Page updated on 04-24-2018

88 Jetta starts, idles rough, but no accelerator response

01-01-2009, 12:34 PM
I just bought an 88 Jetta Slalom, it's in pretty good condition but does need a bit of work to get it running it's best, and recently I've run into some troubles that have me completely stumped since I'm very new to auto DIYing.

I don't know if this is related or not, but in the two or so weeks leading to the current problem there were a few times when my car randomly lost power when accelerating and felt like it might stall, but returned to normal after a few seconds. It then had one incident where the coolant light went on while I was driving, but I was close to my destination, got there, parked, and everything was fine the next time I drove it. A couple days after that incident, one of my lights came on (can't remember which one, sorry) and my car stalled, but started back up and drove fine with no warning lights coming back on. Another couple days later I stalled when trying to accelerate from a full stop and had a hell of a time getting the car to start again, but it drove fine once I did get it started back up.

I was also starting to have trouble starting the car in the morning, and on one particular morning when I was running late, I pumped the gas pedal a few times hoping it would help the car start...well, the car eventually started, but I also lost pressure in the gas pedal. The pedal is completely limp and moving it has no effect on the RPMs. The car also seems to idle much more roughly than it did previously. I have started the car several times since that incident (to see if it was something that needed to just be waited out), and it starts up with no problem at all, but still has a very rough idle, and no change to the gas pedal. I can move the car in first gear and reverse by slipping the clutch. It doesn't stall while I'm idling it nor when I'm creeping on the clutch, and is not giving me the trouble it previously did with starting it.

Had an oil change and oil filter change about 2 months ago, but I checked it anyway and the colour and level is fine. All other fluids are good, except it's hard to see where the coolant level is, but I suspect it might need a little top-up (definitely not extremely low, but probably not at the optimal level).

So, if anyone can help me figure out what the problem is so I can plan my next course of action, I would be most appreciative. Thanks in advance for any tips or advice!

01-09-2009, 11:48 AM
It would help if you told us what engine your Jetta has (I think it could have had a 4 cyl with 8 valves, a 4 cyl with 16 valves, a diesel a V6, & maybe even a turbo 4), and the miles on it and the transmission type - automatic or manual.
The limp gas pedal likely means the pedal linkage has come apart - so make sure that when the pedal is pushed down, the throttle valve opens. Do you have a service manual on the car? I think the manual published by Bentley covers your car, and is the best non-VW manual. The Haynes and Chilton manuals leave a lot to be guessed it as to the electronics of the fuel injection and the bank of relays below the dashboard.
I think the rough idle and the stalling when accelerating are either a lack of fuel or too much air for the amount of fuel. On my 90 Jetta there is a large rubber air duct running from the passenger side of the engine bay back to the throttle valve on the intake manifold. There is a mass air flow sensor in the air filter housing. This along with the manifold pressure sensor is what the computer uses to decide how much fuel it should squirt in via the injectors. If that rubber ducting is loose or has a crack or tear in it - the mass air flow sensor will be sensing less air than is really getting to the intake manifold, and the car will be running very lean. Lean enough to misfire a lot. There is also a rubber tube involved in connecting the idle air control valve to the intake manifold. If that tube is damaged or torn - the air leak can cause misfiring. I believe that once the engine is warmed up, the idle air control valve stays shut, unlike lots of American brand cars where the idle air control valve also controls the 'hot' idle speed.
Of course it could be a low fuel pressure situation. Does your car have two electric fuel pumps? One would be inside the fuel tank, the other one located under the car, below the rear seat. If it has one under the seat, it does have two - since there would be one in the fuel tank in any case. If the pump inside the tank quits working, the car will still run, but might be harder to start and tend to stall often. There is a fuel filter by the pump that is under the car, below the rear seat, but I wouldnt try to change it until you established that there was a fuel pressure problem. I consider it a fair amount of trouble to change - and not damage any of the hoses to it. With the car idling, you should be able to hear and feel that pump running. And by taking the gas cap off, you should hear the pump inside the tank running. Its not a loud noise, or shouldnt be anyway.
If you do a search for 'images', using the search words "+jetta +engine +1988" you might find pictures of what your engine bay looks like, and can tell us the image link. I have a jpeg of the engine bay in my 1990 I could provide, if you sent me an email address. I dont think its possible to post pictures on these forums. I could also upload it to now that I think of it.

Sorry I didnt find your posting sooner. I havent been checking the jetta forums much, due to lack of activity on the older models. I actually have two 1990 Jettas, one of which needs its tranny rebuilt. Im a hobbyist, so will eventually get around to doing that.

01-26-2009, 11:18 PM
Hi, thanks for the response (& sorry for my long delay in getting back to you). I am still trying to figure out the type of engine and everything, so please bear with me. It's a 5 speed manual transmission. I'm pretty sure it's a 4 cylinder engine, no idea how many valves, but I'll let you know as soon as I figure it out. I'm pretty sure it's carburated, but I've attached a photo of my engine compartment, so maybe you can help me out a bit with figuring it all out? I'm also wondering if that's a maintenance-type battery?


Since I posted this, my car no longer starts. It turns over, though, so my best guess is that this is all related to the fuel system, and I don't need to worry about checking the battery, alternator, etc??? I checked the throttle cable and it was quite slack, so I tightened it a bit according to the Haynes manual, but that made no difference to the gas pedal. I haven't been able to find any help for checking the response under the hood when the gas pedal is moved, but I will update when I get that done. I also need to figure out what my fuel pump would look like before I can check if I have the one on the outside of the gas tank. I'll try to do a bit of poking around tomorrow when my daughter is at school.

I have the manual that comes with the car, but it really doesn't have any useful information as far as repair goes, basically just how to operate it and where everything is. I tried to get a Bentley manual, but they are quite pricey. I'm keeping my eye out for a good price on eBay though.

I could definitely use some tips on what kind of tools I am going to need to buy in order to figure out what the problem is (I'll cross the 'fixing the problem' bridge when I get to it).

In any case, thanks so much for any help you can give me.

02-04-2009, 12:04 PM
Sorry for MY delay in checking back with this forum.
Your picture shows almost exactly the same things as my engine compartment. You have the 4 cylinder, 8 valve engine, which was the most common engine for the Jettas from 86-90. It is fuel injected. You would be able to see the 4 injectors by looking down at the back of the engine head, between the head and the funny shaped aluminum casting that is the intake manifold. One end of each injector fits into the fuel rail, the other end fits into the engine head. Each of the 4 injectors will have a connector with two wires running to them.
Its true you dont need to worry about checking the battery and alternator - as long as its turning over. The alternator wouldnt have anything to do with it not starting - since the alts. only function is recharging the battery when the engine is running. However, if its turning over -really slowly-, you would want to charge the battery up. If you cant get a charger to where the car is, you can remove the battery, & take it to where the charger is. A battery will be easier to charge up if it is warm, and will also work better when it is warm.
The manual you have is the Owners Manual. Its only useful for learning what the lights on the instrument panel mean, and where to put the jack if you have to change a flat. BUT... It may tell you which fuel injection system you have. They switched from the Jetronics system to the Digifant II system sometime in the later 80's, and it would be important to know which system you have - whenever you need to get parts for it.
At this point I think your worst problem is the accelerator cable not having any tension on it. When you push down on the gas pedal it should want to push back upward. The accelerator cable could have broken, or it could have come off of the lever where it pulls to rotate the throttle valve, or the spring that is wound around the throttle lever could have broken. If you put a brick on the gas pedal, then under the hood you should be able to see whether the cable still reaches to the lever. If it does, try pulling on the cable where it comes out of its outer sheath. If it is broken at the end inside the car, the inner cable would pull out. I see new throttle cables available at for about $11. They would cost a LOT more than that from a dealer. I hope rockauto ships to Canada.
I will send you a private message with a description of things under the hood. It would be tooo long for posting here.

02-05-2009, 02:43 AM
Thanks very much for this help. I will take a look for my fuel injectors tomorrow. The photo in the Haynes manual shows a very obvious distributor cap-looking contraption (edit: ummm, yeah, that would be the fuel distributor) at the front left of the engine compartment (where my big flat box thingy is) with very obvious fuel lines running to the engine at the front of the intake manifold...which is why I thought mine was carburated, it looks noting like that!

The engine turns over good, so I'm sure that's nothing to worry about, but it has crossed my mind that a problem with the fuel system may have led to leaking fuel, so I may not have the full tank of gas I thought I had. I did check for leaks, but that was after I'd driven briefly in my parking lot by slipping the clutch, and started the car several times just to see how it was responding...plenty of time/opportunity for the gas to leak out and evaporate without me noticing. I did notice a slight fuel smell the last few times it was started.

I will check the owners manual for fuel system info, as I know it does list a bunch of specifications in there. For some reason I never thought of that and have been going crazy searching all kinds of resources trying to figure out what kind of stuff I actually have under my hood.

When I investigated the throttle cable, I was able to tighten it on the engine end, and I was able to tighten the bolt to where it pulled the throttle valve open...from my very limited knowledge and experience, the engine end of the throttle cable seems fine. But tightening it made no difference to the gas pedal, it still just sits flat on the floor, I can lift it but it just falls back down. I think I may just go ahead and replace the cable and spring...are there any other components that would be good to replace at the same time? I'll take a closer look at the engine end of things, and see if I can figure out how to access the pedal end of the mechanisms tomorrow and let you know what I've found (or not found).

Thanks again...I really can't thank you enough. I couldn't afford a mechanic if my life depended on it, so if I don't get my car fixed this way, it won't be getting fixed (at least not while in my possession).

Did I say thank you? :iceslolan

02-05-2009, 02:02 PM
Before 1988 Jettas/Golfs/GTI's used a fuel 'injection' system had that a pump located at the front passenger side of the engine bay, with 4 hoses (with metal braid on the outside) to carry the fuel to each cylinder. It was called the Continuous Injection System (CIS). Beginning in 1988 VW used the Digifant II system for the 8 valve engines (except for some cars in California which had the Digifant I system).
And before you replace the throttle cable (or accelerator cable, same thing) be sure to check that it hasnt simply come off the top end of the gas pedal pivot. The gas pedal is a long lever that is pivoted in the middle. When the bottom (pedal) end is pushed down, the top end moves outward, bringing the accelerator cable with it. Maybe the little metal pin in the pivot has come out. You can see that by shining a flashlight up from the gas pedal to the top of its lever. Reaching under there may be a stretch, as its not spacious.
I still owe you that info on what is in the picture.

02-05-2009, 05:04 PM
One thing that may or may not be of note is that this is a Slalom model that was manufactured specifically for the '88 Winter games and sold only in Canada. It has special features obvious to a layperson, such as the "ski sack" (a little door between the trunk and back seats that allow skis to be put in the car easily). As such, there may be some engine features that are different as well, I'm not at all sure.

I just found this brochure ( which says it has a digifant engine, unfortunately, I can't find my owners manual at the moment :P I will keep looking though.
The only things I could find that looked like they could be fuel injectors to me are these:

The round contraption with the white hose/wire to the right (in the picture) of the passenger-side strut (in front of the strut when standing at the front of the car)

or, the hoses on the side of the big flat box at the front passenger-side of the engine compartment

I also took a closer look at both ends of my throttle system:

The engine part seems fine as far as I can tell

the cable enters the interior of the car somewhere in the neighbourhood of the back of the steering wheel

On the pedal end, I'll have to see if I can spend the day during school tomorrow taking off the casing

Luckily, I'm 5'5"/110lb, so I won't have a huge problem getting in there.

I also took a look under the rear of the car and found two contraptions I thought might be a fuel pump the photos are really not great, but I'm hoping they're good enough that someone with experience, like yourself, will know what they are looking at:

contraption 1 - approx under the rear driver's-side seat

contraption 2 - approx under the rear passenger-side seat, or just behind, under the rear of the trunk

02-06-2009, 03:11 PM
I doubt the Slalom version was different under the hood. There were a couple of other 'specials', like the "Wolfsburg Edition" Jetta's - but I think its differences were the outside and inside trim and maybe fancier wheels. My Jettas both had a fold down center section to the rear seat. It has armrests for the passengers, and coupholders in the middle. On one of them the prior owner had to knock that center piece out - due to having locked her keys in the car, but having left the trunk unlocked.
Anyway, the items in your pictures: The 4 injectors are all alike, and lined up. If you see the 4 spark plugs; they are in the front of the engine head. The 4 injectors are opposite them, in the back of the head. They arent easy to see because the round Idle Air Control valve is in the way.
In your first picture: "the round contraption with the white hose/wire" is a vacuum operated diaphram. When the engine is running the vacuum pulls the diaphragm inside, to open the charcoal cannister so the engine can slowly suck in the fuel vapors. Its part of the 'evaporative emissions' control system.
In the second picture: "the hoses on the side of the big flat box" are vacuum lines. One brings vacuum from the intake manifold. Inside the box (the air filter housing) is a thermal valve, whose job is to let the other hose see a vacuum when the air coming into the air filter housing is cold. The other hose runs to a vacuum diaphragm under the air filter, that opens a plastic flap to suck air in from some sheet metal wrapped around the exhaust manifold. This brings in warm air, since the engine runs better and cleaner - if the incoming air is warm. If that system isnt working - it doesnt matter much, though the engine may stumble in damp weather that is slightly above freezing.

In the 3rd and 4th pictures the engine looks fine.
In the 5th/6th pictures: that plastic cover that is hiding the top of the gas pedal is not on mine. Either someone removed it and didnt put it back, or maybe the Slalom model had it, to keep snow from someon's ski boots from getting jammed in around the gas pedal?
In picture #7/#8. Contraption 1. That little goody is the 'rear brake proportioning valve'. Its job it to limit the amount of brake fluid pressure to the rear wheels - to help avoid skidding on snowy or slick roads. But if there is a lot of weight in the trunk or back seat - then it allows more brake fluid pressure to the rear wheels to help with stopping. You brake system is a dual type. I think one half of it operates the front left and right rear brakes, the other half operates the front right and rear left brakes. This is for safety - in case of the system springs a leak, you will still be able to stop. It will be a little scary though, as the brake pedal will travel further toward the floor.
In picture #9/#10: Contraption 2. That is the main fuel pump and the fuel filter. The pump is sticking out of the side of that plastic housing. I believe the plastic housing contains fuel, as the fuel pump is cooled by being immersed in gasoline. On mine (and probably on yours) there is another fuel pump located inside the fuel tank. You access that tank by pulling back the carpet in the trunk, undoing the round lid. Then you can see the plastic ring that keeps the fuel pump and fuel level sending unit in the tank. Hopefully you will never need to replace the pumps. They tend to be expensive, and replacement always involves doing more work than you plan on: due to rusty fittings, etc.
When you go looking for parts, if anyone asks if your Jetta is a Mark-1, Mk-II or Mk-III, it is a Mk-II. And Digifant II only refers to the fuel injection and emissions control system. The engine is a 1.8L 8 valve, non-turbo.

02-06-2009, 10:37 PM
The ski sack is pretty neat, though I may modify the sack part so it will be more useful for carrying long items other than skis (and I'm glad I took the time to pull it out and really look at it because I discovered that I really need to do a good overall cleaning of all the nooks and crannies in this car :P)

I can see the spark plugs (that's one of the few things I was able to identify right off the bat lol) and I also know the distributor cap (and what it does), and basically how an internal combustion engine works (and what it means to have more cylinders and so on). I know how to change the oil and filter, and how to change a tire, test the pressure, etc. Basic stuff and maybe a tiny bit more.

The idle air intake control valve the metal cylindrical bit (not the black plastic disk)? And the intake manifold is the part on the driver's side of the junction at which the throttle mechanism is mounted?

Thanks for all that info on the stuff in the first two pictures. Knowing what the heck things are is the first step to being able to learn anything about them. :biggrin:

The pedal housing is one piece from the bottom of the steering column down and under, so if yours just covers the front and isn't cut/broken/etc, it must just be a feature of certain years or the slalom or something. I took mine off and sure enough my pedal was not attached to anything engine-related. I didn't see a spring? I couldn't get a very good picture because it's very tight under there, but the red plastic housing where the cable comes in is easy to spot and that has a hook on the end of it that does fit into the rubber grommet at the top of the gas pedal (lower center).

I'm the curious type, so I did start sticking it in to see if it would fit before I thought that I might not be able to get it back out very easily (which I wasn't), so I hope that's the way it's supposed to fit together, because it'll be a pain in the ass to get back off. Pedal seems to be perfectly normal now. I adjusted the engine end of the cable so that there was a tiny gap between the throttle lever(?) and the stop because if I recall correctly it has to not be resting on, but be less than one mm away from the stop. I'm not sure how to measure it properly, but I did notice that there was a point in tightening the cable that I heard a tiny click in the throttle mechanism, so I used that as a guide and tightened very slowly until I heard the click, then checked that the lever was not touching the stop.

The car still does not start. I forgot to say that when I tried starting it yesterday, it tried to catch a few times, but after that just continued to turn over with no attempt to catch. Today, after connecting the hook at the end of the cable to the gas pedal, it still just turns over and doesn't try to catch.

When I was finishing up I decided to check for leaks and found a pretty fresh-looking puddle about the size of a baseball (last time I checked for leaks was sometime within the last week, and I didn't see any) under the end of the oilpan nearest the center of the car. I didn't check what it was, but I guess it could only be oil or gas, right? I'll take another look tomorrow hopefully...depending on how the day goes.

You are right about the brake system, it works on a diagonal basis. That was in my owners manual. :)

Where you are talking about accessing the fuel pump inside the fuel tank, is that in a different spot than where I access the fuel gauge sending unit? I keep reading that the sending unit is under the rear seat on the passenger side. My fuel gauge sits on empty until the engine is warmed up, then properly registers how much gas I have, so from what I've been able to determine, I need to replace my sending unit.

I believe I read somewhere that the fuel pumps should usually work for the life of the car, and that they very rarely that correct?

I was curious about the Mark-1, Mk-II, Mk-III thing, thanks. And I realized that I wrote just "digifant engine", but the brochure actually says "digifant engine management system" can I safely determine that I have digifant II fuel injection without finding my owners manual first?

Add your comment to this topic!