1973 Wagoneer - Full Size Camping Goodness

[Dr. Marneaus]

If the grinding continues after the change in tune it would be worth checking out.

Hunting will be helped by the timing function as well, because it can react immediately, where fueling changes and idle air bypass lag behind. So that's another reason to look at this down the road.
At this point, I'd leave the hunting for last. Unless we are hunting wabbit...

Couldn't adjust lower than 28PSI and at that point the adjustment screw was basically loose and had no tension on it. I set it to 30 and reset the displacement to 400. It fired up kinda sluggish but was idling real nice even when stone cold. Going to give this setup a try.

 

[Dr. Marneaus]

Okay, so it seems a bit improved over the last tune, but still bein' weird.

It has generally only "hunted" one time during cold starts. comes up to around 1000 rpm, tries to settle down to like 750-800 and bogs, then comes back up and idles 100% normal.

However, yet again, when i hope in and try to drive, it struggles to hit 1800 RPM that first time. as soon as i can get it over 1800, it straightens out and flies right. super bizarre that it almost refuses to hit 1800 rpm, then all is well once i baby it there.

That did, indeed, happen before the HEI, but not every time. seems odd.

otherwise its cruising real well. I just cant get over the bogging down when i try to drive it initially.

I also havent noticed any of the hot start stumble either.

 

[Coachgeo]

could why it begins to fly straight be more to do with warmth. As engine warms and expands it seals up a compression loss from somewhere or something else not wanting to work well in a cold chunk of metal that seems to like better a hotter environment? Sparks plugs? Spark plug wires even? Intake sucking in air around base? Hopefully something stupid and easy to fix.

 

[Dr. Marneaus]

I've searched tirelessly for vacuum leaks.

If I fire the truck up and let it sit for 30 minutes until its been at full operating temp while stationary, it still does it when I try to drive. If I hop in after the engine idles for 30 seconds and take off with an engine coolant temp of 50*, it still does it. I dont think its a temperature thing given that it goes away within a minute or two of driving, i dont think thats enough time to effect anything especially since it happens at 50* or 170*

 

[Dr. Marneaus]

looking more and more at FJ cruisers and 4runners on craigslist........lol. oh to be poor.

 

[Comanche Scott]

What does the stoich look like when it's struggling?

 

[Dr. Marneaus]

What does the stoich look like when it's struggling?

When it stumbles, the AFR jumps way up. So, it seems to be a no fuel thing, rather than it being flooded or anything.

 

[Comanche Scott]

That is an awesome find.

Run a hose long enough to clip the fuel pressure gauge to the wiper arm or hood lip. Just somewhere you can see it when you drive.
If fuel pressure doesn't drop, call MSD tech. There is an output issue to the injectors. May be based on an input. Or may be the injector driver.
If fuel pressure drops, then either fuel electrical, or fuel hydraulic issue. We can cross that bridge when you get there if needed.

 

[Jurfie]

Carburetor jets plugged? Sorry if it has been suggested already and/or not applicable.

 

[Dr. Marneaus]

That is an awesome find.

Run a hose long enough to clip the fuel pressure gauge to the wiper arm or hood lip. Just somewhere you can see it when you drive.
If fuel pressure doesn't drop, call MSD tech. There is an output issue to the injectors. May be based on an input. Or may be the injector driver.
If fuel pressure drops, then either fuel electrical, or fuel hydraulic issue. We can cross that bridge when you get there if needed.

Cool got it!

So do we not trust the fuel pressure gauge on the MSD display? Because it never skips a beat on that readout

 

[Comanche Scott]

Cool got it!

So do we not trust the fuel pressure gauge on the MSD display? Because it never skips a beat on that readout

Exactly, think of it as just another input to the ecm that may be an issue.

 

[Dr. Marneaus]

Exactly, think of it as just another input to the ecm that may be an issue.

cool, i think i have a spare nipple hanging around that I can run the gauge to the regulator with.

 

[Dr. Marneaus]

Scott,

One of the folks over on the msd forums suggested that this may be O2 sensor related, and sounds very similar to what alot of folks have experienced with a bad O2 sensor or a short in the wire, etc. Think there's any validity to that?

Several months ago on a trip I had a historic error come up for the O2 sensor. My understanding is that that means something went wrong, but then it went right and the issue went away. I cleared the code on that trip and it happened one or two more times. It hadnt happened in a long time but it popped up a few weeks ago on a cold start. I cleared and it hasnt been back since. Any thoughts on this?

 

[Comanche Scott]

Contact the MSD tech support. If it is a real issue they will know about it, and may be willing to supply a new one free of charge.
You can point them to your threads here, and on FSJ, for a bit of a push.

 

[Dr. Marneaus]

Of course on Saturday in the 20* weather it fired up all perfect idles all perfect and started driving all perfect.

That makes me even more irritated, because I guarantee that wont be the case next time I start it.