weak spark on boost

smithy · Jun 4th, 2010, 16:54

ive been to check my car on the rollers today and found that when the car is on 17psi boost im getting a miss fire and weak spark .and help please i think it may be the coil does anyone know were i can get a high power coil for a strong spark on full boost .the car is 1996 940 turbo with t35 turbo fitted.the fueling is good but the car will not power fully without hesitation.also is the a boost liomit on the standard lh 2.4 ecu .

Chesh740R · Jun 4th, 2010, 18:10

Have you tried a stage colder plugs and tightening the gap??

karlos_uk · Jun 4th, 2010, 22:07

new leads and rotor arm, dizzy cap

check the plugs are gapped properly or they will suffer blow out

then think about buying a new coil

Profpriv · Jun 4th, 2010, 22:45

blow out???

barkster1971 · Jun 4th, 2010, 22:51

I had the exact same problem with a weak spark/ spark blow out. I beleive you've had the cylinder head "pimped" so cross threading of the spark plugs particularly the one nearest the bulkhead shouldn't be a problem. Check for any tiny bits of corrosion on the contacts/wires going to the coil and any other bare metal contacts associated with coil lead/ HT leads. The quality of the seal on the HT leads onto the spark plugs is critical and check that the dizzy cap contacts are spotless and the rotor arm is 100%.
I think the chip(s) from thelostartof advance the timing quite a bit so a strong spark is required. Possibly turn the boost down a tad and see if it is still crappy at 12PSI.
It might be megasquirt time for wasted spark or coil on plug (time and money!).

barkster1971 · Jun 4th, 2010, 22:55

IIRC ipd do an enhanced coil but not cheap. .28 is the recommended gap but I think you can go down to .22. Are you on 95 or super unleaded?

Profpriv · Jun 4th, 2010, 23:02

whats this lingo??

Blow out??

megasquirt??

940SportsEdition · Jun 5th, 2010, 11:37

blow out = spark too weak and the fuel air mix blows out the spark as it is not strong enough to ignight the fuel

Megasquirt = an electronic add on system to control the engine system, very complex, do not know allot about it, but do a google search on both and it will give you the answers.

Cheers
Stephen

smithy · Jun 5th, 2010, 15:04

thanks for the replys im using super unleaded and ive fitted t5 platnum ngks in it.the cap ,rotor arm are 12 months old max.i have manicors leads 12 months old also but the coil is the orginal 1.also fitted the modded fuel chip in and ran it until i put it on the rollers to check fueling and the chip was flooding the engine on boost ,so i put the volvo fuel chip back in and the fueling is good now.i think it is blow out because the car is running 17 psi on the garrett t35 turbo and i wanted to turn it up to 22 psi but i have to sort this problem out first.ok im going to set the gaps on the plugs ,but the orignal leads back on and see what happens .is the a boost limit on the stock ezk or ecu.i dont no why the chips are not working but i will get it sorted asap ready for avon on the 11/7/10.anymore surgestions would be much apreciated thanks

Chesh740R · Jun 5th, 2010, 22:00

Try just a set of Normal NGK's BPR7ES, there far cheaper than the platinum ones.

What may suit a T5 may not be fantastic for a 940.

You could also be maxing out the AMM, have you fitted the larger AMM to prevent the cut?

Jun 4th, 2010, 16:54	#1
smithy VOC Member Last Online: Mar 18th, 2018 19:03 Join Date: Jun 2007 Location: birmingham	weak spark on boost ive been to check my car on the rollers today and found that when the car is on 17psi boost im getting a miss fire and weak spark .and help please i think it may be the coil does anyone know were i can get a high power coil for a strong spark on full boost .the car is 1996 940 turbo with t35 turbo fitted.the fueling is good but the car will not power fully without hesitation.also is the a boost liomit on the standard lh 2.4 ecu .

Jun 4th, 2010, 22:51	#5
barkster1971 VOC Member Last Online: Apr 27th, 2024 13:22 Join Date: Jun 2009 Location: Swineshead/Salford	quality I had the exact same problem with a weak spark/ spark blow out. I beleive you've had the cylinder head "pimped" so cross threading of the spark plugs particularly the one nearest the bulkhead shouldn't be a problem. Check for any tiny bits of corrosion on the contacts/wires going to the coil and any other bare metal contacts associated with coil lead/ HT leads. The quality of the seal on the HT leads onto the spark plugs is critical and check that the dizzy cap contacts are spotless and the rotor arm is 100%. I think the chip(s) from thelostartof advance the timing quite a bit so a strong spark is required. Possibly turn the boost down a tad and see if it is still crappy at 12PSI. It might be megasquirt time for wasted spark or coil on plug (time and money!).

Jun 4th, 2010, 22:55	#6
barkster1971 VOC Member Last Online: Apr 27th, 2024 13:22 Join Date: Jun 2009 Location: Swineshead/Salford	coil IIRC ipd do an enhanced coil but not cheap. .28 is the recommended gap but I think you can go down to .22. Are you on 95 or super unleaded?

Jun 5th, 2010, 11:37	#8
940SportsEdition From sweden with love Last Online: Oct 23rd, 2016 00:52 Join Date: Jul 2007 Location: Brampton	blow out = spark too weak and the fuel air mix blows out the spark as it is not strong enough to ignight the fuel Megasquirt = an electronic add on system to control the engine system, very complex, do not know allot about it, but do a google search on both and it will give you the answers. Cheers Stephen __________________ [URL=http://www.mybannermaker.com][/URL V40 1.9T4, V40 1.8 xs Previous car 940 Sports Edition, Graphite galaxy's, turbo plus kit, roof bars, dog guard, load cover, load tray, seven seats.

Jun 5th, 2010, 15:04	#9
smithy VOC Member Last Online: Mar 18th, 2018 19:03 Join Date: Jun 2007 Location: birmingham	thanks for the replys im using super unleaded and ive fitted t5 platnum ngks in it.the cap ,rotor arm are 12 months old max.i have manicors leads 12 months old also but the coil is the orginal 1.also fitted the modded fuel chip in and ran it until i put it on the rollers to check fueling and the chip was flooding the engine on boost ,so i put the volvo fuel chip back in and the fueling is good now.i think it is blow out because the car is running 17 psi on the garrett t35 turbo and i wanted to turn it up to 22 psi but i have to sort this problem out first.ok im going to set the gaps on the plugs ,but the orignal leads back on and see what happens .is the a boost limit on the stock ezk or ecu.i dont no why the chips are not working but i will get it sorted asap ready for avon on the 11/7/10.anymore surgestions would be much apreciated thanks Last edited by smithy; Jun 5th, 2010 at 15:07.

Jun 4th, 2010, 18:10	#2
Chesh740R Turbobricker Last Online: Apr 14th, 2024 18:09 Join Date: Dec 2002 Location: Wellingborough	Have you tried a stage colder plugs and tightening the gap??

Jun 4th, 2010, 22:07	#3
karlos_uk Master Member Last Online: Jul 13th, 2019 10:01 Join Date: Mar 2009 Location: Derby	new leads and rotor arm, dizzy cap check the plugs are gapped properly or they will suffer blow out then think about buying a new coil

Jun 4th, 2010, 22:45	#4
Profpriv I've Been Banned Last Online: Jun 15th, 2015 21:48 Join Date: May 2009 Location: BURGESS HILL	blow out???

Jun 4th, 2010, 23:02	#7
Profpriv I've Been Banned Last Online: Jun 15th, 2015 21:48 Join Date: May 2009 Location: BURGESS HILL	whats this lingo?? Blow out?? megasquirt??

Jun 5th, 2010, 22:00	#10
Chesh740R Turbobricker Last Online: Apr 14th, 2024 18:09 Join Date: Dec 2002 Location: Wellingborough	Try just a set of Normal NGK's BPR7ES, there far cheaper than the platinum ones. What may suit a T5 may not be fantastic for a 940. You could also be maxing out the AMM, have you fitted the larger AMM to prevent the cut?

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