Author Topic: How to adjust throttle cable (Read 7433 times)

monty23psk · « **on:** May 17, 2011, 11:05:22 AM »

Hey everyone,

Need some help with my newly installed throttle cable. I just did a top end rebuild and my idle has been rough for the last month. I wanted to start to troubleshoot it as it was perfectly smooth before the rebulid. Besides the rebuild I did the heater plate delete which of course can be related to the idle problem. The car works great, has nice power but just rough at idle unless I bump the idle up. But with age, my throttle cable has seen better days and has been getting stuck. So I decided I needed this fix as my gas mileage was being affected also and does not help when you are troubleshooting the idle issue. It will get stuck at almost 1500 when letting go of the gas and would hav to reach down to pull pedal to bring it back down. So I swapped it out yesterday, not hard, and now need to know what is correct. I know the specs have the idle on the m42 to be 850+-40 in the bmw e30 factory manual.

Not really finding the answers on this forum in the search. Is there a setting I should have the cable at, regarding RPM? From researching it looks like the throttle plate should be closed at idle, is this correct? Maybe I need to make sure throttle is WOT when pedal is all the way down. Lastly, is the RPMs suppose to increase when I hit the AC button? Before the rebuild, idle was smooth with or without AC. I need the pedal working at best at it could before tracking down the rough idle.

TIA

DesktopDave · « **Reply #1 on:** May 17, 2011, 05:51:54 PM »

I have mine adjusted full closed with a wee bit of slack in the cable. The DME should regulate idle with the ICV. A/C should increase idle to compensate for the compressor belt drag.

Did you check the ICV? Stomp test? Cam sensor?

The system supposedly compensates for voltage as well (I cannot affirm or deny), so a low battery or misbehaving alt might be causing some of this.

monty23psk · « **Reply #2 on:** May 17, 2011, 10:47:59 PM »

Thanks Dave, was waiting for you to chime in. Tomorrow if time permits, I will remove intake boot from throttle plate to see how closed it is. I also noticed today that when you start to push pedal, the top throttle plate starts to opend before the bottom. This looks normal. I first need to investigat why pedal is getting stuck. Only happens a few times, so maybe return spring is off or I might have to grease shaft where plastic pedal connects to pedal mechanism like factory manual states. Weird part is that it didnt do it before the rebuild.

I will then start to test everything. Stomp test gave me Lambda control error, believe 1244, right after rebuild but after a little bit of driving it now is good with 1444. Cam sensor has been replaced with used one a few years ago.

Battery seems ok but it was dead from sitting a few weeks during my rebuild. I know my SI board is bad and kills the battery. Alternator was replaced a few years ago and tested to make sure it is good.

I will start with adjusting throttle and then moving to sensors and ICV. Also will the check the hoses as I reused most of them with the heater plate delete as it was convenient and only used a new OEM e28 hose from ICV to under intake boot.

monty23psk · « **Reply #3 on:** May 19, 2011, 09:14:33 PM »

Quick update...

Looking underneath today at the pedal area before adjusting the cable as sometimes, and rarely, it would still bind and get stuck. Taking a peek I found that the grommet for the return springs were missing but that shouldnt make it get stuck like I was experiencing. I then move the shaft that conencts the plate the pedal connects to and the plate the cable hook conencts to and noticed the bushing bearing is completely missing. The shaft has total play and the clipt to keep the busing from sliding is binding with the hole, and wala, pedal getting stuck. Ordered the $1.50 worth of grommets to solve my issue. Here is a picture of the right side above pedal, you can see bushing (yellow color) and the left side that is missing.

Here is a pic of the new throttle cable. The design has changed and hard to tell in the picture. You don't need 2 wrenches anymore to adjust, just spind the finger grip to tighten or loosen cable. Also found out issue with stuck throttle, the shaft that connects the bracket to the pedal and bracket to the cable, has has the bushing bearing break off. It cause the shaft to move freeling and the clip to get got. Order the $1.50 grommets and bushing to fix the part of the car for the pedal area.

Here is a picture of the left side and then the right side still with a bushing (yellow item).