Misfire and Light Illuminated

[AlexHillTVR]

I managed to catch this on video luckily enough. According to the handbook the light that illuminates is oil pressure warning, however I'm not entirely sure everything is as standard!

http://www.youtube.com/watch?v=liYMA1xhQBI

Oil pressure is a rock solid 35-40lbs according to the gauge. Recently had the nearside rocker cover off, removed some HT leads, removed one plug extender, removed earths from rocker cover and painted, removed AFM, fitted ACT induction hose kit, new rocker cover gasket, new breather hoses, cleaned and dressed engine bay and removed vacuum advance hose.

All has been put back together of course but I was wondering if that might have anything to do with it.

It's fine until ~4500rpm then bang, get a misfire and there goes the warning light. It died away but then re-illuminated and stayed on later.

Any ideas to what I might have done? Oh and excuse my bouncing speedo, needs to be sorted

[jojackson4]

Your vid is not working

[AlexHillTVR]

Just made it public, hopefully that works

[jojackson4]

Yes it works
Dose the light come on with ingnishion only and not running

[AlexHillTVR]

Yes it does, comes on a lot brighter than when running though and doesn't flicker. Also the top (amber) light is on when ignition is in.

[EGB]

I may be wrong. Seems to be on the over run on closing the throttle. Crackle pop in the exhaust may be? Mine does that, no worries. Look under bonnet in the dark to look for shorting sparks. No shorts, no worries!

[AlexHillTVR]

Ignition On

Yeah I thought that too but it's a different kind of bang on the overrun. It's more like Derek Trotter's van backfiring. That happens at 4000 and one of the usual pops I hear happens at 2500 on the way down.

[jojackson4]

I think I would be testing the oil light switch if I were you what dose the gauge say?

[AlexHillTVR]

Gauge reads 35-40lbs when running

[s p a c e m a n]

Did the speedo bounce like that before you played with it?



Sounds awesome anyway

[jojackson4]

Test the switch it sounds like it's up the spout or a st connection
You may have done it while you have been making every thing nice under the bonnet

I think the s/w is drivers side of the block and near the rear . One wire to it I think !

[AlexHillTVR]

jojackson4 said:

Test the switch it sounds like it's up the spout or a st connection
You may have done it while you have been making every thing nice under the bonnet

I think the s/w is drivers side of the block and near the rear . One wire to it I think !

Have you got a picture of what it looks like jo? I did remove some things and leave them out believe it or not!

And yeah it's been bouncing for a while Why thank you!

[AlexHillTVR]

Pre-Serp by the way if that makes any difference, got a slightly slipping alternator belt too

[PH430]

Check for airleaks after the AFM. My Chim had the same problem with an airleak at the plenum connection.
After hard acceleration and then braking the engine died or almost died. Idle was alsowe worse.
It is posible airleak on the rockercover or hose towards the plenum. Have you alsowe sealend the vacuumconection on the plenum?

Good luck

[s p a c e m a n]

Well, not knowing the wiring on your car but is it possible that the speedo bouncing is because it is picking up interference from somewhere, and the oil light could be doing the same, and you have a missfire...

Tried revving the engine in the pitch dark and looking for sparks?

[blitzracing]

Did you disconnect any earthing straps?

[AlexHillTVR]

blitzracing said:

Did you disconnect any earthing straps?

I disconnected something connected to 2 earthed wires on the rocker cover that seemed to just be holding them together.

[AlexHillTVR]

Will try running in the dark later on, wish it was quieter sometimes

[AlexHillTVR]

Been and had a look in the dark, cant see any sparking or arcing under the hood when revved. Oil pressure is quite high @ 45 lbs rising to 55-60 lbs on open throttle.

I jiggled my plug extenders around as some had the HT lead boot resting on the exhaust manifold Exposed some more bare metal on the rocker cover to get a good connection to earth for the 2 wires earthed to the top. There appears to be a poor connection between the earthing strap and where it meets the block just under the rocker cover on the nearside.

Still the same issue though! I can't see any air leaks after the AFM, the battery connections were tightened, I tightened up the rocker cover bolts too.

Stale fuel? Poisoned Lambda's (recently gutted precats)? Damaged AFM (recently had off, cleaned, masked and sprayed)? Or just in need of new plugs, distributor and leads?

[s p a c e m a n]

Is low pressure warning light and the gauge on two different circuits, or do they both run off of the same sensor?

I have no idea and I'm of little help, I'm just trying to gain knowledge for when my one falls apart