My car is a 2005 GSR. I have a Buschur TBE and open filter, MBC @~20 psi, Walbro 255, and an ETS intercooler and LICP.

My car was tuned by Mellon in the Fall and I had reasonable 3rd gear AFRs around 11.3-11.0. At that time I still had the stock intercooler and LICP. I installed the new intercooler and LICP over the winter and had not done any logging throughout the winter until recently. Recent pulls put me below 11.0 in the 10.8-10.9 area (below 30 degrees Fahrenheit ambient) so I began tuning to lean the AFRs back out a little and the car was responsive until, after a subsequent reflash from my tuning, my AFRs went down into the 9s and below. I recalibrated my WB02 (LC-1, most recent firmware) and flashed back to my final Mellon tune from the fall and the AFRs are still 9s and below. I then performed a boost leak test and found a slight leak from the throttle body (assuming shaft seals) but the turbo to UICP are without noticeable leaks.

After much searching through the forums I checked my fuel trims after a long cruising and idling session (~25 min cruise and ~10 min idle, during which I received noticeably lower mileage). These are from Evoscan Maptracer 2.0 with the standard equations: Low LTFT is ~26.5% and Mid LTFT is ~85.1%. At idle my WB02 and Load are erratic, jumping between 8-15 and 10-30, respectively. I am seeking any advice and will be able to do any requested logging after 3 today to assist in the diagnosis. I appreciate any advice and apologize if this is not posted in the most appropriate section.

 

I just had this problem on my car.

I had a cut in one of my EGR vac hoses under the TB.

I fixed that and all is good in Evo land.

 

I notice my car runs more rich in the colder months. I figure the temp causes it. It certainly runs better when it's warmer, for me that is. Good luck.

 

Much appreciated, I never would have thought of that. That will be the first thing I check this afternoon. Thanks for the quick response.

 

No problem.

Mine was the one that is kinda under the coolant lines that run to the heater core in the dash.

Goodluck, if you need any help I am on aim as mellontuning or just pm me here.

 

Well the weather here is getting a bit nasty so I had to stop working for now, but I checked the vacuum hoses and they were all connected. I pulled each hose-end individually and checked for cracks and they all seemed fine. I did not want to pull the entire bundle of hoses at the moment until I can get a clear idea of how they all connect back together, but I did not notice any cuts along the lengths of each hose that I was able to check. The symptoms remain. Are there any other possible options to explore, or am I just waiting it out until I can borrow a friend's garage and check each individual hose?

 

I was able to gain access to a garage and I proceeded to pull the entire bundle of vacuum hoses for the egr. All were connected correctly and are without leaks. What is the next step in diagnosing the problem? Is there anything else I should check while the car is apart?

 

I proceeded to remove the EGR valve itself and have verified that it works properly and is not stuck.

 

Don't rule out boost leaks.

Not sure if you've tested but they'll cause you to run rich as well.

 

Always looks at the most recent change to troubleshoot issues. You stated that all was fine until you added a new IC and LICP. Suddenly rich AFRs all point to a boost leak.

If you checked all of your vacuum hoses and they are fine, start checking every connection to the IC pipes and IC. That's most likely your issue. Just start with the turbo to LICP connection and work your way to the TB.


Eric

 

I assumed the slightly rich AFRs (the 10.9s) were just from ambient changes and other factors. The sudden richness (9.0s and below) occured between logging pulls after a reflash: the car was responding positively to my fuel changes until the first log after the last reflash upon which it became extremely rich. I am not attempting to imply any causative influence from the reflash, just trying to be clear about the issue at hand and the conditions under which it occured. I did indeed perform a boost leak check as I stated and the turbo to UICP section is without noticable leaks. I did find a slight leak around the throttle body which seems to be the shaft seals but this is a small leak and a widespread issue that would not seem to illict the sudden change in AFRs and the wandering exibited at idle - I have also not come across anyone mentioning these symptoms associated with the shaft seals.

 

Since the last reflash have you read the ROM from the ECU to see if the flash didn't screw up any tables like the fuel maps, maf scaling, etc? From your original post, it looks like you already covered that, since you flashed Mellon's tune back in, but double check just to make sure some table isn't getting screwed.

I'm not used to the EvoScan fuel trim denotations as they use incorrect formulas, but I know that EvoScan uses 100 as 0, which is no correction. So, your trims are definitely way off, indicating some sort of air leak and/or maf reading issues. You didn't change intake, filter, or anything else besides the IC and LICP, right?

There is a remote possibility that the MAF is going bad, but my first inclination is still something wrong with the install of the IC or LICP, or something since then. If there are absolutely no boost leaks and the ROM is still intact, then the MAF could be the culprit.


Eric

 

That is correct. I have not changed anything aside from the intercooler and LICP. That was over a month ago and all has been well until recently. I will check the tables in my rom and try another reflash and then examine the MAF. Thanks for the sugguestions.

 

that's a strange one and when Brad's car did that to us we were flashing the rom. We reset the ecu numerous times to no avail.

one run was 11.5:1 the next was 9's from there on out every time...clearly the ECU was compensating for something or in limp mode. We pulled the CELs and didn't see anything but once we located the vacuum leak in the EGR system everything has been normal.

I think you next step is to pressure test again to make absolutely sure you don't have a leak and pull the CEL to see what codes you're getting if anything.

good luck!

 

Check For Vaccume Leaks