High Idle, but only when driving or warm., Cold, and sitting... 1000 RPM. Driving...1400 ?? Options

[MikeInMunich]

Greetings from Munich gentlemen!

As seen in the title, my car (1973 1.7 converted to 2 liter, D-Jettronic F.I.) idles at 1000 after starting and letting it sit. When I take it out in the road it quickly changes to 1400. It still idles at 1400 when stopped after the car is warm.

1) I think my AAR (auxiliary air regulator) valve isn't working at all. Disconnecting the vacuum hose, the idle shot up to about 3000 and covering it with my finger 100% it went back down to where it was before I had detached it from the AAR. So the AAR should have been OPEN as the car wasn't warm yet, but it seems to be closed 100%.

Strangely, the idle only goes up after the car is out on the road / is warm...but not even yet near normal operating temperature.

I'm thinking the AFR is leaning out under load and after the car is fully warmed up. (IMG:style_emoticons/default/idea.gif) I currently don't have AFR or CO values. I will have the CO measured cold and after warming up in a few days.

Here's another issue and question fer y'all. While looking into the bay yesterday I noticed a substantial leak at one of the fuel injectors. I didn't mess with it much (checking the seating of the seal) but after I drove the car and it was warm, I looked again and it had stopped leaking. I thought it could have something to do with temp and fuel pressure (IMG:style_emoticons/default/confused24.gif) Starting up the car cold this morning however, I checked again, and there was still no leak. Does anyone have any idea what could cause an apparently intermittent leak like this? Perhaps just fudging with it gently got a seal to sit better, but I'm skeptical about that.

Thanks for your feedback! (IMG:style_emoticons/default/beerchug.gif)

By the way, I do know about this thread on Rennlist, which is a tremendous resource:
http://members.rennlist.com/pbanders/djetparts.htm

Mike in Munich

[era vulgaris]

If your AAR is stuck open, or if it is entirely removed from the system, you should have a very low idle on a cold start. So low that you shouldn't really be able to hold an idle at all. You'd basically have to keep your foot on the gas for a couple minutes until the engine was warm enough for you to even hold an idle. If you're starting out at 1k rpm when cold, with no AAR installed, then either your idle screw is set too high, or you have a vacuum leak somewhere.

With the AAR working properly, and no vacuum leaks, and the entire system working properly, you should be starting out at ~1800rpm on a cold start which should then come down to ~900 rpm within the first few minutes of driving as the engine warms and the AAR closes. It doesn't take the car getting up to full operating temp for the AAR to close. It only takes a couple minutes.

If your idle goes up as the engine warms up, then it could be a stuck AAR, however you've definitely got other issues if your cold idle speed is 1k rpm. Where is your idle screw set? Try setting your idle to 900 once the car is warm. Like I said, with the AAR removed your cold idle speed should be so low that you need to hold the gas pedal with your foot to keep the car running.

Also, I'd recommend never driving a car that you even remotely suspect has a fuel leak.

[Perry Kiehl Clone]

I'm thinking on the same lines as EV. Maybe the idle was set with a faulty AAR?

I'm also with EV on the fuel leak, you are literally playing with fire. Never ever drive a vehicle with leaking fuel. This is also a good time to make sure you have a fire extinguisher in the car too. (I mount them to the cross member under the passenger seat)

When I was young and very ignorant I sped home with a leaking injector hose, and when I cornered hard the leaking fuel poured out on the rear tire and caused a very interesting tank slapper.

[MikeInMunich]

Thanks for the feedback gentlemen. I guess I forgot to mention it, but naturally adjusting the idle screw was the first thing I tried. Unfortunately it's all the way in. I can't reduce the idle speed any more that way.

The AAR was stuck closed. Idle is at 1000 when cold. Can't hear or otherwise detect a vacuum leak from visual inspection. As you know, there are like 10 or more places where there could be one. I'm also not yet clear on what the best method for finding them is, so a few tips on that here would be appreciated. (IMG:style_emoticons/default/smile.gif)

Could it be that the timing is advanced too much?

Thanks again!

M.i.M.

[era vulgaris]

It could be that your timing is too advanced. What is your timing set to?

It could also be that your advance plates in the dizzy are stuck in the advanced position. Have you opened up your dizzy to check that the advance plates function as they should?
I had a similar issue as you on my old 1.7 - a high idle that I couldn't cure. After replacing literally every seal, gasket, and vacuum hose I discovered that I had stuck advance plates. After I fixed it, the engine ran like a dream.

BTW, when is the last time you replaced all your seals, gaskets, and vacuum hoses?

[MikeInMunich]

Thanks for your feedback. The engine was rebuilt in TX before being sent over to Germany, where I am. I don't have an answer to your question about all the gaskets, etc. but that all should be new. The timing and the distributed are going to be first up on the checklist next week. Hope that's where the issue lies. I'll post again when I know more.

Thanks again! (IMG:style_emoticons/default/beerchug.gif)

M.i.M.

[ClayPerrine]

Mike,

The D-Jet system will idle high when there is a vacuum leak. If your idle screw is all the way in and it still idles at 1000 rpm cold, then there is air getting into the system from somewhere. The idle would climb just like you describe as the engine warms up because it takes less air to run faster when warm.

I suggest checking the fabric covered hoses between the intake plenum and the intake runners. I had one of them split on Betty's car recently. Also get on the bird board and print a diagram of the vacuum system and check each hose to make sure it is routed and connected correctly.

Another way is to get something that makes smoke or water vapor, and let the smoke cover parts of the engine. Then look for the smoke getting sucked in someplace.

And we would be happy to look at pictures. Lots of brains here will know on sight if something is disconnected or routed wrong.


Good Luck!

[MikeInMunich]

OK! I'll post a pic in a day or two, and do a smoke test somehow and post results.

Thanks a lot! Gotta LOVE 914 World and how helpful you guys are. I personally wouldn't want to own one of these cars without this community & website! (IMG:style_emoticons/default/aktion035.gif)

M.i.M.

[914_teener]

Couple of routine questions and I apologize if these were asked already Mike.

What ecu are you running and what are the valves adjusted to?

[PancakePorsche]

I agree with everything said so far. Do complete tuning process.

Valves
Timing (check cold and hot should not change) very critical.
Set TPS position (enables idle circuit)
start with ECU knob middle of travel
start with idle air screw one turn out
inspect all hoses.

If a 73 F.I. system was used, make sure this one year only system has all the correct components. It is a "fooled" 1.7 system which uses 73 specific MPS, 73 specific temp sensor 2 with a 270 ohm resistor in-line, and a late 1.7 ECU.
Mismatched components create bizzarre driveabilty issues impossible to resolve. Just a FYI, seen it before.

Cheers from the USA !

[MikeInMunich]

Couple of routine questions and I apologize if these were asked already Mike.

What ecu are you running and what are the valves adjusted to?

To the best of my knowledge the ECU and MPS are compatible and correct for this system, but I don't have any numbers. The valves should have been (we're?) correctly adjusted very recently.

M.i.M.

[MikeInMunich]

Thanks for the input and tips. Looking into all of it next week.

[r3dplanet]

Yup. Excellent suggestions. (IMG:style_emoticons/default/popcorn[1].gif)

I agree with everything said so far. Do complete tuning process.

Valves
Timing (check cold and hot should not change) very critical.
Set TPS position (enables idle circuit)
start with ECU knob middle of travel
start with idle air screw one turn out
inspect all hoses.

If a 73 F.I. system was used, make sure this one year only system has all the correct components. It is a "fooled" 1.7 system which uses 73 specific MPS, 73 specific temp sensor 2 with a 270 ohm resistor in-line, and a late 1.7 ECU.
Mismatched components create bizzarre driveabilty issues impossible to resolve. Just a FYI, seen it before.

Cheers from the USA !

[MikeInMunich]

Update!

I got the AAR to work by letting it soak in WD40 for a day.

Searching for a vacuum leak by spraying brake cleaner all over the place in the engine compartment, practically, the idle would drop from 1400 to under 1000 when I sprayed the "tip" of the fuel regulator, where there is an 11mm screw, which I couldn't easily get to turn in either direction (at all). I was curious, but pursued that attempt no further.

Does this tell us anything? (IMG:style_emoticons/default/confused24.gif)

Also, my fuel leak at the O ring of the injector is intermittent. Sometimes when I start the car up its leaking quite badly and more often than not, it's not leaking at all. Any ideas on why this could be the case? (IMG:style_emoticons/default/confused24.gif)

Thanks guys! Really appreciate your help a LOT!

All the best from sunny Munich,

Mike (IMG:style_emoticons/default/smilie_flagge6.gif)

[boxsterfan]

Update!

I got the AAR to work by letting it soak in WD40 for a day.

Searching for a vacuum leak by spraying brake cleaner all over the place in the engine compartment, practically, the idle would drop from 1400 to under 1000 when I sprayed the "tip" of the fuel regulator, where there is an 11mm screw, which I couldn't easily get to turn in either direction (at all). I was curious, but pursued that attempt no further.

Does this tell us anything? (IMG:style_emoticons/default/confused24.gif)

Also, my fuel leak at the O ring of the injector is intermittent. Sometimes when I start the car up its leaking quite badly and more often than not, it's not leaking at all. Any ideas on why this could be the case? (IMG:style_emoticons/default/confused24.gif)

Thanks guys! Really appreciate your help a LOT!

All the best from sunny Munich,

Mike (IMG:style_emoticons/default/smilie_flagge6.gif)

If your injector o-ring is leaking, you need to replace ASAP. Otherwise, you will have a fire on your hands. The o-rings are cheap. Install is pretty easy (heck, I did it).

Have you grabbed the numbers off your ECU and MPS? http://members.rennlist.com/pbanders/index.html

Look for this section:

D-Jetronic

D-Jetronic Injection System Fundamentals
D-Jetronic Parts Table, Setup, and Troubleshooting
Manifold Pressure Sensor (MPS) Analysis and Tuning
D-Jetronic Electronic Control Unit (ECU) Analysis
D-Jetronic PCV (Positive Crankcase Ventilation) Valve Analysis
D-Jetronic Idle Stability and Troubleshooting
D-Jetronic Testers
Fuel Pump Circuit Troubleshooting Flow Charts (Framed Visio flow charts)
D-Jetronic vs. Carburetors - The Endless Debate

[Dave_Darling]

The injectors generally leak from three places. One is a leak of the short hose connecting the injector to the fuel rail. The original injectors had crimped-on clamps holding the hose to the injectors; to replace the hose you cut the clamp off to remove the hose, and use a new fuel-injection hose clamp to attach the new hose. There are formed curved hoses specifically for this, but ordinary straight hose can be made to work.

The next place they leak is between the plastic and metal parts of the injector body. Some of the rebuilders can cure some of those, but often enough the real fix is to replace the injector.

The third place they can leak is around the rubber O-ring that goes around the tip and holds it in place in the intake runner. The O-rings can be replaced fairly easily.

The fuel pressure regulator in a D-jet system has no vacuum connections, so spraying it should not affect the idle at all. Double-check that. The screw on the end can be moved after the jam-nut on it is loosened, but you're not nearly at that point.

--DD

[MikeInMunich]

Thanks again Dave.

I am sure that spraying the cleaning fluid onto the end of the fuel regulator cause the idle to drop significantly. Very odd, no?

Question: Any idea why the fuel leak could be intermittent? Again, sometimes BAD, like two drops a second and most of the time not at all. (IMG:style_emoticons/default/confused24.gif)

M.i.M.

[MikeInMunich]

Hi guys!

Just found this thread...

http://www.914world.com/bbs2/lofiversion/i...php?t51118.html

Under HIGH IDLE: he mentions checking the O-rings at the injectors to make sure they're not leaking. This would apparently be a potential explanation for both my fuel leak AND the high idle. Although the leak is only occasional, which again, is a mystery to me. (IMG:style_emoticons/default/confused24.gif)

[MikeInMunich]

So, it turns out that there was apparently a vacuum leak at the plenum gasket.

The fuel leak was a crack in the hose just prior to the injector.

The timing was reportedly advanced 30 degrees as well. 27 is recommended. They set it at 24. Is that OK, or should it really be 27?

CO was 3%, a bit too rich. Now they're telling me it's 1.7%.

I also changed the FPR. Pressure is 29 PSI. The other one may have had an issue, because the idle was going down when spraying starter fluid onto the 11 mm adjustment nut.

Don't have it back yet, but am hoping that all issues are cleared up and to have it running so that the idle can easily be adjusted to sit nicely at 900 after its warm. In the meantime however, I also need a new (rebuilt) AAR valve. Auto Atlanta has none available. If you have one that's working perfectly, please let me know via PM.

Thanks,

Mike in Munich

[76-914]

I follow Porshe's tolerances to the T except for adjusting the rear brakes which I set @ .04. Send us some pic's of the Big Breasted Beer Maids from an Octoberfest next month. (IMG:style_emoticons/default/biggrin.gif) (IMG:style_emoticons/default/beerchug.gif)