Triumph Sports Cars

engine swaps and other performance upgrades, plus "factory" V8s (Stag and TR8)

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Kevin Deighton

(1 posts)

01/12/2014 07:55PM

Main British Car:

Newbie TR8 Idle problem
Posted by: Yorkie
Date: January 12, 2014 08:04PM

I just picked up a 1980 California spec Triumph TR8 and it immediately failed its smog test so I was hoping someone here could help with suggestions as I'm new to EFI units. The HC and NOX readings were all spot on but the CO was double the permitted limit. The idles fluctuates up and down slightly and there is a slight misfire at higher rpm.

I checked all the hoses for tightness and made sure the throttle body was clean inside. The plug wires look like pretty new malloy wires but the cap is a bit grubby inside. I pulled a vacuum on the advance/retard cannister and it moved OK. I squirted WD40 around the plenum while the car was running but the idle still fluctuates. Plugs are a light brown color.

Any thoughts on what to check next?
Long Beach, CA

Wilbur Cook

(1 posts)

08/01/2012 11:18PM

Main British Car:

Re: Newbie TR8 Idle problem
Posted by: curley03
Date: January 12, 2014 10:15PM

Try adjusting the air flow meter. there is a round rubber plug on top. take it off and use a common screw driver to turn the screw inside. make sure the engine is fully warmed up. timing at TDC. plug gap at 35' RPM at 900 RPM. check the rotor, dist cap and all vacuum hoses. I'm fighting the same fight . engine runs good on the road but idle is rough. Jim Tencate adjusted the AF meter and rebuilt my ECU. Gizmo used for adjusting AF meter. lots of new parts,8 fuel injectors, all fuel hoses replaced, sensors replaced, new aluminum radiator with electric fan and shroud, plugs, 8 mm wires, rotor, cap, luminition parts replaced. not to mention the suspension parts replaced and new tires. it never ends it seems. good luck and keep asking question here.

Martin Rothman
Vancouver, Canada
(215 posts)

01/06/2009 11:41AM

Main British Car:
1980 TR7V8 Rover 3.9L

authors avatar
Re: Newbie TR8 Idle problem
Posted by: bsa_m21
Date: January 13, 2014 10:25AM

A few more thoughts:

Check compression. If a cylinder is low, it might be causing the idle and CO issues

Fix the idle - look for air leaks around the manifold (slowly spray a little brake cleaner around the manifold. If the idle rises as some point, you have a leak.

Fix the misfire. FYI - replace the amp on the distributor with a remote gm one. They are notorious for giving troubles.

Check your smog air pump & hoses for leaks. If leaking, your CO levels will be high.

Check the entire exhaust system for leaks. And, unless the catalytic converter has been replaced, after 23yrs it likely is no longer doing much helpful.

And lastly, always do a smog test with fresh oil and air filter in the car, and with the engine good and hot. Never let the engine cool down before the test.

Good luck.


Clay Thompson

(9 posts)

05/08/2008 10:09PM

Main British Car:

Re: Newbie TR8 Idle problem
Posted by: real_old_guy
Date: January 13, 2014 10:29AM


Only mess with the air flow meter as a last resort. I have found that 90% of the problems with the fuel injection is really the ignition. Check the connector that goes from the distributor to the ballast, in particular, the slip on terminals in the plug. The plug will be tight but the terminals are loose and causing a bad connection.

Contact Jim TenCate through the TWOA website.

Fred Key
West coast - Canada
(1267 posts)

05/14/2010 03:06AM

Main British Car:
What if the Hokey Pokey really is what it's all about?

authors avatar
Re: Newbie TR8 Idle problem
Posted by: DiDueColpi
Date: January 18, 2014 05:00AM

Hey Kevin,
Hopefully you've gotten through the smog test by now.
If not, let's start from scratch.
As a very short thumb nail sketch. Co is the fuel mixture level, HC is the contaminate level (missfire, oil use etc.) Nox is related to the temperature of combustion. All three interact and affect the readings of each other.
Yes to all the techies I know it's much more involved than that but this gives a general feel to the adjustments.
Pull all the plugs and do a compression test, or better a leakdown test.
Anything more than a 5% difference between the highest and lowest readings will be a problem.
Replace your plugs with "resistor type only" and gap them @ 0.028" (even if you have an aftermarket ignition)
Bigger gaps tend to introduce RFI into the analogue fuel injection (yes they claim it's digital but really, it's British not German) and it causes all sorts of havoc.
For the same reason your cap, rotor, wires and that little condenser on the coil need to be perfect. No solid core wires allowed.
While we're on the ignition. There is a buffer resistor pack to the left of the radiator. It's lot in life is to regulate power to the coil, supply a signal to the tach and provide a clean rpm signal to the fuel system.
It very often has some pretty attention starved connectors on it, and or, has the connections mixed up.
Check it out carefully. And reconnect it as mother Lucas intended.
if it's out of whack, the engine will still seem to run ok but no one is really getting what they want.
Another point to check is charge voltage.
The fuel system is "very" sensitive to voltage and it needs to be stable between 10.5 and 14.5 volts with no ripple from the alternator.
Next clean the throttle body carefully. (inside, the outside can look like crap for all I care)
Loosen the throttle cable and set the throttle stop to 0. That little screw and nut is meant to set the minimum throttle opening.
It is NOT an idle adjustment.
Back it off until the throttle butterfly is completely closed.
Then advance the screw until it just touches the linkage tab + 1/4 turn.
Now lock the nut down. And never touch it again. Even if Grandma says you have to!
The intent is to get the butterfly as closed as possible without sticking.
Next we'll set the Throttle Position Sensor or TPS.
Probe the red and green wires (I think, going on memory here) anyway it's red and something.
Turn the key on without starting the car. the voltage needs to be 0.45 to 0.50 volts and nothing else.
If it's 4-5 volts then we've got the wrong something wire.
Adjust the TPS to get the target voltage.
While the volt meter is connected we'll test the TPS.
Open the throttle slowly and make sure that the voltage rises smoothly up to about 4 volts @ full throttle.
Any glitches or spikes indicate a bad sensor. Which will cause massive CO readings
So now lets start the engine, warm it up and we'll set the timing.
Pull the vaccum hoses from the distributor and leave them off.
Set the timing to "0"
Adjust the idle speed with the big screw and 14mm nut at the throttle body to 1000 rpm.
Recheck the timing and confirm "0" re adjust timing and idle as needed.
Retarded timing controls Nox which is going to rise dramatically as the C0 level drops. Which is what we are aiming for.
Now grab a water mister (windex bottle, tm. no affiliation. don't sick your lawyers on me etc.) yes water, I don't enjoy engine fires particularly, and spray down the entire intake system. Any fluctuation in the engine running indicates a vacuum leak which must be repaired. (While your at it add 20% ammonia to the water turn out the lights and spray your ign system. Any ign.faults will show up as a blue glow) (If your car quits. You needed to fix it anyway)
Now we'll adjust the fuel mixture.
Ideally you have a gas analyzer at your disposal. If not, at least a wide band air fuel ratio meter.
How about common sense and a pulse?
Unplug both O2 sensors.
Start the car and warm it up with all the above adjustments in tact.
Remove the adjustment anti tamper plug from the air flow sensor and unscrew, Counter clock wise , the adjuster until it causes the idle to slow down.
If you can't effect an 100 rpm drop in idle speed then the air mixture is too rich.
Adjusting it requires a fairly aggressive air flow sensor modification.
The air flow sensor that your system uses balances air intake against an air flap controlled by a spring.
Chances are, that in the last 40 years, that spring has weakened some. I know I have.
So, pop that black square cover off and cause some concern amongst the purists.
The innards of this unit are very sensitive, so proceed at your own risk!
There is a black toothed wheel inside that controls god and everything.
Mark it's current position so that you can return it back to normal if needed. This is important. Just like putting your name on a test in middle school.
You will notice a W. shaped spring that holds the black wheel in place.
If you use a tool to remove pressure from the right side of that retainer then you can advance the black wheel to reduce the CO level.
Rotate the wheel three teeth clockwise at a time until you reach a100 rpm idle reduction.
Set the idle speed back up to 1000 rpm with the big idle screw and you should be good for the smog test. Wether the cats work or not. (Leave the O2 sensors and vacuum lines off until you have passed the test)


PS once the test is behind you.
We could perhaps make it run much better.

Edited 1 time(s). Last edit at 01/20/2014 12:53PM by DiDueColpi.

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