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1G Mitsubishi Eclipse 1.8 Rough cold start, running rich and rough high idle

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Volif_

Probationary Member
12
4
Nov 20, 2022
Ljubljana, Europe
Hello,

I have bought myself a 1990 1g eclipse 1.8 about 3 weeks ago, and am currently having one major problem.

A quick backstory of the car:

The car has not been driven and on the road since 2001 so about 21 years.
It has 91000 miles on the dash.
I am now the 3. owner the previous owner wanted to fix it but has lost all interest in it since he is now around 70 years young.

I got the car as a winter project and am some issues i could use some help with.

The car sometimes starts and sometimes it just overflows the sparkplugs since it is pushing to much fuel in to the cylinders.
When the car starts it is a very rough start, idling about 500-600 rpm and when it is given some gas it rough idles around 1000-1300 rpm.
The car is running very rich seen by the huge black cloud coming from the exhaust system when it is revved up.
All cylinders are working.
The starting problem is only present on a cold start, when the engine is warmed up it starts fast, but the rest is the same.

Things that i have replaced / checked:

- New fuel filter and pump
- New injectors
- New battery
- New MAF
- Cleaned out the old fuel from the tank and the fuel system
- Checked FPR and it is working as intended
- New liquids (Oil, coolant)
- New oil filter
- New belt and timing done on point

And i have ordered some new parts which could be the problem but I am not sure:

- New O2 sensor
- New cam shaft sensor
- New thermostat
- New coolant temp sensors (both for the dash and ECU)
- New oil pressure sensor
- New cables
- New rotor

The car also heats up fast, the ventilator works, the compression is good, no coolant is in the oil so gaskets are good, and the vacuum is working.
I do not have a OBD 1 tested so i cant see the problem and no error light is present when the car is running.
I can get a video of the car starting cold and running if needed.
 
Solution
Finally some good news!

after months of trying to fix the car I finally fixed it :)

The new Aliexpress injectors from the previous owner were trash to say the least, they were the cause for my rich burning and rough idle.
Yesterday I took my original injectors cleaned them out and tested them. Today I have installed them in my car and it runs perfectly :D, just need to set the idle speed.


Thanks everyone for your help

I will be updating my build on the other post

Greetings
Vid
Hi Volif_

Welcome to the forum and the DSM club. When you get a chance add the details of your car to "vehicles" in your profile to make it easier to give help specific to your model.

It's hard to give you any ideas to help as you have touched/replaced (shotgunned?) most everything that would be suggested. When you describe the rough idle, black smoke, and flooding the cylinders it is all consistent with too much fuel. I was going to suggest cleaning the injectors but I don't think I have ever seen one stick open, and you replaced them. Are you sure they are the right stock size injector? You said the FPR is working- did you measure fuel pressure at the rail? Was it in spec? You changed the fuel pump- is it a stock unit, or did you upgrade to a higher performance unit? Maybe a gonzo Walbro overpowering the small stock regulator?

An injector is pretty simple- squirt gun with electromagnet valve. Apply power, stream on. Cut power, stream off. If they are the right volume injectors (spraying right amount of fuel per time when on if the fuel pressure is correct) and the fuel rail pressure is correct, about the only thing it could be is the computer which is controlling when, and for how long, the injector is spraying. Have you messed with the computer? Are you sure it's the stock unit? I suggest pulling it if you can and opening the cover to see if the capacitors are leaking or circuit board is corroded.

I'm not necessarily saying it is a bad computer- It could be fed bad information from the MAF, or from the oxygen sensor, but something is off A LOT to be so far out of whack. Are you sure about the MAF? Again- is it the correct stock one, not modified, and wired correctly? Try disconnecting the oxygen sensor connector. Any change?

Do you have a service manual (preferably a factory service manual) for the car? Something was missed and you will probably have to back track and do some fundamental checks before replacing more parts. The factory service manual is great as it does have troubleshooting information, and specs for your measurements.

BTW- there is no OBD port on this car. If a check engine light were on there is a sequence detailed elsewhere on this forum and in the factory service manual that would enable you to (with difficulty) read out the code with an analog voltmeter, but error codes are few and broad.

Best of luck. -wparks
 
Thanks, i will add the details of the car to the profile.

First off thank you for the response :)

The injectors are new (as I have seen and heard from the previous owner they were bought from Aliexpress LOL).
I have replaced them with the stock original injectors that I got with the car, just cleaned and refurbished them.

I have not measured the FPR as I do not have a meter but I did it another way and just unplugged the FPR return hose.
Gas came out as it should. I unplugged the top vacuum hose and no fuel came from it therefore I am assuming the membrane is ok.

The fuel pump is a new original stock one i got online.

The stock ECU/Computer is present. Speaking of the ECU I assume that was the problem.
I have taken out the computer and given it a thorough look around and have found that one capacitor has leaked.
I have fixed the issue and the car now starts and runs fine.
The car no longer smells like fuel there is just a lot of smoke leaving the exhaust, I assume it is the carbon buildup in the pipes and catalytic converter, but i could be wrong.

The MAF is working fine as intended as i have unplugged it and the car went berserk.

One thing that is still strange is the O2 sensor that i replaced. When i unplug it the car has no change in anything.
The cables are wired correctly to my knowledge (Used a Universal meter to check it).

As the car has been standing for quite some time the service manual and paperwork was lost somewhere at the previous owner.

Oh and i did not know that it did not have the OBD port i just presumed it had a OBD I port browsing online :)

BTW: attaching photos of the ECU leakage before and after.

Best wishes Vid

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I'm glad you were able to find the problem- Did you (or someone else) replace only the one leaky capacitor, or did you have all four replaced? (if one going bad the others may be right behind.)
The smoke you are still having- Is it still black, or white/blueish? What does the smoke smell like? If it's dark, it's due to excess fuel. If it's white/blueish it's oil typically (could be valve stem seals, rings, etc). If it is white and smells like antifreeze, it's a head gasket. You will not see continuing smoke from carbon build-up. If it still smokes after several driving sessions we have another problem.

For service manual I was referring not to the owner's manual, but to an actual repair manual- you can get generic Chilton/Haynes manuals for the 1.8L pretty cheap on ebay, but if you really want to have detailed troubleshooting, test procedure, and repair procedure information, look for a "Factory Service Manual" made by Mitsubishi for that exact year and model of car- This would be the same repair manual that the dealer mechanics used back in the day, may come in multiple volumes (one for engine, chassis, body, one for electrical, etc.) If you are dedicated to keeping and working on this car, and doing all of the maintenance to keep it alive (you seem to be) this is a GREAT investment.

Thanks again for letting us know what you found- it contributes useful information to the forum.
 
I replaced it myself got all of the surrounding capacitors and changed them.

The smoke is black but the car has not been on the road i.e. driven since the fix just running idle and a few revs.
The antifreeze is clean no oil in the coolant tray which means the head gasket is good (got replacements planing to change when i get the car MOT and on the road).
The exhaust does not create any odors that are abnormal.

And yes i plan on keeping the car as i like the car and that is why i bought it in the first place :)

I will report back when i drive it a bit :)

Thanks for all the help
 
Hey,

I ran the car for a bit and drove it about 5 miles and the black smoke still does not want to disappear.
The car starts fine when cold or when hot it just idles around 1400-1500 rpm sometimes dips below 1000 rpms when cold and when warm it idles around 500-800 rpm.
When full throttle is given the rpms stand at 1600 rpm for about 5 seconds before dipping to 500 - 800 rpm.

And the new MAS started to pop/backfire when given throttle, so i replaced it with the old original one.
That one does not pop/backfire but the rest is the same?

I am now confused on what it could be.

The vacuum is fine no leaks as far as i know.
There is a slight odor of gas when i smell the exhaust fumes but not as much as before the ECU fix.

I can provide a video of the idle and start if needed.

Cheers Vid
 
Ok I could not check it today since I had a lot of work, but I got a video of it starting and idling if that is any help
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Ok so I have got some new information to share.

I plugged my Universal Meter in to the diagnostic port and got some codes out of it.

Code number 6: Throttle Position Sensor
Code number 5: Idle Speed Control Motor Position Switch

And it think at the start it shows code number 7 Engine Coolant Temperature Sensor but i replaced that 2 weeks ago so it could not be that. The code also appears at the very start of me turning on the ignition and is later absent.

I will order a TPS and replace it, but does anybody know how I could fix the ISC motor position switch so I don't have to spent 400 bucks on a new one?

PS: I've read codes like this for the first time in my life. I have probably missed something.
Bellow is the video of my diagnostic.

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Finally some good news!

after months of trying to fix the car I finally fixed it :)

The new Aliexpress injectors from the previous owner were trash to say the least, they were the cause for my rich burning and rough idle.
Yesterday I took my original injectors cleaned them out and tested them. Today I have installed them in my car and it runs perfectly :D, just need to set the idle speed.


Thanks everyone for your help

I will be updating my build on the other post

Greetings
Vid
 
Solution
The injectors are new (as I have seen and heard from the previous owner they were bought from Aliexpress LOL).
I have replaced them with the stock original injectors that I got with the car, just cleaned and refurbished them.

Sorry, thought you did that back at the beginning of Dec and still had the same issues. Who knows what size the Aliexpress ones really were.

Did you fix the high idle and fault codes?
 
Yea sorry that was a mistake on my end xD
I meant that I will replace them not that I already have replaced them. I was tired when I was writing the quoted post above :)

The high idle fixed itself when I replaced the injectors for the original ones.
The fault codes are gone now as well.

In the process of fixing the smoke i found out that my car has a EGR valve even tho it is not the California version. I looked up the vacuum diagram for the 1.8 EGR and have found out that the diagram does not match mine one bit.
Actually my diagram matches the 2.0 FED/CANADA version perfectly LOL.
I thought maybe that was the case for the smoke, so I took it down cleaned it and put a block off plate on it since I think i should not have it in the first place.
Now I known that was not it, but it is still strange to see it there.
The previous owners are either dead or don't know anything about this.

In other news the car is running good now just have to fix the dying at the first 2-3 cold starts, and the assumed vacuum leak somewhere, since the idle sometimes jumps around +- 100 rpm's
 
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