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Won't let me past 4k in 4th gear..

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Blitzeclips

15+ Year Contributor
1,571
6
Aug 5, 2004
Bear, Delaware
Hey guys I've run into a problem with my car. For some reason the car will not go past 4k, especially in 4th gear. 1st pulls hard, 2nd pulls hard, 3rd pulls great but sometimes hesitates, and 4th just stutters so bad it won't go past 4k. It like the RPM's go up 200 or so, then drop back down 100 and so forth, almost as if the car wants to go but something is holding it back. I changed the fuel filter, spark plugs, no vacuum leaks, battery checks out nice, terminals nice and snug. I haven't re-wired the fuel pump though, but I doubt that would be the culprit here. I'm going to install my wideband and FP gauge sometime in the next week when it's nice out so I could get a readout on that too. I'm thinking it's spark though. One of the coils has got to be weak or something I don't know..

I don't know what this could be at all. It baffle me because 1st and 2nd are great, then one I get into 4th its like a stagnant 60-70 MPH diriving speed. I could get up to 80 but it would take a while and the car really doesn't want to build boost in 4th.

I've read alot about open and closed loops the ECU sets. I don't know if this would have anything to do with it but could someone enlighten me as to what that is?

It;s not making the car undriveable but it's making me wonder what the hell is going on.. All suggestions and input are helpful.
 
VelocitàPaola;151442266 said:
I had the same problem if you have mods. I fixed mine when I tried to gap my plugs to .25 no more no less and drive it now my talon can go wot in all gears and top at 153 mph just watch the egt gauge coz it can go really hot mine pass 900 only if u always drive on the top end. Hope this help
 
If the O2 sensor is shot or responding slowly, the ECU could throw the car into limp mode...

Closed loop is when the ECU adjusts the AFR according to feedback from the O2 sensor to get as close to stoichiometric as possible. This form of engine control is the most fuel efficient and predominantly used in the lower throttle range (~80% and less).

Open loop is when the ECU disregards all feedback from the O2 sensor and controls the engine according to its built-in fuel trims. This form of engine control is less fuel efficient, but more geared toward performance and is predominantly used in the upper throttle range (~80% to WOT).
 
Test for spark and note it's colour; if the spark is red or yellow, suspect the coil. Then close the plug gap to check for a weak ignition. If the condition improves with a small(er) gap and the wires are in good repair, suspect the coil.

Too bad loggers weren't more popular with 2gnt'ers.
 
I'm going to assume that your car isn't throwing a code....right? and that you dont' have any aftermarket ecu add ons?

I don't know if it's throwing a code or not. Don't have a logger and I wouldn't trust pepboys with my bicycle. Maybe Autozone. If it were a code, I couldn't imagine what it would be since 1st,2nd, most of third are OK. 5th is fine. But hey it's worth the drive up there to find out.

No ECU add ons.

I wouldn't be surprised if it's my front o2 because I haven't changed it in over 2 years. I could be running rich enough to throw the sensor off pretty bad. I'm really not trying to buy another one but I may have to.

I'm going to check for spark tomorrow and see what happens. Hopefully with the few hours I get I can install the wideband and FP gauge too. I will let you guys know what happens and even if I fix it or not.

Thanks for the replies and please keep em' coming if anything comes across your head..
 
Well naturally anything limiting your rpms would lead me directly to your MAP sensor, but it doesnt make alot of sense, because your saying its only 4th gear related. Your telling me that you can rev over 4k in all other gears? except for 4th gear? If your rev is limited to around 4k regardless of the gear then its most likely the MAP sensor.

:confused:
 
I would guess somethign sprak related as well, if it acts up more with increasing loads. The first thing i would try is replacing the plugs and wires.

Sorry i'm not more help, but if there's no ECU add ons i'm baffled as to what it might be. Also, your o2 sensor is ignored during wide open throttle, so if you are wide open i wouldn't worry about the o2 sensor being the culprit.
 
Just an idea...

My rally car did this during an event. Found it to be the ECU was burned out and running the car full rich. I believe the ECU was damaged due to my welding and cutting on the car.
 
THANKS SO MUCH to ALL the replies. I appreciate all the input it definately gave me some ideas.

OK, so here's what I've learned about the issue and what I've done.

I noticed the issue is apparent in other gears. Most noticeably 4th, because thats the gear I really never romp on... But 2nd and 3rd do it also, just isn't as bad or noticeable.

I took her for a drive on the highway, she is barely doggin' along. I meen, it feels like I'm on damn cruise control but I'm half throttle or about 3/4 throttle. I don't even want to try WOT in 4th because it honestly seems like the car wants to stall out. Even around 3-4k. If my foot lets off the gas, it will be damn near impossible to bring the car back up to speed without shifting down to 3rd..


I haven't had time to check for codes yet, BUT it will be happening tomorrow.

I have changed the fuel filter, spark plugs, checked the gap, checked all sensors, I have no vaccuum leaks and my oil pressure and vaccuum are fine while all this is happening.

What do you guys read as far as oil pressure goes when you build boost??? 50-75 or what? How about at idle? What do you see then??

I am starting to hope and think it's my plugs and wires, pssibly coil, and hopefully a front o2 sensors thrown off by the car running so rich. Maybe even a thermostat or something stupid?? Also, it COULD be my ECU. 95's arte notorious for ECU failure so worse comes to worse I'll just buy a used 95 one for like $30 and see what happens. Car makes no wierd noises at hot idle, no fluid leaks, etc..

BUT, during cold start I do hear some clunking and tapping in the bay. Once the car warms up it goes right away. At time the car will even shut off while it's warming up, or even at a stop light. But it will always start back up and go...


Please help me out here if you have any other suggestions. I can honestly ay I am more frusterated with this car right now then I've ever been. I'll let you guys know what happens regardless...
 
OK all you wiseman I have a few questions.

How EXACTLY does the MAP sensor read manifold pressure?

I ask this because the problem is now gone. I cleaned the MAP sensor a couple days ago, but today I looked a little harder into the chamber for the MAP sensor. All I saw was a sleek yet puddled, gunky buildup in that area. Then I realized when I cleaned my sensor the other day, it was only gunky right on the tip. As if it had been dipped in the shit. So, I began cleaning with some paper towels, and just kept spraying CARB cleaner in there to loosen the stuff up. Went to drive up to Autozone, and the problem is gone. Good thing too, because turns out Autozone can't read CEL's for anything under 1996 models. Here's what I found on and around my MAP sensor..
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Front and back were covered..
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So, heres me theory. Again, I don't know how the MAP sensor actually picks up/reads the manifold pressure so I could be wrong. I don't know if it reads off a negative vacuum created by surrounding pressure, or vise versa.

BUT, I think the area the sensor usually picks up the pressure was drowning in the gunk on the very side of my IM.

Like this.
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But the sensor couldn't pick up the pressure or atleast it was throwing it off like this..

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I have no idea but it obviously did something. LOL..

Thanks to all for the replies again. :thumb:
 
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