Kenbo · Jun 9, 2021

I recently bought a nice 95k mile 2005 Td5 auto, but it feels gutless even compared to my Disco 1 auto. Economy is also poor, under 25 mpg with sensible driving.

I'm waiting to get it plugged in but in the meantime I cleaned the map sensor, egr valve (already fairly clean) and today tried disconnecting the Maf sensor.

This had a major effect on performance and the engine seemed rough or off a cylinder. I reconnected it but performance was terrible, really rough, wouldn't rev past 2000 and struggled to make it up a hill near my home. There were no warning lights

I checked the connection and it seems clean. What have I done?

Edit to this, went out to check voltage at the plug, won't now start with or without maf connected.

Andy Warren · Jun 9, 2021

Kenbo said:
I recently bought a nice 95k mile 2005 Td5 auto, but it feels gutless even compared to my Disco 1 auto. Economy is also poor, under 25 mpg with sensible driving.

I'm waiting to get it plugged in but in the meantime I cleaned the map sensor, egr valve (already fairly clean) and today tried disconnecting the Maf sensor.

This had a major effect on performance and the engine seemed rough or off a cylinder. I reconnected it but performance was terrible, really rough, wouldn't rev past 2000 and struggled to make it up a hill near my home. There were no warning lights

I checked the connection and it seems clean. What have I done?

Edit to this, went out to check voltage at the plug, won't now start with or without maf connected.

Hi, possibly a dodgy fuel pump, can you hear it priming when you switch the ign. on, has the fuel filter been changed, crank position sensor/wiring ? Just a couple of ideas & I know it would be a bit of a coincidence. Have you tried using start ya bast%$d ? As your waiting to get it plugged in, it might be you'll have to wait until then or wait until some more knowledgeable comes along.

Kenbo · Jun 9, 2021

Thanks for the comments, had a full service at a specialist and all filters just before I bought it, I had the tank out to replace a vent pipe, don't think it was ever off before, lovely and clean inside plus pump was clean and also quiet. That was a couple of months ago. I'm concentrating on something related to Maf at the moment though anything is possible.

Stanleysteamer · Jun 10, 2021

Disconnecting the MAF puts it into a fairly decent standard map thing so it is unlikely to be that.
Far more likely to be the MAP/iat which really does influence performance.
But as for not starting, well you are into different territory. Maybe crank sensor?
Do recheck everything to do with fuel pump, and all filters and lines between it and the head.
Best of luck Mate

Kenbo · Jun 10, 2021

Was going very nicely but I always thought it was low on power. I had stopped for 10 mins so took the opportunity to try taking the plug out of the maf to see if there was any difference. Engine was a bit rough on starting, wouldn't rev beyond 2000. I couldn't get stopped for about a mile with traffic. Plugged maf back in, struggled to get home and then wouldn't restart. Could be lots of things but I still think my actions have something to do with it. This is one of the last of these made so more electronics as I understand.
Looks like I can't get codes checked until next week now.

Kenbo · Jun 11, 2021

Can't get my head around this: disconnect Maf, and looks like the fuel pump failed that exact time. Wouldn't go into purge mode so I checked connections at the pump, all good.

sierrafery · Jun 12, 2021

There can be many things, you need a diagnostic tool but it's possible that the pump was failed before you unplugged the MAF cos the engine can run with failed pump too as long as it's not much power request but once the MAF was diconnected the fuel demand was increased due to the restored power and the fuell loop was interrupted

Kenbo

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Andy Warren

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