I'm having an unusual problem. My Evo 8 will idle fine, drive fine until it warms up then car will sputter and die. If I let the car sit for a few hour( let it get cold) starts fine and will go through the same process . I haven't be able to figure out if it's when it gets hot or when I let it turn some rpms.

I've check the fuel pumps, new CAS changed plugs. The car is SD . Any help ??

 

Hey Mate,

Did you ever and anyone find the issue to this. im having exact same problem.

 

Keen to find out too. Im having a similar issues

 

I went digging through more threads and saw that op's issue was a map sensor. Which makes sense it's the only sensor I haven't replaced. Ordered one today, will update when it comes in.

 

My understanding of the OEM MAP sensor is that it is only for smog to sense the EGR. I don't think it adjusts anything to the fuel map. It sounds like when your cars go into closed loop (using O2 sensor) it dies from running too rich. When cold, it is running from a preset map in ECU. Have you replaced your front O2 yet? Can you smell gas from your muffler exhaust as the engine dies?

Too bad OP didn't get any responses when he posted. There are many guys that can chime in these days.

 

It'll happen when you bypass the fuel pressure solenoid.


The purpose of the fuel pressure solenoid is to prevent stalling with hot starts.

 

I used to have a similar issue. Check for vacuum leaks and make sure your ICV is triggering/actuating. Also check your map sensor to see if it is reading erratically at idle or otherwise.

I had a couple things wrong including a faulty ICV along with a BAD map sensor and a leaky Throttle body. When i fixed the ICV thats what did it but I have been told all 3 of these can cause issues.

 

both OP and i are running 4 bar map sensors, not the OEM one.

its not running too rich either, afr's, trims are all fine.

ISCV, cam/crank angle sensor, O2, coils have all been replaced.

im not bypassing the solenoid. and hot starts are not the problem.

 

Let me guess... Omni 4 bar MAP sensor.

 

Since you're on SD, I can how important your 4-bar boost sensor is. Let us know if replacing your 4 bar boost sensor fixes your problem.

 

From a post i found of OP's his was, albeit a 4yo one.

Ironically, i steered clear of omni and went GM. mine is only like 6 months old though.

going to try get my hands on a vacuum pump and test the map for peace of mind even though i have a new one on the way.

 

I will do man, i like closing off threads so that others that like using the search function have some options too, rather than buying unnecessary parts.

 

Yea this is kind of an unsolved mystery in our cars. Not everyone has it, but enough have it that it's not an isolated problem. Looks like all the usual suspects have been addressed. I have had the problem for about 8 years. Good news is it doesn't really get worse or lead to anything horrible, bad news is it doesn't fix itself and there's no clear solution.

I had my money on IACV since I swapped in a rebuilt TB from my OEM due to leaking shaft seals around the time the issue began. This was an entirely new unit that I exchanged my oem core for. I believe I kept my TPS, but received a rebuilt TB from another car with that car's IACV on it. At present, I've got a new 65mm TB that will have yet another IACV on it, not yet installed on the car. I was hoping that would be the fix. Seeaich, what did you replace the IACV with? A new/used OEM unit or aftermarket brand?

What injectors do you have and what is the age of your fuel components? Somewhere in my reading I remember someone, more or less spit-balling, suggested that injectors - especially those that are of dated technology and/or old age - might be leaking small amounts of fuel after the car has shut down. If the car sits for a long period of time, the fuel evaporates. If you restart it soon, the leaked fuel does some witchcraft crap and dicks with your idle. Even after all these years I can't say what my afr looks like when this happens. I'm inclined to say it goes lean but that could just be because I associate that stumbling idle feeling with a lean idle afr.

If you have new fuel system components then I wouldn't go replacing anything. My pump and injectors are well over 10 years old so they could use refreshing anyway. That's just another avenue for you to think on as you rule out parts and systems.

I hadn't considered map sensor mainly because my car is still maf based. That will change soon though. I'm not as active here as I once was...are Omni 4 considered to be no good anymore?

Please keep the thread updated. I've learned to live with the issue but would love to put it behind me so I can expose whatever the next issue will be...

 

UPDATE:

Installed the new map sensor this morning. did around 40 mins of idling and driving. Seems to be all back to normal.

Will confirm when i take it home from work tonight.

Update 2: its been a few days, all is good... zero issues.

 

I was having the same problem with my Evo 9. Replaced the map sensor today. And everything is back to normal so far. Drove it around for about 40mins without any issues. This thread really helped me. Thank you guys!