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Car only runs right at 80% throttle

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nrwtrn6492

10+ Year Contributor
59
0
Jan 23, 2010
East Troy, Wisconsin
So we got my car running a few weeks ago. We got the shell and it was pretty hacked up to say the least. WE fixed everything we saw and built this

2.3 stroker 7bolt
Block
• Forged steel crank
• Scat rods
• Ross 9.0:1 racing pistons
• Acl race bearings
• ARP Hardware
Head
• Evo 9 springs, retainers, rockers, lash adjusters
• Evo2 cams and cam gears
• Arp head studs
• Multilayer head gasket

• FMIC

I am running stock ecu, stock injectors, and stock timing. When car was started it ran great, then was having issues with clutch. We fixed that. THen after driving it for like 100 miles it started randomly running like crap. it would misfire and just studder and would not accelerate. smelt like it was dumping fuel. Then it kept getting a little worse and worse. I then realized my home depot 90 degree coupler blew a hole in it when I was on a 35 mile trip. seeming it started to run better, but was slow bc of a huge boost leak but it ran smoother and didnt backfire. I then got yet another home depot 90 degree coupler ( my new ones were on order and needed the car as my daily driver took a shit on me) Instantly it started running bad agian. THe idle was high(2500) and jumpy then went to 300-500 and jumpy could barley keep it alive. I then checked the spark plugs and they are all black as hell and looks to be running rich crazy rich. so I replace the plugs with some NGK's.

Now I start car and it runs decent still a little lumpy idel but was at lke 1200. I took it for a spin and by a block I was running terrible again. I then realized nothing I would do with the gas would make it better other than giving it 80% throttle. then it will hesitate for a second then just fly and run great. till i let off gas a bit.

I changed ecu's and it didn't fix problem. I checked all couplers and got them all tight and everything seemed great. I know there are prob a few small boost leaks but nothing to cause this kind of problem.

A few other possibly non important facts. When my buddy hooked up his tactrix cable to the 98 ecu he has it didnt work saying not enough voltage, but worked fine in his car we checked right after.

my CEL does not come on with three different ecu's that we have tried (assume the light is out or something)


I know this is a lot but I do not know where I should start.

thanks again!
Chris
 
i would suggest starting with testing the tps like was said above and go to other sensors. When you are under 80% throttle the computer relies on all the different sensors to calculate fuel and timing but at 80% throttle or more it just goes to preloaded base maps so that tells me to look at sensors first and since its free with a digital multi meter and time i would start there along with checking electrical connections and plugs.. good luck and dont get discouraged... it will all work out and you will learn more and have a story to tell.
 
I know there are prob a few small boost leaks but nothing to cause this kind of problem.

thanks again!
Chris

my car only ran right at about 80 percent throttle when i had 2 relatively small boost leaks. if you have more than one boost leak its like having a bigger boost leak. When my car was driving like this i would push the petal to the floor and no power, 3/4 lots of power, why? because the turbo could spool up with the boost leak which as at the fuel injector seal.
 
my car only ran right at about 80 percent throttle when i had 2 relatively small boost leaks. if you have more than one boost leak its like having a bigger boost leak. When my car was driving like this i would push the petal to the floor and no power, 3/4 lots of power, why? because the turbo could spool up with the boost leak which as at the fuel injector seal.


I had a 3inch hole in coupler and ran better than this. I know there is something more than a boost leak. This not even drivable.

i would suggest starting with testing the tps like was said above and go to other sensors. When you are under 80% throttle the computer relies on all the different sensors to calculate fuel and timing but at 80% throttle or more it just goes to preloaded base maps so that tells me to look at sensors first and since its free with a digital multi meter and time i would start there along with checking electrical connections and plugs.. good luck and dont get discouraged... it will all work out and you will learn more and have a story to tell.


I will be doing this when I get home this weekend. I just want to get a few ideas as tow hat to look for before I get to there because I do not have much time.

My new couplers better be in by then, then I will replace them. Get a scanner from my neighbor check that out. Hopefully something will turn up with the scanner. Anything else I can check?
 
if a sensor is failing but not totally gone it might not show up on a scanner. its best to pull the sensor and look in the chilton/hayes manual and check them that way. i hope someone can chime in here that has had simular problems... i am just giving you what i wld check for. im not real familiar with the engie/symptoms. maybe check the turbo its self, wastegate and check all of yor wires and connections to sensors. check your plug wires and make sure teare in the correct order, vaccum lines etc. start with all the basics and sensors. go back to what u know is needed to make the car run good (air, fuel, spark, vaccum, boost pressure, solid 12-14 volts etc) and find out what element is lacking and focus on the parts that deal with that... too much fuel/not enough air means fuel injector, intake, turbo etc. thats all i can tell you. i havent encounteed that problem.

a short story that has stayed with me and taught me to check the sensors and basics... i had a ford v6 that wouldnt start one day. i checked the fuel at the rail and it wasnt getting fuel so i checked the inertia vaulve switch (in case u get in an accident or roll your car it shuts the uel off) and that as ok so idrove 3hrs to the only place that was open on sunday and had the pump in stock, dropped the tank and pulled the pump out. before i put the new one in i decided to test the old one just for st*ts and giggles... it worked perfectly every time but not on the harness with the key on. checked the book for a few hrs and found out that if a coil is bad the ecu wont turn the pump on! now i always double check all sensors and wires the ecu includes in the closed loop enviroment just to be sure.
 
I'm going to be checking everything I can think of when I get there. Any other ideas?

What doesn't make sense is that it got better after I blew a hole in my coupler. So a big boost leak helped the drivability issues, but of course made it slow LOL

Ok so I have been thinking. I know it is gettin spark, fuel, compression, air, ect. I checked all injectors with a ohm meter and they are good (tested them warm). I replaced spark plugs and wires.

So this leeds me to believe something is sending bad information to the ecu. Does this make sense? So one major thing I can think of is a MAF. Would this cause the issues?

thanks a lot for all who contribute!!
 
scanner wont read ecu....
I cahnged ecu and same thing happened....

Any Ideas
 
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