D-Jet sputtering Options

[JtoTheBeezy]

With no consistency my 2.0 fi car will sputter and shutter. Its hard to tell weather its a lack of fuel or a lack of spark. Its fairly speratic but constant once the car is warm. What I usually have to do is stomp it or feather it past 4k rpm and it runs fine above 4k.

Things ive fixed/replaced
New oil and filter
new fuel filter
Checked/replaced any bad vacuume hoses
replaced and calibrated the tps
checked mps
checked aar. Stays closed 24/7 which is better than open randomly
new cap
new rotor
Adjusted timing to the best of my ability (IMG:style_emoticons/default/blink.gif)

I've owned this car for over a month now and it has never run properly due to this problem. Today im going to check the injector points and do a valve adjustment. I can hear the injectors firing with the key in the on position but they could still have issues I suppose. Help me... carbs are calling my name. (IMG:style_emoticons/default/bs.gif) (IMG:style_emoticons/default/WTF.gif)

[JtoTheBeezy]

http://www.webercarbsdirect.com/product_p/wk288.htm ahhh snap. Ill give it a week haha

[Java2570]

Check your fuel pressure and look for any kinks in the rubber fuel hoses under the gas tank. Don't give up on D jet too quickly, it's a good simple EFI system for these cars.

[914Mels]

If the problem doesn't show up till at operating temp, you might be running on the lean side. The mixture will be richer cold and leans out with time and engine temp increasing.

[JtoTheBeezy]

Forgot to mention my fuel economy is crap! I went threw almost half a tank in no more than 60 miles.

[JawjaPorsche]

Injectors? Leaking too much fuel?

[76-914]

Check your fuel pressure, if high check your return line to see if it is blocked or crimped. If fuel pressure is OK pull your injectors, place them each in a jar then test them and watch for one that is shooting streams or stuck open. Don't drive it until you get a handle on it. That's way too much gas and your probably washing one or more cylinders with gas. Any gas smell on your oil dipstick?

[BeatNavy]

I agree with these suggestions (dwell, timing, fuel pressure), but I'd also check the connection to the CHT. Could a bad connection to the CHT or a failing CHT cause symptoms such as this? If the ECU is getting inconsistent head temperature readings it's going to do funny things. If the engine is warm and you sporadically lose continuity with the CHT the ECU is going to sporadically make the mixture too rich.

Just another theory.

[r_towle]

Adjusted timing to the best of my ability (IMG:style_emoticons/default/blink.gif)

Really?

Sears sells both timing lights and dwell meters.
You need one of each to tune up a 914.

It is THE most important thing you can set and adjust on the car, maybe more important than the valve adjustment IMHO...

I can burn up the motor if down by ear, it can do damage.


Get some tools and welcome to the fun.

[JtoTheBeezy]

Adjusted timing to the best of my ability (IMG:style_emoticons/default/blink.gif)

Really?

Sears sells both timing lights and dwell meters.
You need one of each to tune up a 914.

It is THE most important thing you can set and adjust on the car, maybe more important than the valve adjustment IMHO...

I can burn up the motor if down by ear, it can do damage.


Get some tools and welcome to the fun.

I definitely have a timing light. Timing marks is what im missing. When I Time it to the mark I see it runs like crap. I had it at 3500rpm when I did it. Advanced it a little bit more than the mark.

Ive also realized that it is for sure backfiring so for some reason my car is refusing to burn the fuel. How do I check a cht?

[JStroud]

It sounds like your timing is still off, among other things, I'm in the shop fri-sun if you want to bring it by I'd be happy to help you check it out. Just text me.

Jeff

[Java2570]

http://www.pelicanparts.com/techarticles/9.../914_timing.htm
Check out this pelican tech article about timing and timing marks...

[BeatNavy]

How do I check a cht?

I would focus on dwell and timing as suggested, but if that doesn't help then checking the CHT may be worth it:

Cylinder Head Temperature sensor is located near #3 cylinder. You'll see a sensor wire coming out of the engine tin connecting into a wire off the FI wiring harness. When the engine (and CHT) are cold the circuit resistance between ground and the CHT will be high (~2.5K Ohms depending on year) which ECU uses to enrich the fuel mixture by leaving injectors open longer. As engine warms up, the resistance in that circuit drops down closer to 100 ohms, and the ECU leans out the mixture. A proper functioning CHT (and CHT circuit) is extremely important. You check it by disconnecting the sensor from the wiring harness and checking the resistance value (with an ohmmeter) between sensor lead and ground (negative battery terminal). Do this with engine both cold and fully warm.

If you haven't already, check out Paul Anders' site: D-Jetronic Parts Analysis and Troubleshooting which has TONS of good info.

This is some of the info on the CHT from his site:

•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.

•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.

[BeatNavy]

I definitely have a timing light.

Get a dwell meter too. You must set dwell then check timing.

[TheCabinetmaker]

Classic symptoms of a full rich mps. Get Jeff to check vacuum on it too.

[Gcotton92203]

I had what sounds like the same problem with my 73. 914 2.0 Fluctuating idle, mileage seemed to drop, Bad stumble just above idle. It would fall on it's face and stumble when starting out from a stop, but run fine at speed or when the revs were up. Would also buck under load. I checked all vacuum lines , all good. All ground connections good. Adjusted throttle positioner, tested trigger contacts. All injectors firing. Valves good, timing good, dwell good. I could even be sitting still, throttle just above idle and make the engine shutter like it was missing cylinders. Finally after taking a dinner break, I went back and decided to check a spark plug that had once become loose. It was fine but out of habit I tightened the spark plug terminal where it screws into the plug wire. It was a bit loose so I did the same to all spark plug connectors. Bingo. No stumbling. Nice quick tight revs. Much smoother and steady idle. Sometimes the most difficult problems have the simplest solution.