Idle diagnosis experts please come here

[OMFGeofffff]

I'm going to be doing a boost leak check and everything tomorrow. I have a few questions. My idle was always weird. Before I had a steady idle at about 1500. When I first started it up the idle would surge between 1000-1500 until it warmed up. Then a steady 1500. I thought it might have been the fiav so I bought another throttle body.

Put the throttle body in and now it surges around 1500 with vacuum between 15-20. If a blip the throttle a couple times the idle raises to about 3000 and the vacuum will go up to about 22. During this time the wideband reads between 13.5-14. When it surges the wideband maxs out and fluctautes at the low 20's.

I have a video. It's really dark I took it about a half hour ago. The ISC should be good I just replaced it.

click

Any thoughts besides boost leak test. I just need some ideas so i don't have to run back and forth to the computer and car.

 

[Muskrat]

Check and make sure your TPS is reading correctly (on a logger, should go from %10 to about 100%. Car does not need to be running)

Check and make sure your closed thorttle switch is operating correctly.

Check and make sure your ISC motor is functioning properly. (see VFAQ)

Def. check for boost leaks, as from your wideband it's running lean (under vacuum sucks more air in than the MAS reads).

 

Have you grounded and adjusted the base idle screw setup?

 

[AnotherNewb]

doubt its the BISS screw, unless its missing, I would check injector insulators/orings. Take a can of starting fluid and start spraying everywhere that could be a possible air leak. IM/head, injectors, TB/IM, IAC. Start unpluging vacuum lines and plugging them off... BOV W/G Brake booster PVC valve. Did any of that affect/change your high idle?

 

[Muskrat]

Quote:
doubt its the BISS screw, unless its missing, I would check injector insulators/orings. Take a can of starting fluid and start spraying everywhere that could be a possible air leak. IM/head, injectors, TB/IM, IAC. Start unpluging vacuum lines and plugging them off... BOV W/G Brake booster PVC valve. Did any of that affect/change your high idle?



/ubbthreads/images/graemlins/uhh.gif

Or just do a boost leak test.

BTW, I don't think spraying a flamable aerosole all over your running engine is the best idea in the world. Just my opinion.

 

[AnotherNewb]

Brake Clen works well also... Never caught one on fire with starting fluid, yet...

 

[holeshotmoe]

Quoting Muskrat:
...Check and make sure your closed thorttle switch is operating correctly....



Put a new intake on mine the other week and when I started it up it did the exact same thing. Turned out I had knocked the wire off of the switch.

 

[speedyvr4]

a smoke machine is the best way to check for vacuum leaks. I know not everyoe has access to one. but what you do or should have access to is the boost leak tester wich should do the trick. if you find no leaks and everything checks ok. check your ecu for leaking caps and swelled isc drivers. I had the same issue and after going thru the whole prosess of elimination, I pulled the ecu and the isc drivers where really swollen. Changed with my dsm ecu and the surge went away.

 

[mooserage]

I don't understand why people are suggesting a smoke machine and flammable fluid for testing this:
1- pressurize the system
2- listen for leaks (2 heads better than one)
3- spray soapy water from a spray bottle anywhere you suspect a leak
4- if it starts foaming its a leak...
5- ????
6- profit

But everyone has their own method. Some easier, some harder, some cheaper, and some more expensive.
-shamus

 

[1qkfwd]

Boost leak testing mitsubishis is one of the number ones things we have to do. Why does it seem some don't want to get that? People wonder why these cars have a bad rep.

Op boost leak test the system fix the leaks (that means all of them) then report back. You be surprised how much beter the car runs.

 

agreed ordered mine today from click