Stuttering when warm

[84Raggit]

Just picked up a nice 84 Rabbit Convertible. Neuspeed suspension and lowering springs, bilstein shocks, 3 piece 16x7 wheels, 6 speed, hydraulic diff, and near stock (probably ported) otherwise stock 1.8L. When I bought it, the idle was set for about 1800RPM. way too high, but it drove. I drove it that way for a week or two. (Yes, I am that dumb.) It would run just great at speed, but the temp would eventually get hot, up to 120C or so, and at that point, in any traffic, stop and go, etc., it would start to stutter. OK if I stayed at speed on the freeway. OK if I let it sit and cool down a bit. (Note: the car sat in storage for like 5 years, and had some stale gas in it, so I've been running higher octane fuel, and fuel drier in it.) (Note also: I hear a fuel pump whining a bit, and I smell that nasty old gas/varnish smell whenever it does the sputter, choke, gag deal) (Note also 2: I replaced ALL of the vacuum hoses. they were ragged and dry. Why did I not adjust the idle down then? Well, because I really AM that dumb.)

Obviously, it was necessary to adjust the idle down. Did that today. Ran great at all speeds and traffic conditions this morning, didn't have any trouble at idle or in traffic.....until I had to sit a bit behind a blue hair that didn't know she was in the right turn lane at a red light, and I couldn't just go around the corner. Idle was still nice and low at 1000RPM, but it got over about 100-110C, and it started with the stutter, choke, gagging again.

I drove home, and I decided, in my infinite wisdom, to adjust the idle air screw, since it also seemed to be a bit rich with some black deposit on the brand new muffler I put on almost the day I got it. After disconnecting the 02 sensor and warming it up to 80C and letting the fan turn on twice. (No, I don't have a dwell meter any more, it got swiped, or I wouldn't have tried this. I just have a dvom with no dwell on it now.)

I adjusted the idle/air screw anti-clockwise until I got a slight drop in RPMs, and then clockwise a notch. Set the idle at 900 and connected the 02 sensor. It didn't like it. I adjusted back to about 950, so it wouldn't stumble on acceleration, and took it for a quick drive down the block at about 100C. Hot, for a rabbit I think.

Same deal, stutters, chokes and gags. I parked it, and it's cooling down now. My guess is, I'll go start it, and it'll run fine until it gets a chance to run hot again. I think I was better off before I started screwing with the idle /air screw. At least then, it ran well enough to be a grocery getter, but I want it for more than that, and I have to get it in for AZ emissions testing ASAP which is what started all this to begin with.

So...time to go to the local VW repair shop and have them adjust it for me to get it through emissions, since I really AM that dumb, or is there something else I'm missing? Like maybe the sometimes whining fuel pump noise is the root of all evils? I run it on a full tank most all the time.

Thanks for any advice, because I really AM that dumb.

[84Raggit]

OK, now that the fuel pump (external) has failed all the way....it was whining, remember? When I turn the key, it used to whine for a few seconds, car starts, not a problem. runs a few minutes, and stalls out. Not it whirs less each time the key is turned, until it whirs no more. or not much. A block and a half or so at a time, with strategic stops in as many shady spots as we could find on the short trip home, I called, found a new one and will be installing the in stock external pump tonight. I'lll be ordering the internal transfer pump in a few days, I 'spose.

I still have those questions about it running rich. but for now, running beats not, and I'll know at least that it's not dying from being starved for fuel.

[kamzcab86]

First, welcome to TRF!

Now, to the heart of the matter: The fuel pumps (you confirmed your '84 indeed has two, yes?) are toast. Whether or not you have an internal transfer pump, remove the access cover under the rear seat and look down into the tank. If there is a bunch of crud at the bottom you may have to clean it out before going any further. If your car does have two pumps, replace them both at the same time.

Take a day to do all of this because: After replacing your fuel pump(s), replace the fuel filter. After you replace the fuel filter, clean up the fuel distributor. After you clean up the fuel distributor, pull the injectors out and clean them too (inspect the O-rings; if they are cracked or otherwise shot, replace them). You may want to remove the control pressure regulator and clean it too.

I see you're here in AZ (Phoenix or Tucson due to the emissions part). Give the car a complete tune up if you haven't done so already (also verify that the timing is correct). You may have lost your good meter, but owning a CIS car essentially requires a duty cycle or dwell meter to properly tune it. You can do the "adjust by ear" method to get you by, but you need to connect a duty cycle/dwell meter to adjust the idle and air-fuel mixture properly (these two adjustments go hand-in-hand), and this is pretty much vital if you want to give the car the best possible chance of passing emissions. Go to http://cabby-info.com/cis.htm for adjustment details. To give you an idea: Mine failed by a mere .01 on NOX many years back... .01! I could've adjusted the A/F and driven back through and probably passed, but I knew the OXS and cat were overdue for replacement.

Now, about the temps. Those temperatures are perfectly normal. In fact, during the summer months in the Arizona desert you will regularly see 120 on the oil temp gauge (you are using 20W50, yes?), especially if you're driving in stop-and-go traffic and/or at 70+ on the freeways. However, 120 is at the high end of the normal range; 130 should be considered "running too hot". 100-110 is most definitely average for these cars.

[84Raggit]

Thanks for the welcome and the advice. I'd figured on replacing the one in the tank. For another 2 Bills...pretty soon. I replaced the fuel pump, and now need some kind of special wrench, like a strap wrench(?), to get the banjo fitting tight enough not to leak, which I discovered so I won't be driving tomorrow either.

I did check for any vacuum leaks right away with carb cleaner, especially around the vac lines and injectors, fuel dist and fuel lines, didn't find any, but replaced all the vacuum lines anyway. I think the injectors were probably gone over recently....like when it came out of the garage. I think he had the idle set high so it would run/sell even though the fuel pump was about to go.

I get replacing the filter, and the in tank pump, a was little worried about touching, let alone cleaning up the fuel dist, just don't want to take chances screwing it up, so thanks for the link. (I'm waiting for my Bentley's to ship, dwell meter's on the list, along with a 30 day registration.) I figured I'd just get it running ok with the shade-tree idle setting, and fuel/air tune up, which was faulty thinking why do I bother ?.....I should have just bought both pumps and a dwell meter lol

I feel like I paid for the suspension and wheel/tires and nice looking rag, and got a sweet little rust-free rabbit that needs a little work in the deal. LOL You know and I know...it needs to be set up right before the heat hits, gotta keep movin', so I'm on it.

Thanks again.

[gull]

You may have lost your good meter, but owning a CIS car essentially requires a duty cycle or dwell meter to properly tune it. You can do the "adjust by ear" method to get you by, but you need to connect a duty cycle/dwell meter to adjust the idle and air-fuel mixture properly (these two adjustments go hand-in-hand), and this is pretty much vital if you want to give the car the best possible chance of passing emissions.

Yup. It will also give you the best performance during warm-up, and the smoothest transition from open-loop to closed loop. Once the engine is fully warmed up, the O2 sensor takes over (except at full throttle), but until that happens the mixture is governed only by the mixture screw and the control pressure regulator.

I have a digital voltmeter with a duty cycle mode, and a cheap analog tach/dwell meter. I actually prefer the analog tach/dwell for this job. It's easier to see what's going on.

[84Raggit]

OK, anyone have a source for the internal transfer pump? I found one on RSJ Parts
(part# 357906092C) for a measly $60, but it SAYS it only fits 1988-93 Rabbit Convertible, or 1985-88 Scirocco. While that's right handy and all, I do NOT want to order one on line, wait three days to get it, and have it be the wrong one. So...a VW part number, another good source for the correct part, that would make you a very good person in my book, and I'd tell people that you are a god/goddess as you prefer.

[84Raggit]

OK, a little cross referencing, and I thought I found what I needed. VW part number 191906092G looked like it was the schnizzle, but it's not. Mine was built in 2/84, that part number is for 9/84 and later. Less than totally cool. Of course, this may be the time to pop the cover and see if there's actually one IN there, since I can't buy one for love OR money. LOL

Chapter 2:

Got the old in tank pump out of the tank with no undue sweating, even in this heat. (What a lovely little car the Rabbit is, especially if you appreciate simplicity!) The return hose had altogether disintegrated, and was lying on the bottom of the tank in chunks. The short hose from the outlet to the pump to the cap was reduced to the braiding held on by the hose clamps, and the wire insulation on one wire had also disintegrated, and the float will not float, since it is full of gasoline. LOL

I tested the pump with 12 volts, and it works fine. I tested the voltage at the connector, and found about 10v. It runs the pump, but maybe the relay is somewhat degraded? I read elsewhere it should be 12v. I don't know. It runs fine, so this is a decent fix...for now.

So how much different can the pre 9/84 in tank pump be than the post 9/84 pump? I mean....really? I'm guessing same-o same-o.

[kamzcab86]

Well, that makes a lot of sense. A place doing business as "Rabbit Parts" lists a part for '88-'93 Rabbit Convertibles which weren't even called Rabbit Convertibles, and leaves out the, well, Rabbit Convertibles.

For future reference, that IS the part number for the in-tank fuel transfer pump for ALL 1984.5-1993 Cabriolets and Rabbit Convertibles. The 357906092C number supersedes the previous part number. If it needs a new strainer, that part number is 867906098.

And, yes, 12V at the pump is what you want to see. Clean up all of your ground connections, replace the main battery ground cable(s), and buy a new fuel pump relay (even if that doesn't solve the low voltage issue, it's wise to keep a spare in the car ).

[84Raggit]

Sure, that part is OK for an 84.5 and up, but is it the same for 1984.166 Rabbit Convertibles like mine?

[kamzcab86]

Having been built in Feb. '84, yours is a 1984.6 not a 1984.166.

[84Raggit]

Well, I went and got myself a lovely new multimeter with tach/dwell. and connected it as per the CIS instructions you pointed me to.....and as the fan went through its third, fourth, and fifth cycle, connected Red to Blue/White or Black to Blue/White, the dwell stayed at 90 degrees.....for EVER. Nothing I do changes that.

I also checked the green white wire at the Hall pickup, which gave me a solid, immovable 28.7 degrees, which isn't right according to the how to, but at least I know the meter is working......sort of. Any clues? I am just a little bit wheezed off and having a nice cold hefeweizen for the moment.

[gull]

Your readings are almost exactly twice what I would expect. Are you sure your dwell meter is set for a 4-cylinder engine? You could also try duty cycle mode if your meter has one.

It's also possible your test connector is bad; see http://www.cabby-info.com/readings.htm

Normally the reading should vary, but if your O2 sensor is completely dead or disconnected you might see a very stable 45 degree/50% reading as the engine runs in open loop mode. With the engine warmed up fully, you can try closing the full throttle switch on the throttle body with your fingers; if your meter is working and everything is hooked up right, you should see it jump to 58.5 degrees dwell or 65% duty cycle. This provides a richer mixture at full throttle. (If you're using duty cycle mode and see 35% with the switch closed, your meter is reading the trailing edge instead of the leading edge of the pulses, and you should subtract all the readings from 100.)

[84Raggit]

The new meter doesn't have duty cycle.
The 90 degree reading stayed the same with the o2 sensor disconnected or connected.
The 90 degree reading stayed the same when I operated the full throttle switch.
It may indeed have a faulty connector, since that reading is saying it's fully on all the time.
I had more than one hefeweizen, and in fact, had so many (ok 4) that I had to go buy more today after work, in order to stare into the engine bay. LOL
Now I'm headed to a pool party / birthday party and hoping for shade from the 107 degree heat.
I won't be doing much todaaaaay.

So. Maybe I have a short somewhere. I don't have a manual with a wiring diagram, but given that most of my dash and my radio doesn't work, a wiring problem is more likely than anything else. That 28.7 degree reading at the hall effect connection tells me the meter's ok. even though the reading is a little wierd.

[84Raggit]

OK, for now, to heck with the test plug at the cold start injector. I'll worry about that later. So, in a fit of dammit, I went from the negative wire (green) on the coil to ground. I get 26.5 degrees at warm idle, and it bounces a bit (like a up to 8 degrees) when revved. Do I double that 26.5 number? If so that puts me at about 52 degrees. So, do I richen the mix until I'm reading about 22.5? Or figure out what's wrong with the test plug?

[84Raggit]

OK, for now, to heck with the test plug at the cold start injector. I'll worry about that later. So, in a fit of dammit, I went from the negative wire (green) on the coil to ground. I get 26.5 degrees at warm idle, and it bounces a bit (up to 4 degres) when revved. Do I double that 26.5 number? If so that puts me at about 52 degrees. So, do I richen the mix until I'm reading about 22.5? Or figure out what's wrong with the test plug?