Why is my 1994 Jetta sputtering and shutting off on startup?
September 13, 2009 7:57 AM   Subscribe

My 1994 Jetta is sputtering and shutting off on startup. What could the problem be?

I started up my 1994 Jetta this morning and it started, sputtered a bit, and then died. It did this about 6 times before running OK. What could be the problem?

Also, not sure if this could be related, but my temperature light has recently started blinking when the car is started. I assume that it is broken because there is no way the car could be overheated on startup.

Thanks in advance for your help.

posted by *lostatsea* to Travel & Transportation (10 answers total)
If the car thinks it's hotter than it really is, it won't be giving the engine enough fuel for a good start.

However, on a lot of cars there are two temperature sensors...one for the gauge and one for the computer. Your VW is probably this way (my '98 Passat has two sensors, as does my '91 BMW). So, the temp light might be a red herring because it's unlikely that both sensors would die at the same time. Easy check for a mechanic, though.

It sounds like a lean (not enough fuel) start issue to me. Could be a dying fuel pump, fuel pressure regulator, a monster vacuum leak or something else.
posted by paanta at 8:10 AM on September 13, 2009 [1 favorite]

Have you tried pulling diagnostic codes? That's generally where you want to start.
posted by torquemaniac at 8:32 AM on September 13, 2009

Temp sensor.
Fuel filter.
Ignition wires.

It truly could be one of a dozen or more things. As torquemaniac suggests, you need to get the codes pulled. Most places like Pep Boys will do this for free. Or, take it straight to a reliable garage and have them dive-in.
posted by Thorzdad at 9:10 AM on September 13, 2009

stupid question: is there gas in it?
posted by Mach5 at 9:17 AM on September 13, 2009

Did it crank for a prolonged time before it started? Once it started did it run well or just sort of ok?
Has the car been running well up to this point or has it started to run rough recently?

paanta is right about the temp sensors. Late model VWs have a dual sensor (G2 with G62) built into one unit. The ECM gets one signal and the temp gauge in the instrument cluster gets the other signal. However, on your earlier Jetta, there's only G2 and a thermal switch for the fan.
In the past, I've seen bad temp sensors cause rich mixtures, but never no-starting on a VW of this or newer vintage.
The only time that I've ever seen a temp sensor cause a complete no start is in the dead of winter on a vehicle that has an auxilary cold-start fuel injector in addition to its regular compliment of injectors. Your Jetta does not have that.

I agree with paanta about the potential for this to be a fuel delivery problem. The pressure regulator is a pretty typical weak point on any VW 2.0 engine. Either the manifold pressure signal line to it fails or the internal diaphragm just gives up. If the pressure regulator was allowing too much fuel to bypass the injectors, you would have to crank it for a while to build up enough fuel pressure to run the car. And, of course, a weak fuel pump or clogged fuel filter could also starve the engine for fuel.
Are you experiencing any loss of power? Does the car still rev and drive as strong as it used to?

This is pretty easy to check or diagnose, if the car will repeat its symtoms reliably. If your car came in to my shop and I suspected a fuel delivery problem, I would start by clamping off the fuel return line (where unused fuel goes back to the tank after going through the fuel-rail). By clamping the return line, I could confirm that the pressure regulator is doing its job. If I clamp the line and the car starts fine, then I've determined that the regulator is allowing too much fuel to bypass and I've done its job for it by restricting fuel flow. However, if nothing changed, I would suspect a clogged fuel filter or a bad fuel pump.
Fuel pumps have a little non-return valve that works basically like a water bottle in a hamster cage. A check-valve in the fuel pump assembly prevents fuel from flowing back through the supply lines after the engine is turned off, making sure that residual pressure remains in the system to start the car easily next time. If that valve is bad, fuel pressure will drop off when the car sits and you'll have to crank for a while to get it started. Given your symptoms, however, that's less likely. If this had failed, the car would just take a while longer before it started and generally not start and die multiple times.

If you take your car to someone familiar with VWs they should have this sorted out pretty quickly. A pressure regulator or fuel filter is pretty cheap and easy to diagnose.
Worst case, you're looking a fuel pump failure or some extremely unlikely engine management sensor failure.
posted by Jon-o at 9:31 AM on September 13, 2009

my temperature light has recently started blinking when the car is started
Are you sure that's not your low-coolant light?
posted by Jon-o at 9:44 AM on September 13, 2009

lights often blink to signal some other error condition.

When I had this problem a new set of ignition coils fixed it. You need to find a mechanic.
posted by Palamedes at 10:56 AM on September 13, 2009

I would also have the crankshaft position sensor (and its wiring) checked - with a scanner this will show up as 0 or erratic RPM while cranking the engine.
posted by rfs at 6:55 PM on September 13, 2009 [1 favorite]

Thank you all for your responses. To answer some of your questions:

@torquemaniac and @Thorzdad: I have not had the diognostic codes pulled. Thanks for the tip though, this will be the first thing I will do.

@Mach5: Yes, there is 3/4 a tank of gas.

@Jon-o: The car has been running kind of weird for a while. Sometimes the car feels like it will now have as much pick up as usual. It will almost flip into this mode where it feels like it runs kind of ummm dirty? Kind of weak. Also, the oil light will sometime beep on and not stop until I give it a lot of gas. The car has oil though, I have checked that. The temperature light could mean low coolant, I will check into this.
posted by *lostatsea* at 8:22 PM on September 13, 2009

Ok, so you need to get this checked out immediately.
Sounds like whatever's ailing your car is causing it to nearly stall out. You could have a failing ignition coil causing multiple misfires and running on less than all 4 cylinders or you could have a very serious fuel starvation issue that's resulting in extremely low power and rough running.
Either way, you could get it looked at soon.

I would strongly advise against operating your car when the oil pressure warning light is on.
If that light comes on along with, say, the battery warning light, it's possible that it's coming on just because the car is nearly stalling. If it's on by itself during normal operation, it's a serious warning about major lack of lubrication in your engine. Raising the RPMs to turn the oil-pressure light off is certainly not good for it either. A low oil pressure situation is NOT the time to be revving the engine!
Get it checked out. The warning light could be the result of something as simple as a bad oil-pressure switch. I've seen many of these switches leak oil through the switch and into the electrical connector, causing strange glitches. However, in the meanwhile, assume it's telling you the truth and drive with caution directly to a repair shop.
posted by Jon-o at 4:01 AM on September 14, 2009

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