Slight Misfire?

[chimaera]

Hello All,
Am having a bit if a problem with my 1993 4ltr Chimaera. At around 2750 - 3000 rpm I get a misfire and splutter, however it only happens when the radiator fans are on and when using a slow throttle when accelerating/at steady throttle. It does'nt appear to be temperature related as I have a fan bypass switch and even if the engine is cold and I turn the fan on the engine misses. I suspect that it may be the alternator on it's way out as occasionaly the red light on the dash comes on very dimly (can only see it at night) and with the electrical load up this is when it misses. Any advice before spending £250 on a replacement!!
Cheers,
Scott W.

[taylormj4]

Hi, yeah I've noticed this and I've only had my Chimaera for about 2 weeks.
The fans on the Chimaera are quite large and as all motors do, will draw a large current when starting from standstill. As the fans are so large, this current draw could be high enough to drop the system voltage significantly and cause a partial misfire or upset the engine management a bit. You could confirm this by running the fans up to full speed, then turn them quickly off and on again - as they will not be starting from standstill, this should not cause a misfire. Try it and let me know. One answer would be a soft-starter on the fans but it's not really worth it. An alternator may be the cause but its really the battery's job to supply large sudden current demands (once the engine is running) - the alternator is designed to supply a more steady current output.

[GreenV8S]

quote:Hello All,
Am having a bit if a problem with my 1993 4ltr Chimaera. At around 2750 - 3000 rpm I get a misfire and splutter, however it only happens when the radiator fans are on and when using a slow throttle when accelerating/at steady throttle. It does'nt appear to be temperature related as I have a fan bypass switch and even if the engine is cold and I turn the fan on the engine misses. I suspect that it may be the alternator on it's way out as occasionaly the red light on the dash comes on very dimly (can only see it at night) and with the electrical load up this is when it misses. Any advice before spending £250 on a replacement!!
Cheers,
Scott W.

If the connector to the ignition switch is duff, that can cause a voltage drop under load and lead to these symptoms. You can dismantle the connector and clean it, but for a permanent solution bypass it completely and solder the ignition switch permanently into the loom.

[anonymous-user]

My Chim is having the fuse link replaced tomorrow.
I was just about to buy a new alternator as it appeared on the face of it, not to be working.

The car had died on me, then the battery light was on all the time.

Someone had mentioned it on here, but was just going to buy a new alternator when Waldonway (who were really helpful) said try the fuse link first as this catches everyone out.
Wobbling the wire from the alternator confirmed that something was broken (connection or fuse).

I can't risk taking it around 50 miles to them so have got the bits and am getting a local garage to fit it.

I wouldn't replace the alternator until you check that first.

It is under the right hand side near the starter motor.

[Leadfoot]

quote:I can't risk taking it around 50 miles to them so have got the bits and am getting a local garage to fit it.

Hope they dont charge you too much. It's a 5 minute job & only needs a screwdriver,jack & axle stands (or a pit in yer garage).

[chimaera]

Thanks for the ideas, Just a note about switching the fans on and off, Although on initial turning on there is a slight dip in revs at idle it takes it in it's stride when driving round, I only get the misfire at 2750-3000, this is what is confusing me as I thought I would either have a misfire all the time or not at all.
Will also look at the igintion switch connection (I am assuming this is the one on the steering coulmn, or is there a hidden one?)
Thanks again.
Scott.

[anonymous-user]

quote:

quote:I can't risk taking it around 50 miles to them so have got the bits and am getting a local garage to fit it.

Hope they dont charge you too much. It's a 5 minute job & only needs a screwdriver,jack & axle stands (or a pit in yer garage).

__________________________________________

Got it done at a local garage, South Hill in Langdon Hills.
They let me drive the car onto the ramps (as they were afraid it may ground out) so they guided me on.

I showed them what had gone and they replaced the fuse there and then.
They let me look under the car whilst they were doing it and they had a quick look around themselves to see everything was o.k.

All for £10.

Lee.

[david beer]

On a Griff the fan relay supply is actually a permanent supply,i assume yours would be the same, its only the low current side of the relay that is switched through the ignition switch,ie the otter supply. So the supply is direct(ish) from the battery. Of course the fuse box could be a potential problem as the supply for everything goes through it, and asking it to handle the rather large current for the fans is maybe pushing it.