my car idles like a sleeping giant!!!! help

[wks79]

the car, m20b20 coupe 84'

it idles at 700rpm , and it kinda rumbles n shakes the car a bit when its at idle. (sounds like blurb blurb blurb blurb blurb)

is there anyway i can bump up the idle silghty ..so its less nausea-ing to sit in the car during traffic stops.

cheers.

[Brianmoooore]

Idle speed is just about spot on, and, being a straight six, the idle should be silky smooth.
Find the cause of the problem, not bodge your way out of it.

[wks79]

i'd reckon it might be a rough running afm ...
any advise on that department?

thanks again brian

[Brianmoooore]

AFM shouldn't be contributing anything at idle, although I suspect one that gives an unexpected output confuses the ECU.
Check that the throttle position switch is working properly, so that the ECU is actually switching to the idle map.

[wks79]

how do i know if the TSP is workign fine ?
anywhere i can check ?

[d6dph]

The TPS is the suspect of my lumpy idle. I'd be interested to know how to check it too please Brian.

[Peter325iSE]

Correct me if I'm wrong, but the fuel injection system on E30s is the same (or very similar) as on a number of other 1980/90s German cars, namely the Bosch K-Jetronic.

I had constant problems with my previous car, a 1993 Mercedes 190E, which wouldn't idle right. Go on the 190E forum and you'll see that half the posts are about crap idling.

Considering that the newest E30 or 190E is at least 15 years old and probably has 100k miles under it's belt, there's a chance that these injection systems are getting tired.

Unless you know exactly what you are doing I would suggest you don't start fiddling with the injection system. I'm speaking from experience here! I tried to sort out the idle on my 190E and ended up making it a lot worse. Washing out the ICV with WD40 was not a good idea....

Sorry I can't offer more help.

Peter

[rj]

To test the TPS, firstly ensure that it clicks immediately you open the throttle lever, after about 0.5 mm movement. If there is no click audible, then the TPS will have to be removed and cleaned with carb. cleaner.

If there is a click, tt can then be further tested with a multimeter. Set the meter to read ohms and unplug the TPS connector. Place the probes between terminal 18 (centre) and the outer terminal 2 (left, idle switch). With the throttle closed, the reading should be zero ohms (or switch closed,no resistance).

Then connect the meter between terminal 18 and the outer terminal, number 3 (right, full throttle switch). Now, with the throttle wide open you should read zero ohms. withe the throttle in the half-way position, just off idle (about 0.5 mm off the throttle stop screw) there should be infinite resistance.

[marcp1987]

Sorry to barge in... but would a faulty TPS contribute to silly fuel consumption?

Going to check mine again tomorrow, great write up rj!

[Rich_e30325i]

Where is the throttle position sensor ?

Im guessing on or around the pedal ?

Ty

[d6dph]

Underside of the throttle body iirc.

[E30BeemerLad]

black bit on the bottom of the throttle body

[Brianmoooore]

black bit on the bottom of the throttle body

Take the big air hose off to get at it.
If it doesn't switch just off idle, it doesn't necessarily mean the switch is bad. It can often mean that some muppet has adjusted the "idle" screw on the throttle body, and the TPS no longer moves to0 the idle position.

[georgen]

I hate to say it again, but cleaning out the ICV, AFM and throttle body with carb cleaner may just do the trick for you...

[Brianmoooore]

I hate to say it again, but cleaning out the ICV, AFM and throttle body with carb cleaner may just do the trick for you...

All well worth doing, but the idle still won't be correct if the TPS isn't working.
Incidentally, cleaning the throttle body with carb cleaner can be the cause of TPS failure.
The cleaning fluid, complete with dissolved gunk, can drip down the lower shaft of the throttle butterfly and into the TPS, where the fluid eventually evaporates, leaving the TPS full of some of the gunk that was in the TB.

[Paulcovy]

could it possibly be idle air control valve? ... give that a clean with carb cleaner

[TRANSPORTER]

As I havnt got a silky smooth tickover yet I,m gonna do this TPS job, now for a Dumbass question, I take it you test this with the ignition on but not started, as I write this I can see how stupid it sounds Im a wazzok

[Chris]

If your measuring the resistance on the TPS as above, No the ignition doesn't have to be on. You will be unplugging it anyway to get at the terminals.

[TRANSPORTER]

Yeah just had another look at the pictures and now realise that the TPS is the bit on the bottom and not the bit of wire that plugs into it, (must wake up )