QuestionQUESTION: last week i had my catylic covertor changed as i was informed by local garage it needed changing. so i got this done on Satuday just gone. THe very same nite i was travellin long distance so i was on the motorway wen i noticed everytime i put my foot down i cud hear a sound like air was escaping. as the noise got worse and worse i assumed it was the cat that got loose as it prob wasnt tightend properly
as i reached my destination i Noticed the car sounded like a tractor and it wasnt idleing properly at all (like it was about to cut out)
i had to drive home and on monday i took it back to place and they said one of the bolts was loose . they checked everything and also realised it had blown into 2 pieces (the bit that connects inbetween the manifold and the cat pipe i assume) so they replaced this free of charge.
Prev to this my engine management light was on and i was informed that it was my o2 sensors that needed changing. so i had this booked in for today. i dropped my car of to my local mechanic and he informed me once the new sensors are in it will idle normal.
collected the car today and he said he put the new sensors in and it still drove the same and he cud not figure out wat was wrong with it at all. so he just put the old sensors in as i wasnt gona pay him because my car was still driving the same.
nw im in a stuck position i dnt knw wat is causing my car to nt idle properly, even wen im driving wen i hit bout 2500 rpms my car feels like it is pullin back.
can some one advise me asap wat the possibities are coz my mechanic spent 3 hrs lookin for the prob today with no result
thanks faz
ANSWER: Hi Faz,
I need more information to make a proper diagnosis.
What kind of engine do you have?? whats the mileage of the vehicle??
Have all the obvious reasons been eliminated?? Blocked air filter, fuel filter, condition of the spark plugs, has the compression been measured?? have any leaks in the intake and vacuum system been found and rectified?
when you say the idling moves up and down... between what points does it move??(In RPM)
What exactly was touched when they did the CAT repairs??
was the throttle mechanism removed??some vehicles especially the ones that use a motor instead of the cable need to be re-set if the power has been disconnected. while your at it, check the throttle body for excess carbon build up which can cause erratic idling. clean as necessary.
Also check the Air flow meter for function, to do so disconnect it (Ignition OFF) then start up the car and see if there is a difference, if there is it means that the Air flow meter is faulty and needs to be replaced.(disconnecting it makes the engine management go into 'limp-home' mode and disregards the Air flow signals and uses pre-programmed from its memory)
As for the engine management light, did the O2 sensor replacement allow the fault and therefore the light to be erased? maybe its 2 different faults that appear as one.Basically the only reason the light will come on is if the emission system cannot function properly and the O2 sensors play a big part in the emission control. if so then i'd advise you to leave the new sensors in even if it doesn't rectify the idling fault.
send me more information so i can diagnose further, and if possible and fault codes picked up by electronic diagnosis.
---------- FOLLOW-UP ----------
QUESTION: im nt sure bout the codes but i knw it is for the o2 sensors one b4 cat and one on the actual cat.
all that was touched was the exhaust system wen the cat was changed . the sensor was removed and fitted on the new cat.
the car was workin fine and idlein fine until the cat became lose and i continued to drive it.
it idles at bout 0.8 and drops below 0.5 at some points from wat i recall . and the engine sounds and feels all shaky
AnswerIf no new codes have been picked up after replacing the sensors then its most likely a mechanical fault, check for leaks and that all the pipes have been fitted properly.
Also carry out a compression check to make sure no valves were burnt out when the cat was damaged.
then clean the throttle body as required.
