Dropped No.4 ??? Help req.??

[Kenndy]

Hey guy's,
Have read other threads relating to rought idle etc. Checked the "codes" and it stated a 12 and a 49. I have a VR Acclaim.
I replaced the crank angle sensor, coil pack, new sparkplugs, new leads and have cleaned and checked the throttle body etc.
It's still running rough, the compression is even in all cylinders, there is spark at all leads.
When you remove the injector wiring one by one, and compare the engine response, No4 cylinder doesn't respond. Checked the electrical side of injector and it flashed as per manual, swapped the injector to another cylinder to fault find it but it worked and the No4 cylinder played up.
Took off sparkplug leads individually to check how the engine reacted, No4 again no reaction. Check spark and it was there.

Now this is the question, is it possible I may have a cracked head, blown gasket, or stick valve.
This is beyond a joke, as wife needs car back on the road asap.

 

[Kenndy]

Have fixed car, turned out one of the new coils was stuffed !!

 

[Marty's_SV6]

It is possible that the fuel injector on this cylinder is faulty, so even though u are getting spark their is not enough fuel for detination.

 

[denholden]

thats strange....Im having same trouble with my NO.3 cylinder..not responding when I remove injector/ or plug lead...
I tested coils 1 pack at a time, and sparks are strong on all.....so your problem is strange that you were getting a spark on no.4 plug..yet the coil pack was stuffed..?
I thought my problem was a blocked injector no3....?
Any more input would help.......cheers

 

[Pub247]

you do realise this is about 5 years old?

 

[denholden]

Doh..! didnt look..((

 

[Brett_jjj]

thats strange....Im having same trouble with my NO.3 cylinder..not responding when I remove injector/ or plug lead...
I tested coils 1 pack at a time, and sparks are strong on all.....so your problem is strange that you were getting a spark on no.4 plug..yet the coil pack was stuffed..?
I thought my problem was a blocked injector no3....?
Any more input would help.......cheers

How did you test the coils,if it was with a multimeter,then its not going to give you 100% accurate results.Ive seen them show up ok on a multimeter and still cause misfiring etc.And another problem is they will still throw a good spark at idle,they only break down once the engine is put under a load,like when driving along,so looking at the coils throw a spark, is no indication that they are ok either.Ive found the most reliable way to test them is to replace each coil,one at a time, with a new coil,and then drive the car each time to see if theres a difference.I keep a brand new coil in my kit ,just for this purpose.I learnt my lesson,I got caught out a few years ago,I spent days chasing a problem when it was one of the bloody coils the whole time,it sparked ok and showed up ok on the multimeter,but was still causing it to run crook.

 

[denholden]

my vs runs well driving 20Kmh-120Kmh...no problem
Only idles not toooo bad...but rough, standing in Drive or Rev or (with Air-con on in nuetral) No error codes only 12.
The coils I tested 1 at a time, just removed 2 leads of each pack and started engine...sparks arc betwen poles..good.
cylinder 3 injector, I think I can feel it pulsating like the others, but no response from engine when I disconnect it...the other 5 do alter revs a bit...so if its not blocked why doesnt it make a difference...?
the engine runs the same with or without the no.3 injector connected..? Weird..

I just swapped coilpack & dfi from a well working VT... still ran the same, no different..even removed no 3 injector again..no response..

Ive already added injector cleaner to the tank and put ultra 98 in it....so Ill drive it for a week and see if it clears...
If its no better by Friday...I'll have to do injector swap on weekend ... ((((((
the CAS is a very last resort....

 

[denholden]

well....(((( installed new injectors.....didnt make a lot of difference...seems to drive smoother though....

more to check and worry about........(((