Evo8 starts but won't stay running, no DTCs
 

Hi all, I've got an issue with my modded '03 that has me stumped.

While driving my car, it started stumbling and would stall out. I managed to limp home by keeping partial throttle to keep the revs up and constantly modulating the throttle peddle while cruising to prevent the car from bucking. The car will start up and run, although a little roughly, but once it gets warm and the idle speed settles to the normal range (950+/-), it will dip and die and not want to start again until some time has passed. Car runs rich from the outset, but it's cold startup on 272s and 1000cc FICs, so it's going to smell quite gassy when warming up.

There are no codes being thrown and no other changes or variables that I could attribute the problem to such as weather or fuel. I've pulled the spark plugs and they look good. Have also tested the throttle position sensor per the repair manual and it seems ok. I'm now thinking maybe just replace the cam and crank sensors and then the TPS, but feels like I'm grasping at straws with no solid basis.

My questions for the forum:

1. If I purchase an oscilloscope, would it be possible to reliably test the cam and crank sensors? I'm doubtful that the cheaper versions (<$300) will have the resolution and speed needed to give insights into the trouble.
2. Are there any other sensors or components that, when faulty, could cause the symptoms the car is presenting?

if your going to buy test gear, then get an openport 2.0 so you can log the car.


It's strange you aren't throwing codes. I would continue your diagnosis with a boost leak test and see how that goes. IMO if it was your cam or crank angle sensor 1. you would get codes, and 2. the failure would be more pronounced.

Yep, I've got a Tactrix cable so I should be able to log. Won't be back with the car until next Thursday as I'm currently travelling for work.

Will that be able to verify crank and cam sensors are working?

I'll run a leak test too, just to be sure. Thanks for the help!

Well TBH if it starts and runs at all then its probably neither of those sensors. The ECU is really quick to pick up issues with its peripherals and a bad sensor is probably the most likely thing to trigger a CEL. What you really want to keep an eye on when the car sputters and dies would be fuel trims / AFR, ISC Steps, IPW, Voltage, ignition timing etc.

Some of the common issues with evo's as they put on age are:

Leaking throttle body shaft and BISS screw seals, leaking injector seals, leaking EGR valve, failing/bad ISC (Usually because of leaking EGR valve cooking it), bad front 02 sensor, Emissions hoses popping off or degrading, stuck PCV valve, dirty/clogged fuel injectors, misc. vacuum leaks (boost leaks) + more stuff I am sure I am forgetting. All those things I would rule out before tossing any money into replacing sensors (unless you start throwing codes).

Just my .02 Gluck with the troubleshooting.

Is the car on speed density with an Omni 4bar map sensor?

Lol you and the omni 4 bar, your mortal enemy now.

The symptoms align with one of the ways they go bad :dunno:

Im actually having something similar and throwing no codes, except my car won't start unless i give it gas and then when it starts i see white smoke and i have to continue giving it gas or it dies, i was thinking head gasket but these symptoms are similar.

Don't mean to hijack OP's thread.

The car is speed density with the Omni 4 bar sensor. Also, it only has 12,000 miles on the clock so many of the wear and tear items may not apply here but age can deteriorate items even if not used, so I'll be watchful for anything.

Thanks for the help, I will be logging those items you mentioned, Biggiesacks, for certain.

Letsgetthisdone, is there a test for the Omni sensor that can be done?

Add the MAP sensor to the list of things to log and you will see how its behaving.

You could be having multiple issues going on there. Start with a boost leak test and pull the plugs and see what they look like.

You would need to know what load your car normally logs for a given boost level and compare to it to current readings. Or put a known good sensor in..

So on that basis, I've ordered a new sensor and it should arrive tomorrow. I can put it in and compare it to this datalog.

When creating the data file, the car behaved pretty much as it has been doing. Started right up and as soon as it got warm, it started stumbling and the MAP and O2 started fluctuating quite a bit. RPM dips and surges a bit and then it stalled out.

Here's some of the data from the log file. Graph

Just realized I still need to do the boost leak test. I also forgot to log ISC steps and need to hook the wideband up so that data is coming through to EvoScan as well.

How do you know the car was running rich? Also, if the car starts and runs fine when cold then goes bad once it warms up, that screams sensor to me. Since the symptoms mirror a bad MAP sensor, that's a good place to start, IMO. I think you are on the right track.
Also as mentioned, if it were any of your cam/crank angle sensors, you would absolutely get a code.

Either way, I'm posting to be sub'd for the fix, to add to my collection of notes :lol: good luck!

Success! Sensor came is last night and I installed it first thing this morning. Everything is cool now, so it must've been the old Omni 4 bar MAP sensor.

New data log [[url=https://drive.google.com/open?id=10uRe6f3WNB_jtT2IVWroYgBj9aXWNsur]LINK] (forgot to put in 02) and chart [[url=https://drive.google.com/open?id=1Lm8dUzXGIReVDUGYWtjMRdQr7ZX0f_PV]LINK] which shows me taking it for a short drive.

Kaj, I don't have anything to backup the running rich part except for the strong fuel smell at startup which could've just been due to the cold conditions. Still need to add in the ability to log WB02 and start reading fuel trims.

For now, I'm loving having my car back! :D