Edit: Problem gone. Turned out that the ignition module was at fault. Replaced it and it drives ok now.

Thanks anyway for all the help.

/Bjorn


Hey.

In the process of trying to tune I encountered this:

While cruising (any speed at steady throttle) the engine starts missing, it's like it's dropping cylinders... runs like crap... but if I lift the gas, or gives more it clears up... why?

Anyway, here's some info.

I'm using ARAP, now timing around 20-ish degrees (detonation prone), fuel pressure 50 psi, inj const 23,8
(350) 22 lbs injectors (new).
New o2 sensor. no AIR in driverside header (where o2 is).

Some data I got (ease)..

I'm in cell 10 at cruise, blm132 int 128.
tps about .95 V
Revs are app. 1800-1900 rpm
speed app. 50 mph

With the above conditions I see that for about 30 seconds O2 volts drop to 0.08V and around until (this is where I feel engine missing) I let throttle up (0.54V) and observe o2 spike up to 0.9 and then swinging back and fourth...

So.. at acceleration things are ok and also WOT (the little I have done). On deceleration I have some popping (need more timing I think).

So... if someone knows what's going on I would be very grateful...

Thank a million..

Bjorn

 

From the sounds of it, you have Highway mode enabled.

The popping your hearing from the exhaust on decel means your probly running rich.

 

Yeah, does sound like you're hitting highway mode or something. Are you sure you started with a virgin bin? You might be running someone elses modified copy with a too lean hiway mode set or something.

 

Forgot to add, that popping in the exhaust on decel isn't always a true rich condition with EFI. I get some pretty nasty popping in my exhaust on decel or if i rev it hard like an idiot. Watching it on a scan tool the number and magnitude of popping seems proportional to how cleanly i enter / leave DFCO. Meaning, as i approach/enter DFCO i will see some very small pulsewidths, on the order of 0.5 - 0.8mS (off the top of my head). My best guess is that this is actually too lean to fire in the chamber (especially when you factor in injector opening time, basically next to no fuel is flowing) so it instead builds up in the exhaust and goes off when it hits the cats or something.

I'm sure if i cared i could do some more extreme low MAP VE and timing work, but as it is i kinda like the rough edge on the decel sound. Reminds me of my old carbed 85.

 

Sounds like as mentioned in lean cruise, or just missed the tune and going further in the wrong direction. That TPC value for that speed sounds a bit high.

At 20 at cruise seems low.
Might cut an past your timing table.

 

50 MPH seems a bit low for highway mode, unless someone has played with the bin. Take a look at the highway mode parameters, minimum speed, TPS %. It really does seem like someone has tinkered with your bin.

 

Hey..

Thanks for all the info... well tonight I did some testing.

I did look up the lean parmeters and I had min speed 55 mph to enable lean cruise but I was at about 60 mph when O2 dropped..

So, I tested, raised min mph to 160 mph.. burned and drove..

but that wasn't what caused the missing it seems.... but you were all correct, now the O2 drop (lean cruise) was no more (unless I drove it too little time).

Well, that doesn't really matter, since it still misses....

Attached is (hopefully) a shot of a 3:d gear steady throttle run where the engine REALLY misses... it increases until I let off..

Also, my spark table.. which is arap + my efforts to stop major pinging.

My bin is ARAP downloaded from bin archive at ...diyefi IIRC.

Anyway, what is wrong?

Maybe I just need new plugs?? reson being that I had a little incident recently where I managed not having eprom fully seated or so it went limp home.

That was not nice. It barely barely ran and extremely rich.

I don't know if I the plugs are ok but it does run on all cyl's most of the time...



If it's not that I'm lost

Tack (thanks)

/Bjorn

 

Ok, next pic.

 

Out of curiosity, what type of gasket are you using on the distributor?
The charts look ok, do you have a spare Ignition module you could try? If it is dropping spark it may be module related.

 

I should have mentioned that when I ran the car today (ran total of maybe 15 min) it worked fine to begin with..

So, works good when cold and also in open loop.

It MAY be that the missing got worse the more I drove..not 100% sure.

As far as disturbitor gasket.... I'm not sure what you are asking.. nor would I know without looking.... sorry...

/B

 

Pulled a plug this morning.

It's tan/grey. Looks normal to me.

They are Delco R43S if it matters anything..

 

I found that the cork gaskets that come with some of the TPI intake gasket sets is too thick and the distributor gear doesn't mesh properly which causes an ignition "miss".