1973 1.7, FI.

The car starts up fine, and runs perfectly when cold. Idle is at about 1,100 or so, However, after driving for maybe 30 min. and everything's fully warmed up, the car stalls when stopped, like at a traffic light. The idle drops way down, then stalls out.

It will start right back up no problem, but makes stop-and-go driving a rather harrowing experience. I need to heel-toe it every time I slow down, to keep the RPMs up and prevent a stall.

Pretty much everything on the car is stock.

What should I be looking at to address this?

I did some searches, and the three things I came up with are Manifold Pressure Sensor (MPS), Cylinder Head Temperature Sensor (CHTS), and points.

Please note, I'm a noob at working on this car, so please provide specific details, if possible.

Thanks in advance.

Hi Mike,

Sounds like its running too rich. When the car is cold it "likes" that condition and won't display symptoms, but as it warms up it does not. I assume you've been all over Anders' D-Jet site, right? Did something change suddenly or over time? I would check:

1. Fuel pressure at FI rail with gauge (should be ~28 psi)
2. Points condition and dwell (should be 45 to 50 degrees)
3. CHT resistance both hot and cold (can't remember normal values off top of my head - doesn't sound like the CHT is completely bad but could be going in that direction; when completely bad car will die after 5 or 10 minutes tops)
4. Air intake temp sensor to make sure it's connected and giving good resistance readings (it's under the air cleaner, top / back of engine -- two wires going to it)
5. The MPS - check electrical connection, resistance values between terminals, and ability to hold a vacuum at the port (buy a little vacuum pump)
6. Trigger point connection solidly connected at back of dizzy.

I suppose it could be the cold start valve too, but I have no experience with that and I would think that would flood the engine more quickly. Eliminate the variables you can with the tools/knowledge you have and then ask for more help. Because the car still runs I would think the MPS and CHT haven't failed, at least not completely.

I'm sure you'll get a ton of additional input here that's more useful/informed than mine, but hopefully this helps.

rc

Does the car simply stall out...or does the idle begin to go up and down before stalling?

In addition to the suggestions above, I suspect that your auxiliary air regulator (AAR) may be malfunctioning. The AAR restricts airflow and enriches the mixture when the engine is cold, then gradually opens and leans out the fuel/air mix as the engine warms up. If it is frozen in the closed position, it could be causing your engine to run rich after its warmed up - and causes it to stall.

Agree with the poster above...check out the PBanders site - it is pure gold trying to diagnose problems with the D-jet system.

Good luck and let us know what you find.

Thanks for the responses. No, the idle doesn't go up and down, it just rapidly drops down to nothing, as soon as I lift up off of the gas.

Re: "Did something change suddenly or over time?" The issue started happening right after I had it in to the shop for a tune-up. However, I took it to the shop very quickly after buying the car, so it's possible that it had this symptom, but I hadn't driven it enough yet to notice it.

Actually, I wasn't aware of that D-Jet site. I've been reading through my Bosch Fuel Injection and Engine Management book, but it is a bit too general.

I'll check out that web site D Jet web site, thanks!

I've spent hours on that Anders site. It's "the bible" for D-Jet. One other thing I just thought of when I looked at the site again: check to make sure your timing is not retarded.

Good luck, and let us know what you find out or what other questions you have.

I would suspect the tune up since this happened right after it. If they set the idle while the aar is still open, the idle will be low at full warm. Let the motor get warm then set the idle with the air bleed screw. It should idle high when cold and come down as it warms.

But only after you check the dwell and timing.
And make sure your advance plates in the distributor are clean and have new grease.

Then, set the idle when warm.

rich

The advance plates issue is becoming so common someone should do a write up on cleaning one. And not me, my plate is currently full.

I have a writeup somewhere. It's really as simple as taking the plates out and cleaning them with a degreaser. Then relubing with a good dielectric grease and putting it back together. The plates need to move freely - that's the simple goal. Just beware of the fragile braided ground wire between the plates. They like to break loose where soldered if you aren't careful. But there's a fix for that too.

Thanks! It will be great if that's what it turns out to be.

Ok, well I posted this in the wrong threa, but it may help there too...who knows.

http://www.914world.com/bbs2/index.php?sho...lates++cleaning


I know there is a thread with pictures that someone did, might help better.

Dis one

http://www.914world.com/bbs2/index.php?sho...lates++cleaning

Thanks, very useful info! Yeah, that's what I need... info. lots of photos so I can figure stuff out. As mentioned above, a newbie at this.

I had the same problem. Turned out to be the cylinder head temperature sensor was bad. Car would start up and run no problem, at some point lose the signal (maybe an open or short?) then the computer apparently had no idea of how to fuel and the car would just stop. Let it cool for a while and it'd start right back up again.

Just went through this as well.

In my case my MPS was faulty. If you have spares, try changing it out.

If you have many spares I'm hunting for one for my 2.0L

I've got a spare MPS IF YOU WANT TO PLUG ONE IN TO CHECK IT OUT. Sorry for the Caps. Mobile phone misery.

X2. What Rich said.

WHAT? CANT HEAR YOU

Thanks for the input, all. Haven't had a chance to muck around with it yet, so just been heel-toeing it at the light to keep the revs up. Will get to investigating this properly next week.

You may want to find out how the AAR really works....... It is open when cold to add extra air to the cold start fuel enrichment, then, as the engine warms up it closes off the additional air to avoid a lean high idle. They usually stick in the open position when dirty or the heating element no longer closes it.

Mike,

Did you solve this problem? I just bought my first 914- also a 1973 1.7l stock FI and I'm having exactly the same issue. Exactly. Car starts up and idles, and runs really well- I just can't take my foot off the gas at a red light for fear of it stalling. Exactly same symptoms.

I will track through other info in this thread, but just wondered if you fixed yours as I would start there first.

Thanks!

Joe

There doesn't seem to be any action in this thread, but I've got the same issue. The bigger problem is once it is stalled it won't start again unless it sits for about 15 min. Then its starts up and I drive off. Very frustrating.

Could this be vapor lock of the fuel pump when it gets too hot?

Brett

As said above CHTS!

Why have we not closed the book on this thread and problem of the o.p. for almost two years? Cuda? You still around?

It sounded like Kellygeorge needed help so I answered.

I hear that. But it's not about him anymore. If more info can surface, that's good for the rest of us, right?

At least he used the search function and came up with something similar to his problem.

I respect that!

My problem was a little different from yours kellygeorge- car started right up and idled fine cold, but would not idle at a stop light after it warmed up. Mine would start back up right away though.

As it was new to me, I wanted to get her running right anyway. So I replaced MPS with a rebuilt one, replaced all vacuum lines, cleaned and then tested AAR (you can find a write up on this site), tested CHTS (which was good) and ultimately replaced FI harness with one from Jeff Bowlsby. Had to adjust timing etc. after all that, but car ran like a top once it was dialed in.

+1 what rich said. I'm thinking 1100 rpm cold is too low. Open up that bleed screw once the engine is warm and set it to 950 to 1000 rpm. Mine is over 1500 rpm during warm up, until the AAR closes and the car is fully warmed up. Oh, and I guess others said this, too, gotta make sure that AAR is actually working. EDIT: I see the problem has been fixed....