[T3] cool weather idle hunt

[Daniel Nohejl]

Ok, another update. No idle lope after cold start following work, but it was a balmy 61* this afternoon. I drove about 40 minutes in local and highway traffic and the idle was normal. Got off the highway after a 10 minute run at 50mph and the warm idle lope showed up. No headlights or any accessories on. The lope stayed with me for the last 10 minutes of my drive and I stalled twice while parallel parking. Did some errands for a bit less than an hour and soon after starting up the motor, I got the warm idle lope. Headlights on at this point. After a few blocks, the idle went back to normal. It stayed normal for another 30 minutes in city traffic. I turned to go into a gas station and as I exited the turn, the lope returned. 

So how about this: the warm lope is not headlight related, has nothing to do with the FI power relay screw, and probably nothing to do with the AAR either. I also checked the VR ground screw yesterday and it was tight as ever. Absolutely no relays clicking while loping. I have previous experience with loose connections and they produced bad effects on drivability every time I hit a bump. Nothing like that now. This is ONLY observable at idle…..for now anyway b/c the issue is becoming persistent….yet unpredictable. All I can confirm is that it only happens when the engine is warm.

For clarity, I figured I’d link to a video from last February which contains the closest thing I can find to what I’m describing as the “intermittent warm idle lope”

https://www.youtube.com/watch?v=f3phST7MFWE

The major difference is that the current lope sounds even weaker than the one in the video, as if the idle speed is lower. Also, it gets progressively worse….to the point that the generator light comes on and after a while the engine stalls. This video is from when we were testing out a series of MAP sensors to put on our new engine after break in. That lope happened whenever the mixture was too lean as you can see by the AFR gauge. The big difference is that was a constant and the current issue is intermittent.

I tried our AFR gauge out a few weeks ago and it indeed read lean during the lope but nothing astronomical. I didn’t do this to get precidse numbers, but to see if I could observe a trend of lean or rich when loping. 


Daniel








> On Jan 12, 2017, at 3:18 PM, Jim Adney <jadney at VWType3.org> wrote:
> 
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> When replying, please consider trimming your message. Thanks! :)
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> 
> On 12 Jan 2017 at 8:10, Daniel Nohejl wrote:
> 
>> I feel like the words hunt and lope are getting a little
>> confused.....at least in my head. In my head, a 'hunt' is what I've
>> been describing at warm-up idle, where the speed surges very high then
>> dips down until going away and a 'lope' is the weak/stalling idle I've
>> been describing. Is that the correct application of the terms?
> 
> Yeah, the definitions are fuzzy and probably vary depending on who 
> you talk to.
> 
> I use "lope" to describe the situation where the idle goes so high 
> that it hits the FI closed throttle rpm threshold ~1400 rpm. That 
> shuts the FI off until the rpms drop to something like 900. Then it 
> repeats. It sounds much like there's someone on the gas pedal who's 
> blipping the throttle every few seconds.  
> 
> To me "hunt" means more like a random wandering of the idle speed. 
> Could be up, could be down, could be fast, could be slow.
> 
> There's no real idle stabilization in the D-jet system, so the idle 
> on these cars is never rock solid stable. Nevertheless, even though 
> it's not clear to me what you're experiencing, it's clear that it's 
> something out of the ordinary for your car.
> 
> If you didn't have the new electronic VR, I'd suggest that this was a 
> sticky VR relay, which happens when they get old. The contacts weld 
> and then break free. This causes the generator to go from full on to 
> completely off every few seconds. At idle, this causes the engine to 
> slow down every time the generator goes full on. This jerkyness in 
> the generator causes the generator to jerk on its belt, which rather 
> quickly leads to the generator pulley breaking as the belt gets 
> wedged down in the pulley groove.
> 
> Maybe the new VRs have a similar fault, but a loose wire at the 
> generator or the VR could cause the same thing. '69s were the first 
> year that got ground wires on everything, but VW didn't bother to 
> connect the ground wire nicely to the VR at the factory; they put it 
> under the mounting screw, rather than to the less rust prone ground 
> screw. Does the new VR have a separate ground screw? Is the ground 
> there secure?
> 
> 
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
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