93 Se, Breaking Up At High Rpm

[JeffYoung]

My 93 Esprit, after sitting for two weeks (don't ever do that again), started breaking up at higher (over 5k) rpm at full throttle. Symptoms and stats:

1. 93.5 SE, stock except for S4s chip and no cat exhaust.

2. Car hesitates dramatically above 5 k and misses, and bogs at full throttle at 4k or so and then backfires as if a cylinder is loading up wtih fuel, not firing and then igniting on the exhaust.

3. Car runs fine up to 3/4 throttle and 5k rpm.

4. After installing new chip, I've had an intermittent warm up issue. When first started cold, car will rev to 2k for about 2 minutes, then to 3k for 30 secnds and check engine light will come on. Revs will then drop to normal idle (1k) and check engine light goes off.

5. Car ran fine with exhaust and chip for about a month.

6. Pulled one plug and it was badly corroded. Have a new set on the way. Will try those first.

If not, what's next:

a. Coils?

b. Coil packs?

c. Ignitioin leads?

[Bibs]

Err, I'm no expert but I know the leads do fail quickly due to the high temp in the engine bay and proximity to the turbo. I think changing the plugs/leads etc is cheap and not a bad thing anyway so that's perhaps a way to move forward.

More problems after that I'd wait for someone else with more knowledge to reply...

[Paul C]

Hi,

I had EXACTLY your symtoms a couple of months ago. I was busy fooling myself it was the wastegate actuator going doolally.

I changed all the plugs (though the originals showed no probs when pulled).

When i was putting the longer of the HT leads back on the new plug,

It felt a little funny.....

I pulled it off the plug and the crimp end of the lead was left on the end of the plug!

This longer HT lead (nearest the cams) is the most 'stretched' if routing is not done with care. Under stress it had broken down some. Thing is,the point where it split was within the rubber boot. The boot is moulded to the HT leads insulation both sides of the break, thus holding the cable in place to arc away inside the boot.

Were it not the fact the end of the lead had pulled out of the boot complete with it's crimp, then i'd have never have known the exact cause and known only that it was the lead.

Car ran like new

PS, Make sure you make a note of where the leads go