Intermittent mis fire

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superyan
Newbie
Posts: 3
Joined: Wed May 09, 2012 4:13 pm

Intermittent mis fire

Post by superyan »

Hey Please HELP!! I recently brought a MG ZR TD it had a intermittent mis-fire (the mis-fire is like a flat spot) when it warms up with black smoke when you floored it. I have had it in a garage and they have had the pump off and had it checked and it was running low pressure and that has been sorted. But it hasn't solved the problem. Could it be injectors?? PLEASE HELP
E_T_V
Site Admin
Posts: 439
Joined: Thu Jan 29, 2009 9:38 pm

Re: Intermittent mis fire

Post by E_T_V »

By misfire do you mean it runs lumpy? If so when does it do this? At idle? On hard acceleration? All the time?

When was the fuel filter last changed (as if it happens at high load then it could be that the filter is blocked)

Also check the wire to number 1 injectors as if/when it rubs on the engine it can give running issues intermittantly

Also lastly check the earth cable to the headlamp panel as this is a common problem area with corrosion/breaking common.
superyan
Newbie
Posts: 3
Joined: Wed May 09, 2012 4:13 pm

Re: Intermittent mis fire

Post by superyan »

The mis-fire is after it has been started for a little while and it will tick over fine but you cannot rev up and it sounds lumpy. the fuel filter was changed just after i brought the car. It has also had a mk2 dash put in it at some point (its a 52 plate) dont know if that could cause a problem? Ill have a look around the wire to the injector tomorrow
E_T_V
Site Admin
Posts: 439
Joined: Thu Jan 29, 2009 9:38 pm

Re: Intermittent mis fire

Post by E_T_V »

Does it do it just from a startup?

If so then if it won't rev then it could be a MAF sensor fault. The usual symptoms are the engine won't rev for 30 seconds or so until the ECU recognises the MAF was faulty, but that doesn't usually give a misfire.

The other possibility if it is only at startup is an air-leak into the fuel system. Try pumping the priming bulb till it goes hard (or a good dozen times) before you first start it in the morning. If the fault goes away then you have an air leak into the fuel system.
superyan
Newbie
Posts: 3
Joined: Wed May 09, 2012 4:13 pm

Re: Intermittent mis fire

Post by superyan »

What happens is when you start the car it ticks over fine for a while then it is as if it is hunting and you cannot rev up. While driving it it will do this intermittently but if you toe it hard it is fine.
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