Idle isn't quite right, Blah. Options

[corsepervita]

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.

[Dave_Darling]

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

[corsepervita]

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)

[Spoke]

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.

[Cap'n Krusty]

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

[corsepervita]

Intrake leaks will result in a high idle, not a low one.

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

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

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.

[timothy_nd28]

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

[corsepervita]

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?

[timothy_nd28]

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

[corsepervita]

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?

[timothy_nd28]

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. "

[corsepervita]

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

There are 2 "correct" spark plugs. NGK B6ES is a good choice, and Bosch W7CC is, too. The resistor plug, WR7CC will work fine. W8CC and it's variants are one heat range step hotter, and should be fine. They were stock on the '76-'79 VW bus, and may be a better choice for modern fuel. If most of your driving is high speed "touring", I'd stick with the first two choices. NO Platinum plugs! All stock 914s use the same spark plug, and the extended reach plugs (B"P"6ES and WR7"D"S) are NOT recommended.

The Cap'n

:-/

[Cap'n Krusty]

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?

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

[timothy_nd28]

Sorry bad information (IMG:style_emoticons/default/headbang.gif) It has been awhile since I switched to the 5's, I got the numbers mixed up!!

[corsepervita]

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?

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

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

[corsepervita]

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....

[TheCabinetmaker]

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

[corsepervita]

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

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

[TheCabinetmaker]

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

[corsepervita]

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.

Function: Senses engine temperature and sends signal to the ECU to provide mixture compensation. Proper part for your application and proper functioning is extremely important!
Normal Value(s):
0 280 130 003 and 0 280 130 012: about 2.5 K ohms at 68 deg. F, less than 100 ohms with hot engine.
0 280 130 017: about 1.3 K ohms at 68 deg. F, less than 100 ohms with hot engine.
See Notes section below for more data on the resistance vs. temperature values of these sensors.

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

Failure Modes
Open: The ECU interprets an open sensor as a signal to greatly richen (e.g. I've measured an over 3X effect) the mixture. This usually makes the car impossible to start and causes it to stall if the sensor fails open while running. Check by disconnecting the sensor from the wiring harness and measuring the resistance to ground, refer to the values above.
Shorted: The ECU interprets a shorted sensor as a signal to lean out the mixture (about 30% leaner). The car may run and start in this condition, but will have poor idle and drivability. Check by disconnecting the sensor from the wiring harness and checking the resistance to ground. Note that shorts are often intermittent, caused by nicks in the sensor wire and by exposed contacts to the wiring harness touching ground. Check by inspection.
Stuck Value: I've heard of at least one case of the sensor being stuck at a value (e.g. 50 ohms) and not varying with temperature. Depending on the value it gets stuck at, it can result in either poor cold or hot performance, or both. Check by measuring with an ohmmeter as described above.