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Discussion Starter · #1 ·
Well, I'm having running issues again. I think the start of this episode would be Saturday, when I drove down to Massachusetts for family stuff; 89 was intermittantly hammered by showers, so there were places where the car was definitely getting soaked. However, the car ran all the way to my destination without incident and seemed to be running just fine; my gas mileage seemed to be OK, too.
On Sunday, after the car had sat overnight, I tried to come home. It would crank and not start, so I tried pulling off the distributor cap and misting some WD40 on the theory that it probably got wet and just needed to dry out. No dice there, either, so I ended up getting it towed to my uncle's house. He diagnosed it as being extremely weak spark, so he cleaned the plugs, cap, and rotor; once he did, it ran well enough to get home. It did stall out as I tried to pull out from his road onto the main road, but once I started it again and kept the RPMs up a little as I pulled out, it behaved all the way home. It didn't seem to be running quite right, but it seemed to be completely functional. The idle was off, though, mostly on the high side (it had been pretty steady around 850 or 900 previously).
Monday morning, I drove into work without incident and picked up a distributor cap and rotor on the way home. Installed those Monday night, and the car seemed to run a little better Tuesday. Idle was still off, high and not particularly steady. I did hear an ungood noise on startup; it went away quickly, so I didn't worry about it. On Tuesday evening, it came back and went away again; this time, since I wasn't in a hurry to leave work, I popped the hood to find that the main alternator bolt (the 94mm allen-head one at the bottom of the alternator) had worked itself loose again. I hand-tightened it as best I could and planned to drive home that way, as I didn't have an allen wrench and had gotten away with hand-tightening it last time it had worked itself loose (i.e. I had managed to get home and then properly tighten it). It fell out partway down the hill, so I ended up driving home without it and putting a regular (non-allen-head) bolt in Wednesday morning because I couldn't source an allen-head bolt of sufficient length locally.
Last night, I stopped on the way home from work and found the allen-head bolt. Once I got home, I installed it and replace a fuel hose that had been damaged but not cut through, something I had been planning on but hadn't gotten around to doing. I didn't start the car because my garage isn't all that well vented.
This morning, I went to leave for work and got to the bottom of hte driveway before realizing that something was rather wrong. I then pulled back into the garage, killed the ignition, popped the hood, and tightened the hoseclamps on the new fuel line so it wouldn't leak. Following that, I backed out and got to the end of my block before the car started behaving very poorly...low power and bucking. It felt almost like a not-enough-fuel situation, so I ended up returning home and re-verifying the hose clamps were tight enough and that I wasn't leaking fuel. I then pulled the plugs to find all four carbon-fouled; I cleaned them with a wire brush and left again. This time, I got a little further before the car started bucking and such. I limped it to Advance Auto on Main St, got four new Bosch Platinum plugs (I generally prefer copper, but they only carry Platinum and +4), and installed them. Again, the car behaved moderately better for a short distance before reverting to bucking, lacking power, etc. I had gotten on 89 because that was the way I was going, so I limped the car (not breaking 60 MPH at all) to the Williston rest area. I unplugged the CTS and drove in to work in open loop mode, which left me with little power below 3k, some bucking just over 3k, and good power from about 3150 upwards. I think my gas mileage is horrible, as the gauge seemed to move more than it should have, but that's really not a good way to determine much of anything (gauge is flaky). I haven't pulled the new plugs yet, but I'd bet $20 they're all carbon-fouled.
Any thoughts on where to look next would be appreciated. I'm pretty sure that the timing is at least close (it's probably not perfect), the wires should be OK (although they do have 20k on them, same as the old distributor cap and rotor did), and it doesn't seem like this could be a fuel shortage issue (I was concerned about that possibility because I thought I might have overtightened the clamps on the fuel hose the second time around and crimped something), since the plugs are getting carbon-fouled.
thanks.
 

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Re: danged Digifant...1991 8v GTI running issues (sparty)

hey, take your digifant module apart, and let it dry out. I had the same problems that you have before, and I searched and searched and searched for the problem by replacing everything, and found out that it was moisture in the digifant computer. I opened it up and used a hair dryer to dry it out. Then everything worked perfectly. -Let me know if that fixes it.
 

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Re: danged Digifant...1991 8v GTI running issues (sparty)

Since it runs ok (better anyhow) when you unplug your CTS, it makes me think the O2 isn't doing it's job. Have you tested it?
 

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Discussion Starter · #4 ·
Re: danged Digifant...1991 8v GTI running issues (MDVDuber)

Quote, originally posted by MDVDuber »
Since it runs ok (better anyhow) when you unplug your CTS, it makes me think the O2 isn't doing it's job. Have you tested it?


Runs almost normal with CTS plugged in and O2 unplugged; I picked up a new O2 sensor on the way home from work to install tomorrow.
 

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Discussion Starter · #5 ·
Re: danged Digifant...1991 8v GTI running issues (sparty)

Well, it's too bad I don't have a scanner... I put a new O2 sensor in yesterday morning and then went to ye first DubsNorth Dyno Day and put down a whopping...wait, ready for this....51 whp. Interestingly enough, that was around 4600 RPM, too, not near 5500 (where I think power should be maxing on this car); peak torque was just a hair before that and around 57 ft-lbs, so I guess the car won't be tightening its own lugbolts anytime soon.
However, despite ridiculously low power readings, with the new O2 sensor she is completely drivable (and actually not as underpowered as one would think...that's gotta be at least 20 whp below stock, probably more like 30-35 whp below stock, and a butt dyno may not pick up on 5 or 10 hp, but it had better pick up on 20 or 30...so now I'm wondering if the car has been running well below spec since I got it). I'm trying to get my motor mounts done today (new tranny mount and front mount have been sitting on the shelf for a couple of weeks; had to have a shop put in the new rear mount after I sheared the big bolt off in the middle of it), and hopefully I'll get a chance this afternoon to try and reset the timing. Last time I set it was after installing a timing belt, and I adjusted it by starting waay too advanced (not intentionally, mind you) and back it off until the Bad Noises went away. That was less than two months ago, so I suspect that the O2 sensor wasn't giving good readings and that the resulting timing settings were ideal only for a car with a failing O2 sensor.
 

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Re: danged Digifant...1991 8v GTI running issues (sparty)

If your O2 wasn't working correctly you were probably running rich and have a pretty messed up Cat too.
 

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Discussion Starter · #7 ·
Re: danged Digifant...1991 8v GTI running issues (MDVDuber)

Well, tonight I set the timing again...and this time I used a timing light instead of just backing it off from where it was pinging. I popped the CTS off, popped off the green cover on the bellhousing, and took the car up to 2k+ (per the Bentley), and the light showed the notch lining up perfectly with the timing notch. My first thought was, "Dead on? It can't be..."
My next thought was, "wait, is the notch the timing mark?" So I looked at the Bentley, where the diagram is as clear as mud if your'e not already sure what you're looking for, and then decided to move the distributor and see if I saw something that looked a bit more like a timing mark. Heh. So I was off by about 7 degrees.
The butt dyno says that things are much improved now, but I don't know about having 50%-70% more power (since 50% more would be 75 whp and 70% would be 85 whp, and 75-85 whp would seem to be about where the car should be). I'll try to work on it for a few weeks and then see if I can get on a dyno again...I'm really curious now as to how much power I may or may not have with the timing set correctly.
 

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Check you catalytic converter
I have had similar problems for the longest time, but after finally checking the cat(which was totally plugged) and gutting(temporary solution) it, great power/mileage
 
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