Idle adjustment question, Idles high or slowly stalls Options

[emerygt350]

Have you closely examined the stacked elbow? The smallest of cracks, that like to hide, can produce a high and unadjustable idle speed.

The stacked elbow is new, from 914Rubber. I replaced all the vacuum lines and fittings, as well as all gaskets, with new ones. I also made sure there were no rust (or other) holes in the intake manifold.

Put the dizzy on 1 but don't bother hooking up the advance. Disconnect all vacuum hoses and plug them. Put the mighty vac on the mps. Give the mps 17-20 inhg. If the idle is still high, retard the timing and see what happens.

I'll give it a try next time I have a chance. However, it's a pain to change settings on the distributor, since it means pulling it out and then checking/adjusting the advance afterward.

Switching to 1 isn't crucial, just better in case you want advance. You don't want retard. It just doesn't work on the 123. The dizzy is set to turn on at some small level of vacuum where the original was meant to be much more analog.

I have mine set so I can access the pot with the dizzy in the car. I use a little mirror on a stick. Super easy. If your dizzys vacuum port is pointing towards cylinder 1ish you can do it no problem.

[BillC]

Put the dizzy on 1 but don't bother hooking up the advance. Disconnect all vacuum hoses and plug them. Put the mighty vac on the mps. Give the mps 17-20 inhg. If the idle is still high, retard the timing and see what happens.

I'll give it a try next time I have a chance. However, it's a pain to change settings on the distributor, since it means pulling it out and then checking/adjusting the advance afterward.

Switching to 1 isn't crucial, just better in case you want advance. You don't want retard. It just doesn't work on the 123. The dizzy is set to turn on at some small level of vacuum where the original was meant to be much more analog.

I have mine set so I can access the pot with the dizzy in the car. I use a little mirror on a stick. Super easy. If your dizzys vacuum port is pointing towards cylinder 1ish you can do it no problem.

Okay, I changed the distributor to "1" and plugged all the vacuum ports. And..... no difference. It will still hang up around 1600 RPM and then slowly start drifting down and stalling. I even tried connecting the MityVac to the MPS and setting it to 17" vacuum -- no difference, it will not idle where it should.

Also, drivability is noticeably degraded from when it was on the "A" setting with retard vacuum connected. Not horribly worse, but it just doesn't work quite as well. So, I'm going to set it back to "A" with retard vacuum, and will just live with it until @JamesM finishes that MS system for me.

[emerygt350]

What vacuum is the engine making while it is doing this behavior and what is the timing doing?

[BillC]

What vacuum is the engine making while it is doing this behavior and what is the timing doing?

The vacuum is doing the exact same thing it's been doing all along -- getting lower (closer to atmospheric) the lower the RPM gets. I can't measure the timing because the engine won't stay running long enough at 1000 RPM to measure before it stalls.

[emerygt350]

I don't need to know what it's set at, we need to know what it is as the car dies.

[Superhawk996]

I’m sorry that you’re still struggling with this months later after throttle body swap, etc.

If I were you, I’d be going back and questioning all my assumptions.

As I re-read this thread there are lots of assumptions being made about fuel mixture (no photos of plugs - are they rich or lean?).

There appears to be a new reference to timing being as much as 25 degrees at idle? Have you verified the orientation of the dizzy drive? There are 12 teeth on the dizzy drive - each amounting to 30 degrees of advance or retard depending on how it’s installed.

Likewise - as the vehicle is spiraling toward stalling have you tired zapping it with starting fluid and what happens? Has it been confirmed that when the engine is hot that the valves still have some clearance and valves aren’t being held open forcing the loss of vacuum at low rpms? Even silly things like making sure the coil has a solid 12v even as the vehicle is losing vacuum and trending towards stalling.

These things really shouldn’t be in question. Perhaps I’m just not caught up or missing details or things that weren’t documented here?

If all else checked out after re-verification of assumptions I might even pull the oil pump just to see if I could see any ID on the camshaft nose (not all do).

Again so sorry that we haven’t helped you get this resolved by now. I wish I had the magic answer in my pocket but simply don’t have enough info at this point. It’s gotta be very frustrating I’m sure. Keep goin, be data driven, and logical in the methodology (as you have been) and eventually this will get solved.

[rjames]

So you can drive the car, but it idles high and then will eventually stall?

As has been stated, with Djet, a vacuum leak will lead to a high idle, but won't cause it to stall. I wonder if at idle if the engine is not getting enough fuel or too much fuel. How do the plugs look?

Instead of just swapping out the throttle body without verifying if it's bad, I would do a smoke test and verify that there is indeed a significant vacuum leak and where it's at. Undoubtedly the throttle body will be leaking a little (they all do at this point unless rebuilt), but the airbox is prone to rusting out from the inside and could be a culprit. A homemade smoke machine can be made for the cost of an empty jar, some tubing, and epoxy to seal it all up.

In addition to a possible vacuum leak, I'm wondering if the ECU is not sending the correct signals to the injectors, which could account for why it's stalling.

I chased my tail for months trying to figure out why my car would run great but would intermittently stall at idle (rarely in the driveway, but usually when out on the road). Turned out the ECU was bad and would intermittently cause a full rich condition.

I'm not one for just swapping parts out randomly, but the ECU is something to consider.

[emerygt350]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

[Superhawk996]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

In the interest of extending this thread. (IMG:style_emoticons/default/av-943.gif)

In re-reading - recall his vacuum gauge wasn’t accurate. I’m not sure that ever got resolved.

Too many assumptions . . . At least on my part.

Here’s the thing - timing may keep vacuum from reaching something like 17-20” Hg but it’s not going to account for vacuum down at 8” Hg which was what was reported early on but with the questionable gauge? (IMG:style_emoticons/default/confused24.gif)

[emerygt350]

Last I knew the engine had little vacuum across the board and dropping at idle. Timing affects vacuum, that is why I am always pestering you for those two bits of information.

In the interest of extending this thread. (IMG:style_emoticons/default/av-943.gif)

In re-reading - recall his vacuum gauge wasn’t accurate. I’m not sure that ever got resolved.

Too many assumptions . . . At least on my part.

Here’s the thing - timing may keep vacuum from reaching something like 17-20” Hg but it’s not going to account for vacuum down at 8” Hg which was what was reported early on but with the questionable gauge? (IMG:style_emoticons/default/confused24.gif)

I suspect it's still a valve/timing combo. Incredibly off spark timing and valves in combination. The micro squirt won't help any of that.

[Superhawk996]

I suspect it's still a valve/timing combo. Incredibly off spark timing and valves in combination. The micro squirt won't help any of that.

(IMG:style_emoticons/default/agree.gif)

The only thing the microsquirt gets is control over a cam that won’t work with d-jet.

The thing is even some of the most aggressive cams with huge overlap still wouldn’t account for 7-8” Hg of vacuum at idle. Hard to believe that would be in his case unless the builder was incompetent. I’m not even sure if a cam that aggressive is even commercially available for the T4 engine. Again - that comment is predicated upon an assumption that 7-8” Hg was an accurate reading so who knows.

[rhodyguy]

In case I missed it, how long, in minutes, will your MPS hold a vacuum? MPS out of the car.

[BillC]

This thread has gotten too long and there's too much confusion and TLDR. So, starting a new thread with all the data listed as thoroughly and concisely as I can make it. Please go here for all future discussion on this topic.