M42 high idle after throttle body heater delete

[and_e30]

I purchased all new hoses and after completion of the throttle body heater delete, the engine idles at around 1500rpm and slowly creeps up to 2000 rpm where it stays. It takes about 3 minutes or so for it to get there from a cold start only.

Here is the troubleshooting I have done so far:

1: replaced idle control valve with known working one. no change in rpms.
2: replaced MAF with a known working one. no change in rpms.
3: all new hoses and throttle body boot.
4: throttle cable checked for being stuck.
5: used ether to detect vacuum leak, no luck.
6: new throttle body and intake manifold gaskets.
7: fuel pressure regulator hose is secure
8: coolant temp sensor tested to be working with in resistance parameters
9: engine sputtered when fpr hose unplugged, seems to be working

Below is the routing of my vacuum lines after the delete.
I have a hose from the valve cover to the bottom of the intake manifold.
There is a hose from the throttle body boot to the idle control valve.

I am out of ideas. PLEASE HELP!! I will update the list above as I continue to trouble shoot. Thanks guys!!

[Balleristic31]

Check under the new boot. Most new ones don't come with the plug close to the throttle body, causing a huge leak.

[and_e30]

Check under the new boot. Most new ones don't come with the plug close to the throttle body, causing a huge leak.

yeah, i did check that. my new boot did come with a plug.

[E30NJ]

The breather hose running to the valve cover, is it clogged?

[and_e30]

The breather hose running to the valve cover, is it clogged?

Nope. Brand new hose.

[and_e30]

can anyone else who did the heater delete confirm the routing of the vacuum lines?

[Chuck C]

What I can see of the hose routing looks OK, but I can't see the vacuum line to the FPR. Is the throttle plate closing completely? Interesting (to me) to see the throttle cable clip and cooling system heater bypass valve recalls still installed. I must have done a hundred of those cooling system recalls back in the day--that was the first thing I removed from my '91 when I got it in '05.

[uturn]

New throttle body gasket? New intake manifold gasket?

[and_e30]

New throttle body gasket? New intake manifold gasket?

yes, all new gaskets all around. i forgot to add that to the list above.

[and_e30]

What I can see of the hose routing looks OK, but I can't see the vacuum line to the FPR. Is the throttle plate closing completely? Interesting (to me) to see the throttle cable clip and cooling system heater bypass valve recalls still installed. I must have done a hundred of those cooling system recalls back in the day--that was the first thing I removed from my '91 when I got it in '05.

I did look for the vacuum line to the FPR, it is hard to get a pic of that. Everything looks ok there. Yes, the throttle plat is closing completely. I manually moved it back and forth to the limits. I am unaware of the recall on the throttle cable clip and cooling system heater bypass valve, where can I find info on those so I can do them?

I think today I am going to take the manifold and throttle body off to give everything a once over again. I will take some more pictures.

I also did a coolant flush at the same time as the heater delete, do you think this may be the result of that? I have probably put 100 miles on the car since and no overheating however.

[Boris3]

I don't think this would make a difference for your symptoms but...see that connector in the top right of your first picture (small connector with the two white/grey wires coming out of your harness near the fire wall), unplug it. It should only be plugged in for 318i/is models without a cat. Notorious for causing idle and warm restart issues. Maybe it's an issue here?

[and_e30]

I took everything off down to the intake manifold. checked over all the hoses and connections. everything seems to be in working order. I reassembled and the issue still exists.

Here are some pics. Maybe you can spot something that looks out of place.

[and_e30]

I don't think this would make a difference for your symptoms but...see that connector in the top right of your first picture (small connector with the two white/grey wires coming out of your harness near the fire wall), unplug it. It should only be plugged in for 318i/is models without a cat. Notorious for causing idle and warm restart issues. Maybe it's an issue here?

i unplugged it and started it up. didn't seem to change anything.

i plugged it back in while running and no rpm change.

[and_e30]

when i start it from cold, it starts out at about 1500rpm and eventually creeps up to 2000 where it maintains.

maybe this could be a thermostat issue?

[Boris3]

or coolant temp sensor (blue one)? Turn the car off and check is plug tight? Maybe unplug and replug, and/or unplug, spray with contact cleaner let dry and replug and see.