Very high idle

[Touge318is]

Recently swapped m52, it starts wonderfully everytime with only 2 cranks of the starter, however seems to idle around 3k rpm and has alittle rev hang. *keep in mind i still have a 318is cluster, chip, i ordered an m20 one from the dealer but it was wrong, so im guessing its not actually 3k but atlittle less?

What do you guys think? Im thinking clean the maf, ICV, and unplug the 02 sensor i made (a generic bosche 4 wire spliced i to a m42 connecter). Seemed to fit and i dont have a check engine light so i didnt think it was a problem. However it could be.

Its open headers and idles high so im not really trying to have it idle for too long while i try to unplug things/diagnose.

I unplugged the maf and tps while idling and i think it was more or less the same. Any thoughts? Big vacuum leak maybe?

[ThatOneEuroE30]

Vacuum leak start by doing a smoke test. Cheap and easy way to do a smoke test put the intake elbow on and cut a piece of cardboard the same diameter as it and tape it to the elbow. Poke a hole in the middle of the piece of cardboard and then shove a piece of hose through it and tape around it. Buy a cheap cigar open your throttle body and blow the smoke through and find your leak.

[Touge318is]

Thank you, i will try, is this done with the car off or running?

[ThatOneEuroE30]

Thank you, i will try, is this done with the car off or running?

With the car off

[brads2002]

Is the tb fully closing? My e34 cable just fits with it cranked all the way in. With open vacuum mine hunts all over, not just solid rev.

[Touge318is]

I thought that a vacuum leake would bounce around aswell. Its a very solid idle, no check engine light but it forsure idles high and has a bit of rev, hang.

Im using a m42 throttle cable its a bit long but i made it work. It works great from what ive seen. Im also suspecting the little connector under the intake manifold, it was broken but i got it to work using some zipties. Maybe the actual seal is shot ��

[brads2002]

Check that your tps is clicking closed. I had an s14 that was out of adjustment and not closing in closed throttle. On a cold start the car would hold a high idle. On that car the tps was adjustable when you loosened the 2 screws it could be rotated.

[pazi88]

M52 isn't as ancient as s14. It has potentiometer as tps and not just switch. And the ecu also adapts constantly to the tps changes so there is no adjustment for that. It's done automatically.

High idle is caused by vacuum leak or stuck/broken icv. Also m52/s52 should start immediately when you turn the key. If it requires 2 cranks there is something broken. It's not starting wonderfully :D But that could be also because of broken icv. But first thing to do with some fault in m52/s52 is to read fault codes with inpa for example. In 90% of cases it will tell the fault. No guessing required.

Also if you have the original ecu for m52, it doesn't use bosch lamda semsors. The ecu is siemens and uses lamda sensors made by siemens. But the high idle fault is not caused by that.

[Touge318is]

[QUOTE=pazi88;4856955]M52 isn't as ancient as s14. It has potentiometer as tps and not just switch. And the ecu also adapts constantly to the tps changes so there is no adjustment for that. It's done automatically.

High idle is caused by vacuum leak or stuck/broken icv. Also m52/s52 should start immediately when you turn the key. If it requires 2 cranks there is something broken. It's not starting wonderfully :D But that could be also because of broken icv. But first thing to do with some fault in m52/s52 is to read fault codes with inpa for example. In 90% of cases it will tell the fault. No guessing required.

Also if you have the original ecu for m52, it doesn't use bosch lamda semsors. The ecu is siemens and uses lamda sensors made by siemens. But the high idle fault is not caused by that.[/QUOTE/]

Huh? Thanks for the input but lol? It starts like a brand new car. I mean, you hear the starter do that starter noise only twice and it fires up. Maybe you misunderstood. i have no check engine light... there are no fault codes to read..

Im going the pull off the icv today and give it a look.

[brads2002]

Thanks for the TPS info.

I unplugged mine today to see what would happen. Idle jumped but was real bumpy (just like a vacuum leak).

I think you can clean those ICV's by pouring a little gas or starter fluid inside and shaking around. I have done that with success on e30's but not a newer ICV. Let us know how it goes.

[bmwfan52]

Its probably a very minor issue that you are overlooking, like thortle cable, or pedal rest.

most people on the threads that say its a vacuum leak or something that takes an hour to do are wrong most of the time from my experience.

The 24v swap is straight forward, its the minor tweeks and latter tuning that make the major differences as far as having your car run normal.

Threads with advice about minor details usually are either hard to find or are not/rarely get talked about on forums. imo

[ian e30 318is]

You need a coding plug in your cluster from an m20 car (6 cylinder vs. 4 cylinder). The tachometer will be incorrect without this. I'm assuming you still have the same one from the m42. I went though the same thing with my 318is when I swapped in an s50. Try revving the car to the limiter...if the tach goes past 7k, the coding plug is incorrect. It doesn't sound like a vacuum leak to me since the engine isn't surging or dying.

http://s790.photobucket.com/user/sch...plug2.gif.html