87' VW Golf GT 1.8L 8v stutter
Hello,
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I have a 1987 VW Golf GT with a 1.8L 8 Valve engine. It seems to have the CIS-E fuel injection system. I've got a small stumble that I have been working to diagnose for awhile now and I was wondering if anyone had ideas? So far I have replaced the cap and rotor, spark plugs, wires, fuel filter, alternator, oil change with new filter, new belts. I got the timing pretty well dialed in and the fuel/aid mixture seems good. I've checked the coil and it's well within spec. I've gone through and checked things like the Wide Open Throttle / idle switches and the ohms check was good. The cold start valve checked out good. I did check the coolant temperature sensor and I believe that is bad it's reading 65ohms whether the vehicle is hot or cold (I have a new sensor coming in). I've read if you just unplug it then the ECU will go into an open loop and essentially bypass the bad sensor. The O2 sensor seems to have good ohms readings as well. The ISV itself seems to have a good ohms reading, I recently cleaned it out with carb cleaner and that helped a little. One thing I did read is if you have the key "on" but the engine off you should feel a hum on the ISV which I do, however it's not a constant hum, it pulses is the best way I can describe it. The hum is for 3 seconds then off for 1 second and then hum for 3 seconds and then off for 1 second (on repeat). It's not the ISV though, if you pull the plug off and then test the wiring harness you can see that pattern pulse in the two outer pins on the 3 pins harness. You can see the ohms and voltage flex every 3 seconds. I've checked ground and everything seems good on the valve cover ground, body ground near the battery and they have a great reading (ohms wise). I know some would suggest it's probably a vacuum leak but this pulse pattern happens while the key is on and the engine is off so the ECU I would think shouldn't be checking for vacuum because the vacuum shouldn't exist yet (I would think). So that leads me to believe it's a sensor or maybe a relay of some sort? Any ideas would be greatly appreciated.