I was driving at approx 30mph in auto sport mode, rounded a corner, and then accelerated at approx 90% throttle. My revs went very high, the gearbox "forgot" to shift and I hit the rev limiter. The car then slowed down to 5k rpms instead of shifting up. The SES light came on immediately. I forget what gear I was in as it all happened very quickly.

After this I drove slowly and put the car in normal mode, but the gear changes were very jerky. It seemed to me that only the odd gears were being used, but the display showed that all gears were in use. At the time I didn't think to try manual mode. I stopped the car and turned off the engine. When I started again, everything was fine but the SES light remained on.

This morning the car is still fine but the SES light turned off before I could get the code pulled. Are the codes persistent? I'd like to pull the code to compare against the experiences of others - I've heard of the gearbox failing temporarily in this way.

My mods are WORKS drop-in, MBC set to 24psi peak, Zchip. 300whp at 5500 feet elevation.

 

The diagnostic code should still be in the computer. It sounds like the same behavior some people were seeing when their MAFs started going out...

 

I'll be getting the code read today. As I was leaving work just now, the same thing happened - except I was in auto normal, was going slowly in 2nd and then gave it about 60% throttle. I had a closer inspection of what was going wrong.

All gears were definitely being used and selected OK. Upshifts in auto and manual mode were very jerky. Downshifts were smooth.

 

With the CEL on the gearshifts are jerky ..

Possibility of overlimit protection .. shutdown and start the car 4-5 times to reset the CEL and then drive to a shop to retrieve the code .. the codes are stored in persistent memory and will remain until retrieved ..

 

over doing it like the other guy said ....
or dust/dirt on your maf even water will do that coming from a car wash ...
***make sure your air filter is allways clean and with no debrie,
it doesnt mean your maf is no good just means that it wasnt reading right

 

Car never goes into a car wash, and doesn't get pressure washed. We're a fairly dry state so I know hardly any water ever gets into the filter/MAF. I checked the filter and it wasn't too bad. I replaced it regardless and the car is now at the dealership having the codes read whilst they fix some things related to recalls. I wasn't driving hard both times when it happened.

 

P1235, maf sensor. Dealership wrote on the service form "found air box not secured closed properly" and "poss aftermarket intake or filter".

Not sure how the air box wasn't closed properly, I checked it well. Fair enough about the filter comment (though it had a stock filter at the time of service). So the MR has a problem with aftermarket filters and drop-ins? Anyone know how to get around this problem?

 

seems like MAF does not like oiled filters. There were similar problems with HKS drop in and works drop in. I am also using works drop in but did not have problems so far.

Are there any good non oiled drop in filters?

 

I had an HKS, I relaced it with a Cosworth. The HKS, plastic framework that supports the filter element warped.

Both HKS and Cosworth are dry elements, but flow better than stock.

 

My car is throwing this code all the time now with the stock air filter, but with the MBC and ZChip still installed. It doesn't throw the code when 100% stock.

I presume the MAF has been damaged but works well enough when the car is stock to not throw a code then. I'd like to understand why this is the case, if anyone can explain it? It is because of the increased air flow when upping boost and leaning out the AFRs?

 

Might have my answer here - boost spike. Will do some logging and will post results.

https://www.evolutionm.net/forums/7422977-post15.html

Not sure what changed though - haven't moved my MBC all year, and it's warmer and drier now than it was in February when I originally put this tune together.

 

There's no boost spike. From logging, I found that it most often happens at 70% throttle (TPS reads 70) in normal mode. It happens at around 5000rpm. Unless boost is higher than the ECU expects at that particular RPM range, I can't see a problem. For now I have turned down my MBC four clicks (Force Unos) and I'll see if it happens again.

I have logs from last year that show that my boost hasn't increased at all since last year. Like I mentioned, it's warmer and drier now than when I originally did my tune (it was almost 70F today).

 

P1235 is an 'over boost' code.

That code is like many of the protections that the Evo X has inbuilt, regardless of your logging is saying, that is what that code is.
Just remember that the Evo Xs ECU is a full generation ahead of the IX, it pumps a lot of information around the care, much more than previous Evo's as it holds and sends a lot more data, as much as ten times more to put it in context.

Just on that, why do you think the tables are bigger? It's not just allowing for better emission control that's for sure.

The issues people are having with the Evo X are mainly caused due to applying similar principles used in previous Evo’s directly to their Evo X, then finding out the X doesn’t need or like them!

Fitting parts to your car without understanding the way your car thinks and responds is always going to see you end up with results you didn't want.

 

kijima, without access to full specifications of the Evo X ECU and all sensors, anything people do to improve the car is based on inference, investigation and experimentation. Unfortunately no one in the community fully understands the conditions that cause a P1235 code, and if they do, they haven't yet made this information freely available. Therefore the only course of action is to ask questions like these.

Indeed there are many people with a similar setup to mine - tune and MBC - that have these problems, and many more that do not. The differences are likely caused by differences in atmosphere, MBC type/setting and tune type/setting. Replying to a forum post where someone is looking for information on a problem and telling them that their problem is based on lack of information is really not helpful; it's just stating the obvious.

 

Mass Airflow Plausibility.

Just because you don't understand the cause of the code, doesn't mean that no one does. Many people, including myself, and kijima, and many others understand it full well. It does NOT mean your mas is screwed up. Kijima calling it an overboost code is simplifying it a bit, but accurate. The code usually coresponds with an overboost condition however, and this is why it is refered to that way.

I can turn this code on like a switch with my car. It is driver induced, and I am NOT going to make the adjustments to my ecu to make this go away. When my car trips this code, it is driver induced overboost. If I want to see this code, all i have to do is put the car in 5th or 6th manual mode, around 3-3400 rpm, and go to 70% throttle. I have logged this on many occasions, and usually I am pushing around 28lbs of boost when it happens. If I put the car in a proper gear, this does not happen.

What is happening is that at part throttle high load, usually in higher gears, the car is making a lot of exhaust pressure, which can spin the turbo extremely hard. Unfortunately at these high load part throttle conditions, the engine is not turning fast enough to get rid of this air (after all, it is just an air pump), so boost climbs. Aditionally, the waste gate on the stock turbo is not sufficiently large to dump the excess exhaust volume preventing the boost climb. What is triggering the code is that the computer is not set to see this much air coming into the engine at this rpm range ( keeping it simple), so it trips the code. Since its a limp code, it does its whole limp thing, which you describe as "temporary transmission failure". This does not usually happen in lower gears because the actuall load on the engine is less, so the rpm's climb faster, allowing the engine to "inhale" all that extra air.

The reason this rarely happens on a stock car, is that it is not making enough power down in that rpm range, to create enough exhaust pressure, to build enough boost, to get the condition.