89 Cabriolet rough when cold

I've seen some postings about this before, I think, but don't recall the potential cause/s.

I have a 1989 Cabriolet 1.8L 5speed. When I start it up, the idle is rough, and usually quite low (around 400rpm). If I start driving it while still cold, it may (but doesn't always) stall when coming to a stop. Once it's up to temperature, it's as if a switch has been flipped, and it idles just fine and is in no danger of stalling; it actually runs quite well when warm.

What could be the cause? And is there something fairly straightforward that I can do myself to fix it (not much of a mechanic, but have done basic things such as change spark plugs, fuel filter, etc.), or is it more serious?

Thanks!

-Corey

Reply to
Corey
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I don't recall which engine is in the '89, but if it's any Jetronic variant, this sure sounds like something is wrong in the cold start system. In my experience, on ageing VWs it's usually some sort of electrical connection problem in that case.

You can tell whether you have a Jetronic variant by the existence of a fuel distributor. It has a great big air intake going into it -- usually a black hose of some kind -- and five flexible lines, four of which go into the engine rather like the way spark plug wires go, except on the other side of the engine block.

If that's what you have, then the first thing I'd do is chase around under the hood to see if any electrical plugs are unplugged, or any of the wires are frayed, decayed, uninsulated, or just corroded through. On a car nearly 20 years old, that's pretty common, and simply fixing the broken electrical connection will possibly solve your problem.

If you don't find anything obvious, then I'd suggest either getting a Bentley manual for your car and following the troubleshooting steps for cold start problems, or else taking it to a mechanic who specialises in VWs. All the cold start problems I ever had were straightforward to diagnose and solve, but you have to follow the procedures really carefully, in exactly the order specified, or you'll never eliminate the problem.

If you start taking apart the fuel system, two other points of advice:

  1. Be careful! The fuel system sprays highly pressurized gasoline. You don't want vaporized gasoline around anything hot or flammable, and you don't want it getting through your skin.
  2. Be super clean. Tiny grains of dirt getting into these fuel systems will be a plague on your life forever, and you'll end up replacing random parts until you get frustrated and get rid of the car.

Good luck, A

Reply to
Andrew Sullivan

True of any fuel-injection cold-start system.

Of course, it could be as simple as a clogged 'fifth injector'. Run a couple of cans of Techron or other high-quality fuel-system cleaner through before starting down the disassembly and potential-expensive-repairs route.

Peter Wieck Wyncote.

Reply to
pfjw

Fifth injector is just to richen the mixture or give it a little extra gas as start. It does not squirt any fuel once the car has started. It does affect a slow idle speed. But injector cleaner might clean up the other dirty injectors. It copuld be loose or coroded low voltage cables. Some of the older cars hade a digital idle stabilizer to helpboost the idle speed when warming up or when the ac is running. I don't know if a car as new as this one had that stabilizer. Some of the even older cars had solenoids on the strut towers that bled more air in to boost idle speed.

Reply to
Jim Behning

I'm with Jim here, cold start valve usually only operates when the starter is energized. Now ASSuME-ing the ign system is good, timing, good strong spark at the spark plugs, etc....... It should have an electronic idle stabilizer valve on your vehicle. I think to test it you turn on the ign ON (engine not running) and hear/feel this valve hum/buzz. Check the rubber intake boots to make sure that they are tight and free of cracks. Also check the fuel injector seals since they are usually at their most contracted size when the engine is cold. Also checking the fuel pressure when cold might help you pinpoint the problem. I think your fuel pressure is partially controlled by the fuel pressure regulator (many names for it) on the engine or on the fuel distributor. The FPR will also be controlled by the Engine Control Module which may get reading from a BAD Coolant Temperature Sensor. The engine might be running too rich/lean when cold too. I have seen bad wiring to the 02 sensor (3-wire) cause the fuel mixture to be too rich.

SO CHECK: Fuel Injector Seals Intake Manifold Boots Idle Stabilizer Valve FPR or fuel pressure CTS Incorrect Fuel Mixture

later, dave (One out of many daves)

Reply to
dave AKA vwdoc1

from memory, 89's had digifant FI and don't have a cold start valve. If that's the case I would check the idle switches on the throttle housing first.

Reply to
Lost In Space/Woodchuck

yeah I don't see too many Cabriolets either. I know that the '92 Cabriolets had Digifant II injection. This '89 Cabriolet, like my old '88, shows that it does not have the Digifant II on it

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I think VW might have installed Digifant II on the Cabriolets the same time they installed it on the VW Foxes in 1990 or 1991.

Anyone have one of these years?

Reply to
dave AKA vwdoc1

By the picture it's CIS or CIS-E. The cab's were a funny VW in that they were behind a few years on many of the FI systems. My 88 Golf had Digifant FI.

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Reply to
Lost In Space/Woodchuck

Thanks for all the feedback. I don't drive the car much this time of year, so it might be a while before I get around to checking it out, but I appreciate the suggestions.

Funny...the listing on E-Bay is almost exactly my car -- mine is red with a white top, same interior, almost the same mileage, and I also have similar wear on the driver's seat.

-Corey

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Reply to
Corey

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Thought I'd let you know the end results. I finally took the car in to be looked at. It turns out two temperature sensors were way out of range (don't have the paperwork in front of me, so can't be more specific right now). Both were replaced and a loose wire soldered, and now it idles just fine, even when cold.

-Corey

Reply to
Corey

congrats to you and thanks for updating the thread!

Reply to
dave AKA vwdoc1

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