misfire or similar symptom

[stevefoster]

I have been road testing. Two great sessions Friday and then Saturday.

The throttle bodies are great. Combined with the race exhaust it feels like

I have 200bhp on tap or rather would have if I could max out....

 

I have one problem. Somewhere above 6000 rpm I get a misfire or similar like it was a rev limiter.

The rev limiters are set

to 7250 (soft) and 7300 (hard) for my currently standard bolts.

I don't think it is the rev limiter (obviously as they are set higher) and don't feel either that I

am hitting 7250 in ECU reality while the tach feed could be so far off. I can tell I am not getting

up to 7250 rpm as I have been there so many times before.

 

Could this be an exhaust gasket or cracked manifold problem?

 

I cheated and didn't put a new exhaust gasket on even though the manifold pattern is quite

different to the old one.

 

How can I check is I have a crack in the manifold? Engineers blue or some such?

 

Other ideas are fuel mapping too lean or too rich?! above 6000 rpm, restricted air flow. I should really use the ITG air box I guess and not the crappy piper cross socks (they did pull 7500 ob the carbs though!).

 

(VX XE. Upto 2.0l, Standard internals class entrant)

 

 

 

My racing pics, 7 DIY, race prep. Updated often here

Photo's of the year here

Hants (North) and Berkshire Area club site here

 

 

Edited by - stevefoster on 24 Feb 2003 14:44:57

[Mr Locust]

Turn the limiter off (or to 10000rpm) to eliminate it then keep looking if it doesn't go away? 😬

 

Soft valve spring(s)?

 

Edited by - Mr Locust on 25 Feb 2003 17:52:57

[stevefoster]

Thanks Mr Locust,

I have verified and fixed a cracked manifold to flange on cyl no 1.

Changed the plugs and leads for my spare set. No diff.

Put the propper ITG box on so she can breath more (Nice sound).

Verified that the ECU speed RPM is the same as my tach (spot on).

 

Not tried moving the soft and hard rev limiters up though.

 

I tried to drive though the misfire but you can't. A soft rev limit you could. Not so a hard one...

 

I suspect fuelling but who knows.

No reason to suspect the valve springs have suddenly gone soft.

 

Next step is to borrow a set of Steve Mells cream injectors (colour, not what they inject!).

 

Fun and games.

 

 

My racing pics, 7 DIY, race prep. Updated often here

Photo's of the year here

Hants (North) and Berkshire Area club site here

 

 

Edited by - stevefoster on 26 Feb 2003 20:09:55

[16vastra]

allo steve. erm, what injectors you useing at the mo if not creams or do you just want to try another set.