Engine running erratically

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Mike Toy
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I have a 1999 Pajero iO 4G93 and have been having intermittent engine issues for over a year now. There appears to be no rhyme or reason to when the problem occurs; some days it’s fine, some days it’s not. 

Basically the engine will suddenly lose power and feel and sound like it’s not firing on all four cylinders and the engine light comes on. If you pull over, shut it down and restart it’s generally fine and back to normal although it can take a couple of restarts to get there. It also suffers (again intermittently) from low idle and will sometimes shudder and stall immediately after starting or if stuck in traffic. It’s been through a few mechanics and over the last year the coil packs and ECU have been changed and the throttle body and MAF sensor cleaned – on more than one occasion. But still the problem persists.

This morning I put in a new fuel filter in and it started and drove like a dream for 30 minutes. No low idle and it felt a lot smoother. Problem solved or so I thought. Parked it up for an hour, drove it for five minutes and it went again – misfiring, engine light on etc, etc. Soooooo I am out of ideas really, has anyone suffered from the same thing and found a cure? 

fordem
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GDI or MPI

Which of the 4G93 engines do you have?  If the check engine light comes on, there's going to be a code set - have you had it/them read?

Mike Toy
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It's the MPI. No, I haven't

It's the MPI. No, I haven't had it checked but after yesterday's near miss with the fuel pump I have booked it in for a diagnostic this afternoon. Probaly should have done it some time ago but hey ho, better late than never. The trouble is that the various mechanics I've been to have all assured me that it was A, B or C and that they have changed/cleaned the offending part and it's all been fixed. We shall see....

fordem
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If the CEL turns on...

Once the ECU turns on the check engine light, the first step should always be to read the codes - the engine controller is telling you that it's seeing something it should not be seeing.  If you're not reading the codes yourself, make sure whoever does it gives you the actual numerical code, and not just the translation. different manufacturers use the codes differently, and the manuals will often list troubleshooting sequences based on the code.

At this point all we can do is guess at where the problem might lie, based on experience with a different vehicle, and based on your description of the symptoms - we don't even have the luxury of being able to see, hear or drive the vehicle and actually experience the problem.

One question, since you haven't mentioned it - when last were the plugs changed?  Has anyone looked at the EGR system?

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