Sputtery

[stevedee]

My 74 2.0L D-Jet seems to be a little "sputtery" in the 2-2.8K RPM range. At 3-4.5K RPM, this car kicks ass (ahem, for a car its size and age anyway). Going up very steep hill Saturday at 60MPH in 4th gear, trying to keep up with a 911 (and failing badly ), I think I heard a few pings. WTF? That's a sound I only ever hear in my wife's ancient Safari when she puts in the cheap gas (now $2.70 in San Diego).

Recently installed Pertronix and reset the timing.

TPS?
Timing?
Need more info?

Thanks.

[Jared at Pelican Parts]

I'd check the TPS, and maybe clean it up/adjust it..

ALso, make sure you're vacuum hoses are in good shape and that the valves are proerly adjusted.

[jurhip]

If you find out, let me know because mine runs 'funny' at that same RPM range, though I am pretty sure I need to adjust the valves (hopefully this weekend if i get the time)

You should do the same if they haven't been check for some time.

BTW, I have a 1.8l with the Pertronix kit installed. However, I have never heard mine knock.

[stevedee]

Hmmmm. I just "did" the valves about 2,000 miles ago. Doesn't mean I knew what I was doing, though.

I'm going to start with the TPS this Sunday. Arrgh! Mother's Day. OK, Saturday morning, then. Then I'm going to turn the dizzy a few degs to the left (CCW). I think the piece-of-crap tach I use for setting the timing might be off. (You know, use the 8 cyl scale and mult by two. I hate trying to read 1750 RPM on that thing anyway.) If I'm going the wrong way to fix the ping, let me know, but I'm going to wing it on the timing.

[stevedee]

Cleaned TPS Sunday. The car runs much better. But after the car reaches full temp, it's still slightly sputters at low RPM's, and especially from a full stop, it seems like it's hard to "get going". I almost killed it once yesterday trying to jump into traffic. The car accelerates beautifully at RPM's higher than 2.5K. Idles at 1200, and won't go lower, which has always been true and never bothered me.

I will check the timing and valves this weekend after the sceduled oil change this weekend. Anything else I should be looking for? Vacuum leak(s)? Thank you.

[JLD56]

Forgive my ignorance but could someone tell me what TPS stands for? Trying to learn all I can about the 914 and solve a few problems of my own. Thanks.

[phantom914]

TPS = Throttle Position Sensor. With D-jet, it tells the brain when the trottle is closed and also provides pulses as the throttle is opened to enrichen the mixture.

Andrew

[stevedee]

Replaced all vacuum hoses except the large diameter ones that go to the air cleaner (thanks, Pelican). Car runs "better". Still sputtery, though not as bad. I set the dizzy a few degrees CCW and turned the ECU knob a couple clicks CCW, which made the car idle better. The problem really becomes apparent when the engine temp is at peak. Drove the car all over hell this weekend. Cruising at 3500 RPM in 5th gear on the San Diego freeways is a blast! But get off the freeways, and the idle will hang at 1600, and sometimes it will drop to 1000 (and chug loudly) at long stoplights. Sensor? A vacuum leak not yet found? Vacuum gauge chatters back/forth 15-16 very fast at idle - not a steady 15. Pressing the gas at a dead stop causes the RPM's to plummet towards 0 for a split second, then "catches" and revs. MPS holds 20 vacuum.

Did an oil change. Strainer had a few funny-looking shiny flakes in the bottom of the cover. Might have been slightly magnetized. PO rebuilt the engine about 30K miles ago (supposedly). Are these shiny flecks a concern? Are they recent or from a long time ago???

Now I just find out I might be missing the PCV Valve. See other recent thread on this subject. Might that explain the brief drop in RPM's when hitting the gas at a stop?

Won't be able to check the valves and sensors until two weekends from now. I know I'm getting nitpicky, 'cause this car runs pretty damn good, but I want it perfect. What do you pros think?

[karlp]

Steve-
Your symptons of high idle (1600) and then drop to " chug" is exactly what mine does, also a 2.0 with D-Jet.
It seems like two cylinders drop out, #2 and #3 in my case. I've pulled plug wires and injector plugs trying to decide if it is fuel or spark related. I can't tell, of course, because it ain't firing on those two anyway.
I recently vented my valve covers and replaced the PCV with a fixed orifice per R** Green***** suggestions. Now I have an idle around 1800 rpm and no chugging. I can't get the idle any lower. The idle air screw is fully closed. I may make the orifice smaller.

It sure seems like I have a vacuum leak somewhere. This is not to be confused with the fixed orifice PCV as that is a deliberate leak.

I also use the vacuum advance port on the dizzy. I have it hooked to the plenum below the throttle body. The vac advance port on the dizzy is the one farthest from the dizzy body. The vacuum retard port is hooked to the port on the throttle body.


Nothing in my reading tells me this is the "right" way to hook things up, but it has made it run best. I'm probably leaving some performance on the table. With other suggested hook ups I've had the thing so bad you could hardly drive it.

Hopefully some one will chime in with "Hey dummy, set your timing just a hair after the web in the fan at 3500 rpm and tie a knot in both distributor vacuum lines and use a smaller orifice in your PCV line and see what happens"

In the meantime I'll drive it.


Karl

[Dave at Pelican Parts]

The vacuum advance is not supposed to "see" any vacuum except at (VERY!) small throttle openings. When the throttle is closed, no vacuum advance. When the throttle is 1/4 of the way open or more, no vacuum advance. It is only supposed to act when the throttle is open a very small amount.

This is why the correct port for vacuum advance is on the throttle body, just barely "upstream" of the place where the throttle plate sits when the throttle is closed. When the throttle plate opens, the edge of the plate is very close to the advance port on the throttle body. The venturi effect creates a relatively-high vacuum at this spot (the air is going through a small opening so it has to go quickly, so the pressure decreases). This pulls on the diaphragm in the distributor dashpot, pulling the arm to advance the timing.

Having the advance connected to manifold vacuum means that it is seeing a higher vacuum at idle than any other time. So the timing is likely advanced more than it should be at idle--which will result in (among other things) a higher RPM idle than you want.

When you do not have two fittings on your throttle body, you leave the advance fitting open to the air. If it makes you nervous to have a bare fitting, then hook up a hose and tuck the other end out of sight underneath the manifold. Don't cap the fitting, or it will interfere with the vacuum retard somewhat.

Make sure the diaphragm in the dashpot is not leaking.

Remember to set your timing at 3500 RPM with the distributor vacuum hose(s) disconnected. You can fiddle with it a few degrees one way or the other if you like, as well.

The functioning of the stock PCV valve is discussed on Brad Anders' website. http://members.rennlist.com/pbanders . He and Ray disagree somewhat on how the PCV is supposed to function; I agree with Brad more than with Ray. I'm not sure how you check to see if your PCV valve is only opening under light loads, though.

Try a very very small orifice in the PCV line restriction, if you don't want to try going with the stock functionality. That should also bring the idle RPM down. Plugging the line entirely will likely drop it further, though that's not that great an idea for anything other than testing purposes...

--DD

[karlp]

Hmmmmm....
Seems I may have an advance port but no retard port on my throttle body?
The throttle body port I have connected to the advance side of the distributor diaphragm is on the same side as the throttle cable connection.
I'm using an 1/8" hole through a brass plug for the fixed orifice PCV setup. The plug is in a rubber tube that run from the intake plenum to the top of the oil filler baffle.
I brazed 5/16" hose barbs into both valve covers and run hoses from them to a tee to the aircleaner, hooked up between the air filter and the throttle body.
Isn't ~32 degrees BFTD right at that web in the fan, to the left of the TDC timing marks when viewed from the rear of the car?

Karl

[Dave at Pelican Parts]

The throttle body fitting pointing back toward the left-rear of the car (this is a 2.0, right?) is the retard fitting. The advance fitting points toward the distributor. This is what Porsche (VW, Karmann, whomever) did for many/most of the 74+ cars. It was probably cheaper to keep using the same dashpot and simply not machine and install the fitting on the throttle body, when they decided to remove the vacuum advance from the cars.

Try using a smaller hole in the plug.

Yes, 32 degrees is right around that big web. But the correct timing for a stock 2.0 engine is 27 deg BTDC at 3500 RPM (distributor vacuum hoses disconnected). Overly-advanced timing will raise your idle RPM. In fact, I've been able to set my timing after messing with the distributor simply by listening to the idle speed--when I got the distributor rotated to where the idle speed was where it used to be, the timing was just about spot-on. I checked it with a timing light, of course, and found that I was almost exactly on. (Maybe I was just lucky...)

--DD

[karlp]

I guess I'll have another go at it.
I have been setting my timing at the right edge of that large web, hoses disconnected. When I reconnect the hoses the timing will not go past the web at upper RPM, so I felt pretty safe that I was not over advancing things. Set like this, right or wrong, gave me the best drivability.

[robertj]

My 75 2.0 is doing exactly what is desribed above, except for the high idle speed. Mine pretty much statys at 1000, except just recently is dips down to 800 and then back up to a 1000 over and over again while stopped. The sputtering and low power below 3200 rpm is getting really annoying. I'm going to re-read the above postings a few more times, dive into the Hanes manual and see if I can figure out exactly how to check the TPS, along with the hoses and electrical contacts.
Not having done any real work on a car before, I was pretty psyched to have made it through installing an injector, a fuel filter, and all fuel lines (except for the long runners that go from the tank to the engine compartment) without incident.

My fuel pump seems a bid loud, and is sounding like it's pulsing instead of running at a nice steady constant pitch, may account for something? then again maybe not. hmmm I'll start with checking to make sure there's enough air in the tires.....

[RandyLok]

Would someone please clarify what years/engines had different types of PCV valves? I have a '75 2.0 and have no PCV valve. Some of my research indicates this is normal... just an open vent to the air box. But I haven't heard a definitive answer to this yet.

[robertj]

"Make sure the diaphragm in the dashpot is not leaking"

What is the dashpot, and where is this all elusive diaphragm?

[Dave at Pelican Parts]

Dashpot == vacuum gizmo on the side of the distributor. The diaphragm is inside of it; it is the thing that gets pushed/pulled when the vacuum hoses attached to the dashpot see vacuum.

--DD

[robertj]

Are we talking about # 13 in this diagram? http://www.pelicanparts.com/914/parts/engine/distributor_small.htm

If so, is the diaphragm fixable? From the diagram, it doesn't look like there's a way to get in there, and from first glance at mine, unless you get to the innards via the 'bottom side' of the device, I don't see anything to take apart.

Thanks :-)

[Dave at Pelican Parts]

#13 is the condensor; #11 is the dashpot.

Repair is simple--replace the whole dashpot. Two screws hold it onto the distributor body, and there is an E-clip holding the actuator arm onto the points plate inside the distributor.

--DD

[robertj]

Simple if you have one, that is :-) I don't see this part for sale on the site...I'm assuming that it's not available anymore?

Not that I even know if this is actually the problem or not...I'm working with a very limited tool selection at my disposal- volt meter and wrenches. Ack, maybe I should breakdown and let someone else look at it- such a defeating concept though.