OBD1 swapped s52 rough/rolling/high idle HELP

[justin_l_]

Just wrapping up an obd1 swap on an s52. The car was running fine before the swap. I have checked for vacuum leaks and can't seem to find any so I need help.

The when started cold it will idle fairly smooth with a slight miss once in a while, when it warms up the idle will start to drop to normal idle then start hunting between 1200 and 2300 rpms.it will do this for about 1 minute then it will jump up to 3k rpms. It will idle smooth there but not go back down weather you blip the throttle or leave it.

Shut it off start it back up it will idle hunt for about 1 minute again then go back to 3k. Would the icv be causing this? If so how do I test it? I don't have a spare.

Specs on the car are
Under drive pullies, obd1 swap with trm chip and 413 red label, 3.5 in maf, ebay headers, full exhaust, NO O2 sensor yet, in the mail, and a cai.

[e46s54dr]

Don't hold me to this but I'd say that it's probably because you don't have an o2 sensor hooked up. Install it when it comes in the mail and see how it runs.

[justin_l_]

Idk... Had no o2 on a non vanos setup wig success. I think this is something else. It's cold out... I'm calling it a night.

[Adrian_Visser]

Check again for vacuum leaks. How are you going about looking anyway? Using an unlit propane torch with the gas on around all openings and joints is a fairly good way.

Did you block off the nipple on the throttle body for the evap purge line?
It is on the bottom and is easy to miss.

Try unplugging the ICV and see what changes, I would still try another ICV too, late model m20 ones work AFAIK.

[blackhawkimpact]

You probably have leaks. Did you clean the ICV?

Oh, beat me to it.

[justin_l_]

Check again for vacuum leaks. How are you going about looking anyway? Using an unlit propane torch with the gas on around all openings and joints is a fairly good way.

Did you block off the nipple on the throttle body for the evap purge line?
It is on the bottom and is easy to miss.

Try unplugging the ICV and see what changes, I would still try another ICV too, late model m20 ones work AFAIK.

You probably have leaks. Did you clean the ICV?

Oh, beat me to it.

Cleaned the icv when I before putting it on. Plugged the evap nipple on the t , missed that in my first swap, don't think I will ever forget that again.

When the icv is unplugged the idle hunts worse (faster), thiseads me to believe that there is vacuum leaks somewhere. I'm using carb cleaner to trace leaks.

[richardb]

I had weird idle things going on last summer turned out to be a bad TPS. Maybe swap in a good used one for cheap to see if it solves the issue?

[samiam3356]

Yeah my car idles perfect without the o2 sensor in wouldn't think it would be that. Sensors are all new?

[M-technik-3]

Codes? I was getting P1189 and 1190 which after some discussion turned out to be Vacuum leaks. I had low idle issues not high.

[justin_l_]

Ok, have the idle hunting issue figured out but now there is a high idle issue still. It will run smooth for about 1 minute now then the idle will kick up to somewhere around 3k maybe 2800. It will stay there and not miss a beat. If I shut the car off and turn it back on it will do the same exact thing again. Does not matter how long I let it sit.

I can't pull codes, I don't have a scan tool. This is in a 99 M3 FWIW. I'm really stumped

Also the reason for the high idle was a vacuum leak on that stupid plastic thing that goes into the intake manifold, it was cracked and I missed it.

[justin_l_]

Also, the base idle seems to be set at 1500 rpms which seems high.

[M-technik-3]

Autozone or Advanced can pull the codes for you easy.

[justin_l_]

Still, codes with no CEL?

[justin_l_]

Cant check with a scan tool, just tried to and it would not communicate with the car. Tried a good TPS and good MAF with no change.

[M-technik-3]

Duh what was I thinking, tired, was just honing in on the 99 m3 blurb. Not gonna be able to pull the OBD II codes when it has been converted to OBD I. Sorry about that.

No o2 sensor is gonna cause the idle to come up slightly as it will be running full rich in open loop.