Okay, serves me right for bragging. Yesterday my '69 280SE W111 coupe ran perfectly. Drove it for about an hour or more straight. Some highway, some stop-and-go. Idled smoothly, plently of power and smoothness at all throttle positions. Today it's considerably cooler outside, but there's no rain so I decided to take a quick run to grab some lunch. Started right up, idled smoothly at first, then began the intermittent miss again. Engine sounds like when you short out a cylinder to check for misfire/s.

I just picked up my NGK plugs (as recommened on yesterday's post/s) to replace my Bosch W7Ds, and I am running Bosch wires (which have been derided a couple times in some posts).

Mixture? I don't seem to be running too rich or lean, no fuel leaks, and the problem is so random I don't think it's the pump (injection or otherwise) or anything else in the fuel system.

Runs perfect one day, crappy the next. What gives????

I am about to go back to MGs and Triumphs - or maybe something Italinan (!?) Shows you how desperate I am!!!!!!!

This might seem silly but what is your temperature gauge reading? My wife's 250C is one cold blooded beast. It does not want to run below about 160 degrees. Get it up to 165 and it purrs like a kitten.

Intermittent things are electrical more often than not.

You need to go back to the basics and prove the subsystems are "spot on".

- Fuel delivery is perfect (pressure to spec; flow to spec; pressure maintained after the key is off).
- Ignition is to spec (dwell right; timing right).
- Fuel management is correct (CO% is right, HC% is right).

You're not there yet, which is why you're not sure which one to look at next. Keep it simple in the diagnostics and the repairs. Each of those major systems in turn is divided into subsystems.

You might well benefit from having the car on a dyno with a 4 gas meter and a fuel pressure gauge and then let the thing run a while as you take notes about the readings.

-CTH
PS. And if you do want to sell, where are you and what have you got exactly?

__________________
- cth350@gmail.com
http://www.111lakeside.com/

I feel for you brother!
Make sure your plug wires are tight (obviously...or not), rotor and cap not worn too much (just covering the bases here) and try running the engine in the dark with the hood open and see if there's any spark leakage. Move the wires around a little too.
Basil

don't throw in the towel just yet!!!!!!!!!!!!!

use a spray bottle and mist your wires with water, (preferably not in direct sunlight.) if your wires are bad you'll see them arcing into the air.

pop your distributor cap and look inside for any moisture, carbon tracking, pitted terminals, oil streaks, etc.. check your points for proper gap and make sure they are clean. make sure the rotor is in good shape and firmly seated and make sure the distributor shaft doesn't wobble.

you'll figure this out eventually. first thing is to figure out whether the miss is ignition or fuel related.

and please don't get anything british...unless it's an austin healey 3000

Simce you mention MGs.... I had once a cracked distributor cap in my '63 MGB. Took me forever to figure out why the thing ran bad once in a while until I grabbed the cap on a foggy day while adjusting the timing and got a good jolt. We took it off and found a very fine hairline crack. Very tough to see on those black caps. I replaced it and problem solved. Definetely do the suggested leak test in the dark. Once we knew it was there, we also noticed the leak from cap in the dark.

Totally different angle that caused problems with my MGC once: loose/poorly sealed/gasketed inlet manifold. I had this problem with an occasionally poor running engine and it turned out that it was air leaking in between the engine and inlet manifold. Just kept lacking power at high speeds. Once I put some loctice on the gasket and torqued it harder, problem went away.

But as the others say, I also suspect it is electrical. Probably a bad plug wire (do you have solid core wires? - I am told these can break and cause problems). Even with new stuff, you sometimes get unlucky.

Don't give up.

Bert

__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8

first, NO NGK! or any plug other than plain, old orig. Bosch, and not 7's...only 9's! I don't care what anybodys says, I've cured many peoples problems just with right plugs. second, i note that you havethe 6 cyl. injected engine. like the 230/250/280SL's these are real bastards when it comes to cold running issues. take it to someone who has experience with this system and pay them to set it up. its a laborious process going through all the interconnected components and you can go nuts fiddling with the injector settings, etc. the only alternative is to nurse the car til it gets up to temp.

Thanks again, guys. I love this car, but lately she's driving me nuts. The frustrating thing is, all of the ignition components are new. I am not new, so I concede it's possible for one or more of the new ignition components to be faulty - but it's relatively rare for a new condensor or cap, or rotor to be faulty. I do have a new wire set (Bosch - ordered from AutoZone - please don't hate me) and Bosch W7D plugs. Points are new as well, of course.

I truly doubt it's the injection/fuel system. I would have to think that it would run poorly just about all the time if that were the case, no matter what the weather. It gets cold in Germany - right?

I have physically observed the enrichening device lean out as the car warms up. I have a nice, blue flash between the points too.

When I used the stroboscopic timing light, I have observed several times it was hard to get a "fix" on the crank pointer, since the misfire would randomly occur. The timing light is attached to #1 plug lead for the procedure, and occaisonally will not "light" with the trigger pulled, so it would seem that #1 might be the culprit.

If I get wires from Miller's or anyone else, are they going to be the same Bosch's as from AutoZone? I don't mind spending money on all the tune-up stuff again (well, actually, I kinda do) - but I've only put about 600 miles on the car since doing all this before - I just wanna fix the old gal for the Summer!

there are MANY components to the fuel system. as i said earlier, its a ***** to get them all right at the same time. unless you are using a scope for plug firing, you may not get the correct data you need. on these engines, its ususally not the ignition that causes cold running problems. yes, it gets cold in Germany...and yes...they have had the very same problems with these engines and fuel delivery setup....once again, you're running a plug that's too cold for this engine.

I think you should look everywhere else before messing with the injection. Try wiggling the plate that holds the igniton points. The pivot for this plate can wear and screws up the point gap. Try rotating the distributor rotor by hand. It should move in one direction against spring pressure and return quickly.

What's the proper heat range? I have two books that say Bosch W7D. I bought the NGKs - so I'm going to try them. We'll see.

Fuel? I don't think it's the fuel system. It's 50 degrees here today and humid (going to rain) I just took the last 45 minutes to start the car, let her run for five full minutes until the idle solenoid eased off - then I went for a ride. And I mean a ride. I have a personal, curvy, hilly road test course (got to love it when it's Spring break and there are no school buses) of 5.65 miles. My best lap time today was 5.6 minutes - and that includes a standing start, and one full stop along the way. the car ran perfectly. There is very long down hill section (about 1.5 miles) where I can test to see if there's a misfire with lots of vacuum - nothing. My car is a four-speed, floor shift - so I blip the throttle for downshifts while trailing brake, perfect. Got home, let it idle in the driveway - no misfire whatsoever.

Stirling Moss used to say that although one of his best drives ever was the 300SLR in the Mille Miglia - it was a brutal car to drive and responded best to a heavy hand. Maybe that's the secret?

I do have an oil leak from the cam cover, and I will be changing the gasket this weekend while I adjust the valves. Oil isn't a great conductor of electricity - but when the oil is hot and thin and leaks down the plug-side of the head - could it be shorting the high-tension circuit? I'll go out and start the old gal in a few more minutes to see if the problem shows back up. Poor thing is probably hoping for another hot lap time today :fork_off: - but it's starting to drizzle....

Tom W.

You have subbed the coil? You say the ignition seems to drop out from your strobe light description? That may or may not have been a very signifigant clue it just depends. You have checked your balast resistor out by subbing it as well? Does it have one?
Does your tack dwell meter stay stable during the interludes of poor performance. You could also have something like a sticking valve but I doubt it as the consistancy seems absent.
No sense changing out what you have already done in my opinion. If you can find an ancient guy from an auto electric shop he will probably diagnose it without even opening the hood. Some of those guys I found were good. Not really a bad problem here I suspect as much as a frustrating problem. Remember though that I am an amateur mechanic at best.

Okay - the NGK plugs are in. It actually seemed to start quicker, and it's running perfectly - but of course it was as running perfectly earlier today with the Bosch W7D plugs in place. So we'll see what happens. Or perhaps I'm just hallucinating at this point.

The Bosch plugs were not oiled, or black - BUT they weren't that nice tan color either - in fact they are stark white. The electrodes look like new - except not as chrome-shiny of course. Perhaps as "autounion" suggested - wrong heat range plugs? Only time will tell. I'll keep you all posted. Crap weather predicted for the weekend - of course!

You may have a mixture problem if you have white plugs. White plugs mean too much air, or too little fuel (I had white with that manifold problem). It might be FI related, like autounion suggested.

I have to ask: why don't you drive in the rain? You should just so you can switch the wiper system on and prevent it from seizing up. Trust me, you do NOT want to have to remove a seized wiper assembly from a W111.

Bert

__________________
'70 111 280SE/c 3.5 (4 spd manual) - sold
'63 MGB
'73 MGBGT V8

Bert,

I occaisonally get caught out in the rain - but as a rule I try to avoid it. Especially since our Spring rains up here are generally still trying to wash tons of road salt and sand (mixture) away that are still on the road surfaces. My old girl has managed to survive in mostly northern climates for 40 years without turning into a heap of iron oxide - and I'd kinda like to continue the tradition. Had to tap the washer/wiper ring with my left foot a couple times on the way home today after the road test - they're working great - actually very fast! At first I thought it was goofy to have a wash-wipe "pedal" - but now I think it's kind of neat, being able to keep both hands on the wheel and hitting the wipers at the same time!

Regarding the plugs/running problem on this thread - I still don't think it's mixture - the car ran just absolutely perfectly today - at everything from start-up to hot idle, to high-speed running with lots of gear changes, up and down long/steep grades with engine-braking and in relativey cold/humid weather. If my mixture were off enough to create my reoccuring stumble or idle-speed misfire - I just don't think it would run very well at all - ever.