Well, installed new points, set dwell, set timing to 27btdc.

The car runs better than it ever has and it feels fantastic. Of course, it's still a bit cold blooded till it warms up and finicky till warmup temps arrive.

The car has never quite had a perfect idle. After setting the dwell and timing, I decided to try the idle screw, which had absolutely no effect on the idle at all. In fact, I could entirely remove it and it did nothing.

Here is a video of the car idling.

I mean the car runs smoothly. It accelerates fine. It feels fine. The Idle is low and doesn't seem to care whether or not I adjust the idle. It literally just sits there where you see it on the tach. It starts this way and runs this way hot or cold. Obviously after the car exists high idle, but high idle works fine.

(Original injection, not carbs)

I will clarify, this did not change after I set timing and dwell, the idle has been this way for a while and has not changed. Even after new vacuum lines, injector seals, fixing vacuum leaks I could find, it has not changed. Someone some time ago mentioned mixture and to try a small correction on my ECU. My ECU does not have a POTs system on it, so I cannot do that, it's an early '70. Which also baffles me as to how one would "change the mixture" if that is the case.

Try advancing the timing a couple of degrees, see if that helps.

If not, I would suspect a rich idle mixture. Not sure how to deal with that on an early 1.7; those didn't have the idle mixture knob on the ECU.

--DD

Thank you kindly for the response, Dave.

It seemed like it was super rich a few years back. I took it for an autocross in 2011, it was running so rich that it would load up and die at idle. Same idle of course.

I changed the vacuum lines, did a tune up set the timing (admittedly did not set the dwell then) and it was "a little better"...

After that I replaced the injector seals (all of them), replaced more vacuum lines, ensured everything was sealed up and happy and it was even better. Perhaps I am dealing with more vacuum leaks? I figured a vacuum leak or two might actually cause it to run LEAN since more air is going in. At the same time, however, since these are run off of a MAP sensor I suppose it could cause a rich condition, too.

I am not sure if you recall my thread a long while back about my popping on decel, however, it was constant. It would be a very pronounced pop-pop-pop-pop, every cycle. Now I get only one pop (sounds like just one cylinder per cycle) on decel, only at very high rpms, and then the popping is gone under 3k. So it seems to be behaving better. I suppose though that could be the sign of still being a bit rich?

Tad frustrated though that I cannot use a pot setup to tune the mixture on this year.

If anyone has suggestions I'm all ears. BTW I have not replaced the intake manifold gaskets, although I do have them. It may be possible those are leaking perhaps? Would that affect it much?

I can try the advance as well. I did notice that if I advanced it enough the idle would shoot up, but it was more like shooting up to 1500rpm.

(edited because I must have been typing with my feet this morning and typed Dave's name wrong)

I believe rich or lean with the early DJET is dependent only on the MPS and CHT sensors. Both of these units affect the length of the FI pulses to the injectors.

My car was running really lean and wouldn't idle at all. I had to install an AFR sensor in the tailpipe to see what the mixture was doing. With the AFR I was able to adjust the MPS so it runs good and idles correctly.

The idle screw is only an adjustment to allow a bit more or less air into the plenum to simulate slightly opening the butterfly.

Intrake leaks will result in a high idle, not a low one. Unplug the air temp sensor in the intake plenum and see if that helps. Pull and hold a vacuum on the MPS. Check the hose to the MPS. Adjust the valves, tight valves can cause a low idle speed. Check and set the point dwell. Set the timing, hoses off and plugged. Check the fuel pressure while the engine is running. 29 PSI is the goal. Report back.

The Cap'n

Yeah I kind of figured that was the case, baffling to me why nothing has changed even slightly as I've replaced vacuum lines.



I will go ahead and try these and report back later today. I do not have a fuel pressure tester but can at least do the others.

Try changing your plugs to the NGK BR5ES to see if that helps.

I believe I'm running BP6ES at this time. Should I be running something different?

I was too for a long time, then switched to the 5's which made a noticeable difference

As in it was making it run rich? Not a hot enough plug? Or?

I'm not saying that this will cure your problem, but it may be worth looking into. Follow the Capn's procedures first before switching plugs. "

definitely will follow his procedures as well. However, a quick google search just helped me find this (Also good info from the Cap'n)

http://www.914world.com/bbs2/index.php?sho...p;#entry1275731



:-/

It's not "BR5ES", it's "BP5ES". That's a hotter plug than your "6". However, extended tip "P" plugs are not specified for the T4 engine. Rather the standard "B6ES" is called for. I don't think you need the heat transfer characteristics of a "5", which was used in the later Bus 2.0 engines, which use EGR, run hotter, and are set up to run significantly leaner, not richer. Lotta folks don't understand the concept of a "hotter" plug vs. a "colder" plug.

The Cap'n

Sorry bad information It has been awhile since I switched to the 5's, I got the numbers mixed up!!

As I go over your recommendations, do you also recommend switching plugs? I'm more than happy to do so.

On a whim, I got out my multimeter and checked the resistance on my cylinder head temperature sensor. After reading the Djet troubleshooting page I noticed my symptoms seem to be very similar to a "stuck cold" or just rich all the time condition.

I let the car warm up for a few minutes, mind you it is 90F out right now. I then took it for a drive down the block, got lunch, drove it around some more.

Resistance at operating temp? 2200 ohms. Not where it should be. I watched the multimeter as it cooled down. The amount of resistance on the drops was negligible, literally 1ohm value every 5 seconds or so. So as the car cooled over 30 seconds, it went from 2200ohms to 2210. Seems way off.

According to this page: http://members.rennlist.com/pbanders/djetp...tm#troubleshoot

ROOM TEMPERATURE should be closer to where I'm at. Not operating temp....

Did you check it with the wire unplugged from the harness?

Unplugged it from the connector and then went direct to battery. Verified 2200ohms.

Battery? Plug the + on your meter to the lead on the sensor. Place - to ground (sensor body). Read again.

I guess I'm not understanding why this would be any different. If I pull the sensor plug off, clip my multimeter into it (where the harness connects to the sensor) and then connect the other end of my multimeter to any good ground, I should see the resistance value that the ECU is going to see. Battery ground or known good ground in engine bay results in same reading, 2200ohms or 2.2K ohms.



Operates the same as a thermofan switch would, except without the switch, simply providing resistance values.

Alright... so here we go... I finally got some time today to work on this.

Hose to the MPS is new. MPS is also a rebuilt unit (replaced the previously bad MPS I had). Although the numbers are not the same. However, car idles the same with bad MPS or new rebuilt MPS.

MPS will hold vacuum with no issues.

Valves were adjusted to spec less than 1000 miles ago, car ran more smoothly but idle did not change.

Dwell is set and is at a happy 47.

Timing set to 27btdc.

Do not have equipment to test psi, however, I pulled plugs and the mixture is LEAN. Not RICH like I thought previously.

After setting the timing, the idle was still funky. I decided to disconnect the hose for timing retard and suddenly..... the idle became normal and the car would actually react to the idle air screw and the car could be set to 800rpm idle.



Now, regarding Cabinet Maker's previous post... I went ahead and pulled the sensor and indeed, the resistance was where I found it earlier when things were "kind of warm" - I guess I did not wait long enough because after I took the car for a long drive, the resistance was about 50-70ohms, not 2200.

I went ahead and heated up the spare sensor I have with a heat gun and sure enough, it also went below 100ohms as it should.

I emailed Jim (Previous owner "Porsche Rescue") and he confirmed that he replaced the sensor when he gave me the description of the sensor he replaced.

So at this point I am leaning less towards mixture and more towards timing or something else. The plugs weren't ridiculously lean, just a tad on the lean side. With the previous MPS it was so rich the car would load up and just die. It will remain idling, but when hot, will pop a bit if you give it gas just barely at very low rpms. If you let off the gas at higher rpms you get a decel pop pop pop which if I am reading correctly is indeed a "lean thing"...

So I guess I was reading into this improperly.

I appreciate everyone's help.

At this point I can at least confirm:

- Car is LEAN, not rich, as previously thought
- Idle smooths out and will actually react to idle air screw when dizzy retard is disconnected, if it is hooked back up, the idle turns to crap and the car runs terribly again.
- Sensor for CHT is within spec when previously thought it was not, is under 100ohms at running temp

I haven't fixed it yet, but damnit I'm tired and I want a beer.

PS: Part # off my MPS is 0 280 100 049

Mismatched mps units to ecu units can cause issues.

Check this table to make sure you are set correctly with what you have.

http://members.rennlist.com/pbanders/djetp...m#Compatibility

Yep, correct MPS.

Although I have wonderful news! I found my issue. I kind of forgot to unplug the vacuum lines when I set my timing sooooooooo it was off, a lot.

I just went and set the timing and hooked it back up, set the idle and it runs like a freaking champ. Super smooth, idle like butter (as buttery as they can anyway) and it runs and drives predictably. No more hiccups, no more decel popping (I heard ONE pop the entire drive). It even started right up.

So you guys can put this one down on PEBKAC, ID10T or whichever one of those you most prefer since it was all user error on my end. Gee whiz, timing makes a difference?

I will inspect the plugs tomorrow to see if the condition of them changes any. I actually found that I am already running B6ES and NOT BP6ES plugs as I previously thought, so after taking them out I went... "OHHHHHH."

So now I have more plugs for next time around.

Anyway, HAPPY 914 owner right here!

Congrats and I am happy it was a simple error versus more money out of your pocket.

Now, drive it like you stole it before it gets out of tune again...which it will

Glad ya got figured out, and good job on the diagnosis.

The only tune you really need to keep a regular eye on is dwell. Keep it happy at 47. timing should stay the same. Remember, dwell affects timing. I check my valves at least every 5K, and dwell about every 1K just for the heck of it.

Yeah, it ran "okay" when I first got it but the idle was never perfect. It did the stuttering low idle when I first got it and never really was stable. I finally decided to just completely go through it and also do gaskets and points and what not. Night and day!

I appreciate all the help and support here. This is the first "older" car I've ever owned. All of my cars of course are older than me. My 911, my 924 cars and the 914. The 914 is the oldest, however.

I have a strange addiction to Porsche cars and the 914 is just a time machine for me, I love it, and love working on it. I'm slowly starting to understand it better.

I seem to be a bit on the advanced side with the timing. I did get some pinging this morning while driving it around, only at around 3k rpms and only under load. So I will back it off "a hair" and see how that helps. I eyeballed the timing last night but no doubt is a huge difference over setting it with vacuum attached LOL!

What I really need to do is make one of those pelicanparts templates and mark the 27btdc mark on the impeller so I can make it spot on.

Thank you again for all the patience and assistance. I know many of you have been doing this stuff since these cars came out. I'm still a "young'n" in comparison.