engine misfire

[higgie]

Hello all,
TR7 2000cc
Engine temp normal, new plugs and leads fitted but today just experienced slight misfire when engine under load, note this is not all the while, can anyone shed any light on this possible cause please.

Higgie

[nervousnewowner]

at least yours is running....lol, welcome to the forum...

was the miss there before new leads and plugs? check everything secure and no shorts, and do you have points or electronic ignition, if old points in may be pitted and causing problem, rcheck plug gaps too...[:D]

let us know how you get on and remember to call in on the forum from time to time...


the project at birth, watch it evolve...I hope...

[nervousnewowner]

sorry thought it said you'd left two posts not twenty two...... been long day...........[:p]


the project at birth, watch it evolve...I hope...

[Bobbieslandy]

Hi Higgie, welcome to the forum.

Was it causing you any problems with the old leads and plugs? if not then put them back on and see how you go.

Rob.

[Laird Scooby]

Could well be the condensor and/or points breaking down. Also the coil might be breaking down under load as well. In particular, pay attention to the plug gap - a larger gap will be harder for the coil to generate the voltage needed to jump the gap.

What brand of plugs have you used? I've often found certain brands run better in some engines than others. By way of backing this up, when Ford (sorry for swearing lol!) launched the CVH engine, they were getting problems with misfires with any other plug than Bosch and sent a memo to all their dealers to only fit Bosch plugs. Their own brand (Motorcraft) plugs were made for them by Champion and were the worst offenders!

In short, i always use Bosch or NGK plugs, for the 7 engine i would opt for the NGKs but that's a personal thing based on my experience. Legend has it that 1 in 10 plugs from a trade pack of Champion plugs misfire and i've had this backed up when changing plugs on a C3516 Caterpillar engine. For those of you who know this engine and are shouting "It's diesel, it don't have spark plugs!" at your computer screen, i should say it started life as a diesel, yes but had been converted to run on landfill gas (methane) which obviously needed spark ignition. Anyway, out of 2 trade packs of Champion plugs, we could normally get a plug change done and have 1 or 2 spares and 2 or 3 that misfired from first start up! Right PITA when you have to change 16 plugs!

One other question - does pulling the choke out slightly help to get rid of the misfire?

Cheers,
Dave

[john 215]

Hi Dave,

We had the same problem years ago with Unipart Surefire plugs , had to use them as worked a BL main dealer, we called them 'Suremissfire' at a guess they were made by Champion.

Cheers John

LIVE LIFE A QUARTER OF A MILE AT A TIME!
1979 3.5 FHC(STATUS PENDING!!)

1982 2.0 DHC NOW A 4.6,ON THE ROAD NOW KICKING AR5E !!!!

[Hasbeen]

Higge, this sounds silly, but try doing everything you can do to clean & protect the bayonet fittings on the coil, the fittings that go onto then, & their connection to the wires.

Also make sure those connectors are tight, & not a loose fit on those bayonet fittings. They often clip on, & are secure, but are not "tight" when in place.

Caused me a heap of grief.

Hasbeen

[FI Spyder]

How about the distributor cap. If it is dirty inside or has moisture in it or the posts are corroded it can cause misfires. The outside posts can corrode as well. They are cheap to replace as well. The other part of that is the rotor. There were/are badly manufactured/designed rotors out there that have failed within 15 miles of installation. A club member who is a British car garage owner brought a good and bad one, both brand new (they happened to be for a Jag) to a meeting last year. Can't remember how to tell them apart off hand but something to be aware of.

TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT

[Cobber]

<font face="Comic Sans MS"><font size="2">So it's not just me that finds a dud in every box of Champions, I avoid 'em like the bloody plague!</font id="size2"></font id="Comic Sans MS">

80'Triumph TR7, , 73'Land Rover (Ford 351. V8),
'89 Ford Fairlane
85'Alfa 90, 69'Ford F250.
76' Ford F100

[Bobbieslandy]

I bought a pack of NOS Champions and they were as much use as screwing four carrots in.

[higgie]

hi all
I have not ignored your comments as i have been working away since the post, i will try what you have said and perhaps invest in a new coil and set of plugs, what coil do you recommend?.
I have today looked into the distributor and all seems ok, what are your thoughs on changing to eletronic ignition?
Regards
Higgie

[saabfast]

I think its well worth fitting electronic ignition, gives a much steadier idle, no missing from the points/condenser breakdown and no having to adjust regularly. I fitted an Aldon Ignitor (cheapest from Retro Rockets), just replaces the points (extra power lead required) so not much more difficult to fit than new points. I did it all in situ.

Alan
Saab 9000 Stg 1
Saab 9000 2.3 FPT Auto
'81 TR7 DHC

[busheytrader]

NGK plugs all the way for the 2.0L engine.

Back in the day my points needed attention every 4,500 miles or the engine ran a touch rough.



TR7 V8 DHC Jaguar Solent Blue. 9.35cr Range Rover V8, Holley 390cfm, JWR Dual Port, 214 Cam, Lumention, Tubular Manifolds, S/S Single Pipe Exh, 3.08 Rear, 200lb Spax & PolyBushes all round, Anti- Dive, Strut-Top Roller Bearings, Capri Vented Discs & Calipers, Braided Hoses, 4 Speed Rear Cylinders, Uprated Master Cylinder & Servo, AT 14" 5 Spokes or Maestro Turbo 15" Alloys, Cruise Lights, S/S Heater Pipes, Replacement Fuel Tank. No Door Stickers. Mine since July 1986, V8 from 1991 courtesy of S&S V8 conversion and big brake kits.

[nick]

I am having a similar problem on my rebuilt engine. It will accelerate normally above 2000 rpm in any gear. But if it is in any gear higher than 1st, and the rpm is between 1000 and 2000, and I apply throttle briskly there will occur one or more hesitations up to 2000rpm and then it runs smoothly.


nick
'79 TR7

[FI Spyder]

Back in the sixties I worked at a garage while going to U of Vic. and they had a spark plug machine were you push in a spark plug, push a button and a blast of air would sandblast it clean. Then you screw it in another hole and connect it up and through a window you could see it spark. Then it would in crease the pressure in the chamber simulating it being in the combustion chamber. You could see the brightness of the spark decrease and on bad plugs stop altogether. Just because you get a spark with it out of car doesn't mean it will work under pressure of the combustion chamber. That was back in the day when most plugs were made by Champion. NGK were just starting to come into their own with the increase in Japanese bikes. The only thing that would work in my Yamaha Twin Jet.


TR7 Spider - 1978 Spitfire - 1976 Spitfire - 1988 Tercel 4X4 - Kali on Integra - 1991 Integra - Yellow TCT