Hey guys. I need some advice/help in which way to trouble shoot my evo. I will try to be as descriptive as i can to see if anyone else has ran into this issue before. So here is the back story. I had got tuned and the car was running absolutely perfect. pulled hard every gear, no issues at all. I barely drive my evo so it does sit for long periods of time. Anywho i went to start it one day so i can drive it around and she did not want to start at all. Would sit there and crank and crank all day but nothing. I had to persuade her but giving her gas and when she did start she didn't want to stay running unless i kept giving her gas. i trouble shot that for a while and ended up replacing MAP sensor, O2 sensor, Coolant temp sensor. Nothing fixed it. I ended up purchasing a new set of camshafts, intake manifold and throttle body, and UICP because why not. I got everything situated and she started up just fine no issues.

After some time i got her tuned again for the new mods and run after run on the dyno with zero issues. Made great power and i was content yet again. I drive her to work the very next day and had zero issues going into work. On my way home about 1/4 mile from the house i hit a little standard pot hole in the road and the whole car just turns off on me. I tried popping the clutch as i was rolling but nothing. Came to a stop and the same thing again. Would crank and crank but didn't want to turn over unless i gave her gas. Got her started and putted her home. Car ran like crap and would sputter anything over 15mph.

Some more time goes by as i am losing interest, and the car starts up everytime again, with nothing changed, no need to give her gas but she is running so freaking rich. i cannot stand behind my car without my eyes instantly tearing up and i could also feel it in my throat. I am now getting a code for a p0500 vehicle speed sensor malfunction. that is the only code i have ever received and its only until now that i get it. i have been dealing with this issue for over a year now. car is showing 11 to very low 12 afr at idle. pulled out the IACV and operated it and could see the plunger doing its thing. I don't know what else to do or what direction to go towards so if you have had this issue before please please please help a brother out. i just want to drive this turd. Car is an evo 9.

 

Have you checked for boost leaks?

 

What fuel are you running on?

 

I have done a boost leak test. Good to go. Using E85 only.

 

Since it happened the second time when you hit a pothole and the only code you have gotten is for the speed sensor then maybe electrical. I suggest you start at the speed sensor and work you way back on the wiring checking for loose fitting or corroded electrical plugs.

 

Agree with barney sounds electrical,check wiring and grounds. maybe pull some the grounds and clean them up since you say your car sits. Keep us updated good luck

 

Make sure fuel runs freely and smoothly through the fuel rail and injectors. Make sure you have the correct sensors in the correct spots and they are secure, make sure the whole electrical system is secure and that the spark plugs are getting the right amount of amps and volts, also check it is getting air and oil. You need engine compression, spark, air and fuel to make it run properly and the ECU uses the sensors to change all of that around automatically.

I have heard the same thing happen on someone's Jetta and those cars only stopped running properly because people bought a cruddy tune, abused them with launch control and drove them like aholes because most owners are aholes of mk4 Jetta's lol. Also make sure to check your timing. I really am just suggesting slowly and calmly check everything, take a breather and relax and go through one by one. It will get fixed as long as no one beat the crap out of the engine by keeping it red lined or tuning it improperly then you will find out what went wrong and it shouldn't cost much to fix it.

Please keep us updated, upload some pictures and let us know what happened so we can fix our cars when this happens to us. Also if not obvious make sure it is not logging error codes and actually telling you what is going wrong. I don't know the ECU on these cars but even the Jetta would tell you most problems.

 

check all the sensors on the motor. cam and crank will both prevent the car from running and aren't super rare to get knocked out enough to be off spec. especially if the car died after hitting a pothole, that's enough to jar things out of place or knock sensors loose

 

check all your grounds

 

Thanks for all the inputs guys. I really havent been able to look over the car much. I bought a used cam position sensor that I still have to try out. I have gone over this car alot and cant find the issue. The first time this happened to me I replaced all those parts from my original post and afterwards it ran good for a while. Like i stated pull after pull on the dyno with no issues and then blam it cane back so its deffitntly a intermittent issue.

I still need to check timing and replace that sensor. I read the ecu gets input from alot of different sensors and the vehicle speed sensor being of them but i doubt it would cause my car to act up. P0500 is weird to get especially since i havent driven the car since. I erased that code and it came back a few starts later. I hate electrical issues.

 

I watched an episode on YouTube of that guy who buys damaged super cars. He was having similar issues with a Ferrari and it ended up that a lot of the ECU components actually soldered themselves internally and basically fried. His car was running really rough randomly and then ran perfect and vice versa. The computer on the Ferrari was fried in so many different ways partially due to jump starting the car which you can't do on those. It also needs like ten minutes of idling to reset it's computer. I am so new to evos that I have zero clue what computer components we have particularly me who has a GTA with satalite tv, old school DVD player, micro CD player and a gigantic command center that has about twenty buttons lol.

 

My evo ran weird and was throwing random codes until one day I found that the wiring harness on the ECU came loose. Either someone kicked it or it barely popped out somehow. Since the ECU is mounted vertical with the plugs hanging down, it would be easy to check from the passenger footwell that they are all secure. Just a thought. Also, check the connection/wiring to the MAF sensor if you're running one. It will run like what you describe if it's not getting the right readings.

 

Sell your car to me for pennies on the dollar and I will fix it

Otherwise, NoReason has a good option, a plug popping partially loose when you hit the pothole makes sense.

Keith

 

UPDATE......So everything is great so far. Turns out something happened to the MAP and it required a whole new tune. Something was skewed but she's running great again.

 

Evil, not to sound dumb but when you say "MAP", are you referring to your MAP sensor? Or are you saying something happened to the map on your tune?