I have a 93 Eclipse GS model with the 4G63 non turbo. The car has always been tempramental. Lately I have not the power output that it should have. I changed the plugs and they are black. The car is getting to much gas somehow. Here is a list of what I have done as of today. Replaced fuel filter, Fuel Pressure Regulator, Cleaned the plugs. Compression tested the cylnders (all are 125-130psi on the test). Have put new plugs wires on about 25k ago. Also sometimes I get idle surge. When I drive the car I can get the power back at about 4000 rpms and up. It runs rough below that unless I feather the accelerator. I run MMCD and the pressure reading is 66 psi then goes down to 3.5 psi. I read some where that the PSI should be about 47 or so is this right? I haven't really had the idle surge problems like I use to just every now and then. I got a fuel relay and ECU from the junkyard for about 40 bucks and am thinking of putting those in next (one at a time ). I am running out of ideas to try. If anyone has one let me know thanks for the help all.

 

are ALL of them black or just 1 or 2?

 

All of the plugs where black when I took them out today. I cleaned them and put them back in as i did the compression test as well. I also live in Casper Wyoming where the altitude is 5200+ feet if that helps.

 

maybe your plugs werent gapped well, maybe the wires are bad, or maybe you have a leak in your intake system. the ecu would be injecting enough fuel for a certain amount of ait, but not all that air is making it into the cylinders. oh, or an o2 sensor could be bad

 

O2 sensor was replaced a month ago. The plugs are bosch 4 pronged so no gapping is needed. Forgot to add that in my original post. It might be a leak but I would have no idea where to look for it though. If there is more air getting in then I would think the system would be running lean not rich as a leak would be after the MAFS and there by putting more air in than the ECU knows about. I might be wrong though. I am going to put a new Fuel Relay in tomorrow since it is not that hard to get at and see what happens. I have had the idle surge problem for over 2 years but it has just started running rich within the last 9 months I guess. I thought it might be due to winter. Also every now and then the engine will run great like nothing is wrong with it making me suspect a computer or relay problem that I have never fixed yet. Thanks for the guesses though. Anyone else have an idea I will be most greatful.

 

those compression numbers are pretty low. The stock 1g gs runs a low 16 in the 1/4 where the 2g gs runs a low 17. Mostly because the 4g63 non turbo makes more n/a than the 420a, my compression is around 180psi per cyl. I would double check those numbers with a haynes manual because I think your problem with the richness could be bad piston rings or valve seals.

 

Yea I will check the numbers thanks Slow. I was thinking that I might have some bad rings cause I can smell burning oil every now and then. I will look. The car does have about 160,000 miles on the engine. I just need it to last till I get a full time job after I come back from the desert in the fall then I can get a new car and work on this one.

 

Well just checked my manuals and the minimum allowed is 137psi with a 14 psi difference between each cylinder. I did the test wrong though and have to do it again tomorrow so I will let you know what I find out. Thanks all.

 

you might even have a bad valve cover gasket as well

 

Ok did another compression test. This time the engine was warm and I opened the throttle body. I got 150 psi for cylinders 1 and 2. got 135 psi for 3 and 4. I then put a cap full of oil into 3 and 4 and the reading was 165 to 170 psi for both cylinders, whcih leads me to believe that my rings are starting to wear out now which would make sense cause the car has 160,000 on it. Guess I see a rebuild in my future lol. Today the car seems to want to run great every now and then. I would be just driving along and pow all the power is there, then its back to acting like its running rich again with no acceleration etc. Guess this car is going to get the title of project car soon (Once I get a new Mitsu ) was thinking I would like to rebuild the motor and see if I can get 250hp out of it with out running a turbo. Anyway Thanks for all the help guys.

Oh I did readjust the TPS too. My MMCD was saying the TPS was only 8.9% at closed throttle wear it should be 10%. Has anyone else used MMCD to tune there sensors like that. I would like to know if you put your TPS at 10% or have it read close to 0% on the output screen. Again thanks.