Rough running on damp & wet mornings. What is it?
Discussion
Hi All,
My MG ZT 1.8 petrol has a bit of an odd fault when the weather has been wet overnight or if its a bit cold and slightly damp in the air in the mornings. It starts ok but the revs are sat around 700rpm, as if the choke has not come on. This causes it to run rough, it really struggles up hills as if its firing on 3 cylinders. Once its up to temperature it runs fine.
On normal warm or dry mornings it fires up & idles at 900rpm until it warms up and then drops back to around 700rpm as normal. On these days it runs fine from cold, no rough running.
Could it be dampness getting to the electrics. Should I spray some WD40 over the engine somewhere (if so where?) I remember in the old days you would spray the leads & the dizzy cap to eradicate such problems.
So far I have replaced the coolant temp sensor but the fault is still there. I have had it down at the local garage who plugged it in but its not reading any fault codes!
Its not the headgasket either, thats been replaced with the uprated one, the car loses no water whatsoever & the oil is clean as a whistle.
Any ideas? Its annoying as I have started letting it warm up for 10 mins on the drive before I set off for work!!
My MG ZT 1.8 petrol has a bit of an odd fault when the weather has been wet overnight or if its a bit cold and slightly damp in the air in the mornings. It starts ok but the revs are sat around 700rpm, as if the choke has not come on. This causes it to run rough, it really struggles up hills as if its firing on 3 cylinders. Once its up to temperature it runs fine.
On normal warm or dry mornings it fires up & idles at 900rpm until it warms up and then drops back to around 700rpm as normal. On these days it runs fine from cold, no rough running.
Could it be dampness getting to the electrics. Should I spray some WD40 over the engine somewhere (if so where?) I remember in the old days you would spray the leads & the dizzy cap to eradicate such problems.
So far I have replaced the coolant temp sensor but the fault is still there. I have had it down at the local garage who plugged it in but its not reading any fault codes!
Its not the headgasket either, thats been replaced with the uprated one, the car loses no water whatsoever & the oil is clean as a whistle.
Any ideas? Its annoying as I have started letting it warm up for 10 mins on the drive before I set off for work!!
I had a Mondeo that did something similar. It would idle so low that it would rev slightly to stop itself stalling.
I think it was the MAF sensor that was at fault. The type of Mondeo that I had, had a reputation for them being faulty.
ETA: It was reccomended to me that I spray the sensing prongs with some electrical circut cleaner in the air pipe, to try and clean them so the MAF sensor could function properly. It didn't work in my case but the stuff was only a couple of quid so was worth a try.
I think it was the MAF sensor that was at fault. The type of Mondeo that I had, had a reputation for them being faulty.
ETA: It was reccomended to me that I spray the sensing prongs with some electrical circut cleaner in the air pipe, to try and clean them so the MAF sensor could function properly. It didn't work in my case but the stuff was only a couple of quid so was worth a try.
Edited by TheTurbonator on Tuesday 12th June 10:37
Sorry I can't help further on your MG problem - I really haven't a clue when it comes to post '70's stuff really 
It appears to be running like its firing on 3 cylinders, but it may be running rough on all 4. How can you tell? After 10 mins or so when its warmed up its fine.
It runs as if its not getting enough fuel, bit like my old Spitfire used to when I pushed the choke in too early!
Think I will also have a look at the leads.
It runs as if its not getting enough fuel, bit like my old Spitfire used to when I pushed the choke in too early!
Think I will also have a look at the leads.
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