914 lumpy idle
 

Hi,

Not so long ago I traded my 911 for a '75 914 and something else.

Just drove the 914 a few times since aquiring and it has a very rough idle. It smooths out okay over 1500 rpm. It seems to get worse when the car heats up after being driven to the point where it seems like it wants to die if you don't keep goosing the throttle. And if you don't carefully goose it it will stall.

I just put in a new air filter, plugs, plug wires, cap and rotor and will do the points and condenser and check timing tomorrow.

The old plugs had some soot on them which I believe means it is running rich, one was worse than the others but I forgot to note which one came from which cylinder. At start up the exhaust smells rich too. Not totally carboned up but probably more than they should be.

I was vacumming pine needles out of the nooks and crannys and noticed that the vacuum advance has a port on it but no hose connected and I could not see where it was supposed to go.

So, if finishing a tune up doesn't help what should I check next?

Where should the vacuum hose on the advance go (if there was a hose there) and could this be a cause or partial cause of rough idling?

I put my timing light on all the plug wires while running and was getting a pulse on each one so it would not seem to be a miss but it runs like it is only firing on 3 cylinders.

Any help is appreciated.

Thanks,

Craig

Perhaps I should have noted that it has a 2.0 liter engine although I recently found out from a PO that it was a transplant and not the original powerplant.

Does it have the orignal fuel injection? Carbs? Can you get a picture of the engine bay?

Hi Jared,

It is fuel injected, here are engine bay photos.

Craig

PS: I just posted the car for sale on the classifiedshttp://forums.pelicanparts.com/uploa...1310146357.jpg
http://forums.pelicanparts.com/uploa...1310146371.jpg
http://forums.pelicanparts.com/uploa...1310146384.jpg

In addition to a tune up, you also need to adjust the valves to spec. (important)

Ok, it looks like this was orignally a 2.0L car as it has the factory D-jet fuel injection.

The first thing i would do is replace ALL of the vacuum hoses on the engine. The hoses in the pictures look like the original ones it came with from the factory.

2.0L hose diagram

Read this. idle on these cars is almost always affected by vacuum. The whole system works off of manifold pressure.

914 D-Jetronic Parts and Troubleshooting

This is the next thing you should read. It goes over the D-jet system in detail.

Looks like I have some work ahead of me!

Thanks Jared

A lot of the 914s suffer from weak ignition, below 2000 RPM. I solved my issues with the blond with an MSD capacitive discharge ignition. The 914/6 had a CD unit, but it was old and weak. Make sure you run a new wire to the Tach from the RPM output of the MSD, or it will not show RPM but how many sparks.

914/4's don't have capacitive discharge ignition. An MSD really wont do all that much on the 4 cyl cars anyway. One thing I do reccommend is installing an electronic ignition setup, which replaces the points altogether. PEL-PT1847V is the part number. No more burned points, no more adjusting dwell.

Okay I replaced all the vacuum hoses I could find and it did make a big difference, the cold idle is much higher and smoother, seems to run better all around. Still have to finish up some of the other items but looks like I am on the right track.

A couple of questions, I do not seem to have any of the green (9MM) hoses other than those from the auxillary air regulator to the cold start valve and to the intake.

I don't even see a place to hook hoses on with the exception of the front of the right cylider bank and there isn;t anything on it. Were there some changes made on later cars? I am uncertain what year the engine came from, was told it was a transplant by the PO.

Also, the hoses from the decel valve are reversed and I left them that way. Meaning the one coming off the back end of the decel valve goes to where the diagram shows the middle hose on the decel valve should go.

I can easily switch it, what does this affect?

Thanks for the help!

Craig

Make that 12mm hoses.

At least some of the 75 and 76 914s did not have the vent ports in the rocker boxes out on the cylinder heads. I believe those were the ones with smog pumps, but I am not certain on that.

From late 74, the charcoal cannister was moved from on top of the fuel tank to back in the engine bay. There are no lines into the left-front corner of the engine bay; rather the fan shroud hose hooks up to the cannister and the other side of the cannister hooks up to the air cleaner. There is an extra small (don't know the diameter) line going through the center tunnel that also hooks onto the cannister.

--DD

Now it makes a bit more sense. I think all the smog equipment has been removed. There are some things sticking out of the cylinder heads that look like they may have been air injector inlets but the holes have been welded shut. There is no air pump and I don't think there is a charcoal cansiter either.

I think I covered all the vacuum lines there are so on to the next steps.

Thanks again for the help.

Craig