jerky pick - up

[davidra]

Hi,

I have an S13 200SX (1.8 turbo) with a slight engine problem. I tried
asking my local nissan dealer but the best they could manage was "I dunno
about 200SXs but we could try and plug it into the computer - actually I
don't know if they will plug in to the computer so we'll just play around
with it". So they didn't exactly fill me with confidence.

At light throttle (just as it's picking up i.e. transferring from
coasting/engine braking to accelerating) between 1600 and ~3000 rpm it seems
to misfire slightly; there's no noise, just what feels like a braking effect
(loss of power?) and it is impossible to transfer from coasting to slight
acceleration without jerking (put the throttle down harder and it goes
fine). It might happen at higher/lower revs but just be masked by other
factors... I don't know.

I would be very grateful for any suggestions / advice you may have...

Many thanks
dave rawlinson

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[StuyMac]

Plugs????

Fuel Mixture???

------------------
Stu - The Red Devil http://forums.civfanatics.com/ubb/devil.gif


DIY T3(knackered), dented front wing, FMIC, but need more power !!

[Ripper]

Air-feed pipe for the Turbo loose?

------------------
Ripper

Grey '93 S13 Auto
Mods: Uprated smelly tree
Tree uprated at Ripper laboratories, Florida.

[Jez]

could be the position of the micro switch that senses when the throttle is closed.

Just listen (or use a meter) to find out when the switch operates. It should be *just* as the throttle is opened.

[davidra]

Thanks for your comments... I've taken out the plugs and had a look - they're fine, slight light - brown deposits as expected for 8 month - old plugs. Air filter element new too. Have done diagnostic check on ECU which reports no problems... I don't know how to get any other information on fuel delivery?


Originally posted by StuyMac:
Plugs????

Fuel Mixture???

[davidra]

I would like to look at this - where is the micro switch? On the same spindle as the main throttle butterfly valve leading to the inlet manifold?

thanks


Originally posted by Jez:
could be the position of the micro switch that senses when the throttle is closed.

Just listen (or use a meter) to find out when the switch operates. It should be *just* as the throttle is opened.

[Jez]

yeah the switch it right by the throttle spindle. My was set so the throttle has to move loads before the switch was switched - made it very jerky. If I remember correctly my swich didn't make a sound and I had to use a meter. Also there are 3 connection to the switch - can't remember which two you need to measure the resistance through. Just try the combinations and press the switch with you finger - you'll soon find out how it works.

[davidra]

Is it possible to adjust the switch somehow?

I can't see the car right now so I'm trying to guess what problems I'll encounter!

[Jez]

Yup its easy - just undo the bolts a bit and twist the switch.

[Jez]

Just popped out and had a look.
Leaning over the front of the car looking in the engine bay theres a black box thing on the right hand side of the throttle spindle. It's got a connector on the front - unclip this. You'll see 3 connections. Find the 2 connections that give closed circuit and open circuit (on and off) when you move the throttle. Then undo the bolts a little and twist the switch so it switches just as the throttle is moved from the fully closed position. Tighten up the bolts and check again - took me a couple of goes because it moves when you tighten the bolts.

Hope that helps a bit.
Jez

[davidra]

brilliant. Thanks - I'll try it tonight and let you know the results!

[davidra]

It worked! Pick up is now completely smooth. Worth noting that the idle is smoother too.

It's a *very* sensitive piece of equipment - 1 degree of change can add 300 rpm to your idle speed or in the other direction cause idling problems & jerky pick -up. It seems to be the only connection between the fuel map and the air - intake! So if you get it wrong I guess all your carefully tuned system goes to pieces since at all throttle / rpm combinations the fuel map is incorrectly offset.

Thanks to everyone for your help.

dave

[Jez]

no problem! glad I could be of help