A happy medium for idle?

[Jvan_wert]

Should my IP sense the load from my alt when idling? When ever I started the engine it idles just fine unitl I rev it up a bit and turn on the alt. Then it shakes a little. If I turn on the lights or heater it realy bogs down and shakes alot. If I set the Idle so that it idles decently with minimal shake under load of lights or heater fan then it idles high under no load and even higher during initial  start up before the alt starts charging. I do not know what RPM this is all happening at, I do have a tach but no it does not work. I broke my mag pickup during a clutch change.

[8v-of-fury]

Hmm. Maybe you have a weak battery. If it is not helping at all with the high amperage draws then the alternator will be forced to do it all. And you can really notice it drop the idle.

I have a 120a alt in my 84 and i notice when i kick on the highbeams (4 x 100w bulbs) it brimgs the idle down significantly.

[Jvan_wert]

New battery, but that not saying much as it is a vato zone battery. No telling how long it has been on the shelf. New battery and new power wire to the starter and new ground wire. Maybe I have a week ground to my engine, all I have is the wee little braided strap that grounds the tranny to the frame rail.

[bajacalal]

I would just raise the idle.

You can always undo it if you remember how many turns you moved it.

Honestly, I don't think there's anything wrong with having a high idle, especially during a cold start. The newer models had an idle bump associated with the cold start advance. In the days of carburetors (and some early fuel injection) it was normal for the car to idle high until the fuel enrichment kicked off. A lot of police cars had an idle bump for when the thing was parked with the A/C and electronics running. The oil pressure and coolant circulation will be better with a high idle... I really don't see the downsides of idling a couple hundred RPM above what it's supposed to, and I think manufactures spec a low idle for emissions reasons, not because it's that much better for the engine. Maybe, maybe you would wear clutches faster but I doubt it.

[Jvan_wert]

Not sure of the turns. It's kind of a guessing game. The PO to the PO did some turning on the smoke screw and the idle. I had everthing adjusted were were I like it for the most part, kinda slow on the hills EGT up to 800F on full thottle pulls and up 900F on long highway runs. Then I got a little ambitious and turned the fuel down were my EGTs were down 100F almost all around and had the idle up to what I thought was to high. I lost 3 MPG when I did that. I turned the Idle down a little now my bobble head has whiplash.  I might just try to get it back to were I originally set it and call it a day.

[theman53]

if your EGT were 100F then you don't have enough fuel. Turn it back up.

[burn_your_money]

I think me means 100F lower than the other numbers he posted.

I have the same issue with my mom's mk1 Jetta. It idles nice and smooth until the alt kicks in. I wonder if it's the crappy Chinese motor mounts I installed a few years ago.

[bajacalal]

The idle shouldn't much effect the EGTs under power, because the idle adjustment is only the starting point, the minimum amount of fuel being fed.

As an injection pump wears over time, you might have to adjust the idle, to raise it back to where it's supposed to be. So putting it back to "stock" isn't necessarily a going to make it run right, even if you did know where that point was. But I thought you did have it running OK before... If you're turning it up a bit and it's not surging or hanging (failing to return to idle) it think it's within a good range for the idle. I would start turning up the "smoke screw" and by that I think you must mean the "full power screw" because it's not a turbo car, a little at a time, like 1/8th turns in, and then see what kind of EGTs you're getting, to get somewhere in between where it was and where it is now. Hopefully you can turn it up a little and still end up with EGTs you're happy with. And then you will probably have to adjust the idle to get it right, after making the other adjustments, because the power screw affects how your pump meters the fuel, you will then have to re-adjust the idle. But I wouldn't be afraid to end up with a slightly higher idle, especially if it's only during initial start that it idles high. And these always seem touchy, with one little turn too far and it won't run right.

The mk1s also "shake" more than the later cars, even if the engine is not actually vibrating any more, because of the way they're mounted.

I know someone who put a TDI in a 240 Volvo, and mounted it with solid rubber mounts. It would shake the ashtray open and coins and stuff would bounce out. With hydraulic mounts from a diesel Volvo, it's a lot smoother.

[Jvan_wert]

It's a newish pump so I don't think wear is an issue. I turned the fuel back up and adjusted the idle with a warm egine and a load on the alt, lights and heater on. My original goal was to have some power, little to no smoke and smooth (for an IDI) idle. I turned the fuel up past where I had originaly set it when I did the head gasket. It smokes more now during WOT but with the extar fuel I'm not putting my foot that far into the pedal. I don't have to live with the smoke, but I also didn't want to make the guy behind me deal with it. I don't like getting smoked out by those big trucks at the stop light and I'm sure not to many people want to be smoked out by me either.

[8v-of-fury]

Honestly? You'll never get an IDI to stop smoking. The injectors are oversized and the pre combustion chamber is inefficicent. They have smoked since new and always will.

If you've got good power, acceptable EGT's and a good solid idle. Id call this a perfectly tuned IDI engine .

If you dont want any smoke your gonna have to live with very poor power.. Or get a TDI .

[Jvan_wert]

Yep good for power for a 1.6l not sure what good EGTs are but mine saty under 900F on the daily drive. I haven't had a chance to roll it down the highway for a good long full thottle pull, but I image it would be around 1000F

[R.O.R-2.0]

Yep good for power for a 1.6l not sure what good EGTs are but mine saty under 900F on the daily drive. I haven't had a chance to roll it down the highway for a good long full thottle pull, but I image it would be around 1000F

i run ~6-800* going down the road..

~900-1100* (1400 if i want around someone) when pulling hills..

[pointynoggin]

I have AC on my 91so I set my idle to about 900rpm and if it is cold and the AC is on I pull the cold start out to the first detention to keep the shaking down. 

Best thing about these engines is the simplicity and lack of sensors on everything, power to the fuel shutoff and your running.

[Jvan_wert]

All,
   Thanks for the advice and information. I turned up the fuel and adjusted it for smooth idle with a load on the alternator. EGT staying below 1200 and still have good power.