Question about smog

[Vincent Brick]

I am still new to California and the whole emissions testing thing so please bear with me....


There's no point to trying to smog my car if it idles at 1400rpm, right? Its kinda always done this, can't figure out why, I have checked all the common things (no vac leaks, tried other ICVs, etc).


Should I break down and just spend the extra money to have it falsified? A buddy says he knows a guy, though I REALLY can't afford it (I think its like $250 on top of the $130 I have to pay the state - OUCH!!!!!).

Thanks for any advice.

[MrBurgundy]

if its steady up at 1.4k its your tps. When the ICV doesn't have a signal from the TPS, the vane will stay 100% open.

and yeah, it will fail

[Vincent Brick]

Not really a steady 1400, often it varies between 1000 and 1400, or 1200 and 1400. One of the ICVs I tried in it caused it to idle at 1800. Sometimes I will stop at a light and it will randomly idle at 1000, maybe up to 30-40% of the time now that I got the correct injectors back in it. When it idles at 1000 it is a bit rough, shakes the car like it has a cam, but so did the previous M20 I had in this car so I assume that is normal at this point. These are 200k+ mile engines afterall.

Well I guess now I need to research how to see if my TPS has failed or if there is a wiring issue, I have no clue where to even start. I really wish I could afford to just support the illegitimate smog people, they really provide a valuable service, but living in California has me so broke I can hardly afford food.

Thanks.

[MrBurgundy]

The TPS is under the throttle body.

There is a continuity test you can do with a multi meter.

There are three pins on the TPS, IIRC you should have continuity between pins 3 and 2 when the throttle is closed and then continuity between 1 and 2 when the throttle is about 75 percent open.

I'd double check the pins on here.

[McGyver]

The TPS is also adjustable, so you might need to just adjust the position so that it is accurately reading the throttle position. Fixing the issue will not only help with smog, but make it run better and save on gas.

[mr.vang]

Welcome to California. If you know someone in the smog free county, you can have the car registered there and won't have to smog it.

[Vincent Brick]

If you know someone in the smog free county, you can have the car registered there and won't have to smog it.

I really wish I did.




So the TPS tests good, can both hear the idle switch work and see it on a meter. Seems to activate where it should within the throttle's travel. 75% switch good too, though likely not relevant.

How do I tell if the ICV is getting any signal? I'm about to go out and see what happens when I try running the motor with the TPS and ICV each unplugged, not entirely sure what to expect.

Would it be worthwhile to try a different (though untested) AFM I have laying around? Dumb question, I have time and the sun came out, worth a shot.

[McGyver]

Have you read through the Bentley on how to troubleshoot the TPS and ICV? You may want to clean the ICV as well. Also, how old is your Coolant Temp Sensor (the light blue one with 2 pins)? The CTS plays a CRUCIAL role in making the car run right. If its old or anything but Bosch, you should replace it.

Other than that, vacuum leaks.

[Vincent Brick]

ICV was cleaned just a couple months ago when I tried all my extras to see which worked best. Bosch coolant temp sensor is only a few years old and was also confirmed good around the same time, as did IAT on the scanner. Vacuum leaks were also tested at that time, with only a very tiny hole found in the crankcase vent hose from the valve cover which I have since replaced. I also have an issue with intermittent erratic idle at cold start in temps below 55F (revs itself and stalls unless I hold 2k rpm for ~20 seconds), so me and a BMW mechanic buddy checked a lot of related items at that time, but that issue still remains undiagnosed. It barely gets below 55F here so it isn't a huge deal, less so than the car not running right in temps above 120F, getting stranded in the desert like that was no joke.

So after testing the TPS, now the car is idling at 1000 rpm. If I unplug the TPS with the car running, the idle goes up to 1400. This leads me to believe that I have a wiring issue, no?

Are full wiring diagrams out there for these cars? The BMW electrical troubleshooting manual I have doesn't tell me much.

For now I guess I need to drive it and hope really hard that reseating the TPS plug just now fixed it?


EDIT: It is definitely in the TPS plug, when the idle is high I can press down on the plug and idle will drop. I don't think it is the TPS itself, but rather a poor connection at the plug. Going to see if I can get in there with little files and clean the terminals, maybe bend the pins a little?