How to adjust throttle cable

[monty23psk]

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.

[redsubdivisions]

RPM's are supposed to increase when you hit the A/C button; it bumps up the idle to compensate for the extra load on the motor when that compressor kicks in.

As far as your cable goes, I'd check to see if it's not getting snagged on something. That would be my first guess.

[Adrian_Visser]

Just adjust it so that it hits WOT and closes completely when you let your foot off the gas, there will be some slack in the cable with your foot off the gas. It isn't rocket science.

As for the rough idle I'll repeat what has been said a million times before: Check for vacuum leaks.

Don't just say nope no vacuum leaks! Get the intake system smoke checked so you know for sure. Using starting fluid or an unlit propane torch could still miss some of the harder to reach areas.

[monty23psk]

RPM's are supposed to increase when you hit the A/C button; it bumps up the idle to compensate for the extra load on the motor when that compressor kicks in.

As far as your cable goes, I'd check to see if it's not getting snagged on something. That would be my first guess.

Thanks. Right now mine goes up when I turn the AC off. Need to troubleshoot ICV for sure. Cable was all kinked and would get stuck. That is why I swapped it out.

[monty23psk]

Just adjust it so that it hits WOT and closes completely when you let your foot off the gas, there will be some slack in the cable with your foot off the gas. It isn't rocket science.

As for the rough idle I'll repeat what has been said a million times before: Check for vacuum leaks.

Don't just say nope no vacuum leaks! Get the intake system smoke checked so you know for sure. Using starting fluid or an unlit propane torch could still miss some of the harder to reach areas.

This is what I was planning to do, just hoping someone had a procedure because not sure if the throttle should be closed all the way at idle.

Will look at my hoses once I start to troubleshoot it.

Thanks

[monty23psk]

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).