The neverending story – Colt GTI 1996

[Martin]

Hi guys. Im am having trouble with my Mitsubishi Colt GTI. Im planning a very long post. With detailed information of the car, a bit of history and detailed issues im having with it. I will try to put the additional information on spoilers and leave the basics for those who dont want to read all through. Even if I think that to gain a full understanding of the problem a full reading will help.

The car: Mitsubishi Colt GTI 1996 1.8L 4G93 DOHC
More info:
[spoiler]It is like the Mirage in the states, but in DOHC configuration, also Colts are only hatchbacks, it has the same engine as the Lancer GSR (Evo1 predecessor). With the CA5A frame its a very rare car but in UK/Australia/Japan. Its like an hybrid between the Mirage 1.8LS and N/A 2G Eclipse. Actually most of its parts are borrowed from one of those two engines.[/spoiler]

I did two rebuilds of this engine in less than a year. I ve done 400 miles only after the second rebuild.

A bit of story on why 2 rebuilds
[spoiler]I purchased the car with the engine already rebuilt about 30k miles ago. The engine seemed fine at the time and in good condition. 6 months later I was on a highway going 100mph and the engine died. An exhaust valve head broke and then hell break loose in Cyl 1 (this is a very important fact as it is the cylinder giving me trouble now) piston got trashed, head destroyed, etc. As I would discover later, rebuilt was done with low quality valves.
The first rebuild was done in a shop, it took them about 4 months to rebuild, the engine. the cylinders were bored to 1mm. I couldnt find 4g93 pistons of that size with good quality so I used 1mm 4g92 pistons that some other guys in my country have used and had good results, CR went from 10:5 stock to about 12:5 using this pistons. Also new rings, new lifters, new bearings, new whole set of good quality valves, a proper rebuild. I purchased the parts used so I know that the spares used were good.

When they ended the car, the car was knocking horribly, timing looked way off the mark, basically a terrible job. Under heavy accel the car sometimes had terrible misfires I went to the shop to have them recheck. About a month a the mechanics had no clue about what went wrong, I finally had a fight with the chief mechanic so I took the car to a known (expensive) tunner on my city who fixed the timing and the car ran good albeit a bit down on power. 130HP vs 140 stock. Then with 2500 miles since the rebuilt the engine started to burn oil. I went to the tunner. They took the head off and said that the engine was a mess and they charged to me a lot just for taking the head and pistons off (without my permission)

So tired of all this drama I took the dissasembled car, left it in a friends backyard (he works as a half time mechanich and he already did rebuilt an identical engine with same pistons I was using and the other car has 20k miles and no problems). I borrowed his tools and he helped me to do a second rebuilt, but now I was working on it, so I could be sure everything was done how it should.[/spoiler]

Even if I am not a mechanic, I studied a lot and Im pretty good with machines so I performed a second rebuilt of my engine. Also Im tired of dramas with not so honest mechanics (Im not blaming any of you reading this, I just had a lot of bad luck i think). But im pretty confident that everything was done properly. As I did it with the mitsubishi service manual and software. Respecting torque specifications, with good cleaning of all pieces. Also i purchased a lot of new pieces in the process.

Details of the rebuild:
[spoiler]The engine was totally torn apart for this second rebuilt. I used same pistons, same valves, same lifters. All were less than 2k miles old so everything looked like new. I also sent the head, the crankshaft, and the block to a machine shop, everything was checked by a very reputable shop in my country. Crank was corrected, block was honed again. Then everything was cleaned, oiled and assembled.
New parts:
Piston rings
Gasket set
Bearing set
Crank position sensor
Cam position sensor
Coolant temp sensor
O2 Sensor
MAF Sensor
and a lot of other stuff not engine related as clutch system, engine mountings, etc etc.[/spoiler]

I went through various problems after the rebuild and now Im in the verge of opening the engine again what is driving me nuts. I came here with hopes that I can avoid a 3erd engine rebuild in less than a year.

Car symptoms:

-Rough Idle.
-Low Power.
-Strong fuel smell.
-Engine vibration.
-Fart-Like noise on acceleration.
-Dataloggin shows knocking.

I have been troubleshooting and doing checks and solving some problems.

Last thing i tried is a power balance check that told me that cylinder 1 was JUST firing. Removing sparkplug wires or fuel injector connector from cyl made very little difference while doing the same on 2, 3 or 4 made the engine a lot worse.

So I exchanged cyl 1 and 2 plugs, wires and injector. Problem stayed in cyl 1. Sparkplug I pulled from Cyl1 was full of carbon deposits.

A bit of additional info on this:
[spoiler]Before I put the first miles in the car after the last rebuild a friend of mine helped me to measure dynamic compression and Cyl 1 was about 50 psi less than the other 3. He said that with the break-in of the engine that would be solved. Im starting to feel that no break-in will solve this[/spoiler]

So considering that this is probably a compression issue, Im kind of desperate as I dont want to again remove the head off. If I had to, probably im going chop MY head off first. 🙁

Then…. I am missing something? Is there anything I can check or do (without a leak down test as I dont have a compressor or the tools for that) to diagnose the problem?

I would like to eliminate all other factors before taking off the head. As like all very rare cars in my country. Even the gaskets are purchased in the UK and sent by mail. So it was a long and tedious procedure that I dont want to repeat.

Finally. Please forgive my english. Im not a native speaker. And thanks for reading all this, all help will be greatly appreciated.

Topic

[college man]

If your smelling raw fuel you may want to check ignition components.

https://www.ericthecarguy.com/faq/solving-automotive-performance-issues

[Martin]

Thanks for the reply. As I wrote I already checked sparkplugs and wires for that cylinder. What else in the ignition system would cause a single cylinder misfire? Is a two coil wasted spark system. Maybe I missed something in the FAQs.

Thanks

EDIT: Reducing the gap in cyl1 sparkplug by about a 40% make the engine run a bit less rough. Does that make any sense?

[college man]

[quote=”martin511989″ post=176639]Thanks for the reply. As I wrote I already checked sparkplugs and wires for that cylinder. What else in the ignition system would cause a single cylinder misfire? Is a two coil wasted spark system. Maybe I missed something in the FAQs.

Thanks

EDIT: Reducing the gap in cyl1 sparkplug by about a 40% make the engine run a bit less rough. Does that make any sense?[/quote]

smaller the gap the stronger the spark. You may want to check spark output with a tester.

[Martin]

Well finally got my hands on a compression tester.

Cyl 2 3 4 about 120psi
Cyl 1 50 psi 🙁

So a leak down test is in order I think. Now I need to get my hand on a tester.

I ll keep you guys posted.

[Author]

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