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Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 9:22 am
by Alloy
I wonder if anyone can help.
I have a low mileage (52k) MGF 2001 which I had sitting around all winter sorned. I got it back on the road but it has developed a mis fire and hesitation both when warm or cold. It’s ok for the first minute then problems from then on.
I have changed the fuel filter and taken tank pump out of the tank to clean which it didn’t need.
I bought a cheap scanner and it showed cam sensor and lambda. My assumption was these may show anyway with a bad mis fire as a symptom not a cause. Even so I changed cam sensor and coolant temp sensor. I also replaced coil packs, spark plugs and leads. All have made no difference.
I could go on replacing sensors - lambda, crank, idle control etc but suspect there is a more systematic approach.
Any advice appreciated.
Re: Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 11:01 am
by Chris Tideswell
Is this the MPI or VVC engine?
Re: Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 1:48 pm
by Alloy
Mpi
Re: Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 2:29 pm
by Barbour
Perhaps a reset of the throttle position sensor will help:
- Turn the key to position II.
- Give it full throttle 5x
- Then wait 15 seconds
- then start the engine.
Also, a bottle of injector cleaner before a refill helped a lot on my F and TF, old petrol tends to gum up injectors etc, worth a try I guess. Are you running on 98?
Re: Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 2:55 pm
by Alloy
Thanks will try that. Premium petrol make a difference ?
Tx
Re: Engine Miss fire and hesitation
Posted: Thu Aug 05, 2021 9:16 pm
by nigelandjo
New leads needed possibly. Coil packs starting to fail?
Re: Engine Miss fire and hesitation
Posted: Fri Aug 06, 2021 10:03 am
by Barbour
Alloy wrote: ↑Thu Aug 05, 2021 2:55 pm
Thanks will try that. Premium petrol make a difference ?
Yes.
Don't use 95/E10 anyway, they don't like it..
Re: Engine Miss fire and hesitation
Posted: Sat Aug 07, 2021 5:22 pm
by Alloy
I have unplugged the lambda sensor and the misfire stops so I think I should conclude I need a new sensor. My question is should I bother if the engine seems to work without this sensor plugged in ?
Thanks
Re: Engine Miss fire and hesitation
Posted: Sat Aug 07, 2021 9:10 pm
by Barbour
Alloy wrote: ↑Sat Aug 07, 2021 5:22 pm
I have unplugged the lambda sensor and the misfire stops so I think I should conclude I need a new sensor. My question is should I bother if the engine seems to work without this sensor plugged in?
Yes, it's there for good reason.
Re: Engine Miss fire and hesitation
Posted: Sun Aug 08, 2021 1:20 am
by talkingcars
Barbour wrote: ↑Thu Aug 05, 2021 2:29 pm
Perhaps a reset of the throttle position sensor will help:
- Turn the key to position II.
- Give it full throttle 5x
- Then wait 15 seconds
- then start the engine........<snip>
It is actually "firmly and fully depress the gas peddle fully 5 times in 30 seconds" and "wait 30seconds".
Re: Engine Miss fire and hesitation
Posted: Sun Aug 08, 2021 1:22 am
by talkingcars
Barbour wrote: ↑Fri Aug 06, 2021 10:03 am
Alloy wrote: ↑Thu Aug 05, 2021 2:55 pm
Thanks will try that. Premium petrol make a difference ?
Yes.
Don't use 95/E10 anyway, they don't like it..
All MGR cars since '96 are designed to run on E10.
Re: Engine Miss fire and hesitation
Posted: Sun Aug 08, 2021 1:54 pm
by Barbour
talkingcars wrote: ↑Sun Aug 08, 2021 1:20 am
Barbour wrote: ↑Thu Aug 05, 2021 2:29 pm
Perhaps a reset of the throttle position sensor will help:
- Turn the key to position II.
- Give it full throttle 5x
- Then wait 15 seconds
- then start the engine........<snip>
It is actually "firmly and fully depress the gas peddle fully 5 times in 30 seconds" and "wait 30seconds".
talkingcars wrote: ↑Sun Aug 08, 2021 1:22 am
All MGR cars since '96 are designed to run on E10.
I stand corrected...
Re: Engine Miss fire and hesitation
Posted: Sun Aug 08, 2021 10:12 pm
by CubMG
I had the same problem on my 01 MPI it was the first Lambda sensor before the cat , I bought a replacement and went to a local exhaust center who managed to remove the old one .it needs to be on a lift for access . The car runs better now , Running with it disconnected may cause it to over fuel which is not good.