1.8 DX Surging idle

Good morning Forum!

Looking for some help!

I'm new here, long time lurker though! Currently have a 1992 Scirocco Scala! I know it's no golf. But you guys seem to know the DX inside out. Information on this forum is immense.

The engine is 1.8i DX. 

The problem I have is a surging idle. From about 600-1200. It's really consistent, and does it under load too. Hot or cold makes no difference either.

The car starts perfectly. There's no rust in the system. 

I have checked every vac line, and replaced. 

It has a new WUR and AAV. All ingnition parts are new originals. And timing is spot on. 

I'm just totally lost now!

Sorry for the long post! Hope someone can point me in the right direction. 

I'll post a video when I get home, as I'm not the best at explaining.

Thanks,

Matt

Welcome to the club first of all. 

I'm mobile at this moment but I'm sure members will get back to you over the next day or two!  

Sent from my mobile phone. 

Thanks for the warm welcome!

Welcome to a fellow Scirocco owner, you could also post on the scirocco register website as I m on there as well and come over to the dark side!
I guess what's happened is your idle control screw has come lose they have do rattle them selves lose as the rubber O ring perishes, the screw/bolt behind the throttle body near the bulk head try removing it and see what the o ring is like 7mm spanner is needed the try increasing the idle when the car is warm to 950-1000 rpm and see if that helps.
The revs are going up and down as the idle control valve is keeping the car running.
Picture of the idle control screw/bolt which someone tried to glue in on a engine I'm rebuilding.

Thanks! I shall indeed try the Scirocco register.

I'm having a play with the car this morning, I'll check that 'O' ring! I'v been spraying carb cleaner everywhere to attempt to find leaks to no avail. 

After checking the the idle adjusting screw I can confirm that's not the problem. Nice and tight. Requiring small spanner to adjust. 

Adjusting the screw decreased and increased idle speed as expected, while the surging remained throughout this.

Ahh it's driving me mad!

I'v taken a small video, in the hope it may help someone hear/spot the problem.

First video upload to a forum, I hope it works! 

Dropbox - VIDEO0013_01.mp4 - Simplify your life

Something I tried to catch in the video is the fuel pump relay clicking! Kind of in tune with the surge.

What that tells me I don't know. 

the relay could be the cause of, or the result of your issue. it is controlled by a rev counter pulse from the coil so for a start make sure the coil wiring is all good as is all the spark system, hall sender in tyhe dizzy, tci unit in the scuttle and all the wirign in between. if it all checks out then try a 17/18 relay in the fuel pump relay socket and see if the problem goes away, if it does try a new relay

Many thanks for that rubjonny

I haven't been able to look at my car! My appendix had to come out instead! Ugh. Once i'm fit again i will check and report back

Thanks again

Thank you John!!!

I checked all wiring and cleaned connections. Made no difference.

I swapped my 'Topran' relay for vw number 18 and bingo. Perfect. Started better then it has in two years with no surging!

My only question now is, what is the correct relay. The current one doesn't have any markings at all. Doesn't work right either. 

Any other brands to go for? Or is second hand VW best? If so, would anybody kindly give me the correct relay number.

Thanks,

Matt

heres a list for you:

VW relay number/VW part number/KAE part number/gsf part number
2 = 321906059D / 3.300.210 / 935VG0090 = no limiter (superceeded by 321906059E-F)
62 = 443907385B/321906059G / 3.300.220 / ? = 6.5k limiter?
63 = 321906059E-F / 3.300.210 / 935VG0090 = no limiter
65 = 321906059H / 3.300.230 / 935VG0080? = 6.5k limiter

earlier cars have the limiter in the rotor arm, later in the relay. you can have neither if you like, just make sure you dont over rev. so basically choose if you want one with limiter in or not then use the part numbers above

Just got one ordered from VW Heritage!

Many thanks for all your help John, and others who helped me. Much appreciated!

Matt