Spark Plug Gap

solarsailor · 23rd April 2017, 23:06

After a year's ownership - and clocking up a massive 1,650 miles - I'm taking 'Wedgie' in for an oil service next week. I fitted a new air filter yesterday and I intend to replace the spark plugs as well, although I'm a little confused as to what gap I should set them to. My Haynes manual specifies 1.0mm, but on the forum I've read recommendations for 0.7, 0.8 and 0.9mm as well. I'd be grateful if someone could suggest what's best for a 1.8T engine. Thanks in advance.

Andrew

T-Cut · 24th April 2017, 09:17

Based on the statistics/popularity alone, I'd say 0.7mm. I set mine at this and everything's fine.

TC

chris75 · 24th April 2017, 11:12

And at the other end of the scale ..... I've had several K-series engines and set them all to 1.0mm , and they have also been fine

So , somewhere between 0.7 and 1.0 , unless your spark is weak for some reason when the bigger gap could be troublesome

0.7mm is about 28 thou in old money , which was common back in Morris Minor days when spark voltages were lower . With more modern engines the voltage is much higher and supports a bigger gap , hopefully giving a bigger spark and better combustion ?

T-Cut · 24th April 2017, 11:34

The 1.8Turbo in particular seems to benefit noticably in cases where the foot down acceleration is slightly grainy. Reducing the spark gap to about 0.7mm is a recognised solution. At this level of change, individual engines may vary in their response.

TC

olliesgrandad · 24th April 2017, 12:19

Quote:

Originally Posted by T-Cut

The 1.8Turbo in particular seems to benefit noticably in cases where the foot down acceleration is slightly grainy. Reducing the spark gap to about 0.7mm is a recognised solution. At this level of change, individual engines may vary in their response.

TC

I agree, i treated mine to new plugs and coils, it seemed a bit, not quite right, pulled the plugs and closed the gaps up, briliant

solarsailor · 24th April 2017, 13:49

Thanks everyone. I've had a minor issue with 'rough' running for the past couple of weeks. When the engine is completely cold all is well, and once up to full operating temperature all is well too, but during the warm up period between the two it seems to feel a bit sluggish. To say it's only running on three cylinders would be overstating the case but it certainly doesn't sound or feel like it's firing smoothly. I guess that changing the plugs will tell me if this is purely down to the current ones being past their best, but if it doesn't then what else might give these symptoms?

Ravinder · 24th April 2017, 18:14

See my thread.

http://www.the75andztclub.co.uk/foru...d.php?t=264145

arodriguez · 24th April 2017, 20:44

My 1.8T used to misfire terribly when I was accelerating hard and the only solution after new plugs, coils, leads, solenoid valve etc. was to reduce the plug gap to 0.5mm. It was fine at 1mm so long as I drove it sedately. There seems to be a large variation in what these engines need.

23rd April 2017, 23:06	#1
solarsailor Posted a thing or two 75 Saloon 1.8T Club SE Join Date: Jun 2016 Location: Colchester Posts: 1,225 Thanks: 87 Thanked 653 Times in 344 Posts	Spark Plug Gap After a year's ownership - and clocking up a massive 1,650 miles - I'm taking 'Wedgie' in for an oil service next week. I fitted a new air filter yesterday and I intend to replace the spark plugs as well, although I'm a little confused as to what gap I should set them to. My Haynes manual specifies 1.0mm, but on the forum I've read recommendations for 0.7, 0.8 and 0.9mm as well. I'd be grateful if someone could suggest what's best for a 1.8T engine. Thanks in advance. Andrew __________________ This vehicle was born on Wednesday June 4th 2003 @ 08:24:38 This vehicle was the 73,905th 75 to run off the production line, out of 112,381 This vehicle was the 1,862nd 75 1.8 T Club SE to be made out of 3,980 This vehicle was the 6,856th 75 in Wedgewood Blue to be made out of 7,515 Wedgewood Blue 75s

24th April 2017, 11:12	#3
chris75 same car since 2005 2001 Rover 75 2.0 v6 Connoisseur Saloon Join Date: Nov 2006 Location: Ellesmere Port , Cheshire Posts: 3,811 Thanks: 379 Thanked 549 Times in 466 Posts	And at the other end of the scale ..... I've had several K-series engines and set them all to 1.0mm , and they have also been fine So , somewhere between 0.7 and 1.0 , unless your spark is weak for some reason when the bigger gap could be troublesome 0.7mm is about 28 thou in old money , which was common back in Morris Minor days when spark voltages were lower . With more modern engines the voltage is much higher and supports a bigger gap , hopefully giving a bigger spark and better combustion ? __________________ Who said it was simples ? Last edited by chris75; 24th April 2017 at 11:24..

24th April 2017, 13:49	#6
solarsailor Posted a thing or two 75 Saloon 1.8T Club SE Join Date: Jun 2016 Location: Colchester Posts: 1,225 Thanks: 87 Thanked 653 Times in 344 Posts	Thanks everyone. I've had a minor issue with 'rough' running for the past couple of weeks. When the engine is completely cold all is well, and once up to full operating temperature all is well too, but during the warm up period between the two it seems to feel a bit sluggish. To say it's only running on three cylinders would be overstating the case but it certainly doesn't sound or feel like it's firing smoothly. I guess that changing the plugs will tell me if this is purely down to the current ones being past their best, but if it doesn't then what else might give these symptoms? __________________ This vehicle was born on Wednesday June 4th 2003 @ 08:24:38 This vehicle was the 73,905th 75 to run off the production line, out of 112,381 This vehicle was the 1,862nd 75 1.8 T Club SE to be made out of 3,980 This vehicle was the 6,856th 75 in Wedgewood Blue to be made out of 7,515 Wedgewood Blue 75s

24th April 2017, 18:14	#7
Ravinder This is my second home Rover 75 saloon x2, Rover 75 Tourer x2, Rover 220 Coupe Turbo Join Date: Aug 2010 Location: Kirkcaldy, Fife Posts: 9,036 Thanks: 2,278 Thanked 2,852 Times in 1,718 Posts	See my thread. http://www.the75andztclub.co.uk/foru...d.php?t=264145 __________________ Wanted - Indian bride. Cash waiting. (All sorted - bargain) First name and forum name: Ravinder Rover 75 2.0 CDT Connoisseur SE 116 (160 remap) Royal Blue (JFM) This vehicle was the 50,481st 75 to run off the production line, out of 112,381 This vehicle was the 2,238th 75 CDT Connoisseur SE to be made out of 3,775 This vehicle was the 5,002nd 75 in Royal Blue (code: JFM) to be made out of 14,420 Royal Blue 75s

24th April 2017, 20:44	#8
arodriguez Loves to post Rover 75 Club 1.8T SE Join Date: Mar 2013 Location: Bristol Posts: 310 Thanks: 28 Thanked 35 Times in 32 Posts	My 1.8T used to misfire terribly when I was accelerating hard and the only solution after new plugs, coils, leads, solenoid valve etc. was to reduce the plug gap to 0.5mm. It was fine at 1mm so long as I drove it sedately. There seems to be a large variation in what these engines need. __________________ Tony

24th April 2017, 09:17	#2
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	Based on the statistics/popularity alone, I'd say 0.7mm. I set mine at this and everything's fine. TC

24th April 2017, 11:34	#4
T-Cut This is my second home Rover75 and Mreg Corsa. Join Date: Nov 2006 Location: Sumweer onat mote o'dust (Sagin) Posts: 21,753 Thanks: 341 Thanked 3,660 Times in 2,924 Posts	The 1.8Turbo in particular seems to benefit noticably in cases where the foot down acceleration is slightly grainy. Reducing the spark gap to about 0.7mm is a recognised solution. At this level of change, individual engines may vary in their response. TC