CNG Backfire Problem

[yoboy]

My CNG idle was not set properly so get it adjusted at a mechanic, shortly after that every few starts on CNG it back fires makes a LOUD firecracker sound and burns part of the air filter. In the process it also knocks out a pipe and the car wont stay turned on even on petrol.

Anyone know whats causing this backfire and how to correct it? Dont like the feeling of knowing at any random time the car could break down!

[hash4u]

which spark plugs are u using?
how much gap do they have ?

[SER_GTR]

Hello!
Mixture plays imp role in that.....all you need to do is to adjust mixture as fine as you can to get rid of backfires......!
or it will blow up your air cleaner box or burn the whole air cleaner.....!
which car was it.....problem mostly occurs in almost all new cars with box type air cleaners and Efi engines....
Thanxx

[mercielago]

may be ignition timing is not correct

[yoboy]

I'm not sure the standard spark plugs? It was working fine until the mechanic adjusted some CNG settings. Its a 2004 SE-Saloon. Guess will have it adjusted again and put a clip around the pipe that pops out when there is a back fire.

[tauseen123]

Someone please Explain me What is actually BackFiring. What are the Observations. Is there any harm caused by it. And Just What EXACTLY iT iS..?

A simple as well as a Technical explaination is required.

[spectra]

Corollas are not prone to backfires like this as u are mentioning but the main problem is mixture and spart timing. Aprk is taking place at a time when inlet valve is slightly open. U can imagine what will be the result iof that. Instead of going out of the exhaust after power stroke the burnt and unvurnt gases find an escape route from the inlet valve towards air intake manifold and ultimately air cleaner assembly.

Timing advancer can be at fault because corollas are not habituals of such backfires unless there is some major problem. get advancer checked for proper function.

[yoboy]

I been driving for more than 12 months on CNG now and not a single back fire. Just the idle adjustment needed done yesterday and as soon as he did that I had the first backfire. He did some more adjusting and said it was ok now but in the evening it backfired again.

[spectra]

did he open the plugs while adjusting?

Maybe he has damaged it while putting it back. this can also cause the same problem due to improper gap of plug.

[BKid]

similar problem with my corolla se saloon , backfires with a bang ,, and then dosent start on petrol, the air filter has big pin holes well, lot bigger then pin holes after 2-3 weeks when i putt new filter in. One CNG wala did one thing , he wraps around black-tape (nitto) type around the manifold and make it semi-circle left open after air cleaner box. I asked why did he do that , but he has no proper answer and says , gari ziyada saanss lay rahi hai , is liya is ko half band kar diya hai,, lol,
anyways i dont have emulator or advancer in my car.

i appreciate if any suggestions from pakwheelers.

[spectra]

@Bkid

u need to install an emulator and advancer first.

contact kkoool at 03219562277 and 03009562277
he will guide u best about what to install and from where to install.

For both of u guys having backfire problem, if u can spend 15k on a lambda controller, it will definately solve this backfiring problem

[yoboy]

Nope, he just adjusted the settings on the CNG regulator and set the idle higher. Also on CNG the car would stall whenever you put it on reverse so he did some more "tinkering". Didnt even though the spark plugs. Thinking he not done a good job of the adjustment.

As for the Backfire BANG it causes a pipe on the front of the engine to blow off thus causing the car to be inoperable on cng OR petrol until you squeeze it back in.

[hash4u]

looks like a mixture problem in this case
as plugs were not touched and it was running fine before this

[SER_GTR]

Hello!
MIXTURE was looking culprit here...afterwards timing......
man....these plastic air cleaner bOx suxx on CNG...and blows like anything :P.....sounds funny to me when they blow...!
Thanxxx

[imtishal]

May b the plug wires are crossed.i saw a similar problem in a cultus at a workshop and the machinc just changed the plug wires settings.plz check that the proper plug wire is connected to proper plug.

[muddy786]

bro tell me which advancer u r using in ur car tell me the brand name and clean ur crank sensor and clean ur coils and check ur plug gaps an 1 thing more get ur intake manufold if it is leaked then change it it always leaks after back fires tell me brand of ur advanser

[spectra]

good suggestions muddy

[kkoool]

too much advancing and a lean mixture that pre-detonates is causing a backfire.

the remedy is

1. check plugs (replace)
2. Check continuity of wires
3. Check coils (usually good)
4. Advance as preffered(stock + 10-12 Degrees)
5. Adjust mixture

Bye

[yoboy]

Went to Al-Mubarak, they did some adjustment and now its not backfiring anymore and driving great. But now when I'm at a stop light the car is vibrating a lot, its really annoying even though the idle/racer is at around 800 idle. And the sound coming out of the exhaust when I start to accelerate sounds kinda like a sore throat, kinda rough etc. Now what =-)~

[yoboy]

cough