VR V8 Flatspots when cold

[Paul Stratis]

:hit: I have owned my vr v8 since new. It has 130000kms on clock. It has no engine modifications.Last week it developed a flatspot on acceleration when mainly cold but may also idle lesser when the airconditioning is on. At times it will cough through the throttle body. The engine dose not misfire and performance is not affected. Adout 6 months ago the coil body cracked. I replaced it and also decided to replace all leads, rotor, distridutor cap, etc. I checked the throttle body and idle valve, all ok and cleaned. The engine dose not blow smoke. Could this possibly be a map sensor or running lean problem. Any advice or past experiences would be helpfull.

 

[Demerit king]

Hi Paul, i have a v8 manual vs, have owned from new (270,000 klms)and have the same issue. Seems to be gradually getting worse.Have had plugs coil, ignition module, temp sensors, O2 sensor replaced, still no joy.Does the same on gas as well as petrol, slightly worse on petrol.Is fine once warm, about 2klms after cold start.I to would love to know what makes them do this. cheers

 

[MBS206]

Have you checked the coolant temp sensor which controls the auto choke?
It may be stuffed and causing too much fuel to be put in when cold, and hence, flat spotting from running too rich

 

[Demerit king]

Yep I have, no change, also tried manifold air temp sensor. the good news is they are not to expensive, $20-$30 each from gmh.

 

[ChRiDDa]

i found it out it was my injectors.. car runs average for the first few minutes, but is then fine.. think its sticking injector solenoids
when i did a test, i put some bosch motorsport injectors in, never had a problem in the few days they were in!
went back to the standard injectors, and you guessed it, the problem returns

 

[nevrl8inaV8]

I've solved Demerit king's vs v8 problem. (hesitates when cold) After talking to vs v8 guru at holden ,it seems that over time as the cam wears ,the distributor timing gradually retards. Should be 10deg BTDC with aldl earthed.Tested demerit king's and it read 0 deg. Advanced it up to 10degrees and what a difference !!!!!!!!!!!!!!!!!! and we thought the motor was just getting tired with 280000klms, but it goes heaps better now. The bloke at holden says even 2degrees can have an effect. Anyway hope this may help some of you other guys out there ,,, cheers

 

[Mr Ute]

:hit: I have owned my vr v8 since new. It has 130000kms on clock. It has no engine modifications.Last week it developed a flatspot on acceleration when mainly cold but may also idle lesser when the airconditioning is on. At times it will cough through the throttle body. The engine dose not misfire and performance is not affected. Adout 6 months ago the coil body cracked. I replaced it and also decided to replace all leads, rotor, distridutor cap, etc. I checked the throttle body and idle valve, all ok and cleaned. The engine dose not blow smoke. Could this possibly be a map sensor or running lean problem. Any advice or past experiences would be helpfull.

i had the same prob with my V8 ute VR.Gave it a full service and turned out the fuel filter was blocked.What do you no now she starts and drives like a new one :thumbsup:
and it only cost me $6