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> Fuching DJet issues, Running out of things to try
ChrisFoley
post Jun 16 2019, 07:28 AM
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QUOTE(saigon71 @ Jun 16 2019, 07:12 AM) *



my 914 idle hunts the least with mixture knob set to full right (clockwise).



This is a clear indication that the MPS is adjusted too lean.
When the MPS is properly adjusted, the best idle can be found near the middle of idle mixture knob range.
Of course I am assuming that no other FI problems are contributing to the lean running.
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JeffBowlsby
post Jun 16 2019, 07:58 AM
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A lean condition may also be corrected by increasing the fuel pressure a psi or two, by eliminating vacuum leaks, unplugging TS2 sensor.
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rjames
post Jun 16 2019, 01:44 PM
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The idle hunt isn’t a slight hunt. It’s from 1000 rpm to almost 0. The ecu and throttle body screw are adjusted to allow it to run that good.

Thinking about this more as I wait for a new fuel filter to be delivered, I’m starting to question fuel being an issue since when the engine is cold it idles high for a good couple of minutes. Then I remember that the fuel pump gets quieter when the idle drops.

I’m still going to replace the filter and check the pump while I’m at it and then we’ll see where I am at. If it’s not one of those, then I think it’s the MPS.
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rjames
post Jun 20 2019, 08:34 PM
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Okay, problem remains after replacing the fuel filter and verifying the fuel pump is doing its job.
Some new info though that I can’t believe I didn’t notice before:
I verified the timing (again). It was slightly off. Vacuum line was disconnected and plugged. After setting timing and with the vacuum line still plugged, it idled steady at ~1800 rpm. No fluctuations in idle. As soon as I plug the vacuum line back into the distributor vacuum canister, the idle drops to 1000 and fluctuated between 1000 and almost dying. Remove and plug the vac line and it’s back up to a steady 1800 or so.

No amount of adjusting the throttle body screw will bring it down to 1000 with the vac line connected. I can get the idle higher, but not lower. The ecu knob is effective at only keeping the rpm stable at idle (as it should).

AFR reading reads a steady 13.4 when I the vac line is disconnected and plugged.

Does this mean it’s my distributor that’s the prob? I know the canister leaks, but shouldn’t it still idle around 1000 even with the dist vacuum line off and plugged? Does that point to an mps that is bad or needs adjusting?
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JeffBowlsby
post Jun 20 2019, 09:16 PM
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No effect during adjusting the air screw points to a vacuum leak.
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rjames
post Jun 20 2019, 10:45 PM
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QUOTE(JeffBowlsby @ Jun 20 2019, 08:16 PM) *

No effect during adjusting the air screw points to a vacuum leak.


There is effect- I can increase the rpm, just can’t get it down past 1500.
If there was a vacuum leak, why would the rpms drop to 900 and fluctuate down to almost 0 when connecting the line to the distributor? Wouldn’t the rpms stay up? At least enough to keep it running without opening up the TB screw a ton?

Seems odd that’s it would do exactly what it did when my original MPS failed, especially after replacing all vacuum lines, gaskets, intake boots, injector seals, verifying no leaks in plenum and installing a NOS throttle body.
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JeffBowlsby
post Jun 20 2019, 11:15 PM
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If the air screw is fully closed, the engine should shut down because it would have no air for the combustion process. When air is still getting into the intake from somewhere, it keeps the engine running when the air bleed screw is closed. This is 'free air' or uncontrolled air - air that should not be getting into the intake. A vacuum leak.
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rjames
post Jun 20 2019, 11:31 PM
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QUOTE(JeffBowlsby @ Jun 20 2019, 10:15 PM) *

If the air screw is fully closed, the engine should shut down because it would have no air for the combustion process. When air is still getting into the intake from somewhere, it keeps the engine running when the air bleed screw is closed. This is 'free air' or uncontrolled air - air that should not be getting into the intake. A vacuum leak.


Why do the rpms drop so much when hooking up the distributor? The RPMs don’t go above 1000 when the vac line is connected.
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jcd914
post Jun 21 2019, 12:40 AM
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QUOTE(rjames @ Jun 20 2019, 10:31 PM) *

QUOTE(JeffBowlsby @ Jun 20 2019, 10:15 PM) *

If the air screw is fully closed, the engine should shut down because it would have no air for the combustion process. When air is still getting into the intake from somewhere, it keeps the engine running when the air bleed screw is closed. This is 'free air' or uncontrolled air - air that should not be getting into the intake. A vacuum leak.


Why do the rpms drop so much when hooking up the distributor? The RPMs don’t go above 1000 when the vac line is connected.

It is the vacuum retard that you are hooking up and when vacuum is applied the timing is retarded several degrees (I don't recall how many degrees).
Since this is all part of the original equipment and designed as a system, the engine should idle fine with the retard hooked up.
What is your timing set to?

Jim
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BeatNavy
post Jun 21 2019, 05:28 AM
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I think you may also want to verify your vacuum lines are hooked up correctly.
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Spoke
post Jun 21 2019, 06:05 AM
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QUOTE(rjames @ Jun 21 2019, 01:31 AM) *

Why do the rpms drop so much when hooking up the distributor? The RPMs don’t go above 1000 when the vac line is connected.


So a question could be what is the vac line to the dizzy doing to the timing? It obviously changes the timing such that when the vac line is disconnected and plugged the idle stays at 1600RPM.

When you plug the vac line and idle stays at 1600RPM, have you tried adjusting the timing to reduce the RPM?

How did you verify there are no vac leaks? Did you spray carb cleaner on everything with the engine running or do the smoke test?

Is the AAR closing when warm?
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rjames
post Jun 21 2019, 03:55 PM
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AAR is good.

Eschewing vacuum leaks for a second…

Questions about the distributor operation under current conditions. Bare with me…

My distributor vacuum canister is bad- but will hold vacuum for a second.
So the advance plates move with retard line connected (retards timing/slows idle) but because the canister leaks, the advance plates return to their resting position quickly even though vacuum is still applied.
This would explain why the RPMs drop to the correct RPM when the line is hooked up (retard is applied) and why the idle doesn’t hold steady (canister can’t hold vacuum; timing doesn’t stay retarded), but not why the idle drops to almost 0 RPM, vs going up when the timing is no longer being retarded.

Shouldn’t the idle go up well past 1000 RPM when the canister stops holding vacuum? (retard not applied anymore, timing is advanced), especially if there was a vacuum leak? If there was a vacuum leak, why would it even drop to the correct idle speed when I first hook up the vacuum line? Wouldn’t it always remain higher than ‘normal’? My AFR reads full lean when the idle drops to almost 0, and the idle drops when the distributor canister can’t hold (retard) vacuum. The engine almost dies, and then retard vacuum is available again (canister diaphragm is 'reset' and holds vacuum for a second) , RPMs go up, and then the dance repeats itself.

Could the distributor be directly or indirectly responsible for the drop in idle when it can’t hold vacuum for retard? Is there a way I can rule the distributor out of the equation besides installing a new one?
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914sgofast2
post Jun 21 2019, 07:42 PM
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Sounds like the source of your vacuum leak is the bad distributor advance/retard can. Put another one on the dizzy that will hold a vacuum on both the advance and retard ports, and your problem should be solved. Djets are extremely sensitive to fantom vacuum leaks.
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rjames
post Jun 21 2019, 09:34 PM
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Playing with it again, now it only idles high when cold. After idling high (AAR is working), it warmed up, dropped idle to 1200 rpm and held there for a minute or so. Then it did it’s usual go from 1000 rpm then drop to almost 0 unless I opened the throttle body bleed screw quit a bit. This time it didn’t matter if the hose to the vacuum canister on the distributor was connected or not.
Now it runs for a few seconds with the idle fluctuation and dies after a few cyclyes.
If there was a vacuum leak it would idle high, right?

Could this all be sign of a bad distributor? (BTW, I verified the MPS holds vacuum).

Ugh.
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914sgofast2
post Jun 22 2019, 10:46 AM
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In my experience a vacuum leak causes the idle to hunt as the mps tries to adjust for it, resulting in your symptoms.
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Rand
post Jun 22 2019, 01:05 PM
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I'd say not dizzy. The thing about the dizzy that affects idle timing is the vacuum ports / advance plates. You've been through that. Or have you? The gunk between the advance plates can cause intermittent sticking. Might need to take it all apart, clean, relube, and try try again. (I've been through that and can share pics and tips if you go there.)

Seriously at this point, just get a 123 dizzy. Even if it doesn't solve your problem, it's an upgrade you'll be happy with. You won't regret that expense even if it only rules out problems.
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rjames
post Jun 22 2019, 05:09 PM
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QUOTE(Rand @ Jun 22 2019, 12:05 PM) *

I'd say not dizzy. The thing about the dizzy that affects idle timing is the vacuum ports / advance plates. You've been through that. Or have you? The gunk between the advance plates can cause intermittent sticking. Might need to take it all apart, clean, relube, and try try again. (I've been through that and can share pics and tips if you go there.)

Seriously at this point, just get a 123 dizzy. Even if it doesn't solve your problem, it's an upgrade you'll be happy with. You won't regret that expense even if it only rules out problems.


Rebuilt the distributor trying to fix this issue. A 123 dist is in my future but need to figure this out this first.

Will try looking for vac leaks if I can keep it running long enough.
Although I don’t see how it could be a vac leak if the rpms are low and it won’t stay running. Idle should be HIGH with a vac leak, no?
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rjames
post Jun 22 2019, 09:59 PM
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Any chance this is a compression issue?
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Rand
post Jun 23 2019, 01:17 AM
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QUOTE(rjames @ Jun 22 2019, 07:59 PM) *

Any chance this is a compression issue?

It ran fine. No. Unless there are unspilled beans.
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rjames
post Jul 5 2019, 07:21 PM
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Updates and new info:

Installed new coil and 123 ignition distributor. Install was cake thanks to posts by others here.

Homemade smoke machine revealed 2 vacuum leaks which have been taken care of.
Current situation: I am able to get the car to idle at a steady 1200/1300 rpms. AFR is ~13.
The only way I can get the idle lower is if I move the TPS counter clockwise, but as soon as I do that, the idle drops to almost 0 and maybe comes back up a bit once or twice and then the engine dies as the rpms drop again. Calibrating the TPS puts the idle at 1200/1300.

The ECU knob will change the enrichment when the tps is adjusted to iallow a steady idle at 1200rpm.
When it’s at 1200 rpm the throttle body idle screw won’t bring the rpms down any further.
No vacuum leaks under the butterfly. If I take the air cleaner off and cap all lines, I can easily get the car to die by closing the bleed screw, indicating no vacuum leaks.

So could my TPS be bad? Is there a condition by which it could not allow a correct idle? Was thinking maybe I tweaked one of the contact arms when I cleaned the board. Looks ok though and the board is in good shape.
Or am I in MPS adjustment territory now?
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