High idle after turning up fuel [Did search, but no answer]

[HP]

First off, I’m a noob when it comes to hands-on...  
And let me clear this up: is max fuel screw the same as idle screw?!  :?
Also, I did search for idle on all the Troubleshooting section pages, but haven't found anything similar.


Passing onto the situation itself; some days ago, when my car was at the mechanic doing some services, I took the chance to ask him to turn the fuel up a tiny bit.
Until so, the idle was finely set at around 900 rpm. It was OK, pretty stable under all circumstances. But the mechanic warned me that raising the fuel for more power would inevitably raise the idle too, which surprised me a bit...:?
Anyways, I said it would be fine if it didn’t go past 1000rpm, and he agreed.
The man did the trick and the idle didn’t really go up that much at that time (nearly no difference), which I thought was perfect!
When I drove it home, I soon noticed the engine was then idling well above 1000rpm, and that’s where it's been staying for now, when warm: 1100-1200rpm.
The engine was also already well warm when the mechanic did the thing.

I’m pretty sure the only thing the man adjusted was the max fuel screw. I don’t think he has turned any other screw, like that one with a spring, sideways to the IP, close to the injectors (service idle adjuster, that is?!...) or whatever! I didn't watch it closely, though.


Now, by the description of things here, can you see the cause for the high idling?
I definitely want the idle set back as it was.

As for the actual performance, I didn’t even notice any considerable improvement, really. Maybe it’s a bit better now at higher revs (>3000), I guess. :idea:



I hope people here can help me, cause I’m thinking of messing with the screws myself, as the mechanic went out for vacations... :oops:

Sorry for the looong text.




PS: ‘89 1.6TD JR engine.

[zukgod1]

did you turn the idle screw back out?



dan

[Quantum TD]

did you turn the idle screw back out?



dan

If you want to drop the idle, do as suggested above and loosen the idle set screw. When looking at the pump, it's on the right hand side, where the backside of the throttle lever rests. Loosen the 10mm nut, and back out the bolt with a flat-screwdriver till it's idling where you want it. THen, lock the 10mm nut back in place.

[HP]

Thank you for the replies.


So, fuel screw is actually not the same as idle screw, eh?!


Well, according to this picture from the FAQ 1.9TD topic (I guess the pump is similar enough to comprehend things here):




#5 is the said max fuel screw, right?
Where is the idle screw then??



Let me also put this straight: Idle is normal when the engine is still cold. Only as it warms up, the idle also gradually goes up to 1100-1200rpm.

And yeah, after considering it better, the car is indeed a bit faster now.  

[jtanguay]

i think it has to do with the service idle screw... but that thing is almost like a black art or something... i've messed with it before and the result was my engine would want to die from a stand still.  made the car run weird too.  you would only want to back it off a little bit so the rpm's don't 'stick'.

best bet is to use a combination of the service idle screw, and the residual fuel screw:

IF Idle do not want to go down again or that when you release the pedal on the motorway and that the car does not seem "to compress" correctly, it is possible that you have to unscrew the screw #6 a little (residual fuel quantity adjuster).

[HP]

Hmm, I see...


And what about EGT's? Can this be a problem for my engine now that it has the max fuel screw turned up a bit (and that is currently the only mod)?
Or is EGT supposed to be OK?

[coke]

If your car has the setup that boosts the idle up when you pull the cold start lever out the idle screw is on the backside of the pump. The screw pictured #5 is actually the "Residual fuel pressure" screw on the later pumps, as long as the pump you have matches what I've just said.

[jtanguay]

Hmm, I see...


And what about EGT's? Can this be a problem for my engine now that it has the max fuel screw turned up a bit (and that is currently the only mod)?
Or is EGT supposed to be OK?

you should heed the warnings on the FAQ.  take note of the amount of black smoke coming out of the rear of the car.  too much = bad.  if it concerns you that much, an EGT probe & gauge will run you around $70USD, and gives you a really good idea of what is actually going on in your motor.

[HP]

Alright, today idle rpm's have been lower when warm: 950-1000rpm. As like as a magic touch or something...  :roll:  Any ideas?!
Unsurprisingly, power went down a bit too..



jtanguay, no, smoke-wise, everything is cool. That, at least, is fine.