[Rossco]

I'm getting some sort of detonation in the exhaust that sounds like someone tapping in the fuel tank with a hammer. It's less then a backfire but more then a burble from the 2" pipe. This just started out of the blue a few weeks ago.

I'm wondering where to start. I'm thinking it could be:
Exhaust leak somewhere in the system
Timing (although the car is running great)
Fuel cut off solenoid?
Idle sensor is stuffed


It seems to happen more at slow speeds and on deceleration with no or partial throttle. It does not occur at Idle and the engine is not running hot. The engine is an early model G16B going through a 2" straight through system.

Any Ideas?

[Rossco]

Anyone have any thoughts on this?

-Its not timing related, I have run it rich and lean
-no exhaust leaks, I put a wet rag over the tail pipe
-Cleaned out the afm with special afm juice. The car drove better but no change to the popping

There is almost no change in fuel economy maybe 20-30kms if that. Usually exhaust detonation is a sign of a problem but the car is driving great that is what has be stuffed.

[fordem]

Lean mixture or retarded ignition timing used to be the common causes for what I term "spitting" through the exhaust on the overrun (deceleration).

The reason I'm saying "used to be" is that was back in the days of carbureted engines - with EFI, the system should be in "fuel cut" - the ECU should kill the injection with the vehicle on the overrun, so I'm going to suggest your TPS may be out of calibration or defective, causing the ECU to not recognize that the throttle is closed.

[MrRocky]

U have a hole in your exhaust

[Rossco]

A hole in the exhaust was number one on my list, I have checked it thoroughly an unfortunately that is not the problem. Interesting idea with the TPS I have a second one so I'll pop it in and have a fiddle around. It would certainly explain the over fueling.

When I pulled the AFM there was oil in the air intake pipe. I cleaned the PCV and all of the oil out of the intake. This significantly reduced the amount of popping but I'm not really sure why.

[Rossco]

Just an update.

Swapped the TPS and moved it around with no difference.

The amount of popping through the exhaust has been getting worse daily over the past week. pulled the intake hose off again and it was filled with oil. Cleaned it out, and again almost no noise in deceleration.

I have cleansed the PCV are there any other ways oil is getting into the intake? This isn't an oil mist either, it is a pool probably about 30ml.