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V8 Esprit Popping noise/rough idle


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I have had a popping noise from the exhaust at idle for a while which is kind of annoying and am currently chasing down vacuum leaks. I have a steady -15inHg at idle measured at the back of the plenum - is this in the normal range?

I've found a couple of leaks: split pipe leading to climate controls)and am in the process of changing the crankcase breather non-return valve, which had turned into a tube. Apart from the popping/lumpy idle the car runs great. Suggestions welcome and appreciated.

Cheers, Graham

Y2K V8. Black on black.


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Are both cats in one piece ??

is it a car that's used regularly ? I did have a pop on mine and run some injector cleaner called Lucas oil through the tanks - that made a massive difference.

o2 sensors are the other thing to look at on some diagnostic kit - just to make sure they are doing the right things.

vacuum leaks need to be eliminated of course

Only here once

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Thanks Barry - any opinion on the vacuum reading?

In response to your comments, the car is driven at weekends only and I keep the battery on a tender between runs. The O2 sensors and 200cpi cats are new this season. RC  injectors were cleaned and calibrated prior to installation last year. They only have about 3000 miles on them but i guess i could try the injector cleaner. 

The popping noise has been present since i bought the car and i've been slowly trying to eliminate it by adding the items mentioned above.

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This is tough to find.  The secondary injectors could be dripping if they were not replaced at the same time as the primary injectors. If it is consistently doing the popping at idle you could temporarily remove the CATs (generates an error code) and see if the popping stops. If it does that would be a strong indication that excess fuel is being touched off in the CAT.

The Older I get the Faster I was

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