfire could be from several things.


Did you fill up recently? Bad gas...
Check plugs & wires, see if any are loose.
When's the last time you cleaned you MAF?


Without a code I'm just throwing out the most common issues. May be a clogged CAT (if you still have them)

First off thank you for the reply! Second, I apologize for the grammar, my autocorrect was turned on because this is a new phone.

I do need some gas but hadn't recently filled up. I am definitely due for a tune up and will be the first thing I do when I get time. I've never cleaned the maf before though. Is this something cleaned with brake cleaner?

Its still weird that the car stalled after the backfire. i've never experienced that before.

[elevario]

Oh and I do still have the cats, can I check for a clogged cat in some way or is this better done by a shop?

[theorangeguy]

Do you run 93octane when you put gas in the car...?

[elevario]

Do you run 93octane when you put gas in the car...?

The highest we have in Tucson is 91 and that's all I put in.

[SMWS6TA]

First off thank you for the reply! Second, I apologize for the grammar, my autocorrect was turned on because this is a new phone.

I do need some gas but hadn't recently filled up. I am definitely due for a tune up and will be the first thing I do when I get time. I've never cleaned the maf before though. Is this something cleaned with brake cleaner?

Its still weird that the car stalled after the backfire. i've never experienced that before.

MAF Cleaning - NO, DO NOT USE BREAK CLEANER!!! Use a MAF cleaner, they sell them at any parts stores. Easy to do, 1st to not touch the wire, 2nd spray the cleaner on the wire for a few seconds, repeat after 15 seconds, do this a couple of times. Let it air dry.

Checking CATS - most times it will throw a code and the check engine light will come on. Either that or the car runs like poo and is hard to keep running if the CATS are clogged.

91 OCT is good enough.


Could you tell if it was a back fire out the exhaust side or through the intake? Kinda hard to tell unless your listening to the motor.


When's the last time you did a tune up?

Backfires are usually when you running rich in fuel, bad/weak plugs &/or wires might not burn off the fuel and if it hits the CATS that will for sure light the unburnt fuel. If it's through the intake then there's other issues that come into play.

[elevario]

MAF Cleaning - NO, DO NOT USE BREAK CLEANER!!! Use a MAF cleaner, they sell them at any parts stores. Easy to do, 1st to not touch the wire, 2nd spray the cleaner on the wire for a few seconds, repeat after 15 seconds, do this a couple of times. Let it air dry.

Checking CATS - most times it will throw a code and the check engine light will come on. Either that or the car runs like poo and is hard to keep running if the CATS are clogged.

91 OCT is good enough.


Could you tell if it was a back fire out the exhaust side or through the intake? Kinda hard to tell unless your listening to the motor.


When's the last time you did a tune up?

Backfires are usually when you running rich in fuel, bad/weak plugs &/or wires might not burn off the fuel and if it hits the CATS that will for sure light the unburnt fuel. If it's through the intake then there's other issues that come into play.

I am not exactly sure but it felt through the exhaust but I could be mistaken. It's been a couple years since a tune up and I will be doing that asap.

Thank you for clarifying the correct cleaner for the maf. I will get back to you all on the progress

[pajeff02]

Kind of an odd issue. Fuel filter been replaced lately? Wouldn't hurt to check your fuel pressure.

[SMWS6TA]

Has it sat for a long period of time?

[RONS98TA]

I would check fuel pressure also.

[Naaman]

Hmmm.... I bet once all the maintenance is taken care of, he'll see a gain of 20 horsepower over what he's got now... Might want to seafoam or clean out his throttle body as well. If the plugs are an issue, I heartily recommend the NGK Iridium IX TR-5s (couldn't find the TR-55s and bought the TR-5s instead; they seem to burn the fuel better than the Autolites I was running prior... fuel economy when up by about 35-45 miles per full tank). Check out the air filter while you're at it.

Air filter
MAF cleaner
Throttle body cleaner
Fresh plugs
Fuel filter

[cammed goat]

Are the airbox, air filter factory spec? Are you running a K&N or any aftermarket air filter? I ask as if you are running an air filter which requires oiling, you could have sucked some of that oil into your MAF.

[Too Fast]

Catalytic converter(s) won't cause a backfire. They can clog, allowing poor performance or even a no-start, but by themselves they don't cause a backfire. Sometimes engines can run rich on overrun, causing the burbling/backfiring thru the exhaust that sounds so cool, but that's not a backfire that will stall the engine.

I'd be looking to clean the MAF first, then check fuel pressure. Fuel pressure should be at 58-60 Key On Engine Off, every time you do a 2 second prime. 2 second prime is every time you do a KOEO.

If a backfire is severe enough, it can stall the engine.

[theorangeguy]

did the backfire happen in a certain RPM range...for instance, was it while you were cruising around at 2-3,000 rpm, while you were downshifting into 2nd gear to get onto an interstate at like 4500-5000rpm, or while you were going through the gears etc? Trying to get an idea of what you were doing when it happened.

I've heard backfires when somebody puts it in low gear and lets the engine do the braking "sounds really cool" but if you have an exhaust leak or a vacuum leak it will backfire...

Just throwing ideas out there...but I would recommend pulling some of the plugs to see how bad they are and also checking the fuel pressure like Steve recommended.

[Too Fast]

Also, backfiring can happen with low fuel pressure/volume. Just because pressure is good at idle is no garauntee it's okay under load. If you are lean from a low pressure situation or an under-reporting MAF, that can cause a lean misfire/backfire, and this is not good for an engine. Best to run a bit rich rather then a bit lean.

[elevario]

Also, backfiring can happen with low fuel pressure/volume. Just because pressure is good at idle is no garauntee it's okay under load. If you are lean from a low pressure situation or an under-reporting MAF, that can cause a lean misfire/backfire, and this is not good for an engine. Best to run a bit rich rather then a bit lean.

Gosh thank you so much for all of the replies! I haven't had a chance to start pulling plugs or check the fuel pressure (don't have a gauge) but I did get a chance to clean the maf witht the designated cleaner. I did somewhat recently clean and re-oil my k&n fipk and feared that I may have over-oiled it. I don't know if it did anything at all but I haven't had the same problem happen yet as I've been babying the throttle everywhere I go.

Btw this happened under acceleration but not heavy. I was in 4th gear around 1750-2000 rpm when it bogged, I released the gas and thought "wtf?" Then I gave it more gas which started the backfire, then the stall. Luckily I had speed and could use the momentum to pull off the road.

I have replacement plugs and wires ready to go as well as a fuel filter just in case. I had replaced the fuel filter a couple years ago as a random preventative maintenance.

Thank you all so much for the replies! Work has made it so I don't have the time to give the full treatment but I should be able to pull plugs today and not looking forward to the one near the firewall on the passenger side :/ will update on how that goes.

[SMWS6TA]

yeah #8 plug is always a fun one with stock manifolds.

There are a couple of ways to approach it. Take off the #6 & 8 coil packs and go at it from the top (small, nimble hands almost a must) or jack it up and go at it from the bottom with extensions and maybe a universal. You may have to remove the starter to have more access. It's been 5 yrs since I installed LT headers so I can't remember if the starter has to be removed or not.

[theorangeguy]

yeah #8 plug is always a fun one with stock manifolds.

There are a couple of ways to approach it. Take off the #6 & 8 coil packs and go at it from the top (small, nimble hands almost a must) or jack it up and go at it from the bottom with extensions and maybe a universal. You may have to remove the starter to have more access. It's been 5 yrs since I installed LT headers so I can't remember if the starter has to be removed or not.

you can do it without removing the starter. Going from the bottom is easier for me...

[pajeff02]

Agree -- get number eight from down below.

Our car had a stumble in the rev range when we bought it due to a hacked up MAF.