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What could be the cause of hesitation when accelerating?

infrasilver

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I have been experiencing a bit of hesitation when accelerating and want to get to the bottom of it ASAP as I was hoping for a blast out on Sunday. I have changed spark plugs already and I have a set of coil packs to be fitted next but I wondered if it may be something else before I start chucking more money at it on parts that are not the cause, MAF etc. I had a misfire a month ago which turned out to be a coil pack, I wonder if more are on their way out?

I also thought fuel delivery may be another problem, I was going to check fuel pressure as it also seems to crank the engine longer before it actually fires, more than it did before this issue, this has been happening as long as I've had the hesitation in acceleration, probably for about 3 weeks but the car has hardly been driven in this time so not many miles to actually get a decent idea.
 
Coil packs would be my first port of call for sure.
 
kas750 said:
Coil packs would be my first port of call for sure.

Agreed, they are paid for and are an easy swap, just thinking ahead that if I need to order parts in advance to make sure they arrive and are fitted before Sunday so I can do that in advance. If there is a known problem this would help that situation.
 
As soon as I saw the thread title I thought fuel delivery due to something not being right after your tank replacement.

Does the car live outside? If it's not being used much and we've had a lot of damp weather, could also be some water ingress with your coil packs.
 
Since watching the videos in the below link, if I didn't have coils ready to fit, I'd be bringing my car to someone with an oscilloscope and proper testing equipment as I had never realized how good they are at identifying misfires.

Worth a watch even if it only out of morbid curiosity

https://www.picoauto.com/library/videos
 
My thought too with the recent tank issues but every chance it could be something electrical?. The 996 is locked away and has been for the last few months apart from a few trips, the 944 know's who's boss, that's on the drive under a cover.

I hate not using cars, they don't like it.
 
That's the beauty of the picoscope as it can map ignition, injection, compression etc simultaneously. It can check the MAF, TPS ETC ETC.

I did think of your fuel tank problem, but thought that had been solved...

I think the money spent getting it tested would give you peace of mind. Nothing worse than heading off for a long trip wondering if a problem is really solved or just hibernating.

The guy Frank Massy that does the videos really seems to know his stuff. If you don't know someone with a scope, might be worth phoning him to recommend someone near you as he trains people too from what I can gather.

Best of luck solving it.
 
Could be that replacing your tank has dislodged some shoite and caused a slight blockage in your injectors :dont know:
 
Fuel system and coil packs are the logical first choice as Chris, Adrian, Alex et al have mentioned.

If the problem isn't these things, maybe look at the throttle system? Could there be a fault in the fly by wire system? :dont know:
 
Does it seem to be Rev related or pedal related. Mine hesitates slightly if you let the throttle pedal all the way up. If I keep slight pressure on the pedal it doesn't seem to do it.
 
His doesn't get chance to get junked up. Its up and down like a brides nightie!! :grin:
 

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