Flat spot when cold

[junior]

Hi all, I have noticed that when my car is cold I have a very bad flat spot when it changes gear, mainly 1st to 2nd. I have changed the plugs/leads, any ideas??


Gary

 

[naughtika]

what gap did you set the plugs at? how about your gear oils?

 

[Sydo]

Engine flatspot in the rev range, or a slow gear change from 1st to 2nd in an auto??

 

[junior]

Plug gap 8mm as stated here, all the oils (auto/diff/transfer) have been changed in the past month. The flat spot is hard to explain, when the car is cold, I drive out of the driveway and head down the street, when it changes into second it feels like it is going to stall but them comes back to life. Same thing happens 2nd into third, once on the open road, no problems.

Gary

 

[Kitty's VR4]

O2 Sensor

 

[naughtika]

hhhmmm... have you reset your ecu lately?

 

[junior]

New o2 sensor also, reset ecu just after plugs were done. While I think of it, it only really started doing this AFTER I changed the plugs. Thinking of pulling them out tomorrow and have a look to make sure everything is okay.

Gary

 

[Bennyboy]

any more details? what have you done previous to fault occuring?

 

[Bennyboy]

yeah swap the plugs back and hope for the best. keep the updates coming...

 

[junior]

any more details? what have you done previous to fault occuring?

Nothing.

 

[junior]

Okay, pulled plugs out and rechecked the gap - 8mm, checked all the leads with a multi-meter, everything okay. Spoke to the guy who did the auto trans flush and he stated the oil in the tranny may not be getting warm enough. Does this sound like it could be an answer? And to pre-empt the question of what oils was used it was Penrite ATF MHP.


Gary

 

[Kenneth]

Are you saying that the engine feel like it has a flat spot when warming up? say up to about 2500rpm in low gears?

 

[junior]

When you first drive off and it changes gears, yes, once its warm everything is okay.


Gary

 

[Kenneth]

I have only ever owned manuals, so can't comment on anything to do with the transmission.

However, all my cars have that flat spot, which is mostly noticeable in low gears.
I believe it is the cat converter warmup map which reduces ignition advance significantly to heat the catylictic converter up.

So if it is engine related rather than transmission, I say its normal and don't worry about it. I do assume you don't drive it hard when cold anyway.

 

[junior]

I do assume you don't drive it hard when cold anyway.

No, rarely drive it hard, I know probably a waste but I just prefer to look after my cars instead of thrashing them

Gary

 

[steveP]

seems weird it only started happening after u changed the plugs.

in my previous car i had similar symtoms, ended up being the fuel pump dying.

maybe also check that the fuel filter isnt blocked or something.

 

[Sydo]

'To me' it really does sound like the auto box taking it's time changing gears when cold. I know my car (and myself) is feeling a little sluggish on these cold winter mornings.

I would check your fluid levels and colours just in case.

 

[Kenneth]

Out of curiosity, how stuffed were your old plugs?

 

[junior]

Out of curiosity, how stuffed were your old plugs?

A couple were on their last legs so to speak, the rest were just plain dirty, not worth keep though.