my car "jolts" at 90km (like im hitting reflectors on the road)

[lockmac]

Hi guys. Just wandering if you could give me some advice. My car is playing up a bit and its gotten worse since i put a smaller pulley on my charger.

Anyways, at about say im doing 90km/h... if i want to go to say 100, ill slowly put my foot down just a tiny bit, and the car will speed up but it will almost "jolt" numerous times (it feels like i am running over a set of reflectors in the middle of the road almost). It only happens around this speed (so i spose the same gear)..

Any ideas why?

Many thanks

[chargedvx6]

Did you change the plugs when you upped the boost mate? What sized pulley did you end up fitting

[redcv6]

pinging???

[Shounak]

Could it be the transmission? Or do you suspect it's something more along the lines of the supercharger or engine?

[accentstencil]

My guess is a bad lead or plug.

[lockmac]

put an 87mm stealth pulley... dont think its the charger because i was actually having this problem before the new pulley went on.

it feels like the tansmission though... like it wont change gear strait away if i plant it, like it will do a few jolts, then drop a gear.

[mirlin]

I have the exact problem only my car is an N/A 6. but mine happens at about 1500-1700 rpm in any gear whenever i slightly increase the throttle, normally up a hill or incline. i replaced the leads and plugs a while ago and juz recently replaced dfi and coils from a pik apart car, only thing i can think ok now is the tranny? any thoughts?

[ESS364]

Its your transmission...assume it is an auto...If it only happens in high gear it is probably due to the extra load but would happen with the lower gears if you are pulling something heavy or going up hill. My VN did that particularly when towing a trailer . A service fixed it.

Otherwise it might be more serious.

[chargedvx6]

put an 87mm stealth pulley... dont think its the charger because i was actually having this problem before the new pulley went on.

it feels like the tansmission though... like it wont change gear strait away if i plant it, like it will do a few jolts, then drop a gear.

I would get a DTC scan done and take it from there. Will probably only be a minor issue but most likely electrical. Spark or sensor issue or at worst a solenoid in the tranny.

[CANYONERO]

mate had a similar problem under throttle in his VT NA6 manual. replaced the knock sensor and all was good.

[Doctor Bob]

its a tracking spark plug, replace the plugs and leads

[neobristol]

Im so glad i found this thread ive had the same problem for nearly 2 years! mine happens only when pulling away, or when in overdrive on my vx v6 and only when Im on gas, just last night i started thinking maybe it was the gear box, as every time it judders it tries to change down a gear, when it does it, it doesnt do it smoothly and you get a lot of transfer noise into the diff, it seems too violent for a mis-fire. I change the filter and fluid every 6 months in my gearbox, it seems in good health considering the 280,000k's no black sludge on the oil pan. And i cant get the engine to mis-fire when in neutural.

So anyone like to hazard a guess on what my problem could be? I just wish something would break so at least then i'd know what the problem is.

[neobristol]

I would get a DTC scan done and take it from there. Will probably only be a minor issue but most likely electrical. Spark or sensor issue or at worst a solenoid in the tranny.

Whats a DTC scan, mate? being a pom im not familiar with auto boxes

[accentstencil]

Im so glad i found this thread ive had the same problem for nearly 2 years! mine happens only when pulling away, or when in overdrive on my vx v6 and only when Im on gas, just last night i started thinking maybe it was the gear box, as every time it judders it tries to change down a gear, when it does it, it doesnt do it smoothly and you get a lot of transfer noise into the diff, it seems too violent for a mis-fire. I change the filter and fluid every 6 months in my gearbox, it seems in good health considering the 280,000k's no black sludge on the oil pan. And i cant get the engine to mis-fire when in neutural.

So anyone like to hazard a guess on what my problem could be? I just wish something would break so at least then i'd know what the problem is.

As stated above, try replacing the leads and plugs. They tend to break down easier when the engine is labouring a bit, especially in overdrive.

[neobristol]

As stated above, try replacing the leads and plugs. They tend to break down easier when the engine is labouring a bit, especially in overdrive.

I changed the leads and plugs, straight after i had the gas fitted, this problem only came about after installing gas. Have been back to the installer over 2 dozen times and he cant find a fault, it is the easyjet sfi system i have. When his laptop is plugged into my car and the car jolts his readings from the gas management go haywire but he has never experienced anything like it before apparently,

[chargedvx6]

Whats a DTC scan, mate? being a pom im not familiar with auto boxes

VT on run On Board Diagnostics II (OBDII) which is a computer protocol that has self diagnostics checksums in the program. If a self test doesn't add up a DTC (data trouble code) will be logged in the history. There are history codes and current codes. A TechII scan tool is used to view there status.

[lockmac]

Hey guys just changed the plugs and leads and it seems to have fixed my problem. thanks heaps for the help.... one of the plugs on the coil pack was full of green stuff (corrosion im guessing)

so happy thanks guys

[Doctor Bob]

glad to hear its fixed, the reason it happens under those driving conditions is the torque convertor is locked & as you open the throttle gently it stays locked placing the engine under heavier load.

the VT doesnt have OBD2 diagnostics, it is a proprietry protocol used by GM based on UART communications

[neobristol]

Just spent my day off changing the knock sensors, which didnt make a difference so went back to holden and picked up a set of coil packs and fitted those again which made no difference, so $360 spent and no improvment. Does anyone have anymore suggestions?

[chargedvx6]

glad to hear its fixed, the reason it happens under those driving conditions is the torque convertor is locked & as you open the throttle gently it stays locked placing the engine under heavier load.

the VT doesnt have OBD2 diagnostics, it is a proprietry protocol used by GM based on UART communications

I stand corrected.

[Nighthalk]

Thanks guys for all the replies to this thread as im also having the same problem with my 99 vt but mine only jolts when i take off at the lights or going up hills when i put my foot down a little.

I leave for work everyday at 4am and drive around 60km to get to work but it doesn't seem to jolt, but when im coming home around 2pm and the car gets hot it will start jolting everytime i take off from a set of lights and is starting to worry me as this is my only means of transport to get to and from work as there is no public transport that early in the morning.

Would this just be like stated above, change my leads and spark plugs? or will this be more?

Thanks in advance for the replies.

[Emackulation]

Thanks guys for all the replies to this thread as im also having the same problem with my 99 vt but mine only jolts when i take off at the lights or going up hills when i put my foot down a little.

I leave for work everyday at 4am and drive around 60km to get to work but it doesn't seem to jolt, but when im coming home around 2pm and the car gets hot it will start jolting everytime i take off from a set of lights and is starting to worry me as this is my only means of transport to get to and from work as there is no public transport that early in the morning.

Would this just be like stated above, change my leads and spark plugs? or will this be more?

Thanks in advance for the replies.

I would give it a go, cheapest option for sure.

[Nighthalk]

Ok changed the leads and spark plugs but this jerking etc is still going on, car is booked in for a system check on friday but i would love some suggestions from everyone before i go there incase they cannot find the problem?

Thanks

[Nighthalk]

Or maybe just dirty fuel injectors?

[chargedvx6]

Alot of new leads need some adjustment on the plug boot to grab the plug properly. Double check maybe?