Weird Running And Other Issues

[adigra]

Hi all,

I feel really stupid but I can't make any sense of what's happening with my car. Before taking it to a mechanic I was hoping to at least get an idea of what might be happening. I've been reading through the archives for days, but am no wiser other than thinking I could spend the rest of my life trying to diagnose it.

A couple of days ago I posted about the engine not revving past 5700, then it was fine. Well, since then other symptoms have developed, all in a space of a couple of days, but I can't determine how many are connected.

OK, so the ignition light started coming on randomly, taking a while to go out on start up, then pulsating, etc. But, if I rev the engine it goes out, but it comes back on randomly (I am suspecting a failing alternator/regulator, but I still can't explain the other issues). The battery is getting charged though and the car starts fine. The rev counter is very bouncy (it was always bouncy, but it's got worse) and sometimes it stops at 4000 and slowly rises to 5000 not matching the engine (based on road speed), but sometimes it works fine. The engine seems to run out of steam at around 6300-6400 (75mph with a 3.5 dif on 155 tyres) completely, as if not getting enough air or fuel, or spark.

It also seems to idle unevenly and seems to take longer to drop down to idle speed. On start up, even after being gently warmed up, it idles at 600rpm, while after a run it tends to do 1200, both of which is off, obviously. When I pull the lead to plug 2 (from the front), there is no difference and no drop in revs. When I do so to plug 1 there is a slight difference, but not much. When I do the same to 3 and 4, the difference in running is quite a bit. Putting a working plug into No.2 made no difference. The plugs are pretty sooty. But when on the road, the performance is OK, I certainly wouldn't have suspected that it wasn't running on all cylinders, except at the top of the rev range, as mentioned.

Any ideas?

Thank you.
Adi

[mbell]

Given messing with your distributor made the problems go away last time, problems with the rev counter and the quick onset of the problem. My guess would be your electronic ignition module. Have you some point/contacts or another electronic ignition unit you could test with?

Touching the carbs unless you know your ignition system is good is probably not a good idea and likely to cause more problems.

[jimj]

For one thing your rev. counter is miles out, 6200rpm with a 3.55 diff should be 100mph+. I suspect your fuelling, electrics, and maybe timing are all at fault and trying to fix one thing will get you nowhere. I`d recommend, as I have before, expert help on a rolling road.
Jim

[adigra]

mbell, I really hope it's as you suggest, as it's the only thing that doesn't make me want to cry.

Jim, of course, you are right, but I made a mistake and didn't mention that I measured that in 2nd gear, which should be roughly at 6400rpm at 75mph, but my engine starts struggling at 70-ish, so well before the redline (satnav verified speed).

I also should add that I will take the car to a professional as soon as I can. I was mostly hoping to get some ideas as to what might be the cause of this for my own sanity as well as to possibly direct the mechanic better.

[PBrown60]

Check the inside and outside of the distributor cap for arcing and cracks. Also look for carbon buildup or pitting on the electrodes inside the cap.

Check that the plug wire connections at the distributor cap are good.

When I first got my 67 Elan SE/SS DHC there was a bad wire connection for plug 3 inside the cap. It was one of the cap/wire setups with the fixed wires.

Let the car idle at night in the dark and look for sparks between the plug wires and the engine. I've seen some nice light shows with bad wires.

If you have never or it has been years since you replaced the cap/rotor/wires, and you find any of these I would replace them all.

Hope this helps,
Paul

[adigra]

The distributor is about 3 years old, same as the coil, electronic ignition and all leads. When I was removing the leads I would get a shock from the wire if I accidentally grounded myself (by touching the wiper as I was leaning over). Am I right in thinking that this shouldn't really happen through the rubber on the wires?

I will do a compression test tomorrow just to get that out of the way as a potential cause of the cylinder not firing (or discover that I am in even more trouble and have a bent valve). The first thing I'll do though, is book it in with an expert as soon as they can fit me in.

[adigra]

And Paul, thank you very much. It definitely helps to put my mind in order a bit regarding the potential causes. My main worry is that there is something off with the engine itself, so as soon as I rule that out, the rest of the issues become more interesting rather than scary. The major concern is that I have damaged the engine by over revving it due to the faults with the tacho (which was reliable up until last week), but all of the electrical issues started happening gradually, but all together, so I am hopefull that that is the cause.

[adigra]

Well, nothing wrong with the engine. The carbs are definitely off balance, but it doesn't explain the electrical issues. I'm taking it to an expert as soon as they can take it to have the carbs, etc. set up. I'll fit a new alternator as well and see how far that gets me.

[billwill]

If you are sure that the distie cap and leads are OK, get a new rotor arm anyway. They are not expensive and I think I heard that there have been cases of them failing early in life. {under high voltage they can track through internally from the top contact to the distie shaft. They can look perfect but be bad.

See adverts for these RED rotor arms which are supposed to be much better against this type of fault.

http://www.distributordoctor.com/red-rotor-arms.html

Kelvedon even seem to have the original type with the built in rev-limiter (bit pricey though)

http://www.kelsport.net/parts/products. ... ectionID=5

[adigra]

Hi Bill,

I am not sure, no, and it's quite possible. I am taking the car to Pat at Kelvedon next week and will have them go through it and replace anything worn, and set up the carbs. From my description Pat suspects that it's the alternator fluctuating output, but we'll see when he gets the car. I'll have one of their lightweight alternators fitted, and possibly have the whole thing upgraded (flamethrower coil, dizzy, ignitor 2, etc.). I find that with budget/reconditioned parts I just end up chasing my own tail for days each time one of them fails.

I've also pulled the tacho out and will have it rebuilt locally before taking the car to Kelvedon.

Adi

[billwill]

NB Kelvedon Lotus are in Spalding Lincs, don't get lost by going to Kelvedon Village in Essex.

[adigra]

If I end up in Essex it will at least give me the chance to go fit the 10" exhaust pipe I've been thinking about!

[memini55]

Adi,

Just reading thru the posts and you may have done this already, I would get a new set of plugs and install all four as this is a cheap and easy thing to do. We have a motor which we autocross and when a plug fails it will shake at low RPM's and won't run above 5800 or so. If you have a IR thermometer you can measure the temps on each leg of the header and if one is lower in temp swap that plug or wire or cap for that matter as that is the one not working correctly.
These things are always fun to sort!
Best of luck
Mark

[el-saturn]

rev-limiter rotor: not worth the money, not necessary and half the FUN boys --- but not all of us
like to rebuild these lovely TC?s and therefore you may have to be more cautious - but here it?s
nice to pass Ducatis (downhill, of course) and high revs call for good workmanship-------------
asta la vista - keep on haulin? ass! 36/4982

[adigra]

Thank you Mark. Yes, I've swapped the plugs, but it made no difference. However, I have determined that both cylinders 1 and 2 are not getting enough fuel on idle, but get going fine if the throttle is blipped and/or revs are kept up. I think the electrical issue might be just confusing the matter and making it worse, rather than causing it. I feel that at least I've now eliminated the most serious of the potential issues (cylinder damage), but, it has dented my confidence quite a bit, so off to the expert it goes.