C20SEH Jerking Help!

[Jonny Martin]

Hi all,
I've got a C20SEH 2.08v engine in my nova, last night it developed a problem, When trying to maintain a constant speed (be it 10mph or 70mph) it 'jerks' violently, almost as if its running out of fuel, if you rev the engine when the cars stood on the spot it rev's up fine, it only seems to do it when the engines under load. It also does it under hard acceleration, It does it in any gear and at any point during the rev range.. Any idea's?

Thanks :)

Jonny

[Paul]

sounds like a real bad misifire, but its a bit odd for it to suddenly go from un noticeable to as bad as youve described.

[Sloth]

fuel pump dying then going again?

[Jonny Martin]

Tried new plugs ect today and its made no difference :( also engine temp makes no difference. was just as bad this morning when the engine was cold. Yeah its just gone from being spot on to this! I dont understand it! :(

[chimp007_uk]

my cs20seh was exactly the same... No it wont even start! I' sure it's an earthing problem, but i'd like to see what other people think!

[ant_tay]

i agree with sloth sound like fueling to me

[dougie_boi]

could maybe be one of a few things but couldnt guarentee(sp) just a few things i would check. air flow meter, co2 (lambda) sensor earth wires also check and make sure its not drawing air anywhere through a split pipe or that between air flow meter and throttle body as its giving off the the impression that the fuel mix ratio isnt right on a steady flow

[AlexW]

May sound silly, but have you checked the cam belt? My brothers 5dr was similar untill the belt was changed. It was slighly stretched and eventualy jumped 5teeth!

[Jonny Martin]

It does seem to be getting worse. when it starts to Jerk if you put your foot on the clutch and rev it, then carry on it seems to clear it for 30 seconds or so. its totally random when it comes in. the only time it seems to be ok is when giving it some. Its started idling really badly too. up and down from about 500 up to 2000Rpm... Very stuck :( up until yesterday it ran 100% with no problems then this all of a sudden!

[Steve]

I had the same problem, I power washed my engine bay and after drying the coil and leads it was better but then took off the dizzy cap and cleaned that up and it was fine. The fuel pump is also worth checking out.

Oh and for the last time, there is no C20SEH its a 20SEH!!

[Jonny Martin]

I've had the dizzy off and cleaned it up but it's not made a difference :(. I'll try a pump on it and see if that does any good. could it be the coil? Sorry i always thought it was C20SEH| :(

[Jonny Martin]

One thing i was thinking, like i mentioned when you really put your foot down its ok, would this not rule out the fuel pump? as it's delivering fuel when accelerating hard? if it was the pump would it not be worse the more you accelerated?

[ant_tay]

fueling was sugested because it says in your first post it does it under hard acceleration

[Jonny Martin]

fueling was sugested because it says in your first post it does it under hard acceleration

sorry my bad, it does it under normal acceleration but not under hard acceleration,

[craig green]

Dont spend any money on sensors etc.
Cleaning the dizzy cap is no substitute for a new one, if its had it, cleaning it wont do anything for it.
Renew the CTS wont do it any harm either.
Check the inlet trunking for holes or leaks after the AFm.
Lastly earth the alternator bracket to the -ve battery terminal with decent gauge cable & see if it still does it.

I had an 8v GTE Astra that kangaroo'd badly on light throttle & it was the CTS sensor playing up.

[chimp007_uk]

cts? is that crank sensor?

I'm intrigued as i have a seh nova that did the exact same thing now wont start...

[Mikey_J]

coolant temp sensor