DSMTalk Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum banner
Cancel
Create thread New Garage Forums

1.8L no power above 3k and poor throttle response

Jump to Latest
1 - 11 of 11 Posts
P

Project84

· Registered
Joined
·
71 Posts
Discussion starter · #1 ·
My '90 Laser 1.8L 5sp is giving me trouble.

First and foremost the battery is overcharging and boiling through the vent caps. I'm hoping to address that ASAP.

I put 200 miles on the car after my recent tune up and it drove fine until now so I don't think it's something I messed up. Plugs all looked good when I pulled the old ones. I cleaned the MAF with throttle body cleaner at the same time.

This problem I'm having now is probably (hopefully) linked to the battery issue but here goes...

Last night while sitting in traffic before getting on the interstate my idle went from 700rpm to about 1500rpm and then kept going up and down between those two every few seconds. I figured maybe a vacuum leak had happened or if there's an IAC valve maybe it's going bad... I also questioned the coolant temp sensor because I know they can do crazy things when they go bad.

I then get on the interstate and drove 40 miles. Once up to 65 mph the only way to maintain speed or accelerate was to give the pedal a very light pressure. Too much pressure and it seemed to bog/dump the fuel and the car would actually slow down.

I also noticed when I got off the highway that there's about ZERO throttle response above 3,000 rpms. It's like at 3,000 no matter how far my foot is on the pedal or what gear I'm in, the call falls on its face really bad.

No check engine lights, car is not overheating, and I don't think the clutch is going bad because no matter what above 3,000 rpm there's just no power/response whether I'm flooring the gas or I'm light on it.

Help?
 
#2 ·
Since you are saying you have made no changes to your car, and your car is maintaining idle, with the symptoms you have I'm willing to bet your Throttle Position Sensor - TPS took a dump.
 
#3 ·
^^ This is exactly what mine was doing when I first got it.

Turned out was the fuel filter. Never had that issue again. I remember would be on the highway and all of a sudden no power, like a sputtering unless you eased on the pedal. No throtle at all over 3k, you could hear it wanting to suck in air but nothing.... maybe a backfire. Try the filter, I tried 3 different brands and none of them fit the threading on the OE fuel line, Wix made the best fit. My roomie just did his on the Talon and he said the Autostoned brand fit fine.
 
Save
Reply Quote Like Like
Discussion starter · #4 ·
This is going to be one of those mysterious problems to figure out.

The fuel filter looks brand new though I did not replace it. I did buy one but after locating it on the firewall and finding what appears to be a very recently replaced one, I went ahead and figured it was good and I left it in there.

The TPS might be a good place to start because there has been no power above 3k since I bought the car and first drove it even before my tune up. It's only a new addition that it searches for idle between 700 and 1500.

I should add that I turned the car off once in the driveway and when I restarted it settled down to its normal 700rpm and stayed there. I didn't attempt driving again because I had things to do and couldn't spend more time working on the car.

Seems like as soon as it reaches operating temp the idle gets wacky, and like I said, there's been no power over 3000rpm from the start.
 
#5 ·
Not having a turbo is going to make it much easier to diagnose, try running the car with the TPS unplugged, the ECU should maintain a MAP without the TPS sending a signal, and will give you a better idea if it is sending wacked voltages to your computer resulting in your car acting the way it is acting.

Also, look into some of the write ups on vfaq.com. When I had my 93 Elantra 1.8, vfaq helped me to really get the car running like it should. Tons of great info on helping DSM powered cars run their best.

Good luck, keep us posted on anything you find out, I'll keep an eye out to see if I can help more.
 
Discussion starter · #6 ·
Where do I source the best option for alternator replacement on a 1.8L? My alternator is a 65A for a 5sp 1.8L.

I can get one through NAPA for $122 or Autozone for $105. If the voltage regulator is what always fails (my battery was charging at 20vdc) should I just disassemble the alternator and repalce the regulator inside? That part is $42.

I couldn't find any alternators at the local junkyard and the 2.0L alternator apparently does not work (though under the hood they do look to mount the same.... parts places say the mounting feet are a few inches off...?? What do I know. They list one as mounting feet are 3 1/16" apart, the other is 1 7/8" apart.
 
Discussion starter · #9 ·
I have not done a compression test but there's significant power under load until 3,000 rpm. I did an oil change when I got the car and been monitoring the oil level and color and it still looks brand new at 300 miles on it and level hasn't moved.

The speedometer and tach both work so I do not think the VSS is bad.

I still haven't replaced the alternator because I got into researching whether or not the Saturn swap corresponded with the 1.8L and my results are inconclusive! Thinking of just having the current alternator rebuilt for $60.
 
Discussion starter · #10 ·
So the alternator was bad. Not sure if I mentioned or not but that bitch was charging at 21 vDC. WOW. Wiring didn't melt.

New alternator on I started the car after a jump and the idle was still searching. Could visibly see the IAC valve moving in and out, unplugged it and it stopped. Idle steady now but at 1,300.

Test drive - still falls flat on its face above 3,000 RPM... could feel it pulsing and sputtering. Swapped fuel filters (although the one in there looked to be very new) and the one that came out was dumping rusty fuel. Not good. New filter on, start the car.....


ZING! All my power is back! Very very pleased with this.

Now.. wtf is rusting in my fuel tank causing the filter to fill with rust/chunks.
 
1 - 11 of 11 Posts
About this Discussion
10 Replies
5 Participants
Last post:
Project84
DSMTalk Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum
posts
2.3M
members
104K
Since
2000
A forum community dedicated to Mitsubishi Eclipse, Plymouth Laser and Eagle Talon owners and enthusiasts. Come join the discussion about performance, turbos, builds, modifications, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
General DSM Tech and Tuning Help! Tech Newbie Questions Forum Body Tech and Appearance Electronics Tech