I've been searching a lot and piecing together information, but I haven't been able to figure out what exactly to look for to fix this problem.

I have a 2003 Evo 8 still stock except for exhaust which has been there for almost 2 years.

I did a boost leak test by removing the air intake box a few weeks ago. At the time, I disconnected the battery. I did find a small leak in the throttle body shaft seals. I put the car back together before ordering the new seals. When I started the car, it was idling high, around 1200 and sometimes 2000 RPM. I drove the car a little while and the CEL came on. I figured maybe I didn't plug something back in correctly. I then got the new throttle body seals. While I was putting those in, I used a lot of throttle body cleaner to clean up the intake and throttle body. I again disconnected the battery to clear out the CEL.

I started it up, and it still has the same high idle problem, and after driving around for about 10 minutes, the CEL comes back on.

I just got a tactrix 2.0 cable yesterday, and tried to read the codes using EvoScan. It came back with "Barometric pressure sensor" and "speed sensor".

Reading some other posts said that EvoScan isn't reliable for reading codes. I'm not sure if that was just an old version or not. I tried a couple other free tools, but nothing else was giving me anything. I cleared the CEL for now and havent driven it much.

Can someone give me some pointers to where I should start looking? I haven't tuned the car yet, since I would like to figure out what's wrong with this first.

Thanks everyone.
Mike

 

Will you enlighten us as to what ROM your using. I am on the 94170015 for my 04 GSR.
There are tables in this ROM that deal with that. Once we know what ROM, the more help we can be.

Get back to us.

 

Mine is 94170008. I got mine pretty early when the '03 evo's first came here.

 

The ROM of choice is the 94170015, a brother to the earlier released 94170008.

Sounds like the MAF might need some tweaking, on the intake. Do you have any upgrades in this regards on the intake?

Some of the pros around hear, should chime in. Also, use the search if you haven't, I am sure there is a topic on here somewhere. Infact, you might check to see if it got plugged in all the way. I could be way off, but just a suggestion. Did you get the code's name, like the p0300 code, etc. NOt that it is the p0300 code(knock) but that will help identify where it is.

Do any of your friends have COBB AP. Reason is, it can give you the codes. I am sure that there is a way or shareware software that can do the same...

More homework, but, it will help in understanding what is triggering the cell.

 

Thanks Raceghost. I'll definitely keep searching some more. Is it possible the MAF got dirty or something while moving it around? Is there a test procedure for that or proper way to clean it?

Thanks

 

I do not know if there is a method. So you do have an aftermarket intake(cone filter), or aftermarket silicone intake to turbo? I am using a K&N drop in filter, stock plenum and box. Any chance an upgraded filter, or resprayed some oil on the filter? If so, it can screw with the MAF as well. I am no guru on the MAF, but if cleaner got on it, could be something...

 

The idle condition makes it sound like your maf may have gotten damaged (if so, likely the wires to it or the plug itself, make sure it is firmly plugged in and you are getting all the proper signals for airflow/baro/IAT) or you created a leak past the butterfly.

The CEL makes it seem more like the latter (if you are reading the correct one, it has been reliable for me so far but grab the actual PXXXX code). Did you install the shaft seals yourself (creating a different leak)? Did you possibly remove anything while cleaning it? (EGR, EGR lines, ISCV) Is your BISS/SAS screw set properly? Are you sure there is a good seal on the TB?

If you cleaned it too well (especially if you let it sit) you may have damaged a sensor or gasket.

Also, after you pull the actual code, try removing power from the ECU / car to reset it and see what happens. Are you modded/flashed at all?

 

He has tried that multiple times, the ecu power thing. Good point on the seals, I didn't even think about it...oops.

 

Hi fostytou, I'm driving the car to work today, so if the CEL comes back on I'll try to grab the actual code.

I did install the seals myself, but the weird thing is that this happened after I did the first boost leak test. For the test, I just removed the stock air box and the intake pipe that goes to the turbo. I then hooked up the boost leak tester directly to the turbo. After the test, I put everything back, and thats when the problem started happening. I didnt touch the throttle body at that time and I didnt clean anything yet.

While changing the seals, I cleaned the throttle body while it was off the car. I also sprayed the cleaner inside the intake manifold since it was all black. I did the boost leak test again and the only leak is from the stock BOV which I expected.

I didnt touch the SAS screw at all. And as raceghost said, I have disconnected the battery a couple times to reset the code. I'm not currently flashed yet, and the only mod is exhaust which has been there a couple years.

Also, I noticed my battery is reading 11.4 V while the engine is off. Its 14 while its running. Could the weak battery be causing any of these symptoms?

 

Frosty is on the right path.....Something is damaged or disconnected at the MAF. Double check the MAF plug. The wires are fragile and the plug can be difficult to tell if it is fully seated. I recommend some dielectric greas in the plug to seal out any moisture and assist with connectivity.

When you pulled the stock air box there are some wires that are tied off to it. You may have damaged some when you pulled the box. Pull it out again, carefully, and re-check every connection you can find.

Since you pulled the throttle body..double check that all of the vacuum lines are correct and that the electrical connections are tight. Again, dielectric grease in the plugs as stated before.

Paul

 

NM, wrong thread.

 

I pulled the intake box off and double checked everything is good. I put it all back and together and still the same thing. I havent seen the CEL come back on yet though, so its just the high idle problem.

I upgraded my ROM to 94170015 now too. After the car warms up, the ECU is reading 850 for target Idle RPM, but actual RPM is around 1000 to 1100.

Soemthing is not working correctly with my evoscan 2.6 though. It seems some of the values are not logging the correct data so i,m guessing i have the wrong definitions. I copied in the 94170015.xml definition file but some values are still wrong. I'm still searching to learn how to use it and figure this out, but maybe someone can give me some pointers.

For example, my boost (MDP) value is readin 22 PSI at idle. Cruising around will make it max out at 47, so I know its not correct. I'm not sure what other values are incorrect.

 

Im having the same issue on my ix... stock airbox. I have sprayed starter fluid up around the throttle body to check for a vacum leak... have not found anything.
The code mine is pulling i think is po507 idle speed to high
Stock flash ... havent touched anything w the throttle body I adjusted the screw on the tb and it helped a little but after the car sits idling it seems to venture back up to 1000.

Car idles fine w ac on at like 850ish when i turn it off it goes to roughly 1000.
I have checked the flash and its programmed to idle at 797 w ac off

Cleaned maf and noticed a little corrsion around one pin where the maf plugs in also which i cleaned out and put electric grease.. will see if this helps

 

I was finally able to get the DTC's. I dont have the codes with me right now, but they all point to the wire harness connector on the airbox as fosty and applaud suspected. I'm going to do some diagnostics on that connector tonight to see if I somehow broke something.

 

Ahhh and after all....we do know what we are talking about.