3.0sc lack of performance

johntom · 04-27-2011, 01:57 PM

Hi
I have a 1980 3.0 SC (UK) which basically doesn't have much acceleration and generally feels very slow, (i counted 10 seconds between 60 and 70 mph in 5th gear) . Since buying the car last June I have fitted new plugs, dist cap, rotor, fuel pump, accumulator (cured the hot start issue) , had the CO checked and tonight I checked the timing which seemed ok. The engine has done 107,000 miles with a top end refresh at 50,000 miles. There aren't any leaks, strange noises and the oil pressure is 1 bar per 1000rpm. What would be the next thing to check or any ideas about the lack of performance ?

Walter_Middie · Walter_Middie's Garage

Timing is the first thing that came to my mind. What do you mean that you checked the timing and it seemed OK? What was the advance at idle and at 6,000 RPM? This will tell us if your advance is working correctly.

James Brown · James Brown's Garage

The CIS system! Fuel injectors, dirt/crud in the fuel distributor, check the movement of the air plate to make sure there is no binding from varnish/dirt. Fuel pump pressure, fuel filter, ignition timing, ect. All normal things that should be done every couple years. The CIS injection system is a little restrictive when new so keeping it in tip-top shape is important.

Grady Clay · 04-27-2011, 02:10 PM

johntom,

It looks like you have been chasing this since last year.

Have you measured the cranking compression and cylinder leak?

Have you inspected the internal element in the catalytic converter. (Or tried driving with a tube in place of the catalytic converter?)
Can something inside the muffler have come apart?

Best,
Grady

johntom · 02:24 PM

Hi
using a strobe, at idle, i had 5 degrees. When revved to 3000rpm i measured 24 degrees (using the advance feature to realign the fan/flywheel marks) and at 6000rpm i got 30 degrees. I had forgotten to disconect and block the vacuum hose so i checked at 3000rpm again and got 20 degrees? It was my first time using a strobe hence not 100 % but i think the timing is advancing ?

The fuel pump, check valve, accumulator and fuel filter are all quite recent fitments with hardly any mileage done and it doesnt have a catalytic converter as far as i am aware, also the air pump was removed before i bought the car.

IanTBoyd · IanTBoyd's Garage

Valve adjustment?

James Brown · James Brown's Garage

I would look at those injectors next. See if there is a Bosch fuel injection tech around there that could test them.

kiwiokie · 04-27-2011, 05:07 PM

Gas/accelerator pedal not opening throttle fully?

Flat6pac · 04-27-2011, 06:00 PM

Bushings gone on the trans bell swivel or on the engine bell swivel console.
Bruce

GeorgePoulias · GeorgePoulias's Garage

Had a similar problem last week, the connector to the frequency valve had come loose and was not getting a single, had no power at all.
Plugged it back in and was good to go.

trond · trond's Garage

I believe you might find the problem in the CIS system

Mine too (1980SC) was gutless until I converted to EFI. I was always thinking it felt like it had about 90Hp and it felt as slow as my landrover.

With EFI it is good, almost as quick as a modern family sedan

James Brown · James Brown's Garage

Quote:

Originally Posted by trond

almost as quick as a modern family sedan

nice!

johntom · 04-28-2011, 02:00 AM

Quote:

Had a similar problem last week, the connector to the frequency valve had come loose and was not getting a single, had. no power at all.
Plugged it back in and was good to go.

Whereabouts is the frequency valve?

GeorgePoulias · GeorgePoulias's Garage

its a plug behind the CIS on the same side as the throttle, flash a light and check with a mirror in behind to see that there are no open vacuum lines or electrical connectors.

javadog · 04-28-2011, 06:38 AM

Quote:

Originally Posted by johntom

Whereabouts is the frequency valve?

There isn't one on your car. The CIS system used in the UK is not the same as the one used in the US.

JR

DaddyGlenn · DaddyGlenn's Garage

Lots to check.

I had a similar issue and found that the throttle bushings on the engine end were shot and I was only getting about 1/2 throttle. Changed the bushings and adjusted the throttle cable and... Zoom!

johntom · 05-03-2011, 10:07 AM

Hi
if the throttle bushings were bad would it stop me from being able to rev to 6000rpm or would it just open the throttle slower making the car feel slow ?

What are the correct timing settings/rpm for a 1980 UK 3.0SC (180bhp?) ?

javadog · 05-03-2011, 10:27 AM

Bad throttle bushings prevent you from opening the throttle completely, which reduces power. I'd think you'd still be able to rev to 6,000 rpm in neutral and in the first few gears.

5 degrees BTDC @ 900rpm
23-29 degrees BTDC @ 6000rpm
Vacuum control detached, in both cases

JR

johntom · 05-03-2011, 10:32 AM

Hi
many thanks, i can still rev to 6000rpm in neutral (ie when i looked at the timing) but it doesn't want to go there when driving !

How would i confirm the bushings are shot and is there a throttle cable as such ?

javadog · 12:07 PM

You have to look at the cable and the linkage. Start by looking at linkage attached to the throttle pedal, then the forward end of the cable, then the linkage underneath the car and finally the linkage on the motor. Just follow it from one end to the other. The bushings will be obvious, when you look at the various parts.

A simple test is to have someone floor the throttle in the car, with the engine off, and then check to see if any additional rotation of the throttle shaft is possible. If you can turn the throttle shaft more than what the linkage achieves on its own, you have a problem.

JR