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rpm fluctuating in 1st gear when cruising, any ideas?

arronleeds

Active Member
Jul 27, 2017
196
5
if i try accelerate in 1st gear when im in traffic, if i hold a steady throttle below 2k rpm the car bucks and the rpm fluctuates up and down, is this normal?
 

mty12345

Active Member
Jun 17, 2011
3,907
538
bristol
Doesn't sound it. I'd start by checking all the pvc hoses for splits and leaks, they can cause those sort of issues if they are allowing unmetered ar in.
 

arronleeds

Active Member
Jul 27, 2017
196
5
Doesn't sound it. I'd start by checking all the pvc hoses for splits and leaks, they can cause those sort of issues if they are allowing unmetered ar in.
the thing is, my fuel trims are well within spec, short term is like -0.8 and long term fuel trims are at 1.6, ive changed the pcv and hoses, the diverter, the n80 valve, charcoal canister and the rocker cover gasket and its done nothing, even changed the spark plugs twice.

only thing i havent changed is the brake booster hose
 

mty12345

Active Member
Jun 17, 2011
3,907
538
bristol
Oh right, in that case probably best to run some datalogs with VCDS or an equally capable scanner, and see if they show anything. If they don't show anything obvious and it's a direct injection engine, then possibly carbon build up on the intake valves.
 

arronleeds

Active Member
Jul 27, 2017
196
5
Oh right, in that case probably best to run some datalogs with VCDS or an equally capable scanner, and see if they show anything. If they don't show anything obvious and it's a direct injection engine, then possibly carbon build up on the intake valves.
forgot to mention, had the car to r-tech, had injectors cleaned and also the inlet valves, no fault codes or anything, ive logged things like fuel pressure, misfires etc etc and nothing shows at all.
 

rafletcher

Active Member
Feb 18, 2021
531
214
Why are you driving in first gear at all? Only time you need that is pulling away from a dead stop. Try using second and see if that cures your problem :)
 
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