Car running crap.

[vrooom]

I am working on hyundai accent for my parent in law.
The engine is unwilling to rev.. it revving up very slowly after 4,000 rpm ish. I noticed there is a big crack on exhaust manifold. Would this cause the bad running?

Also i cleaned 02 sensor on exhaust manifold, air meter sensor on air intake, and some other sensor. is there anything else i should clean with wd40/petrol ?

[steve_d]

If you cleaned the o2 sensor with WD40 it may well be dead now. Not sure what you are supposed to us just that they are very sensitive and not to be messed with.

Steve

[Zad]

The catalyst could be breaking up, clogging up the exhaust.

[motorwise]

if you've got a big crack in the exhaust manifold you've answered your own question - the oxygen sensor adjusts the mixture by measuring the amount of oxygen in the exhaust flow,if oxygen (via the crack) is being introduced after combustion has taken place then the oxygen sensor will give the ECU a duff reading based on the (incorrect) amount of oxygen it's seeing, the ECU will then adjust the fuelling and spoil the running

the sensor will have probably survived the WD40 attack as it no longer contains silicone but if you've killed it you've killed it and you'll have to replace that as well as the manifold

I would replace the manifold first and then get it on a scanner for live readings check to see if the sensors switching correctly or not

good luck

Edited by motorwise on Thursday 25th January 22:25