Strange Dead Spot 850R Auto

2Diesels · Oct 10th, 2016, 22:16

Since putting my R back on the road after a 4 month mini rebuild, it's been running like a sack full of chisels, very underpowered & drinking fuel. I however noticed some vacuum pipes in very poor condition which I have replaced. This has restored the fuel consumption & smoothness & has improved the performance no end BUT when going in for the kill in sport mode it seems to hit a brick wall at a shade over 4000 revs, if you persevere with it the revs slowly pick up & then all of a sudden it gets a second boost & takes off like a rocket, what do people think?

doingitsideways · Oct 11th, 2016, 10:40

Is it remapped?

Any MBC or anything fitted?

Sounds like you're hitting boost cut.

What does the boost guage do before it happens, during, then after?

2Diesels · Oct 13th, 2016, 11:22

It's not remapped no, haven't a clue what an MBC is.
To be honest I haven't watched the boost gauge but it's like you say as if it stops boosting but it then starts again & takes off like a rocket, it's actually been slightly better behaved this last day or so but I'll try 7 watch the gauge next time & report back

2Diesels · Oct 16th, 2016, 18:17

New update................when this happens the gauge is still showing boost, makes me think it's an ignition issue.

doingitsideways · Oct 16th, 2016, 21:11

I'd be inclined to agree with you.

My S70 had a misfire on hard boost.
New HTs/king lead, plugs, dizzy cap, rotor arm and coil made it drive like a different car.

2Diesels · Oct 17th, 2016, 10:31

Thanks for that..............my reckoning was if there was no fuel there would be no boost & also if I was still leaking vacuum the boost would be poor as it was before hand, so came to the conclusion it was ignition scatter or was blowing the spark out

2Diesels · Oct 27th, 2016, 10:42

Turns out it was the distributor cap, never seen one as bad for years................all sorted now though

Oct 10th, 2016, 22:16	#1
2Diesels Premier Member Last Online: Dec 23rd, 2023 14:13 Join Date: Apr 2011 Location: .	Strange Dead Spot 850R Auto Since putting my R back on the road after a 4 month mini rebuild, it's been running like a sack full of chisels, very underpowered & drinking fuel. I however noticed some vacuum pipes in very poor condition which I have replaced. This has restored the fuel consumption & smoothness & has improved the performance no end BUT when going in for the kill in sport mode it seems to hit a brick wall at a shade over 4000 revs, if you persevere with it the revs slowly pick up & then all of a sudden it gets a second boost & takes off like a rocket, what do people think?

Oct 11th, 2016, 10:40	#2
doingitsideways The Daddy Last Online: Feb 29th, 2024 15:07 Join Date: May 2010 Location: Manchester	Is it remapped? Any MBC or anything fitted? Sounds like you're hitting boost cut. What does the boost guage do before it happens, during, then after? __________________ XC90 V8 Exec, C70 2.4T Convertible, S70 T5 CD, 850 TDI, 2 x Escort vans and a 2.8i Capri. Clearout has begun, but must continue!

Oct 16th, 2016, 21:11	#5
doingitsideways The Daddy Last Online: Feb 29th, 2024 15:07 Join Date: May 2010 Location: Manchester	I'd be inclined to agree with you. My S70 had a misfire on hard boost. New HTs/king lead, plugs, dizzy cap, rotor arm and coil made it drive like a different car. __________________ XC90 V8 Exec, C70 2.4T Convertible, S70 T5 CD, 850 TDI, 2 x Escort vans and a 2.8i Capri. Clearout has begun, but must continue!

Oct 13th, 2016, 11:22	#3
2Diesels Premier Member Last Online: Dec 23rd, 2023 14:13 Join Date: Apr 2011 Location: .	It's not remapped no, haven't a clue what an MBC is. To be honest I haven't watched the boost gauge but it's like you say as if it stops boosting but it then starts again & takes off like a rocket, it's actually been slightly better behaved this last day or so but I'll try 7 watch the gauge next time & report back

Oct 16th, 2016, 18:17	#4
2Diesels Premier Member Last Online: Dec 23rd, 2023 14:13 Join Date: Apr 2011 Location: .	New update................when this happens the gauge is still showing boost, makes me think it's an ignition issue.

Oct 17th, 2016, 10:31	#6
2Diesels Premier Member Last Online: Dec 23rd, 2023 14:13 Join Date: Apr 2011 Location: .	Thanks for that..............my reckoning was if there was no fuel there would be no boost & also if I was still leaking vacuum the boost would be poor as it was before hand, so came to the conclusion it was ignition scatter or was blowing the spark out

Oct 27th, 2016, 10:42	#7
2Diesels Premier Member Last Online: Dec 23rd, 2023 14:13 Join Date: Apr 2011 Location: .	Turns out it was the distributor cap, never seen one as bad for years................all sorted now though

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