HELP! Weird intermittent sputtering problem w/92 Jetta 8v, GF is pissed!: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Sept. 27, 2011 5:18 p.m. SlickDizzy SuperDork

Recently picked up a '92 Jetta GL 5-spd with the Digi "RV" 8v for my girlfriend to motor around in. I bought it from a buddy of mine after he let it sit for like a year...before I even drove it away, I did plugs (NGK copper @.032), and OEM Bosch wires/cap/rotor. Got it going, noticed it ran a little rough, and when I was back home, did the fuel filter (Wix) and topped off the 1/4 tank of ancient gas with a full tank of 89 octane and 1/2 bottle of Seafoam in the tank.

I noticed when driving it around that it would run absolutely awesome, and then not, back and forth suddenly...like you could drive at WOT, then it will sputter, then take off again, etc etc, and it's never consistent (sometimes it will pull like a freight train the whole way, sometimes it will barely sputter up to 2k).

So I Seafoamed it twice today, and put in some OEM Bosch (out of box gap @.031) and it seems to run a lot smoother and pull a lot harder...BUT IT STILL DOES THE WEIRD SPUTTERING! It will pull like a freight train, then sputter and not want to rev, then go back to pulling hard through the rev range...then it will rev out just fine for a couple minutes...then it will go back to doing it again! It seems to only happen under load too, like in neutral just revving it up it doesn't sputter or anything.

Where should I even look? I noticed that the PCV breather was sloppily RTV'd down to the valve cover (I ordered a new grommet), and I went ahead and ordered a new coolant temp sensor just in case. Should I put in ANOTHER fuel filter? Maybe O2 sensor (will probably do tomorrow)? The weird thing is that it is so intermittent, because it will run totally awesome for a few minutes, then run like crap, then back to running awesome, all the time!

It seems to be worse when the car is warmed up. It (usually) runs like a raped ape all the time until it is warm. ANY HELP WOULD BE AWESOME, she is sweating me to fix this, and I'm tired of driving her to work and back every day!
Sept. 27, 2011 5:25 p.m. ransom HalfDork

Do these things have a sock on the fuel pump pickup?

Did it make any difference when you did the fuel filter initially, or had it not really started doing this before you swapped that out?

Caveat: I may just have fuel filters on the brain. My truck's been eating them every couple hundred miles and I've got a new tank on the way from rock auto...
Sept. 27, 2011 5:29 p.m. Streetwiseguy Dork

Go back around the throttle body/firewall area and tug on wires. I have a faint memory of issues with poorly routed wires/vibratingengine/crap german wires. Ground wires maybe?????
Sept. 27, 2011 5:45 p.m. doc_speeder Reader

Firstly, I've had a bunch of these cars, and they never, under any circumstance pull like a freight train with a 1.8 8v...

I had a similar issue with one of my '92's. Turned out to be the air flow meter. If it does it at WOT, then it's not an O2 sensor. Coolant temp sensor is plausible as well, and cheaper than the air flow meter.
Sept. 27, 2011 7:20 p.m. Travis_K SuperDork

Probably not it, but I would check the timing. It's very complicated to set and you need to have the service manual to do it, so most people do it wrong.
Sept. 27, 2011 7:33 p.m. SlickDizzy SuperDork

I am starting to lean towards the CTS. I was driving it around some more today and I noticed the gauge bizarrely sweeping back and forth across the spectrum while driving...I had a hunch the O2 had nothing to do with it, as it would probably run rich/E36 M3ty all the time if that was the case. Part should be here Thursday, we'll see.
Sept. 28, 2011 1:16 a.m. Travis_K SuperDork

BTW are you sure it is an RV code car? Those are the california emissions ones, the other ones have a different code (PF maybe?). There are a few things that are different, like the oxygen sensor plug, sequential rather than batch fire fuel injection, etc.
Sept. 28, 2011 8:24 a.m. docwyte Reader

It's a Digi car, so don't be surprised. Check all the grounds first, coolant temp sensor second and air meter third.
Sept. 28, 2011 9:01 a.m. 16vCorey SuperDork

Travis_K wrote:

BTW are you sure it is an RV code car? Those are the california emissions ones, the other ones have a different code (PF maybe?). There are a few things that are different, like the oxygen sensor plug, sequential rather than batch fire fuel injection, etc.

If it's a '92 it should be a PF. I thought the RV code was the lower compression 8v (non-gti) in '88-'89, then they all went to the PF in '90 or so. I could be wrong, but that's what I remember. Of course someone could have easily put an RV in it if it had engine problems in the past.
Sept. 28, 2011 9:03 a.m. 16vCorey SuperDork

I've also had weird intermittent problems that came from the ECM on digi cars, so if all else fails plug another digi ecm in and see what happens. But at this point I'm voting CTS.
Sept. 28, 2011 10:12 a.m. Cone_Junky HalfDork

Check pre-pump. Although usually not intermittent, those symptoms match a non working pre pump.

CA Digi I cars are still batch fire, they are just wired differently to be able to detect a dead injector for fault code requirements.

Air leaks, air leaks, air leaks. Check for any broken boots, hoses, or leaking injector o-rings. A torn intake boot can spread open intermittently and give similiar symptoms too.

BTW- an 8V is absolutely capable of pulling like a freight train. (of course that requires a few modifications to happen ;)
Sept. 28, 2011 11:20 a.m. Travis_K SuperDork

RV is the 1992 California emissions 8v, I know tha for sure because my sister has one.
Sept. 28, 2011 2:27 p.m. ValuePack Dork

The GF is upset that a 19yo Digi car runs like crap? She should be thanking you that it isn't CIS!

Another vote here for CTS and pre-pump.