I have been driving my 1985 Volkswagen Scirocco since I purchased it new in 1985. It has always started and run without incident all these years. I have about 140,000 miles on it and keep it maintained as best I can. Just this summer, I began to notice some changes that have been getting gradually worse. I have had it into the shop a couple of times and the root problem still seems to exist. Here is what I am experiencing: When I start the car (especially in this cold weather), it runs very roughly, so I keep the car parked and depress the accelerator, revving the engine up to about 1500 RPM. While holding the pressure of my foot on the accelerator pedal with a steady force, the RPM increases gradually over a 1 to 2 minute time period until it “opens up” and smoothes-out at around 2500 RPM. Then I let off the accelerator and can drive away with the engine running fairly well. Occasionally, the car will not start on the first try. I have NEVER had this problem with my car. Do you have any idea what could be the root cause of these symptoms? My spark plugs, plug wires, distributor, rotor, timing belt and water pump were all replaced by my mechanic this summer with no significant effect on the engine performance - except that, after the tune-up, the idle speed was too low (around 600 RPM) which would almost kill the engine. My mechanic advanced the timing which helped the idle speed but, according to him, put the timing out of spec. Now it usually idles at a reasonable 750-800 RPM but occasionally will get stuck at around 1200 RPM after driving for about 20 minutes. Any ideas? Thanks for your help!
The first step should be putting the ignition timing back to what it should be; especially if it was advanced more than a couple of degrees. Too much advance, some extended highway driving, and you may kiss the engine goodbye.
The second step is have the car diagnosed by a VW dealer or an independent shop that is familiar with CIS fuel injection. (also used on SAAB, BMW, Mercedes, Volvo)
The problems you’re having could be related to air leaks (fuel injector seals) which are very detrimental to CIS, a problem with the control pressure regulator (also a cantankerous affair), faulty fuel distributor, or any one of a half dozen other things.
Checking and repairing injector air leaks is easy; testing the fuel pressure, fuel press. regulator, etc. requires a special pressure tester and knowledge of the system.
Those 2 things should be the first items looked at.
How about the cold start injector or the warm up regulator(the one you could adjust pressure by driving a pin in) I had one poor cold start SAAB 900 that had a feed wire broken at the starter. You are right the potential faults while not endless but are many.
I am not sad at all to never work on a CIS car ever again.
If you want to keep this running, get the Bentley manual:
How’s The Compression?
When I worked at a VW dealer in the late 70s, early 80s, I drove a Scirocco company car. They had little pucks of various thicknesses to lash the valves. Does your’s have these? Has it been done recently? You did a lot of electrical tune-up stuff, but I’m wondering if you have poor or uneven compression.
Yes, thanks for asking about the valve discs (“pucks”). At the time I had the tune-up, I requested that the valves be checked and adjusted. I don’t know if the compression was measured or not.
Thank you. These are good suggestions. I don’t want to ruin my engine, so I’ll ask my mechanic to put the timing back to where it should be - then I’ll suggest your second step.
I do already have this manual and it is great for most of my needs. But when it comes to problems like this that are difficult to analyze, I have trouble knowing where to start my troubleshooting.
Whenever there is an engine performance problem on a CIS injected car Step One is connect the special fuel pressure guage and follow the CIS diagnostics.
Without that guage and the CIS troubleshooting chart you’re just about dead in the water.
The only easy thing you can do yourself without getting too deep is verifying whether or not the injectors are sucking air or not. With the car at idle take an aerosol can of carb cleaner and give a quick shot to the area where the injectors plug into the intake manifold.
What you should be surprised by is if they DON’T leak! Most do after a few years.
Go over all vacuum lines, fittings, etc. following the injector check because any vacuum leak can cause CIS to go stupid on you.
Another possible cause of rough running is a bad injector spray patterns. This is very common with CIS injectors; just as common as air leaks. There is a method a DIYer can use to check the spray pattern and I will be glad to describe it if you would like.
(And I can’t stress enough about correcting the ignition timing. A couple of degrees is not an issue but 5, 6, or more could mean a trashed engine on a highway trip.)
As an afterthought, I can probably post a pic of my homemade CIS fuel pressure gauge and explain how to assemble one if you would like.
The “store bought” ones are pretty pricy and I think mine cost about 20-25 bucks to build.
If the injector seals are as easy to replace as they were on my '83 GTI, I’d just replace them now, especially if they haven’t been replaced already. Mine were just a pull out replacement, no tools, IIRC.
If a CIS car came in the shop and the car had driveability problems and I told the Service Manager I wanted to replace the injector seals because they were easy to do, things would not go good.
Why? A common problem, cheap parts, do it yourself? These things fall under ‘maintenance’ instead of ‘repair’. I don’t understand.
Wow! 83 GTI. You Just Triggered A Falshback To The Black 84 GTI Company Car I Had In 84.
I think that was one of the most fun cars to drive that I have driven. I had trouble keeping that little thing near the speed limit. It was a blast!
Not proper diagnosis to say “common problem” thats good enough for me. It’s like thinking a TSB will be the fix for your car even if its fits in the year and model called out, it may it may not.
For the DIY have at it. If you are going to charge or expect to get paid you better have customer approval and it better work,none of this "it was a good guess NOW lets do some diagnosis. Very dangerous to rely on the “common problem” approach in auto repair.
I got bit once on a BMW V-12 the sympton was rough idle (would not pass emissions high HC) common problem with those engines was intake manifold gasket leakage,test with spray was inconclusive,just couldn’t say idle changed with spray. I went ahead and changed the manifold gaskets (required lots of fuel line replacement and injector seals 5.5 hrs labor) didn’t fix it.
Another “common problem” with those engines was secondary ignition wire failure,did that to $300.00 a side just in parts,didn’t fix it.
I’m not recommending that the injector seals be replaced because they’re easy to do.
Only that it takes about 10 seconds to verify if they’re leaking or not before proceeding to the fuel pressure check.
The amount of fuel is controlled by the fuel distributor which is controlled by the air sensor plate and any air leak at all is going to affect the amount of fuel discharged by the injectors.
Injector seal leaks, faulty injector spray patterns, and problems with the control pressure regulator (warmup regulator) are all very common problems with CIS systems.
Considering the OP has a problem with accelerating or not starting on the first try this could also point to a weak fuel pump, faulty fuel pump check valve, faulty cold start valve problem, or even an electrical glitch in the fuse block. All of those things are not unheard of on CIS cars. Back to fuel pressure check again and diagnosis time.
Same here, most fun car I’ve had (12 years, after a Scirocco for 3 years), got to drive it flat out frequently, no tickets!
Sometimes wish I still had it…
If this '85 still has its original seals, I’d replace them, regardless. OP, what’s up?