Ignition timing & idle

[Matteo1991]

Hi everyone, I have a range rgover classic with 3.9 v8 rebuilt with a kent cam h 180 ... new oem stepper motor and I have no air leaks in the plenum chamber, rover pressure gauge has no fault code, my problem is in the gear shift, when the clutch is released with little gas the engine accelerates revolutions per minute 1200-1500, or stopping at an intersection before descending to 700 rpm takes about 3 seconds. I have setting the idle but i have a small difference... i have setting high timing ignotion 19° i think is the causes.... whow do you think?

[Pedro_The_Swift]

I have the same cam,, but try the advance at 10-12...
I thought the slow engine wind down was a pollution thing?

[Matteo1991]

I hadn't thought about pollution, so it could be a characteristic of the cam

[PhilipA]

If the car is moving and foot off accelerator , the stepper motor will raise the revs to about 1200 until you stop.

The formula in the ECU is speed signal positive +Throttle position sensor less that 0.49 volts ( ie foot off accelerator) + revs less than 1500 then the stepper will raise revs to 1200.

It is primarily to give a smooth shift to 1 in an auto, but AFAIK they fitted it to manuals as well.
It is normal but exaggerated by your incredible static timing. Reduce the timing to 10degrees BTDC. You maybe should also check that the centrifugal advance is moving freely and maybe oil the shaft under the rotor if you haven't done so.
Regards Philip A

[Matteo1991]

I can't keep the times at 10 ° because I would have no performance....the rotating masses are lubricated but compared to another distributor the springs are harder, could this be the cause?

[ian4002000]

When setting a distributor timing there are three settings to check
1 Initial timing.
2 Amount of timing advance when the revolutions are increased
3 Vacuum advance when the vacuum pot is given vacuum

You need a timing light with and advance dial to check a distributor properly and check all three settings

The other item to check is to ensure that o degrees is actually zero and the piton is at top dead center.

I am not sure of the specifications of a rover V8 distributor but most engines run something around 8 deg initiial and total advance of 36 deg
Vacuum advance can be around 8 degrees and vac advance was normally used on with automatic transmissions in the old days.

The advance weights in your distributor can become stuck or may have been set incorrectly. If you are lucky you may find someone with a distributor checking machine available in your area.

Sorry to confuse the issue.

Ian
Bittern

[Matteo1991]

Thank you for your tips!

[Red90]

Yes. If you are needing to force the static timing to get performance your distributor is not working properly. You can determine the timing curve with a timing gun by increasing the engine speed.

[rick130]

Yes. If you are needing to force the static timing to get performance your distributor is not working properly. You can determine the timing curve with a timing gun by increasing the engine speed.Or the curve isn't correct for the cam/compression/chamber shape/fuel.
But as say, you can determine what you have with a timing light.

[Red90]

Or the curve isn't correct for the cam/compression/chamber shape/fuel.
But as say, you can determine what you have with a timing light.

I don’t think these ancient engines care much about the timing curve. But a broken centrifugal advance would cause these symptoms.

[DiscoClax]

I'd be checking that the timing marks are still accurate on the harmonic. I've had a couple that have moved considerably and they tend to move in the retard direction. Also check the harmonic isn't loose on the shaft. These engines aren't overly sensitive to timing really. I had my stock 3.9 LC locked at 15deg (ie 15 deg static and no advance) for a couple of years before fixing the distributor. Barely noticed a difference after fixing it... My v.high comp stroker is much more sensitive to timing, but the lower comp stockies just don't really care that much (as long as you are in the ballpark, within reason). And that little cam still counts as basically "stock" in my book... If you need that sort of static timing then there's a problem somewhere.

[fredd63]

If you have raised the compression ratio, you will need to have your distributor re-calibrated. Engine will be underpowered at low revs, and have too much advance at higher revs. That is why you find that it regains it's power when you advance the timing. Does it vibrate badly at high revs?

[Matteo1991]

the engine at high speed does not vibrate. if I keep the advance below 19 ° I have the power at high revs from 2500-3000 onwards, at low revs I have no power. when the engine was rebuilt, the heads were leveled and normal pistons were placed. Can it have increased so much compression to cause these problems? I have to clean my distributor because it is full of old and hardened grease ... for the moment I lubricated it with the wd40

[Meccles]

A poorly operating distributor can cause havoc with engine performance. It’s as critical to get correct as rest of engine. If you have to useWD40 to sort of keep it going - then I’d be giving it to an distributor specialist for rebuild if you didn’t want to do that yourself. To have it at 19 degrees says it’s not advancing correctly.

[350RRC]

If its full of hard grease the weights on the centrifugal advance mechanism won't be able to move............. hence the 19 static degree advance.

If it is really bad the vac advance might be somewhat inhibited as well.

Clean it up and enjoy life.

DL

[5380]

Hi everyone, I have a range rgover classic with 3.9 v8 rebuilt with a kent cam h 180 ... new oem stepper motor and I have no air leaks in the plenum chamber, rover pressure gauge has no fault code, my problem is in the gear shift, when the clutch is released with little gas the engine accelerates revolutions per minute 1200-1500, or stopping at an intersection before descending to 700 rpm takes about 3 seconds. I have setting the idle but i have a small difference... i have setting high timing ignotion 19° i think is the causes.... whow do you think?

Matteo,
I agree that sticking advance weights/ dry hard gease in the shaft will cause this. I worked at a country Land Rover dealer for 12 years and this problem often arose. One of the causes was caused by people wriggling the multi pin connectors to the air flow meter etc.when they were un-plugging things. This wriggling often opened up the female pin sockets causing intermittent/poor connections. This caused lots of head scratching for us. One day, I had a customer with a 3.9 Disco with this problem and I as I moved the airflow meter connection the idle suddenly behaved normally. When we separated the connector, some of the pin sockets had wider slots than the others. We tightened them up with a fine jewellers screwdriver until all the pins and sockets looked even and straight and all was well! The owner addmitted pulling some of the connections apart looking for water after a wet 4WD trip. I always checked them after that and advised home mechanics to pull all electrical conectors apart without twisting or wriggling them. A simple fix if this is the problem.
Good luck!
5380.

[Matteo1991]

hello guys, I cleaned every part of the distributor, I removed all the grease and I lubricated the rotating masses with oil ... I reassembled the distributor and now the tdc moves alone from advance to delay from the pointer illuminating it with the strobe gun