Let the flaming begin!!!!! (gasser question)

[rabbitman]

Sorry guys but this is a gasser question........vdub though.

The car is a 91 jetta 1.8L Digifant with about 230,000 mile on it and the engine is all original.

It starts fine with a warm engine or in warm weather but after sitting all day at about 0F or colder it won't start good at all. It cranks really fast and slowly begins firing more and more and finally starts.

I have no idea what the compression, spark timing or cam timing is at. The poor car gets little to no maintenance ever and usually when it's sat a while it'll puke out a blue cloud on start up.

Anybody have any ideas?

Thanks

[Vincent Waldon]

Obviously the answer is "check yer glowplugs"...er...wait....

Assuming that cold start is the primary issue: Digifant uses two temp sensors to determine if it should enrich the mixture for a cold start:

- air intake sensor mounted on the MAF (Bosch unit between the air filter box and the throttle plate).  To test pull the harness connector and use an ohmmeter to check between the two left-most pins... should see somewhere between 200-6000 ohms.  The Bentley has a graph of resistance vs temp.. for example at freezing you should read 5000 ohms or more.

- our traditional beloved coolant sensor... blue two-pin connector found on the head coolant flange that feeds the upper rad hose.  Proper resistance is again somewhere between 200-6000 ohms.

You could start by confirming that both sensors are ok... the blue coolant sensor is particular is known to be temperamental and many mechanics replace it summarily at the first sign of *any* engine trouble.

You mention blue smoke... which suggests something else may be going on....compression for example... but two quick tests with an ohmmeter will pretty much rule out the specifics of the cold start circuit itself.

[burn_your_money]

I know nothing of digi2 but I would do a voltage drop test

[Rabbit on Roids]

digi2 is garbage. thats all you need to know. and if you are (un) lucky enough to have a DIGI 1 car that isnt a corrado, good luck. un boosted digi 1 is a complete waste of time.

[rabbitman]

I guess I don't even know if this is digi 1 or 2, I'll make my bro check some stuff on it.

[the caveman]

Some basic things to check on all digifants jettas 1- check the plugs [duh] but not just the usual. make sure they are good and snug when putting them back in. 2- there is a ground connection near the side coolant flange. cut the wires, put on a new terminal attach with a new bolt to the side of the intake manifold.3- get a volt meter and check the O2 sensor. 4- check inside the distributor cap and clean the terminals on the inside and the rotor-or replace.5 - the dipstick funnel, they often break and will fool with the mixture.

[burn_your_money]

5 - the dipstick funnel, they often break and will fool with the mixture.

Can you explain how a broken dipstick funnel fools the mixture? Something to do with the PCV presumably?

[maxfax]

Can you explain how a broken dipstick funnel fools the mixture? Something to do with the PCV presumably?

You got it.. False air as it's sometimes referred too.. IF the system uses some sort of air flow metering device such as a MAF, vane airflow sensor, kharman vortex sensor, or the flapper on a Bosch Jetronic, and air is getting into the engine that is not measured (such as through the breather or PCV) it'll screw all sorts of things up..   Older Jetronic systems generaly won't even run with the oil cap removed...

[the caveman]

Like all later FI systems,they are closed crankcase and use the crankcase fumes as fuel - or at least are meant to burn them. So any kinda leak in the PVC or breather or whatever else can vent to atmosphere will play with fuel management. It's just that some cars are more sensitive than others and the 88-92 digifants were. And lord help you if you had a 1990 16V passat with it's setup. It would adapt and adapt to changes [like broken dip stick funnels] to the point of running like garbage. Then when you got everything fixed or tuned, it would still run bad, unless you "forced" it to RE adapt to your now fully functioning system. Took a while to figure them out boy.

[burn_your_money]

LOL That sounds like something VW would build

Thanks for the info guys. Back on topic

[the caveman]

digi2 is garbage. thats all you need to know. and if you are (un) lucky enough to have a DIGI 1 car that isnt a corrado, good luck. un boosted digi 1 is a complete waste of time.

Well like lots of things when they ran properly they were okay. I have a few friends and past customers who had those cars and some are still running fine. My good friend Martha gets sick highway milage with hers-up to 40 mpg and nothing more than the occasional tune up, oh lots of oil changes.

[Rabbit on Roids]

digi2 is garbage. thats all you need to know. and if you are (un) lucky enough to have a DIGI 1 car that isnt a corrado, good luck. un boosted digi 1 is a complete waste of time.

Well like lots of things when they ran properly they were okay. I have a few friends and past customers who had those cars and some are still running fine. My good friend Martha gets sick highway milage with hers-up to 40 mpg and nothing more than the occasional tune up, oh lots of oil changes.

my 92 digi 1 cali jetta had under 85k miles on it when the digi went tits up. it just started eating ignition amplifiers. i replaced 3 and it ate them all, even put on a MSD, but no luck. i know it was probably my stupidity, and probably a broken or bad ground, but i felt like blaming VW, its a pretty crappy injection system anyways. CIS rocks..

[the caveman]

"it just started eating ignition amplifiers."

That was because the spark plugs were not tight enough. saw that happen on a couple of cars. For some reason ,on those digifants they needed a good ground though the plugs . I do agree they were problematic. When we first got them in late 87 we had to push a couple off the transport truck. Cars with 5 kms on them with cooked catalytic converters and more gas than oil in the sumps form all the short start and stops.

[Rabbit on Roids]

"it just started eating ignition amplifiers."

That was because the spark plugs were not tight enough. saw that happen on a couple of cars. For some reason ,on those digifants they needed a good ground though the plugs . I do agree they were problematic. When we first got them in late 87 we had to push a couple off the transport truck. Cars with 5 kms on them with cooked catalytic converters and more gas than oil in the sumps form all the short start and stops.

what the hell would that have anything to do with anything? the spark bolts were tight in the head. i know they were, i just took them back out of that head 2 days ago, and they were TIGHT for sure. that doesnt make sense to me, because its like the ign amp its self had a bad ground or something. you put a new amp module in it, fire it up, let it idle all day fine. but then get in the car, start goin down the road, less than 5 miles later you would be pulled over dead. another thing it used to do, was occasionally it would not start. you could hold the key in the start position all you wanted, but no fire. then turn the key off and back on and it would usually fire right back up.

any posibility it could have been the spark bolt wires? i tried using them on my GTI and when i put them on, it developed a pretty good misfire. and just wouldnt run good. but they seemed like they ran fine in my jetta, no back fires or misses. and they are genuine bosch wires too.

[the caveman]

Get it running and tug at the wires that come through the firewall beside the coil. good place for breaks, esp. the injector connection and wires. And while you're there remove the connections at the coil and clean it up. Dirt and grease seems to collect there. Maybe the body ground under the battery.