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 Post subject: 4th gen misfire
PostPosted:Sat Oct 25, 2014 5:33 am 
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Big Block

Joined:Sun Jun 02, 2013 7:20 pm
Posts:160
Car Details:80 T/A with a BBC
79 Z28
68 Firebird F 400
67 Firebird Convertible
Location:Penzance, Cornwall
OK this is a 94 V8 lt1 convertible and it has a regular misfire on one or may be 2 cylinders its hard to tell, its there at tickover and all through the range, it appears to be on number 7 or 5 as if you pull those leads off it doesn't make much difference to the running.

Changed plugs and leads, also new CAT and 2 Lamda sensors.

Vacuum gauge reading is High and steady so no valve train problems.

still run's lump lump lump lump. and when you bring the rev's up its still the same and shakes the car at a steady miss.

Now the OBD1 conector, if you put the jumper wire in A and B the fan's on the rad come on like they normally do but,

With the ignition on it does not flash the check light it just stays on, there's no code 12 or any code it just stays on!

But if you start the engine it does flash at the 2.5 times a second to say it running to rich, but when you inspect the plugs they look OK and dry so its only a little rich I'd say not enough to cause a misfire and the exhaust smells a little but is not throwing out any black smoke and the pipes look dark grey.

Any help please, I hate this modern crap and I slowly loosing it with this one!!!


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4th gen misfire

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 Post subject: Re: 4th gen misfire
PostPosted:Sat Oct 25, 2014 8:14 am 
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Big Block
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Joined:Sat Jun 28, 2014 6:55 pm
Posts:808
Location:Croxley Green, Hertfordshire
If when you changed the leads they didn't all go back exactly as they were originally that will cause a misfire, friend had a similar issue and said the leads run inside a cover or metal tube, how much fun are this plugs to get at eh :!:

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1997 30th Anniversary SS SLP
1993 GMC Typhoon


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 Post subject: Re: 4th gen misfire
PostPosted:Sat Oct 25, 2014 9:38 am 
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Big Block

Joined:Mon Aug 25, 2014 12:06 pm
Posts:131
Car Details:1971 2nd Gen Camaro
RS, 350ci auto
Location:Devon
Injectors? Sounds similar problems mine had (although 3rd gen, not 4th) and it turned out to be two injectors faulty.

Got mine tested by a mate in the AA, think it's a a resistance test from memory. It wasn't throwing up fault codes, it was just running like crap with misfires and smelt like a petrol station from behind.

Good luck!


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 Post subject: Re: 4th gen misfire
PostPosted:Thu Oct 30, 2014 11:37 pm 
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Big Block

Joined:Fri Jan 02, 2009 11:58 am
Posts:565
Car Details:"Overdose"
Iroc convertible
Custom airride, SLP exhaust, 20" Iroc rims, Mini tubbed, Everything new or uprated.
Corvette C6 Z06 Brakes,
Procharger on the way.
Location:Watford
You have to check for spark before doing anything else

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 Post subject: Re: 4th gen misfire
PostPosted:Thu Nov 06, 2014 6:41 pm 
Offline
Big Block

Joined:Sun Jun 02, 2013 7:20 pm
Posts:160
Car Details:80 T/A with a BBC
79 Z28
68 Firebird F 400
67 Firebird Convertible
Location:Penzance, Cornwall
Yep leads are correct.

Havn't tested injectors but I have checked that the wires to them are good and they appear to be working OK.

Yep got Spark at the end of the leads and its a good one, you can pull off a lead or two and it don't seem to make much difference to the idel.

I've ordered an Opti spark unit and ignition modual for it so I'll fit those first and I've found out the this 1994 model has what is known as an OBD 1.5 and you need to use a OBD 1 reader and join pin's 5 and 9 to the A and B terminals to read the codes as it will not flash any up on the check light. Why is it always me that end's up with this electrical witchcraft crap to work on!!! I hate it :crazy:

Anyway thanks for the replies and I'll let you know if I BASH IT!! oop's I mean fix it.


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 Post subject: Re: 4th gen misfire
PostPosted:Thu Nov 06, 2014 7:08 pm 
Offline
Big Block
User avatar

Joined:Sun Jan 13, 2013 7:00 am
Posts:1158
Car Details:1986 Camaro, bought into Spain by me in 1993.
305 replaced by a 355, 750 Demon carb, RPM AirGap intake, Brodix heads, Hedman Hedders, 3" Flowmaster exhaust.
Wheels are Summit aluminium 5 spokes, tyres are 245 rear 225 front BF Goodrich.
B/M transmission, battery relocated to the rear, GoodMark 4" cowl steel hood.
Location:Spain East Coast
I ripped all that "electrical witchcraft" out....... :D


But what are the plugs saying, any of them oily ?


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 Post subject: Re: 4th gen misfire
PostPosted:Thu Nov 06, 2014 8:59 pm 
Offline
Big Block
User avatar

Joined:Sun Jan 13, 2013 7:00 am
Posts:1158
Car Details:1986 Camaro, bought into Spain by me in 1993.
305 replaced by a 355, 750 Demon carb, RPM AirGap intake, Brodix heads, Hedman Hedders, 3" Flowmaster exhaust.
Wheels are Summit aluminium 5 spokes, tyres are 245 rear 225 front BF Goodrich.
B/M transmission, battery relocated to the rear, GoodMark 4" cowl steel hood.
Location:Spain East Coast
Check this post out by, it seems, a one time poster here.
http://www.classiccamaroclubuk.com/phpB ... =33&t=4167

Maybe got miffed no one replied, good point made though.


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 Post subject: Re: 4th gen misfire
PostPosted:Sun Nov 09, 2014 3:41 pm 
Offline
Big Block

Joined:Sun Jul 25, 2010 3:40 pm
Posts:206
Location:Roswell New Mexico
It looks like you have eliminated the spark as a possible cause,
Take the air filter snorkel off the throttle body and get the motor nice and warm. Now CAREFULLY spray a gently stream of carb cleaner into the throttle body. If the engine smooths out because you have added extra 'fuel' you have an injector / fuel pump / fuel filter / regulator problem.
Cost so far, $0

And as for those who hate the modern electronic engine controls, take the batteries out of your TV remote control and tell me how much of an improvement it is :mrgreen:


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 Post subject: Re: 4th gen misfire
PostPosted:Tue Mar 31, 2015 7:39 pm 
Offline
Big Block
User avatar

Joined:Fri May 11, 2012 10:54 pm
Posts:463
Car Details:4th Gen ls1
Lowered,rollin on 18"s
Lots of std stuff
Location:Wiltshire
Whats the latest with this then Pa's F-bodies did you sort it :think: :think: :think:

_________________
Some days it just isn't worth chewing through the restraints !!!!


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 Post subject: Re: 4th gen misfire
PostPosted:Tue May 19, 2015 6:20 pm 
Offline
Big Block

Joined:Sun Jun 02, 2013 7:20 pm
Posts:160
Car Details:80 T/A with a BBC
79 Z28
68 Firebird F 400
67 Firebird Convertible
Location:Penzance, Cornwall
OK in the end it was the opti spark unit :)


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