Hesitant Punto - northender
At low revs in all gears, my daughter's '96 Punto 55S (60k on the clock) is hesitant to accelerate, but get it above 2,000 revs & it goes OK.
I've put some Redex throught the carb again & it seemed to improve it. She's filling up with Optimax now to see if that keeps up the improvement, as previously this action only seemed short term.

Anyone had a similar problem & can give me some advice, as I'm not totally convinced this approach will work?
Hesitant Punto - Adam Going (Tune-Up)
Sorry to contradict, but you don't actually have a carburettor on this engine, but a single-point injection system. Be careful with Red X administered directly into intake as it may harm Oxygen Sensor and Catalytic Converter.

Possible cause for the actual fault include faulty Throttle Position Sensor, Stepper Motor micro-switch, and HT lead / plug problems, as well as Oxygen Sensor. Strongly advise you get an expert diagnosis before shedding pennies - sorry, multiple pounds !!

HTH, Adam
Hesitant Punto - Japanese Elvis
I had this a few years back with an N reg Punto 55.

It turned out to be the Lambda (oxygen) sensor. Apparently this is quite common.
Hesitant Punto - northender
I was thinking about the Lambda sensor being the problem.
Is there any way of testing it (without replacing it obviously).

Should I get the dealer to check it out, or can I, or any garage test it out?

P.S.
Thanks for both replies
Hesitant Punto - Adam Going (Tune-Up)
Checking Lambda / Oxygen Sensor is easy providing you have a suitable low-voltage oscilloscope. Critical point is switching frequency. All too often sensor is passed as OK because it IS switching, but too slowly. Suggest you find yourself a good tuner / diagnostic expert to check this out.

Regards, Adam
Hesitant Punto - paulb {P}
I had a '95 Punto 55SX a few years ago which did something very similar, and also developed a tendency to hiccup at about 2,500 rpm.

The problem turned out to be a warm-air intake pipe which, if you look below the black plastic air-filter housing, is the flexible paper-and-metal tube which connects at the bottom to a plate on the middle of the exhaust manifold, and at the top to the underside of the air-filter housing.

Mine kept coming off at the top, which meant that some temperature sensor or other inside the air intake was misreading (at least, that's what the garage told me!) Anyway, I managed to cure the problem permanently by buying a new pipe (about £5 in 1998) and a £1.50 jubilee clip from Halfords, which I used to clamp the top of the tube gently (so as not to damage the plastic) but firmly to the filter housing.

You may also find that the engine runs better generally if you use Texaco clean-system unleaded mixed with regular doses of Redex injector cleaner - in the last few years I've either owned, or driven regularly, several Puntos with various versions of the FIRE 8v engine and they all seem to give their best on Texaco and Redex.

Hope this helps....
Hesitant Punto - northender
The intake tube is OK thanks.
I replaced the Lambda sensor yesterday (& it seems to have improved it slightly, & will run it on Optimax for a few tankfuls to clean the engine out.

Not sure about running Redex through after the previous comments regarding damaging the Lambda sensor, hence the Optimax route, then in future, either Texaco or Shell normal unleaded rather than the Asda fuel we used to use.
Hesitant Punto - paulb {P}
Redex shouldn't give you any problems if you put about 25 ml in the fuel tank before filling up - we use it all the time in my wife's V-reg new-shape 1.2 8v & the car runs like clockwork. Actually, your comment about supermarket petrol reminded me - when my mother had the 55 before me, she used Sainbury's u/l for a while, & the car ran very unhappily on it - flat spots, poor response etc. Makes you wonder what they put in it! Good luck.
Hesitant Punto - Adam Going (Tune-Up)
Redex added to the fuel tank in the correct concentration will not cause a problem. The original suggestion in this thread was to administer it directly into the throttle body, which is not a good idea on a car with an Oxygen Sensor and a Cat.

Redex is a very good upper cylinder lubricant, but even their injection additive is not a particularly good injector cleaner. The best products, IMHO, are from Forté (only available from the trade ie. a specialist engine tuner/diagnostician or a garage) or VW's own-brand additive available from any VAG dealer. Best available (injector cleaner) on the high street is probably Wynns or STP.

Regards, Adam

 

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