Engine stutter

[westhamtim]

Morning all

Recently my 98 V8 has started stutterting a bit. It happens whenever I ask for any kind of torque ie accelerating from low revs in a higher gear. If I accelerate from higher revs it's fine, or if I accelerate in first it's fine. This has been happening for a few weeks now and happened last winter too (not as severely but then it wasn't as cold). I had a similar problem with my Elise after I had it laid up for a year and was told by Sinclaire's that it was probably condensation in the cylinders and should sort itself out, which it duly did. Sadly I pretty much only get to use the car at the weekends so it's sat, garaged, for most of the week.

I guess my questions are 1) Does the above diagnosis sound right, 2) Should I be worried, & 3) Is there anything I can do to limit this happening in the future, short of heating the garage?

Many thanks in advance

Cheers

Tim

[peter_england99]

Hi Tim,

I would have thought that condensation in the cylinders would cure itself within seconds when the engine is running.

Regards,

Peter.

[mike_sekinger]

Hi Tim,

With those symtoms, it could be coil packs, plugs or even leads. When were the plugs/leads last checked/replaced?

Are the coil packs from the original car?

I would focus my attention in this area.

Cheers,

Mike S

Edited January 13, 2009 by mike_sekinger

[jonwat]

Tim,

When you put you foot down at low revs this allows more air into the cylinders which increases the compression ratio and so increases the resistance across the spark plug gap.

If there are any deficiencies in the HT circuit then the spark will find it easier to jump to earth rather than the spark plug gap and this causes the misfire.

This is almost certainly caused by damp getting in to connections and normally clears up once the engine is warm but it does point to possible future problems so it's worth overhauling your HT system at the next service.

Hope this helps,

John W

[dave excell]

I had the same problem after I rebuilt my engine. It was cured by replacing the set of HT leads. The originals were well worn out with the insulation breaking down. The fault dissapeared at high revs. Now with new leads I have no problems.

[westhamtim]

A few hours and a raft of excellent and very useful responses. Thanks very much chaps. I'll get the plugs, leads etc looked at at the next service, if not before (I have a nagging feeling that this is something reasonably straight-forward but just wouldn't trust myself!)

Cheers

Tim

[Günter]

Tim, maybe I'm totally on the wrong lane -but how old is your V8 [miles] ?! Have you ever tried to look inside your exhaust system, especially the catalysts ? In the time my system start to fail they have done what you describe, as the gas flow was slightly blocked . That means it was complicated to accelerate in some mid load/revs -or to change from load to free run, and back.

[Zhastaph]

I have a nagging feeling that this is something reasonably straight-forward but just wouldn't trust myself!

You'd think so wouldn't you ..... but when it comes to changing leads on the v8 nothing could be farther from the truth!

I'd certainly echo the responses of those above, coil packs and leads would be chief suspect especially if either are the original fit.

A misfire is generally felt as quite a noticeable sudden shudder through the vehicle whilst accelerating whereas; blocked cats, misfueling etc tends to be felt more like a resitance, as if someone is applying the brakes.

[westhamtim]

Engine has done about 10k miles, cats are about 2/3 years old so around the same. I'm fairly certain it's not that - only happens during winter so I'm sure it's a condensation / temperature problem.

Thanks again for all your input.

[westhamtim]

Update:

I'm not sure it's a condensation problem anymore.

I had to go to a wedding yesterday and thought it an ideal opportunity to give the car a run (50 mile drive) and burn off any condensation / damp. The car behaved as described above for most of the journey. Sometimes the problem wasn't evident at all, but most of the time I struggled when looking for acceleration in high gears. I was somehwat surprised and certainly disappointed that the problem didn't appear to be improving during the journey. The final 30 minutes were spent negotiating the one-way system in Colchester, sat at lights and gernally moving slowly. At this point the problem became noticeably worse with the engine apparently struggling across the rev range and in all gears. When we finally got parked I got out and could notice an obvious popping coming from the left exhaust. Temp was normal and no warning lights.

This morning I was uncertain whether to drive the car at all or have it trailored home so I gave it a quick spin and it seemed OK, slight resistance when accelerating in higher gears as before. This was the pattern for most of the way home with the problem again being sometimes more or less obvious, and occasionally totally problem free. However, about 10 miles from home as we hit traffic and traffic lights the problem became a lot worse and the engine sounded odd - too throaty and struggling for power. With nowhere obvious to pull over I decided to limp the car home and completed the journey at a steady 40mph. Again, temp was normal and no lights.

When I got the car in the garage I noticed two things - a chalky, looking residue around the lhs exhaust outlet (thought it could be salt but not present on the rhs), and, even more worryingly, steam coming from the front passenger wheelarch.

I'll be getting the car trailered to Morland Jones ASAP as there is no way I'm driving it anywhere! In the meantime, can anybody speculate as to what the problem could be? I am totally bracing myself for the worst....! I'm now thinking some kind of exhaust problem, or possibly even something extremely sinister with the engine (waiting for it to cool down so I can check for mayonnaise).

Cheers

Tim

[Günter]

'steam' ? you mean as if the water and mist from the wet roads was gone over the LH side oil-cooler, and also over the brake disc in the LH side !?

Was/is it gone after the car is cold and you start the engine again , and let it run on idle ??

And again, even with the negation above: the only chalky thing i can imagine is the ceramic base structure of OEM catalysts. But your car is too young for that !!

Is there still a lot of salt on the road in GB ? I can not imagine that the air inlet side or any other part of the fresh air/turbo , or even the combustion is influenced that much by the winters condition on that point... .

hope you get it sorted !!

[Zhastaph]

The steam will be irrelevant unless you've got a loose radiator hose or something, and then she'd obviously be losing water ...

The white residue and popping is possibly relevant and may be an indication that the left hand side cat has disintergrated, I think mine had destroyed 2 oem cats {same side} before it had done 20odd thousand miles, as Gunter says it's a bit young for that but certainly not impossible. With a blocked cat the car feels awful the more throttle you apply, with very light throttle it can almost feel fine but the harder you press the more strangled and less power you seem to get.

It's easy to test for; start the car, rev it to about 2/3,000 rpm, then stick your hand against each pipe - if it's a blocked cat there's a very noticeable difference in the air flow.

[westhamtim]

Another update:

So at the third attempt (attempt one - no lorry sent, attempt two - wrong lorry sent, despite me having made clear it was an Esprit with low clearance!!!) the car was taken by flatbed to Morland Jones. MJ diagnosed that cylinders 2 & 3 were not firing and recommended replacing the coils, leads and plugs. Not the end of the world.

This was done but the problem is still there ie when warm there is a misfire apparently caused by a spark not being generated. MJ have called around and believe the problem is likely to be with the ECU and it needs to be sent off to a specialist to have it checked out (the MIL is not coming on so no clues from that corner).

Anybody got any insight?!

Cheers

Tim

[Zhastaph]

Because of the amount jammed under the plenum and around the fuel rail I've seen the low tension wire to the coil packs get chaffed and grounded.

A bit of insight:

The Esprit uses wasted spark with each half of each coil pack feeding 2 cylinders, to all intense purposes when a spark is generated it starts at the ground of a spark plug, jumps the gap to the centre electrode to generate a spark, flies up the HT lead, through the coil pack, down the partner cylinder's HT lead jumping that gap to generate the second spark. So pretty much always if you lose a spark at a cylinder you will actually lose it at 2.

Any one of the following will cause you to lose the spark in a cylinder; Spark plug, HT lead, Coil pack, Condition of the grounding between the coil back and the engine, LT cable to the coil pack or ECU

The 2 things most likely to be effected by heat are the HT lead and the coil pack, as any cracks in these tend to expand with temperature and get worse, though it's also possible that a dry join on one of the coil pack tranny's in the ECU is likely to give similar results.

[USAndretti42]

If you've lost a plug or a coil, you probably have killed the catalyst. The fuel that should have burnt in that cylinder(s) will get blown out the exhaust valve and end up burning in the catalyst severely overheating it in the process. The catalyst may not be blocked as it may have broken up and spat bits of itself out the back. Sorry to be the bearer of bad news.

[WEllison]

I don't know if your mechanic took the coil packs off the block and cleaned the grounding surfaces as part of the plug wire replacement process, but he should have. The plug wires and coils packs are open to the environment and water from rain or washing the cars drains down through the louvers and gets everthing wet. coating the gounding surfaces with a carbon conductive grease should also have been done after the coil pack grounds were clean. I tend to be bit paranoid and cover the engine with towels when I wash it.

Wayne

[westhamtim]

Final update:

Car is back and after a 15 mile (but 1.25 hour - London rush hour) drive, seems fine. As before coils, leads and plugs were changed with apparently no positive impact. The issue was with the ECU which was sent to a specialist down South, I believe on the advice of SJ Sportscars. MJ were a bit vague about what the exact issue was (and yes, if this was the non-Lotus main-dealer thread over on General Esprit Chat I'd perhaps be a bit suspicious), but the upshot is that it now works.

Thanks again for all your input, and here's to a decent period of trouble-free motoring!

Cheers

Tim

[westhamtim]

Not the final update. Took the car for a quick spin to the shops yesterday and didn't seem 100% - didn't seem to be getting full speed, although only a short drive and not great roads so couldn't really test it out to be sure. Today, went for a 60 or so mile round-trip and towards the end the symptoms came back - racket coming from the back and no power. I managed to limp the car home and put it in the garage where the left exhaust was popping constantly. Looked underneath and the left cat is glowing red hot! So I think it's something to do with the cat! (as has been suggested above). However, I'm in the position of havign spent a not inconsiderable amount of money to get the car not fixed. I;m going to speak to the garage tomorrow. What would you do?!

Cheers

Tim

[outtamyway]

You might give that Cat a good smack with your hand to see if you hear anything rattling internally. I would guess

that is your problem as my left hand cat went with 7K on it. The good news is it may under warranty.