Technical hesitant

[AJ 96]

Hi
i have a problem on my Seicento Sporting MPI, in 3rd gear at about 3,500-4,000 tpm my car seems to slow down and not accelerate them it starts accelerating again after a few secconds
last week i had an engine light on but replaced both lambda sensor's and crank sensor fixed that.
also it was in third and fourth now just third, has anyone else had this and can anyone help, thanks Alex

 

[tduknet]

Hi,

When the car hesitates does the engine management light come on or flash?

 

[AJ 96]

no engine light it just hesitates

 

[fingers99]

Does it just miss fire temporarily or just seem to be hesitant around that point?

 

[AJ 96]

Hi, its just around that point it was in fourth as well but now just 3rd it was also around 3,000 to 4,000 rpm now just around 3,600 to 4,000
i was thinking perhaps its just some crap built up on the injectors or something

 

[fingers99]

Unlikely to be injectors.

Can't see it being dependent on the gear (after all, the car doesn't know what gear you're in).

Code read might throw up something interesting. Otherwise we're just guessing.

When did the car last have plugs and leads?

 

[AJ 96]

Hi I've code scanned it, there's no codes
the car last had plugs at 40,000 miles its now on 53,000 so im going to get some tonight so I'll se bow that goes, thanks

 

[fingers99]

Leads generally go first, though.

 

[AJ 96]

Hi
ok so i bought some spark plugs on my way home went to go fit them, and theyre the wrong ones, so i thought i would just re-gap and clean my current ones for tomorow and it doesnt loose power at 3,500 however it does at nearly 5,000 (thought id just try) i will replace my plugs when i get some correct ones tomorow.
i scanned my ecu again and it says ready for everything except for a/c (it doesnt have it) and catalyst not sure if it is something wrong or just because i only had igniton on and not the engine. anyway the car runs alot better now, thanks Alex

 

[AJ 96]

ok, so yesterday i re-gapped my old spark plugs because my new ones were wrong and fitted a new air filter and the car ran fine.
today i fitted some new plugs (the right ones now) and the car splutters in 2nd onwards when under 2,000rpm. its really bugging me how on old plugs it ran fine now with new ones it splutters. anyone got any ideas what it could be?

(i gapped the new plugs to .9 incase that helps)
thanks, Alex

 

[fingers99]

Look at the plugs.

My guess is 0.9 (mm?) is a tad too big.

Remember what I said about leads?

 

[AJ 96]

Hi the leads look new theres no damage on them and insides look new also
.9mm is what it says in cinquecento manual for ohc engines, ive also used some carb and throttle cleaner on the throttle body
thanks Alex

 

[fingers99]

But you don't have a Cinquecento! You have a Seicento with a completely different ECU. The factory manual is in the Downloads section.

Still, I'd expect it to be throwing a fault code. Lambda sensor going sleepy? You might try swapping the lambdas round. (You have 2)

What were the old and new plugs? Make and spec?

 

[AJ 96]

Hi
gapped my plugs a bit closer and torqued them in to what it said on the box, they are the make as the old ones and now the car runs brilliant, no hesitation, no spluttering (so far) so i hope thats it fixed.
thanks Alex