manual how to adjust the 3.5 engine (ignition and A/F ratio)

[werminghausen]

Set dwell at 30 degrees, Ignition timing at about 3 degrees ATDC (w/vacuum) about 8/9 degrees BTDC (w/o vacuum)..vacuum at 13" (w/vacuum) and 17" (w/o vacuum).
Idles poorly in a way...set pressure at 32psi...drives poorly. Not much power.

I measured AFR 17.4 on the way coasting, 13 at acceleration and 24 at idle...
How can this engine be so lean?
Didn't touch MAP sensor.
I was guessing that AFR is too rich but it is the opposite?
What is wrong?
Is this the reason the engine performed poorly?
Need help

[Frank Reiner]

W:

I think that with the O2 sensor at the present location, the readings, unfortunately, will not be useful. Typical sensor location is just downstream of the joint between exhaust manifold and the downpipe.
Even with an electrically heated sensor, the active sensing components need the heat of the exhaust gasses to reach a dependable 600 degF.
If the sensor is not heated, it really is imperative that it be located as far upstream as possible.

[Graham]

Originally Posted by werminghausen

Did you stuff a rag in the pipe of the sensor or the other one?
No excuses.. I knew that it is not 'correct' when I did it.. I was lazy, didn't want to mess with R&R the muffler... too bad.
I'll try to deal with it. I'll try it out.
Any more suggestion in order to get better readings?

I'll try to use the other MAPS.

Stuffed rag to partially block other pipe so as to force most of flow to go by sensor. Did that when I tried a home made clamp-on sensor holder before going to permanent installation.

Regarding sensor location. For cars with cat converters, the first narrowband O2 sensor is normally close to the manifold. But for wideband sensor in non catalyst cars like this, Innovate even sell a pick up that clamps on tailpipe and say that is a valid option. But with double pipe system, I would put it closer to engine in a place you can get at. I posted pic of where I chose upthread. For LM-2 I would have chosen same place but put sensor on outside of pipe so it could be more easily accessed to replace bung plug.

[Graham]

Originally Posted by werminghausen

Set dwell at 30 degrees, Ignition timing at about 3 degrees ATDC (w/vacuum) about 8/9 degrees BTDC (w/o vacuum)..vacuum at 13" (w/vacuum) and 17" (w/o vacuum).
Idles poorly in a way...set pressure at 32psi...drives poorly. Not much power.

I measured AFR 17.4 on the way coasting, 13 at acceleration and 24 at idle...
How can this engine be so lean?
Didn't touch MAP sensor.
I was guessing that AFR is too rich but it is the opposite?
What is wrong?
Is this the reason the engine performed poorly?
Need help

Those lean readings could be due to the sensor location. Try the rag trick and see if they go up, especially at idle. It could be you are measuring a mix of exhaust and outside air.

If the figures are right, fuel is just not getting to the engine or through the injectors. Forget MPS for moment.

At idle, the MPS has no function if the TPS is set up properly. Make sure that is set properly (see link upthread), then set ECU knob in center (11clicks either way?) and turn it each way one or two clicks at a time and see how AFR changes. Give engine a short burst in-between settings and give it a few minutes to settle down. Try to get to about 4% CO (13AFR) at idle with engine warmed up.

If mixture remains lean even with rag in one tailpipe, then maybe you have another problem. But maybe relocate bung first!

Then, I would check fuel delivery rate downstream of fuel pressure regulator. You should have 1L/30sec flow. You can measure this by connecting a hose to FPR or damper outlet and either jumpering Fuel pump relay or power fuel pump directly from battery (need a friend to help!). There is also a method in manual for checking individual injector fuel flows. (also in this link, along with much more!)

One other thing - do try and confirm that you are getting centrifugal advance (even if you don't know what rpm are exactly) Rev engine hard and you should see advance go up to 30deg+ BTDC.

[Tomguy]

There's a big issue here IMO, that is if you're using a genuine wideband O2 sensor that would be used in an actual car (not a tailpipe sniffer), they need heat to read it accurately and it won't be hot enough that far back.

[Graham]

Originally Posted by Tomguy

There's a big issue here IMO, that is if you're using a genuine wideband O2 sensor that would be used in an actual car (not a tailpipe sniffer), they need heat to read it accurately and it won't be hot enough that far back.

The manufacturer of the Innovate meter Martin has sells the tailpipe adapter I posted a picture of and says that measurements can be made at the tailpipe.
So do several other meter manufacturers.

The wideband sensors used in these meters have built in heaters that are accurately controlled at the required temperature. In fact it is recommended that they be mounted away from excessive heat as you might get from cat converters or turbo charged engines.

Only issue IMO with tailpipe location, is the dual tailpipe which can cause backmixing with air.

[werminghausen]

Graham, thanks,

TPS should work properly. I have it set up and never touched it again...well I have removed the intake during R&R of heads but other than that...nothing.
I also believe that trigger points work, but didn't check proper angles. I had them out lately when I worked on the distributor. Do you think trigger points are in question?
Fuel flow: I have a new fuel pump going strong... I don't think that something is wrong here. Fuel pressure is very constant, not moving anywhere during driving. I have the gauge inside.
I had the injectors remanufactured and flow tested...should be all set.
Do you think this is enough? I cant open the link.

I am reading 17.5 cruising with 60 mph (I mentioned coasting...which was wrong)
I'll try and stuff the other pipe for reading the AFR at idle. During driving the readings are more reasonable compared to idle. I can try and remove the bung and choose another spot...
grrr. I'll look into your spot or alternatively right before the second muffler (instead of after the second muffler/end pipe). I could weld there without removing the pipe I think.

distributor: It advances well to 30 plus ATDC at higher engine speeds..no problem here.

[Mike D]

I hope you mean BTDC at engine speed.

[Graham]

Originally Posted by werminghausen

Graham, thanks,

TPS should work properly. I have it set up and never touched it again...well I have removed the intake during R&R of heads but other than that...nothing.

The important thing with TPS, is that the stop is set correctly to signal to ECU that throttle plate is closed and it should use ECU idle circuit rather than MPS for mixture control. More to do with linkages than TPS itself. You will find out if it is correct when you try adjusting the ECU knob. If it causes AFR to change then TPS & linkage is set up properly.

I also believe that trigger points work, but didn't check proper angles. I had them out lately when I worked on the distributor. Do you think trigger points are in question?

No way to know from here, but when my Trigger point rubbing blocks wore down I had a rich mixture, not lean.

Fuel flow: I have a new fuel pump going strong... I don't think that something is wrong here. Fuel pressure is very constant, not moving anywhere during driving. I have the gauge inside.
I had the injectors remanufactured and flow tested...should be all set.
Do you think this is enough?

Sounds like fuel system is good. But if you are not getting enough fuel, then fuel flow test is easy enough.

I cant open the link.

It works here. It is a large MS Word file. Try this zip instead.

I am reading 17.5 cruising with 60 mph
I'll try and stuff the other pipe for reading the AFR at idle. During driving the readings are more reasonable compared to idle. I can try and remove the bung and choose another spot...

I tried the easy way myself first At highway speed, you are getting more exhaust flow, so less chance of backmixing, I guess.

grrr. I'll look into your spot or alternatively right before the second muffler (instead of after the second muffler/end pipe). I could weld there without removing the pipe I think.

Using a clamp on saddle is another option.

distributor: It advances well to 30 plus ATDC at higher engine speeds..no problem here.

30 deg BTDC is good.

Where did you measure vacuum? The figures you quoted were confusing because you gave vacuum with and without vacuum! The manifold vacuum should be measured with all vacuum lines connected (to distributor and off back of manifold to Transmission, chassis systems etc.) Don't measure on line to distributor. Either use tee into MPS vacuum line or tee into the line that goes to the chassis locks etc on passenger side rear of intake manifold.

If you have 14-17" vac at idle, then your MPS "should" work. If mixture is still lean when driving, next step would be to try spare MPS.

[werminghausen]

Originally Posted by Mike D

I hope you mean BTDC at engine speed.

Sorry my fault...of course BTDC

[werminghausen]

[Where did you measure vacuum? The figures you quoted were confusing because you gave vacuum with and without vacuum! The manifold vacuum should be measured with all vacuum lines connected (to distributor and off back of manifold to Transmission, chassis systems etc.) Don't measure on line to distributor. Either use tee into MPS vacuum line or tee into the line that goes to the chassis locks etc on passenger side rear of intake manifold.

If you have 14-17" vac at idle, then your MPS "should" work. If mixture is still lean when driving, next step would be to try spare MPS.[/QUOTE]

Hi Graham , thanks so much.

fuel delivery rate: I guess that fuel delivery is fine as I checked fuel pressure during driving an even if I floor the thing the pressure doesn't drop a bit.

I am measuring vacuum from the line that draws vacuum for central locking
I disconnected the check valve and put a gauge on.
It shows around 13" at idle with the vacuum line of the distributor connected
If I pull this line vacuum rises to 17" Hg.


So now there is the question (assuming the lean AFR reading during driving @17.5 is correct) how to get the mixture richer?
Or would you check the plugs? in order to verify if mixture is really too lean?
I can try and go richer if I install the spare MPS? or if I turn fuel pressure further up?

How can I get some progress here?
Martin

[Graham]

Originally Posted by werminghausen

fuel delivery rate: I guess that fuel delivery is fine as I checked fuel pressure during driving an even if I floor the thing the pressure doesn't drop a bit.

You are probably OK, but pressure doesn't guarantee flow. You can have 2bar pressure and almost no flow.

I am measuring vacuum from the line that draws vacuum for central locking
I disconnected the check valve and put a gauge on.
It shows around 13" at idle with the vacuum line of the distributor connected
If I pull this line vacuum rises to 17" Hg.

I don't understand those numbers. When you pull the vacuum line to the distributor, unless you plug it, you are creating a vacuum leak and this should cause the vacuum to go down.

So now there is the question (assuming the lean AFR reading during driving @17.5 is correct) how to get the mixture richer?
Or would you check the plugs? in order to verify if mixture is really too lean?
I can try and go richer if I install the spare MPS? or if I turn fuel pressure further up?

How can I get some progress here?
Martin

You could try any of those ideas - changing the fuel pressure would be easy. But just do this to see if it makes a difference to your AFR. If it does, then change to other MPS and try adjusting it.

But I wouldn't do much adjustment with the bung perhaps not in the best place.

[Tomguy]

I assume the 3.5 is the same as the 4.5 and the distributor vac is from the throttle body, NOT the manifold - so any leak there wouldn't affect manifold vac. Make sure you're actually measuring manifold vac (I used to pull off the central locking line & measure straight from there).

[Graham]

Originally Posted by Tomguy

I assume the 3.5 is the same as the 4.5 and the distributor vac is from the throttle body, NOT the manifold - so any leak there wouldn't affect manifold vac. Make sure you're actually measuring manifold vac (I used to pull off the central locking line & measure straight from there).

Martin did say he was connecting off the central locking connection.

Re a leak on vac line to distributor not affecting manifold vacuum. I must say I haven't tested that recently enough to remember.

But think about it. With the throttle plate closed at idle, and the port that connects to the distributor under the throttle plate, wouldn't the vacuum in the throttle body below the plate be close to same as in manifold and therefore affected by disconnecting the vac line at distributor?

[Mike D]

Not quite. Vacuum measured at right below the throttle bottle will be a bit less than what is measured further down the plenum. Compare it to a funnel. Pressure is highest at the narrowest part of the neck and less at the widest part.