Uneven acceleration

[gmg31]

yesterday I took my 91 car out for a blast and noticed some uneven acceleration. It wasn't misfiring as such but more like hiccups or fluttering particularly in higher gears accelating hard. I also noticed that when I lifted off the exhaust note was a little different. Any ideas please. My car is normally very smooth so it was quite noticeable.

[rip]

I've seen this on someone else's Elan & it turned out to be a CAS fault.
If you can get some Elanscan logs they may help, but a CAS fault can throw up all sorts of strange errors, so this may or may not be revealing.

[gmg31]

Sorry but what is a CAS fault

[Candles]

Cam Angle Sensor - it's the thing on the top front of the engine, just right of where it says LOTUS, and it measures the position of the cam and tells the engine control computer. Stby for pictures etc....

LEC Wiki - awesome huh?

[gmg31]

Thank you.

[gmg31]

I've just spoken to Steve at SJ and he thinks it is very unlikely to be a CAS fault, but he doesn't know what it is. Any body got any other ideas please

[Fredjohn]

I had a very similar problem: the car would occasionally hesitate in the higher gears when accelerating hard. Not a miss-fire, just a brief hesitation.

I lived with it then changed the plug leads......the problem disappeared, so it may be worth checking the leads. I got some from the USA, can't remember which make but they were much cheaper than UK sourced leads and of a very high quality.

[rip]

may be worth checking the leads. I got some from the USA, can't remember which make but they were much cheaper than UK sourced leads and of a very high quality.

I think the US ones are Kingsborne & the UK ones are Magnecor.

[Fredjohn]

Thanks Ian: yes Kingsborne:


Website here

Various colours and sizes available.

[Enright]

If no fault codes have been generated by a Check Engine Light being illuminited, and if your leads are covered in crud then the cheapest fix is to (carefully - especially due to their age) remove each one, clean with petrol or paraffin and replace.
The Hall-effect sensor in the CAS will start out with similar misfiring symptoms but eventually generates a fault-code. However they are only about £22 from SJ's, so if you don't feel like waiting for the problem to get worse and it's never been changed before, then it might cure it.
However I've found that coil packs usually wear out before leads on Elans, and can get really quite bad without setting any fault codes, so if they have never been changed then I'd suspect those first. Coil packs will definitely be needed sooner or later so if there's no improvement you haven't lost anything.

Check the "ignition and fuelling" section of the forum for more fault-finding clues, as misfiring issues are usually in that area.

[gmg31]

One of the things that became very noticeable was that the exhaust note was very different on lift off (after hard acceleration) I know the plugs are new and the leads have been cleaned so my first thought was un burnt fuel which lead me to think about the coil pack. I'll have a look at that first, thanks

[epipete]

I agree with Enright, but quite honestly, if you are going down this route you may as well do the lot; Coils, Leads and plugs then you know that 'end' is sorted!

The other thing to consider, again as Enright says, is the fueling system, I have had a similiar occurrence (though I can't work out why) when the fuel pump was on its way out - these can be got from Castle Combe at a good price.

[gmg31]

The NGK coils on ebay are £31 each and the leads range from £70-£93 is there much difference in the quality of the leads and are the coils adequate to the job?

[Enright]

NGK is generally a good make and that sounds like a good price, but I didn't know there were any coil packs on eBay - can you post a link please?
I wouldn't bother with leads until you have tried the coil packs. Otherwise you don't know which component you have replaced was the dodgy one.

[gmg31]

http://www.ebay.co.uk/itm/New-NGK-Ignit ... 1644813121

[Brit-Car-Nut]

Rock Auto has the standard coil for a much better price:

Go to Isuzu, 1991, Impulse, Turbo, Ignition, Ignition Coil.

DR39 is the most common coil of it's type due to GM using it on every car thru the 90's.

Dr39T is the non-retail packaged version. It is the same coil but in a plain white box.

STANDARD MOTOR PRODUCTS DR39T ........ £9.18 and postage is £8.91 to my address near Doncaster.

£31.00 is crazy - even for a UK price.

eBay UK has this listing: http://www.ebay.co.uk/itm/SMP-Standard- ... 1c57ec867c

It comes from the US but still less expensive than the other listings.

[Enright]

Oh, and remember that you'll need to buy 2, unless you use one half of your engine more than the other!

[gmg31]

You know what, I really must remember to start with the simple stuff first before panicking. On the way home last week after that drive out, I filled up with higher octane fuel and a bottle of redex and she's been fine ever since.