Skip the auto shop - Our mechanics make house calls

Q: Backfire

asked by on

Hello i have a serious backfire issue and here are the points. Checked timing Checked carburator cleaning and synchronisation. New sparkplugs New fresh petrol Good petrol pump Very high compression of 11.

Good stationary running but when i increase around 2500 rpm the engine backfires and doesn't come trough to higher rev's. Driving is nearly impossible.

1/ is the very high compression a possible cause 2/ cdi ignition is not working but on stroboscope measuring it seems working well 3/ a petronic is installed to replace the points

I'm scared the high pressure is the cause and means I have to rebuild the engine.

Would be great to hear an experts opinion

My car has 9999999 miles.
My car has a manual transmission.

Hi there;

In most cases a backfire issue occurs because the air to fuel ratio is too rich, the timing is off (which you’ve checked) or the spark plug tips have excess carbon build-up (which you’ve also replaced). Typically when compression is high, ignition timing is retarded or advanced to ensure optimal engine performance. Without being there to examine your engine with the stroboscope, it’s hard to tell you exactly where timing should be set. I’d reach out to a local mechanic with experience with smaller, high performance engines or with Porsche certified technician for those timing recommendations. Cheers and good luck.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: How do I keep my 72 ford ranger from stalling out while in idle? Does it deal with the carburetor, certain gas, or gas line?

Hi there. Actually, all three items you listed have a hand in the idle of an early 70's Ford engine. As a vehicle ages, some parts that are typically never replaced, like fuel lines and the fuel tank will eventually...

Q: Car won't go into gear ocassionally, 1990 Porsche 944

Hi there, thanks for writing in about your 1990 Porsche 944. A severely worn clutch will cause slippage and the vehicle will not move. Another common concern is the linkage between the shifter and transmission assembly. The cable and the...

Q: Excessive oil consumption and sooty exhaust

Hello there, A few different items can cause oil consumption. The most common is oil leaks, valve stem seals, PCV faults, or engine mechanical issues. Porsche 911's are known to have some oil consumption that is considered normal due to...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
P2428 OBD-II Trouble Code: Exhaust Gas Temperature Too High Bank 1
P2428 code definition A P2428 trouble code signifies that the PCM has detected a problem in the exhaust gas temperature sensor circuit in bank 1, which subsequently contains the number one...