It is a 1992 Jetta, with the RV code Digifant 1 8V engine (california only with sequential fire fuel injection, and a few other differences from the normal ones). Its my sisters car, but I have done alot of work on it. It was purchased with about 90k miles, and the valve guides were worn to the point of what i would consider failure (about 1 quart of oil per tank of gas) and it had loud lifter clatter for a few seconds after a cold start. Swapping the cylinder head with a rebuilt one cured the oil consumption, but not the lifter clatter.
Recently, she drove it to school and said it had run slightly rough on the way there, then when she went to come home it would crank but not fire. After cranking it for several minutes it finally restarted and made it about half way home, then died and would not start again. Since it has already had one distributor failure (and so has another car with the same engine that belongs to my friend) I swapped the distributor with a junkyard one, but no change. With new spark plugs it fired and would idle with the gas pedal held to the floor, then rev slowly to about 3k rpm in 30 seconds. it is getting spark, and fuel pressure is 45psi at idle, which I believe is right. Any other suggestions?
How's the oil pressure....clattering lifters, very slow to rev engine, things could be getting bound up internally. Hope I'm wrong, but...
Don't these also have temp sender problems that throws off the ECU?
Its possible something in the bottom end is bad, but it still cranks as fast as it normally would, so idk. It just has an oil pressure light, not a gauge but the light doesnt come on. I do think the engine isn't in wonderful shape though, but if its dead i will just get a new downpipe and a couple other things and swap an ABA bottom end into it. They do have the coolant temp sensor that makes them run weird if it dies, but when they car is working normally it will run with it unplugged. I tried that and it didnt change anything.
Hook up a gauge. I have an engine with a large rod knock, oil light doesn't come one, and it spins over with no problem. Runs well, too--until the oil heats up--then it exhibits characteristics your sister described. At least you ruled out the temp sensor possibility.
Grounds? My 92 (non cali- digi II) ran terribly till I did all new grounds. Still needs an ABA transplant but......
Oh and hit up the 8V forum over on VWVortex, they are all pretty helpful.
How's the fuel pressure under load? If the pre-pump goes out it will idle fine, but struggle to accellerate and have hard cold starts.
I can't get it to run well enough to test the fuel pressure under load, but the symptoms are more severe than should be caused by a failure of the in tank pump. Most of the common issues will cause driveability problems but still let it idle normally, but this will only barely idle or sometimes not at all.
Check the ECT for correct operation. ECM may not be adjusting fuel correctly if it's not getting the correct signal (doesn't know if the engine is cold or hot). Check O2 sensor as well. Check fuel filter for blockage as well. On a digifant car it's easy enough to remove and reinstall.
Last possibility is that the replacement distributor from the junkyard was also bad, then its getting towed to a shop. I will try another used one today, and I guess it will lead to 1 of 2 conclusions. 1. if a digifant car starts running bad for no obvious reason, swap the distributor before you waste much time (its not testable, and a common failure item), or 2. (if the distributor doesnt fix it) dont buy a digifant vw.
I converted my 92 Passat to Digi1 and had very reliable experience with it. Much easier to diagnose with the right tools compared to CIS (flame suit on) and an experienced technician.
Did you check the intake boot plenum for cracks on the underside as well?
I did, the reason i think its the distributor is that I had it running (very rough at around 3k rpm) and within a minute the downpipe was glowing bright orange. Distributors are a common failure (already replaced once, but the car still ran when the first one failed), so maybe thats what it is. If not i really dont know. VW 8vs seem difficult to get running right becasue they can still work with alot of stuff really wrong, and most people dont use them anymore (mostly swapped to Vr6, etc).
maybe the cat is clogged?
Well I thought it might be, but it still doesnt work with the downpipe unbolted from the cat.
Extreme hot exhaust? Too lean?
Fuel pressure is ok, I guess it could be lean, but glowing exhaust can be timing related too.
Take a look at the MAF resistance and compare it to the Bentley manual. I had a '92 Digifant 2 Jetta and had some drivability problems caused by that sucker.
So, to summarize, cranks, starts, runs like hell. Good fuel pressure, glowing exhaust? Take a look at the oxygen sensor too. Had that fail on my car, but she went full rich, not lean, and was much akin to a mosquito fogger when I flogged it. Pop off the timing belt cover and make sure it didn't jump time. Since the 8v's have a dizzy driven off the oil pump and crank, it's possible that you wouldn't see a jumped belt thru ignition timing.
Computer doesnt read the oxygen sensor when its cold, so thats not it. i checked the air flow meter and its within spec (it also doesnt run any different with it unplugged, and a properly functioning one will idle normally without it. Timing belt doesnt appear to have moved, and compression is good. I tried another distributor, and still no change. I did notice that the distributor moves side to side with the engine running. I will have to do more investigation, but it may be a more serious failure. Its kinda annoying that 8vs will often go 400k with lots of abuse, and this one may be dead at just over 100k.
Ok, still no luck. I have tried everything that was suggested here, and it doesnt seem that any of those things are the problem. I guess I now understand why there are lots of really nice Mk2s going to the crusher.
Thats the whole problem with Mk2s. lol No one bothers to figure out how to keep the 8vs running, because engine swaps are so common. I dont have time or space to do an engine swap, so thats not happening with this one. Its either going to get fixed at a shop, sold or scrapped unless I happen to find out something else to check.
Would anyone be interesting in buying this if I cant get it running in the next week? Its alot of money to throw away, but I dont have time or space to do an engine swap if it either needs one or it turns out to be impossible to find the problem with this one.
