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Jonathon
 
Join Date: Apr 2012
Location: Chicago il.
Posts: 22
Question Low Idle

Hi, on my '73 914 2.0 (D-Jetronic )the idle drops to 200 RPM's or so after the engine warms up. On start up the engine idles at about 1200 RPM's. I changed the head temp sensor (#2 for fuel injection), checked the ohms on the manifold pressure regulator ( readings are correct) and I also tried adjusting the air bleed off valve to bring the RPM's up after warm up, but none of this has helped. However, If I push down on the distributor cap, the RPM's come back up.
Now I'm wondering if it's the points or something else located within the distributor, or could the car possibly be running on 2 cylinders after warm up. I am not an experienced mechanic, and have not had the car for very long so any Suggestions would be greatly appreciated. Thanks, Jon
Old 08-10-2014, 06:52 AM
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On D-jet idle is often a bit higer during warm up than when warm, this is thanks to the extra air fed by the AAR-valve.
But your problem could be in the distributor cap, it should not be flexible and possible to press it down if fitted correctly in the right position and by both springs on the side of it.

Yes there are points in the distributor, one set (at the top under the cap) for the ignition and two sets (hidden in the wery bottom) for the FI. The ones in the bottom are connected by an outside 3 pole plug at the base of the dizzy, check that this plug is seated properly.

No i dont Think your Engine is running on 2 cylinders only it would then be running wery bad.


/Lars S
Old 08-10-2014, 08:58 AM
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If you just got the car, and if you didn't change anything, then you have to do the basics before you do any serious D-Jet troubleshooting: valve adjustment, dwell, and timing. Whenever I notice my idle has dropped really low it's because my dwell has gone out of whack. Check the valves, get a dwell meter and verify 45-50 degrees, and then adjust timing. Dwell takes 10 seconds to check, and timing only slightly longer. Valves should be done first, but if you don't have time to get it on jack stands and get under it, then at least check dwell and timing. With practice you can do both in about 5 minutes.

How are the condition of the vacuum lines? If they look old or cracked at all, then you should replace all of those as well. It's amazing what craziness will occur on D-Jet with vacuum leaks or incorrectly connected vacuum hoses.
Old 08-10-2014, 09:16 AM
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Link to an ignition troubleshooting guide:

Pelican Technical Article: Ignition Troubleshooting



/Lars S
Old 08-10-2014, 09:21 AM
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Jonathon
 
Join Date: Apr 2012
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Thanks for all the suggestions. The vacuum hoses are all in good condition and hooked up properly. The valves were adjusted right before I bought the car. I have never checked dwell or timing on a car, so I'll look online to see if I can find a step by step how-to on the procedure. Thanks again, Jon
Old 08-10-2014, 04:58 PM
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Yes, there are lots of resources here and around.

Here is Pelican's tech article for dwell and timing: Pelican Tech Article
This is considered kind of the D-Jet "bible" for troubleshooting (at least I know I've referenced it dozens of times): D-Jetronic Parts and Troubleshooting.
Another good reference from Anders on idle: D-Jetronic Idle Stability

Good luck!
Old 08-11-2014, 01:56 AM
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Jonathon
 
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Thanks a lot, I'm picking up the necessary equipment tomorrow, and will take a crack at it sometime this week. Seems a little intimidating right now as I've never done it, but I'll let you know how I make out. Jon
Old 08-11-2014, 05:44 PM
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Jonathon
 
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Checked the Dwell and it's 44. I'm going to check the timing next but I need to know if I should wait until the car warms up before I check it? Also, Should I replace the distributor cap and rotor ( points) before I do this? Thanks, Jon
Old 08-16-2014, 03:49 AM
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Ok, good. You can (sort of) scratch dwell off your list. I don't think technically the car has to be fully warm before you check timing, although the age and dirt/wear of some components (like distributors) means they sometimes behave differently when hot. I think it's much more important to check the timing correctly (correct mark, right RPM, vacuum lines plugged, etc.) as described in the Pelican article. Replacing the points and cap are up to you. If they're old and worn, sure. If you do replace the points then you have to set dwell again. I'd recommend going ahead and checking timing first before replacing those things. That way you're not introducing more variables into the mix.

Don't mess with the air bleed bypass screw until the car is fully warm, however.
Old 08-16-2014, 05:06 AM
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Forgot to add: adjusting the timing is a more pleasant exercise (esp. if you haven't done it before) if you a) have an assistant to help keep the engine near 3500 RPM and b) have a 10 mm combination wrench long enough to easily reach down to the base of the dizzy and adjustment nut.
Old 08-16-2014, 05:16 AM
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Jonathon
 
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Hi, I thought I'd check the dwell one more time before I figured out how to do the timing, and evidently I didn't calibrate my engine analyzer. My dwell was actually 56, not 44 like I thought. I brought the dwell down to 44 or 45 and then the RPM's on the engine shot higher, up to over 2000 RPM's. Then I turned in the air bleed off screw under the air intake, and got the RPM's down to about 1000, with the car warm. I will check the timing next. Thanks, Jon
Old 08-17-2014, 12:48 PM
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Excellent! Not only will your idle be better the car will perform better. Now you know how to check dwell, and when you get timing down those are two important things you need to know maintaining the car going forward.
Old 08-17-2014, 01:46 PM
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Jonathon
 
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Thanks, I am working on the timing now, and I found a red line on one of the fins of the impellar. I have gone around the blade twice but I cant find a zero or any other mark to indicate TDC. I looked to the right of the red line thinking the Red line was the timing mark, but nothing. Then I looked to the left of the red line thinking the the Red line I found was actually TDC, but there are no other marks. Any Suggestions? Thanks a lot!!
Old 08-17-2014, 02:21 PM
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Have you checked the tech article on ignition timing here? It has pictures of a couple of different fans, and the markings on those fans.

Usually a red line is the timing mark, and a '0' is TDC. The TDC mark is not always present. The position of the marks versus the fan blades is pretty consistent, so if your mark is next to the fan blade shown in the pictures of the article it is most likely correct.

--DD
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Old 08-17-2014, 02:47 PM
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Jonathon
 
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Yes I have been following the articles recommended, and the red line I found is consistent with the pictures in them. So I am fairly certain that I have the timing mark. I would just like to find TDC to be absolutely sure. I think I'll need to find them anyway when I have to adjust the valves. Correct?
Old 08-17-2014, 03:11 PM
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There may be no TDC mark. You can make one, though.

--DD
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Old 08-17-2014, 03:33 PM
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Jonathon
 
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Thanks for all your help!!!
Old 08-17-2014, 03:34 PM
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Jonathon
 
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Hello again, I just adjusted the timing on my car and it's now perfect. The dwell is set to 45. The car still looses RPM's after warming up. If I press hard on the distributor, the RPM's come back up. Any more suggestions? I have not replaced any parts yet, so would that be the next course of action? Thanks, Jon
Old 08-19-2014, 01:28 PM
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Thanks for the feedback. That's great that you've made good progress and learned a bunch in the process.

I'm not sure why your engine would surge unless it has something to do with the vacuum advance connection or something similar. If you're up for the effort, it would be a good idea to not just replace the cap and rotor but perform a pretty thorough cleaning of all the moving parts within the distributor. They do get dirty over time and the advance plates don't always behave properly.

Consider adding a spacer to your cylinder head temperature sensor. They're primarily designed for 2.0's, but I thought it made warm-up (and even after) a much smoother process on my 1.7. You can get them on 914 Ltd's site (look for Cylinder Head Temperature Sensor Extension). It does require removing the CHT, which can be a slight chore if you don't have the right tool, but I was very happy with the result. Essentially it just delays the warm up of the CHT so the ECU thinks the cylinder head is cooler, longer. That keeps the mixture richer significantly longer as the engine warms up.
Old 08-19-2014, 04:49 PM
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Jonathon
 
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Thanks, what do I clean it with? Should I spray in there with something, use q-tips with a solvent on it, a vacuum? Thanks for responding!!
Old 08-19-2014, 04:54 PM
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