Running rough - like it has for years...

[TR7Aaron]

Hi Everyone,
After over a year of neglect, got my '76 to start and run, but it ran very poorly and had a horrible miss (like it's running on 3 cylinders). I added some fresh gas, and checked all the parts from the plugs to the distributor. The compression is good (within 10 pounds of each other), and it starts easily, so I'm thinking it's not an ignition problem. The plugs all look good and with a timing light, I checked that each cylinder was getting a spark. It does NOT run hot. The distributor cap had some slight corrosion, but I cleaned that up as well as the rotor. One thing I did notice is that the center button in the distributor cap is slightly off center and has worn out it's hole that way. This car has electronic ignition and I haven't changed that setting at all and the engine ran OK when I last drove it, so I don't see how the timing could have changed.
A vacuum gauge shows about 16 - 17 at idle (rough and at 500 - 600 rpm) with just a flicker of the needle. When I rev the engine and hold it at about 1800 - 2000 rpm, there's a popping sound when you hold you hand at the tailpipe. I have a laser temperature reader, and cylinder #3 runs a bit hotter than the rest (measured where the exhaust manifold bolts to the head).
Could this be a valve sticking slightly? The compression readings and plugs aren't indicating that, but I'm running out of ideas.
I've used the search function on this website but drew a blank on valve adjusting. Are the valve clearances in the 2.0 engine adjustable and if so, how?
Thanks in advance for any ideas or advice.

Aaron
1976 TR7 FHC (an ongoing project)

[Hasbeen]

Arron, I have found a riding, or near riding inlet valve can give that popping.

Remove the air filter, get 3 feet of plastic hose, hold one end in your ear, & the other end the the front of each carb, & listen. You should get a constant sucking sound. If one carb has a stronger/louder sucking, try adjusting the throttle stops, until the sounds are equal. You do not have to disconnect the carb linkages to do this check, usually.

If you get a flutter in the sucking of a carb, you probably have a problem with an inlet valve in one of it's cylinders.

Yes the valve clearances are adjustable, & it is not really very hard, although some are frightened by it, & it can be time consuming.

Remove the valve cover, & check the clearances with a feeler gauge. Clearances should be 8 thou inlet, & 18 exhaust. any more that a couple of thou out will rob you of quite a bit of performance, & anything down to 4 thou is in danger of burning out.

Clearances are adjusted by fitting thicker or thinner shims under the cam followers. It is not too technical really, most can do it if they are patient. If you need to adjust the clearances Jclay probably has the directions on his sight, or just ask for advice here. There are a couple of little traps for the unwary, so get advice first.

Hasbeen

See my post about STP on the TR7 section, about STP help in engines that have stood for a while.

H

[nick]

You adjust clearances by changing the shim sizes under the tappets. It's a bit of pain since you have to remove the cam shaft and then each of the tappets. If you go on Jclay's web site, you can download the Leyland manual and in it you can find the procedure.


nick
'79 TR7

[TR7Aaron]

Well, I'm not 100% sure it's a valve or valvetrain clearance problem.
I took the car out for a good hard drive and ran it through the gears briskly a few times. It now runs much better, but not where I'd like it to be. The idle is inconsistent - sometimes it's OK, other times it really rough. There's still a consistent miss or roughness in the transition from idle to about 1500+ rpms, so now I'm thinking it may be a carb(s) issue. I balanced the carbs quite a while back, so maybe there's some dried sludge or stickiness inside them from sitting too long. I may just run a tank or two of fresh gas (along with some kind of additive) through them and see if that doesn't help.
Unfortunately, the drive also jogged my memories about things I don't like about this car, so now I have a list of improvements to work on.
The fun never ends!

Aaron
1976 TR7 FHC (an ongoing project)

[FI Spyder]

I would check any source of vacuum leaks on the intake, old hoses, where they're clamped on etc. Don't forget the rubber mounts of the carbs can leak to the point where they actually separate from the metal they are molded onto.



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

[Hasbeen]

AAron, it does not make much sense to talk about things, when we have a problem, but not then eliminate them as a source of problems.

It is perhaps an hours work to check the valve clearances. They should be checked every 10,000 miles or so, as adjustment avoids any larger problems developing.

Yes your problem could easily be water or dirt in the fuel, so I'd be checking them too.

Our old care demand more service & checking than new ones, but we do save massive deprecation.

Hasbeen

[TR7Aaron]

Hey all,
I finally found some time to tinker, so I checked my ignition system using a timing light and it's firing on all 4 cylinders regularly. I checked the valve clearances while the engine was still slightly warm (not cold, but the daytime temps around here have been around 100 for the past week, so the engine really won't get 'cold', but I digress) and the intakes were all 8-9 thousandths and the exhausts were each 17 thousandths. The cam lobes all looked perfect and unworn, so I'm feeling confident that the valvetrain is in good order (the compression tests I did a few weeks ago were good too).
I noticed my back carb was almost out of damper oil and that the two pistons do not rise and fall in unison, but I tinkered and tuned the carbs and they are now much closer and they open with no lag on quick throttle openings.
It still has this irregular idle thing going that it's pretty much had since I bought the car a couple years ago. I think I'm going to just have to live with it or turn my idle speed up to about 1000 - 1100 and forget about it. I should be thankful it runs, moves under it's own power and doesn't leave Exxon Valdez sized oil puddles on my floor. And, it looks damn good!
I'm also thinking that I need to drive this dang thing instead of working on it all the time - that's what it's for, right? I've kinda forgotten about that aspect of TR7 ownership...

Aaron
1976 TR7 FHC (an ongoing project)

[FI Spyder]

Sounds like your rubber diaphragms may need to be replaced. As they are made of rubber they do deteriorate with micro cracks. Part of the Zenith carb over haul kit.

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

[Workshop Help]

Replace the vacuum line from the front manifold to the distributor with a fresh hose. Cost will be less than $2.00U.S.

You've got a vacuum leak.

Mildred Hargis

[Beans]

Or an air leak somewhere, check condition of carburettor mounting blocks.

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[TR7Aaron]

That was one of the things I checked for, but will do it again.
Thanks.

Aaron
1976 TR7 FHC (an ongoing project)

[HDRider]

It could be the joint between the mounting blocks and the manifold/carbs. I found that the built-in seal on mine had shrunk and was allowing air past into the manifold. I made gaskets as the blocks themselves were OK.

You can check these by using a butane torch. Start the car and the gas on the torch (don't light it) and hold the end near the mounting block joints. You will here a change in the idle if there is a leak.

Edward Hamer
Petaluma CA

[nervousnewowner]

having the same problems with mine trying to get it back in for its mot, idling really fast, hc emissions over 3000, got to be 1200 or under for mot.
changed the carbs over and now will idle lower but really rough then for no reason revs itself up to about 2500rpm for a good few seconds then drops again, then will cut out.

turning into a real pain as i need to get it in for its mot and this is all thats holding me up.

with limited time to work on car with work and all the other jobs i have on it just seems to be dragging......

even contemplated raiding the bank and getting a set of refurbed carbs but £250 a bit dear for me right now especially if the problem still remains, and the flexible mountings for the su carbs last time i phoned robsport were out of stock.

wonder if anyone does them in ally?


Dave...

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

[saabfast]

It is probably quicker to strip and clean the piston and needles and then retune the carbs on the car. As long as they are not too worn a reasonable state of tune can usually be obtained.

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

[nervousnewowner]

yeah going to see what the emissions readout is tomorrow hopefully and if still no luck will get a rebuild kit for them, probably the better option moneywise.........


Dave...

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