[Rob]

I need some help in diagnosing a pinging problem.

It happens at low revs (1.5k to about 2.5k) either coming off the clutch when moving from stopped or driving up small hills. Only happens once the engine is warmed up to normal operating temp (never when cold). Pinging stops if I accelerate or back off slightly then accelerate.

Mechanic originally diagnosed faulty computer - changed computer, seemed ok for a while then started again.

Then mechanic diagnosed faulty air mass flow meter due to oil from K&N filter. Replaced mass flow meter with reconditioned unit (and filter with standard paper type). Again seemed ok for a while then started again.

The only engine mod is I have fitted a Promax chip.

Any thoughts would be appreciated.

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[flash]

well, first off, i presume you are running at LEAST 90 octane (RON + MON/2)



do a "blink test" and see if your anti-knock sensors are faulting



then, if that isn't it, pull the chip and see if that solves the problem

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[Rob]

Yes, running 98 octane.



"Blink Test"???? Whats that.

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[PorscheDude]

http://www.968forums.com/index.php?showtopic=379

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[Rob]

Interesting.... Australian delivered cars dont have a Check Engine light (and yes I have checked the owners manual).



I'll try swapping the chip back to original. Other than that looks like its back to the mechanic.



Thanks anyway.

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[flash]

bummer - that does make it tougher



didn't know you were in australia - please update your profile

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[FRporscheman]

You need to change your mechanic. I can't stand mechanics that approach a problem by replacing "likely" culprits with nothing but a guess, at the owner's expense.



My boss is like that... and I try to communicate with the customers when I can. And my boss is always bitching to me about how he can't make money. He'll fire me one day but at least I'm honest.



It could be many things. How old are your plugs, cap, rotor? How much mileage, and would you call them hard, medium, or gentle miles? Gentle mileage will let carbon build up on the pistons, increasing compression ratio, and will cause detonation. As flash said a bad knock sensor would surely cause problems but they don't really go bad that often.



A friend of mine solved a knock problem by changing his fuel filter. Seems strange but the conclusion he came to was that the clogged filter was restricting fuel flow enough to create a lean mixture.



Remove and inspect your spark plugs. If you have a fuel pressure tester, try it with engine hot and cold. What is Australian 98 octane in US octane?

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[SILVY968]

I have the same issue. I just talked to my PM and he suggested that I check all vacuum lines, especially to the brake booster, for cracks that let in air. Air, that enters the engine, past the sensor,will lean out the engine causing it to ping. Also check for air leaks at the intake manifold gasket.



My PM can perform a smoke test with a piece of gear that replaces the throttle body with a fitting that can tell if there is extra air getting into the cylinders causing it to run lean.

He said that he would not run a car that pings on a track, but a DD should be ok until the cause if found.



Check plugs, wires, knock sensors, gas grade, fuel filter,vacuum lines and intake manifold gasket. There is also a water temp sensor that tells the CPU to add or subtract fuel, if the sensor is broken in the lean position, it could also be the problem.



I'll post my results when I get her back from my PM.

Brian

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[Kim]

I had a problem like that for the 1st year of ownership. Found out that there was an aftermarket chip in the car. Went back to stock (courtesy of Jay) and all is well. I replaced a lot of stuff first, however, to get nowhere.

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[Cloud9...68]

[quote name='Kim' post='52630' date='May 16 2008, 05:39 AM']I had a problem like that for the 1st year of ownership. Found out that there was an aftermarket chip in the car. Went back to stock (courtesy of Jay) and all is well. I replaced a lot of stuff first, however, to get nowhere.[/quote]

Do you know what type of chip it was? I've had a Racer-X in mine since I've owned it (over four years), and have never had an issue with pinging.

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[Kim]

Autothority chip.

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[RS Barn]

This may sound strange but you may have fluid in the intake manifold. If you have a leak in the coolant seal at throttle body and draw any fluid into manifold it will pool on bottom and be drawn up under load and cause pinging.

You could also check intake manifold gaskets for air leak by spraying wd-40 around each while running. Idle will drop/stumble if wd is being drawn in.

Pete

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[SILVY968]

[quote name='RS Barn' post='52677' date='May 16 2008, 05:28 PM']This may sound strange but you may have fluid in the intake manifold. If you have a leak in the coolant seal at throttle body and draw any fluid into manifold it will pool on bottom and be drawn up under load and cause pinging.

You could also check intake manifold gaskets for air leak by spraying wd-40 around each while running. Idle will drop/stumble if wd is being drawn in.

Pete[/quote]



Pete,

WD-40 is safer than gasoline. I'll try it on mine and see.

Brian

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[Rob]

Thanks for all the good advice guys.



I swapped back to the original chip (was running Promax chip) and problem seems to have gone ..... mostly. I did notice small amount of ping just once over the last few days.



In answer to some of the questions raised in previous posts:

- No loss of coolant noticeable at plastic fill tank.

- I'll try checking for leaks in hoses and at manifold (WD40 test is interesting).

- Car has 165000 km (about 100,000 miles). Driving generally not very hard. A lot of stop go in city traffic which probably isnt good. Only the occassional run on the track.

- Wires probably original.

- Plugs not very old.

- Distributor cap and rotor I think is reasonably new but will check my records.





Thanks,



Rob

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[xrad]

Next tank of gas, buy from different fuel source. 93 or whatever at one station is not entirely the same at another, and 93 at one station can vary between tanker loads (although this is supposed to be regulated)

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