Have a Mitsubishi u42t (Be very honest I’m not sure what year it is I’ve got it kind of figured out to a 98 through 02 Because it’s got the EFI motor) Extremely hard to start You have to put your foot down all the way on the gas pedal. It’ll spin over for about 20 seconds if not a little bit longer start spitting and sputtering And then start And then not every time, but the biggest majority of the time once it finally starts it starts surging at idle I am 100% completely lost because I changed Fuel filter, all 3 injectors,Air idle control, throttle body possession sensor, Fuel pressure regulator, Both of the temperature sensors, Made sure the throttlebody is extremely clean and not stopped up anywhere, Made sure the fuel pump is good Replace the muffler Which was completely rotted out (The only thing left I could possibly think of maybe that oxygen sensor??) And to be honest, there may be other parts that I’m forgetting I’ve changed As well Is a five speed With air conditioning I am about ready to ship it back to Japan lol
Oxygen sensor shouldn’t be in play at start up as far as I know. Has fuel pressure been verified compared to factory spec? Have you done a compression check? Does it seem overly rich from exhaust when it does start? My guess would be iat or ect sensor but I see that didn’t work, has any change had a positive effect? Apologies for the barrage of questions.
Never have found factor fuel pressure anywhere to see I more or less did it to see if it had a small leak I didn’t think o2 sensor would either but hell I’m at my wits ends ya know compression was a lil low on number 3 if I member correctly but had well enough to run properly I’d be lieing if I told you what it was cause I don’t member. Truth be told I can notice a little improvement over all on each one I’ve done just a very little though I mean he’ll replace enough shit you’ll eventually find it on total accident lol right lol
I couldn’t find a spec on fuel pressure either. I’d assume 40-50psi based off working on other Japanese vehicles of the same vintage.
First check fuel pressue. It should be around 30 to 35 psi. You can also pince off the return line and see if pressure goes up. Oxygen sensor will not play in start up.check for vacuum leaks and is you tps adjustable? If so try adjusting little at the time to see if makes a difference.
I’m not sure what year it is I’ve got it kind of figured out to a 98 through 02 Because it’s got the EFI motor) >> The EFI motor has nothing to do with understanding what you're driving. Start by going to www.partsouq.com. Enter your VIN and view the production date Extremely hard to start You have to put your foot down all the way on the gas pedal >> Isn't it EFI? Putting your foot all the way down shouldn't haven any affect on a fuel injected ignition system It’ll spin over for about 20 seconds if not a little bit longer start spitting and sputtering And then start And then not every time, but the biggest majority of the time once it finally starts it starts surging at idle >> You've got performance issues for sure, it could be anything at this point in your troubleshooting / information provided >> You need to go back to the basics. An engine needs fuel, air, spark, and compression. You are lacking one, if not more, of those 4 key items I am 100% completely lost because I changed Fuel filter, all 3 injectors,Air idle control, throttle body possession sensor, Fuel pressure regulator, Both of the temperature sensors, Made sure the throttlebody is extremely clean and not stopped up anywhere, Made sure the fuel pump is good Replace the muffler Which was completely rotted out (The only thing left I could possibly think of maybe that oxygen sensor??) >> Hmm well now I'm lost too, it sounds like you just threw a bunch of parts at it but nothing helped Is a five speed With air conditioning I am about ready to ship it back to Japan lol >> Don't do that, these engines are basic and with some troubleshooting you can figure it out. Here is an idea to help narrow down which of the big 4 you're missing without trying to hard >> Remove air intake >> Turn key so engine turns over like you described >> Spray a shot of carb cleaner ( not ether, too harsh ) into the intake >> If engine fires up and runs, your compression, air, and spark are probably fine. Then you can focus on why you aren't getting fuel >> If it doesn't start / run on a shot of carb cleaner, then you have spark or compression issues. ** Are you the same member who was talking about messing with idle air screw and a bunch of other stuff? I suspect you've made one too many "fixes" and something just isn't right. Also, why would a fuel injected motor have idle air screw, that's usually carb only but I may be mistaken.
@MikeD FWIW I have read in the past that putting pedal to the floor on some efi systems is a way to “clear flood” and it won’t fire injectors while doing this.
Interesting. I didnt know that , thanks for sharing. Hmm well since OP has a handful of possible culprits id try the carb cleaner right into the intake concept to see if it fires right up . May be a quick way to narrow it down to a fuel or other issue . Hope you can get it going
I was having a very similar issue to OP, [also replaced the fuel pump and filter to little effect] and sprayed carb cleaner right into the intake, fired right up, did some tweaking on the carb for the mixture and sprayed a whole lot more gum cleaner in and around it and it seems to have helped a lot with the problem, sometimes it still struggles to start, I think the problem is the either still relating to the fuel pump [dont trust it, cheap chinese junk] or I just need to rebuild the carburetor, but it feels like the problem is coming from there!
