91 VW Fox cuts out HELP!!

I have a 1991 VW Fox that cuts out when I am driving at just about any speed for no reason. It acts like the engine dies for a second but starts running within a second. It does it at highway speed, on streets speed or sometimes at idle. It seems to happen more at crusing speed of 65mph.A code said a bad ECU. I replaced it but no difference.I replaced fuel pumps and filter with no difference. It is expensive to keep replacing a lot of parts without any results. My mechanic is also stumped. I need some reliable advice from someone that has had this same problem. Thanks , Bob

Try to catch it when it cuts out & see if it's losing ignition. Perhaps if you put a timing light on it & vary the RPM's and watch to see if the light cuts out in conjunction with the engine or if the light still flashes as the engine dies. If the light stops flashing then the engine dies, it's ignition. I've had similar problems with bad ignition modules, but it could also be a problem with the Hall sender in the distributor or wires losing connection (the plug at the distributor was very problematic on VW's).

Thanks for the advice. It gives me a starting point to narrow the problem down!

Now the crazy car started to act like it is loosing power but when you give it full throttle it picks up! It still does this at any speed. I haven't purchased a timing light yet to check the spark. Please help!

Sounds like you need a new fuel accumulator - you may just be having trouble holding fuel pressure when the car is cold - if you turn on the car - press on the gas - the throttle will go down - then when it does - hit the gas again - when you take you pedal off it should go back up - keep doing this (if you stall just keep turning it on and doing this it'll eventually get back to idle - unless it doesn't hold idle after about 5 minutes or so - then you may need a new auxillary air valve - if your car idles really low when its cold out but then goes back to normal as the engine warms up then this may be a symptom of needing to replace this part) but just hit the gas - the throttle will go down but when you take it off it'll go back up - what happens is your accumulator usually holds fuel vapor pressure to your car - and then injects it through the distributor to the cold start valve until the thermo time switch gets a reading from the coolant temp on the thermostat that the engine is normal temp - where it will cut off the cold start valve to allow the regular injectors to take over - but if you have any of these symptoms then the parts mentioned need to be replaced - may as well replace your fuel pump check valve (ball bearing may be also leaking fuel vapor pressure) if you have a whiny noise but can't figure out where it's coming from - that's also a sign of a shot accumulator for its job is also to keep the fuel pump noise quiet - a bad spring in the accumulator will cause this - if you don't have cold start problems and you have a CIS - they'll likely happen in the future - I've had this happen to me on both my Foxes -

The car seems to run fine when it is cold. When it warms up and driving at highway speeds or street speeds it actsw like it is starving for fuel. When I push the accelerator pedal down it picks up speed again. The fuel pumps and filter have been changed. The old ones did make noise but the new ones are quiet!

If it's fuel pressure related I would replace your fuel accumulator and fuel check valve - if its air pressure related I would replaced your auxillary air valve - one of these parts should solve the problem - (but if it doesn't hesitate when cold but does when its warm there may be a fault in the thermo time switch - which may be causing it to keep the cold start valve on - even if it means to cut off its residual vapor pressure (coming from the accumulator) so that the injectors can take over once the engine has reached normal temp - the car is very temp sensitive when it comes to its normal operation - I would also check the spark plugs just to make sure there isn't anything that may be causing it to spark irrationally - I remember though that until my auxillary air valve was replaced - mine would lose air pressure causing me to press on the gas even more to bring the car back up to speed (cause what this part does is once the spring activated bi-metallic metal heats up - the valve closes once temp is reached - but if the part is faulty - it would stay open causing air pressure extra uncontrolled air pressure to interfere - if you have low idle in the cold but normal when it warms up this may be a symptom that it needs to be replaced - other than that though I would have to go with the accumulator and check valve - (unless its electrically related due to spark plug/distributor/wire/ignition coil/etc. fouling - but it doesn't sound like that though) but either way - hope this helps! The thermo-time switch I would clean just in case - if there's enough residue covering the material for it to do its job it may also interfere with the performance and functionality of the car itself :)

The car seems to run fine when it is cold. When it warms up and driving at highway speeds or street speeds it actsw like it is starving for fuel. When I push the accelerator pedal down it picks up speed again. The fuel pumps and filter have been changed. The old ones did make noise but the new ones are quiet!

Are you saying this seems to be a different problem from the one first described or is it the same? Anyway, your car should be Digifant so would not have all that CIS cold start stuff mentioned & the check valve is part of the fuel pump. Since you live in CA, can you tell me if it's Digi I or II? If you can read it's codes, what are they exactly? Are you saying it will sputter when at constant throttle (like driving straight down the road), but if you give it more it will clear up and accelerate? It only takes a very basic guage to check the fuel pressure (port is on left side -of the car- of the fuel rail with a 7mm plug in end); 35-40 psi running, 40-45 psi w/vacuum disconnected from fuel pressure regulator. Also make sure it holds at least 25 psi for a few minutes after shutdown. That can eliminate alot of fuel system questions.

If you live in Cali more than likely it is a Digifant II - these cars were specifically designed for that state - you're right about the cold start - my friend has a digifant and where you would usually find the cold start it is sealed up yet connected by two wires this should be found on the intake - the wires connect to something that looks sorta like an o2 sensor near the manifold - yes the car will sputter and hesitate if the right amount of fuel pressure isn't sent to the injectors either from the in-tank fuel pump, fuel pump check valve, fuel accumulator or electric fuel pump - or from the fuel pressure regulator - any one of these parts could be at fault - (trying to remember if the Digi has a fuel pressure regulator or not though since the car is more electrical than mechanical unlike it's predecessor) but if you're losing pressure then there definately seems to be a malfunction with the fuel accumulator for this is what maintains proper fuel pressure regardless of cold starts or not it may still allow normal starts but the spring inside may be damaged and should be replaced - I would have to say that this is your best guess if you are losing fuel pressure - I know that this was the problem with mine before I replaced the accumulator - so this would probably be your best bet

I don't know how to read the codes. How do you tell if it is DigI or II? Thanks, Bob

It sputters at constant throttle and it is the same problem but as I study the problem it seems to be more of a sputter than die at constant throttle that seems to clear up when the throttle is fully depressed. Thanks guys for a lot of good ideas to check!

The easiest way to tell would be to look at the hood sticker & see if it says anything about California emmissions or just Federal emmissions (CA used Digi I). Otherwise, you can drop the module down (it's behind the glove box) and read the label. Digifant I will sometimes only say "Digifant" without the "I", Digifant II will always say so. Reading the codes is the same (repairs can be different). To get the codes you will need to access the diagnostic connectors located inside the center console near the shifter. There are two, one black & one white two pin connectors. One has two chamfered corners, the other has one, I'll call this the top of the connector. Turn on the ignition first then connect a jumper between the two bottom pins for about 4 seconds, then remove. The check engine light will flash once then begin to flash it's four digit codes. One flash, pause, two flashes, pause, one flash, pause, three flashes would be code 1213. Then a longe pause before the next code. Code 4444 is no problems found. Getting the 4444 is common since it is a very basic system. Again, I would check the fuel pressure, which is very simple.

It's hard to tell with Digifant's because they're more computer based than their earlier models with the CIS-E engine - I would have to say that it might be a malfunction with the MAF or the ECU itself - this has been the most likely cause for cars that I have heard of to have this type of problem - but if a decrease in pedal pressure is causing the car to lose normal pressure I would also have to say that there may be a fuel problem somewhere between the check valve, accumulator, or the injectors themselves - these are usually the parts responsible for lack of fuel pressure - fuel pumps may be as well but I know that they'll take quite a beating before they give out so I seriously doubt that would be the problem - lack of residual fuel vapor pressure perhaps - esp. if the car cuts out sometimes (or more often over time) then the accumulator and check valve I would tackle first before dealing with the injectors - the accumulator holds and maintains the fuel pressure needed for the car to run normally - if the spring is bad then the fuel may be cut off more than usual under normal driving conditions (it feels worse when it is cold - or hesitate more I should say) but if you're getting a low idle then it is more air related than fuel related - if you're getting cut offs and deceleration while giving normal pedal pressure than it is more fuel related than air related - you could also get a Bentley and a fuel pressure gauge to see if its fuel related rather than air related - I have also heard that if you have a bad O2 sensor - it might be a miscalculation in the accuracy of your air/fuel mixture - esp. if you need a new catalytic converter - you can buy cat cleaners at auto part stores for about $5 - if there is a clog in the filter in your cat this should help both your cat and your sensor (and possibly lower your emissions as well) allowing a better sensor reading if you're running too rich (too much fuel) or too lean (too much air) anyways - just some thoughts to think about - I love this car - it really is a good car to have - reliable - but when it has a problem (which it usually shouldn't - but when it does) it can be very frustrating - some say that ya really have to get to know the anatomy of this specific car (which also has the same fuel system of the Porsche 928 or as some would say 'the poor mans Porsche') in order to keep it running inexpensively - my mechanic even has probs figuring out this car - which is why I try to know as much as possible about it's processes of each part to help myself as well as hopefully helping others with new and similar situations - hope I have helped you with this reply! :) Good luck!

Frank -
89 VW Fox sedan (R.I.P - starter finally went - transitioned to 90 and used as a parts car before being towed away)
90 VW Fox coupe

My car does that exact same thing. Except mine usually cuts out when I am turning a corner, not usually on straight-a-ways, I always thought it had to do with my car getting too hot because that's usually when it happens but my temp gauge isn't working and when it does it, my car usually isn't overheating, so it's hard to say. Any ideas?