I've been using my mk2 as a daily for months. I dropped in a hotted up 2.0, ported head, cam, using a mk2 head retaining all Digi running gear , and an AGG bottom end with the block breather. My issue is, ever now and then , all too regularly in fact , if I've been cruising and come to traffic for example, the Rpms will "hang" , at between 1500-1750 . Enough to make the car a bit fast for urban traffic. Hit the clutch, a quick blip of throttle , and it'll fall back to 1000 where I set it. Blue temp sender is oe and almost new. Vac lines all fresh. Inlet boot is perfect . I had a torn bung in the rocker cover for the "flying saucer", replaced. I fitted a different AFM. timing and CO are good. The only thing I'm thinking is possible, is the flying saucer, I got a non OE one with an inlet for the block breather, as well as the rocker cover inlet . If I pull out either the rocker cover breather or block breather , the Rpms drop a lot and the idle gets very lumpy. Thoughts and suggestions please .
check the throttle cable isnt sticky, if its the original its probably way past it. also work the throttle body by hand and slowly let it come to rest, listening out for the click from idle switch, might need a slight tweak. while there, check the wiring to the throttle body round the back, give the wires a gentle tug in case they're split inside the plug housing where you cant see
You know John, you're a bit of a star . Don't know if it's the issue or not, but the inner section of my cable is starting to get frayed, I wouldn't have spotted it for your suggestions. Top man.
good stuff, while you're replacing it check your pedal arm isnt bent, the cable should pull nice and straight thru the hole in the bulkhead. the rubber bush for the cable hook to pedal is dirt cheap from VW or GSF if its a little worn. when setting the new cable you want the throttle to be just wide open when your foot is flat to the floor else the pedal will end up bent again
So.. Its not the cable anyway. Although it did need changing. I noticed last night , the butterfly is definitely fully to the closed position and the cable slack, but the engine idling at 1700 rpm ish. A couple of quick taps on the accelerator and it dropped to 1000. It's a bit of a nuisance as it's due test shortly, so I'll have to sort it. It has to be an air leak/bypass somewhere? I'm going to bypass the current twin entry "flying saucer" next. Any other suggestions?
Sounds like what mine did when the idle switch wiring was boogered. Have you confirmed that the info is getting to where it needs to when that microswitch gets clicked?
I haven't Pete, and you're right , I must. Though I thought the wot and idle switches were just for fuel trim?
you definitly need idle switch working to get it to idle nicely, also if you tried to set it up without it the settings could be a bit off as well. next time its doing it, try pressign the WOT switch on top. if it immediately drops then check idle switch adjustment underneath. if nothign happens hold throttle open slightly and repeat the test, the idle should at least change./ if not then you need to have a look at tyhe wiring roudn the back, loves to snap off. or the best one is when the wire fractures under the rubber boot where you cant see give the ends a light tug to check for that
I finally got an hour to myself. In checking the wires for continuity, I discovered a lot of nasty corrosion on the ecu plugs / pins.. Also shaking the Ecu plug could make the car idle high or cut out .Cleaned that, fitted another ecu I had. ..and no difference. It did however seem to fix another issue where the car would randomly falter for a blip of a second while cruising. Went back to the TB, pulled it off and studied it at length. The resistance through the idle switch was almost 0 ohms, better than the spare I was planning to fit! The only thing I could see was the idle switch could be pressed closed a little more than the linkage allowed. A small adjustment and that sorted that. Upon leaving it run til the rad fan kicked in, I couldn't get it to idle high... So maybe when everything heated up the idle switch wasn't always getting pressed ? Literally on the knife edge of on or off? This switch had been off before so it's not impossible I guess . Old cars, gotta love them.
Aaaaaaaahh no. Bugger. Car drove smoother than usual I thought, on a 15 mile spin to the lake for a swim . Not once did the idle rpm raise. Out of the water , to come home and it was worse than before! I stopped, tried the throttle blips, and even that didn't work. On a whim I disconnected the ISV .. And it drove and ran fine again. Disconnecting the ISV before DIDN'T make a difference before, so I'm thinking I had/have 2 similar problems. New ISV on order.
