D-Jet ECU Idle Mixture screw CCW to idle Options

[Morrie]

Let me start with saying I need to go through the system in more detail soon. I am collecting vacuum hoses, will get injectors tested, and so on.

Meanwhile, the car runs very fast and strong. The two symptoms I have are odd, and seem contradictory to me.

First, the car wants to idle high when warm. I can adjust that out mostly with the idle speed screw on the throttle body, but there is a tipping point there where the idle speed becomes very sensitive, up to that point large changes in screw setting do little to nothing.

Second, the ECU idle mixture screw needs to be full CCW to idle. If I move the setting off of full CCW it starts to stall and die.

Third, maybe unrelated, is a puff of blackish smoke on decel. (is that over run?). Not sure if this is related, or just some wear showing.

The car runs smooth and strong under throttle, will smoke the tires off the line if asked, and starts easily both cold and warm. It actually does run pretty well with the above considered, but it doesn't seem like these conditions are normal.

Still a learner on D-Jet here, reading and understanding as I go... Having fun, not frustrated.

Thanks guys!
Morrie

[BeatNavy]

So...I agree that these things potentially seem to be contradictory, at least the way you've described them. Likely more than one thing going on.

I do think you're running too rich. That would explain the idle knob having to be full CCW on ECU, the "puff of smoke" on decal, and very sensitive idle bypass screw. Verify if this is the case: pull the plugs and check to see if they are dark and sooty. (I assume you don't have a wideband sensor?)

The following are some possible causes of running too rich:

-Fuel pressure too high (should be approx 28-29 psi)
-MPS not holding vacuum
-Leaking CSV (disconnect fuel line to see if that makes a difference)
-Failing CHT (check resistance both warm and cold)
-Leaking injectors

The fact that you have a high idle even though I think you're running rich would suggest you may have vacuum leak and/or timing too far advanced. The latter is easy to check. The former takes some real hunting.

If you haven't already, read this a few times and give us some more info: https://members.rennlist.com/pbanders/djetp...tm#troubleshoot

[Morrie]

Hi, Rob,

Your advice was just what I needed- somewhere to start. I was in a state of analysis paralysis.

I have the WB O2 setup I used to tune my 912 that is going into the 914. That will be one of the first things I do.

I'm getting some help from my friend Jason at Paragon who just did the vacuum line replacement on his bee- he is putting together a set of new lines for me.

I will start by validating the timing is set properly, recheck breaker points, and ignition points, and then do a check to make sure there are no obvious vacuum leaks. While I am at it I will pull the plugs and check condition, though I expect soot as you commented. From there I will use my CIS kit to check fuel pressure, and go to the other items.

Thanks for your advice, and patience...

[BeatNavy]

Awesome, all good steps to take. D-Jet can be simple to troubleshoot - unless more than one thing is wrong (which is often the case, especially for those souls trying to revive a car that hasn't been given TLC in a long while). That WB 02 will help definitively answer at least one question. If you get info that validates running rich, make sure to check your MPS as a possible suspect, too.

Good luck!

[mgphoto]

Morrie,
Going to need a little more info about your engine and D-Jet set up.
Engine mods?


Sounds like your TPS is adjusted but your MPS might be an issue.
Black smoke not good, check the condition of the plugs.


All of the items mentioned are important to a good running engine.

A bit of advice, 914's were not built to smoke the tires, major stress on the stock drive train.
Mike

[Morrie]

Morrie,
Going to need a little more info about your engine and D-Jet set up.
Engine mods?


Sounds like your TPS is adjusted but your MPS might be an issue.
Black smoke not good, check the condition of the plugs.


All of the items mentioned are important to a good running engine.

A bit of advice, 914's were not built to smoke the tires, major stress on the stock drive train.
Mike

Hi, Mike,

The engine is a 2056 with what is supposed to be a standard D-Jet setup, as near as I can tell.

Smoking the tires- that was a bad analogy wasn't it. I was trying to say that the performance is strong. I have a 68 912 and have rebuilt 901s before, 1st gear is fragile and the car needs to be treated with more respect than that. If you are looking for tire smoking performance, best to go to old school american iron in my opinion.

I've got my list of actions now. Let me collect some information and come back with updates and results. While I have the plugs out I will do a compression test to see where I stand there also. If things look off I will get out my leak down tester and collect some more data. I also have an endoscope I can use to inspect cylinder walls and get a look at valves if needed.

[Beebo Kanelle]

I'm in the middle of a similar situation.

My problem is the vacuum canister on the distributor...

Hope this helps a little bit.

[JOEPROPER]

Is the MPS calibrated for 2056???

[boxsterfan]

Is the MPS calibrated for 2056???

(IMG:style_emoticons/default/agree.gif)

[mgphoto]

Your signature says a 76, does it have all the emissions plumbing?

[Morrie]

Your signature says a 76, does it have all the emissions plumbing?

Most all the emissions stuff is long gone, thank goodness. Makes it a lost cause to ever license in CA but here it Texas it does reduce the complexity.

Vacuum advance hose for distributor was definitely not holding vacuum but that is not the problem. I managed to work the idle speed adjustment (air bleed screw basically, right?) and the mixture screw to get the car to idle better with a slightly more balanced idle mixture. Can't do too much more with mixture till I get my WB AFR installed. I will check FP, timing, plugs, points gap/dwell, etc...

[mgphoto]

Ok, what exhaust set up are you using?

Are all of the FI components '76? Is there any mix and matching?

Miles since 2056 update? Any other mods? ie: cam, lightened flywheel?

Mike

[914_teener]

So non working vac diaphram on the dizzy....unknown MPS on a 2056 which may or may not have been claibrated....hasn.t checked the valves...points....timing.....ect.

And it won.t idle because.....?

Start with all the mechanicals first and make sure what parts you have...first or you will be chasing your tail for some time.

My .02

[Morrie]

So non working vac diaphram on the dizzy....unknown MPS on a 2056 which may or may not have been claibrated....hasn.t checked the valves...points....timing.....ect.

And it won.t idle because.....?

Start with all the mechanicals first and make sure what parts you have...first or you will be chasing your tail for some time.

My .02

Fully aware sir that I have yet to check things out. I probably should have never started the thread. I have been traveling on business and was dreaming of the car, got curious, and started a thread.

Give me a couple weeks till the temps here get below 100 in the daytime, and a weekend when I can devote some time to it, and I will go through everything. I suggest nobody waste their time responding to this thread until I can make the time to do a proper evaluation of the mechanicals and injection system.

Respectfully submitted......

[Morrie]

Ok, what exhaust set up are you using?

Are all of the FI components '76? Is there any mix and matching?

Miles since 2056 update? Any other mods? ie: cam, lightened flywheel?

Mike

Hi Mike,

I'll be collecting a more comprehensive evaluation of the engine condition and configuration in the coming weeks.

Exhaust- Bursh quiet street with SS heat exchangers.

Mix and Match- possibly/probably. Until I get the PN of all the components documented I will not know for sure. This is on the list to do.

Miles since update- approximately 10,000. Done my Ed Mayo about 10 years ago, car sat quite a bit until about 3 years ago.

Mods- I have limited information there, need to see if Ed remembers anything about it and how he set things up back in the day.

Have a good weekend sir!