1G Misfire Diagnosis Help

[Chuck Boone]

Hi DSM tuners,
Been working on a very stock '90 Eclipse 1.8L as a project car for/with my kids to get them learning about cars and mechanical things. Definitely outside of my profession and I'm learning too, but fairly mechanically adept. Car had been sitting idle in a field for about 12 years before we started working on getting it back in running condition again. Starts up easy and it's been running fairly well off and on, but now has a hard misfire we can't seem to get right. Pretty sure what's going on, but would like to get some experienced advice before I dive in the deep end. Engine stuff that's been done to the car (some perhaps irrelevant)...

• Fuel pump and filter replaced
• ECU replaced
• MAF, oxygen, coolant temp sensors replaced
• Injectors replaced
• Distributor rotor and cap replaced
• Plugs and wires replaced
• Catalytic replaced

What I know...

• Fuel pressure OK - maintains about 43 psi on the rail at idle and rev'd up to 3000 rpm
• Spark OK - test light shows spark on all 4 cylinders
• Compression - 1: 182, 2: 195, 3: 167, 4: 180
• Number 2 plug fouled and wet - all others OK (see pics). Seems not to be wet with fuel as it wouldn't burn.
• Noticed after compression test on #2 steam-like vapor from spark plug hole after removing gauge.
• Very rich odor from exhaust

So that makes me think that coolant is making it into #2 cylinder. Head gasket or crack? Pull the head and take a look? If it is the head gasket, I'm up to the task of replacing (I have the Mitsubishi service manual set) - but what other maintenance things should we be thinking of doing while that's apart? Lash adjusters (has been pretty tappy)? Timing and balance belts?

Thanks for any and all help!
-Chuck.

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[1990TSIAWDTALON]

Hey Chuck. As with any old car that runs a belt for timing, it is DEFINITELY time for those. I think putting new timing pulleys is always a good deal along with a OEM tensioner. I am not up on the 1.8's but its all a matter of maintenance on an old car. Check all hoses and fluids and R & R as you need to.
Glad you jumped on the board to trust good advice, thanks and Welcome!
Marty

 

[311oneG]

Working on the same thing with a 46g3t. I'll be following!

 

[pauleyman]

Hi DSM tuners,
Been working on a very stock '90 Eclipse 1.8L as a project car for/with my kids to get them learning about cars and mechanical things. Definitely outside of my profession and I'm learning too, but fairly mechanically adept. Car had been sitting idle in a field for about 12 years before we started working on getting it back in running condition again. Starts up easy and it's been running fairly well off and on, but now has a hard misfire we can't seem to get right. Pretty sure what's going on, but would like to get some experienced advice before I dive in the deep end. Engine stuff that's been done to the car (some perhaps irrelevant)...

• Fuel pump and filter replaced
• ECU replaced
• MAF, oxygen, coolant temp sensors replaced
• Injectors replaced
• Distributor rotor and cap replaced
• Plugs and wires replaced
• Catalytic replaced

What I know...

• Fuel pressure OK - maintains about 43 psi on the rail at idle and rev'd up to 3000 rpm
• Spark OK - test light shows spark on all 4 cylinders
• Compression - 1: 182, 2: 195, 3: 167, 4: 180
• Number 2 plug fouled and wet - all others OK (see pics). Seems not to be wet with fuel as it wouldn't burn.
• Noticed after compression test on #2 steam-like vapor from spark plug hole after removing gauge.
• Very rich odor from exhaust

So that makes me think that coolant is making it into #2 cylinder. Head gasket or crack? Pull the head and take a look? If it is the head gasket, I'm up to the task of replacing (I have the Mitsubishi service manual set) - but what other maintenance things should we be thinking of doing while that's apart? Lash adjusters (has been pretty tappy)? Timing and balance belts?

Thanks for any and all help!
-Chuck.

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Does it always misfire or just some of the time? I would do a leakdown test and check the injector clip wiring. Test to see if that one injector is firing. Easy tests

 

[Chuck Boone]

Does it always misfire or just some of the time? I would do a leakdown test and check the injector clip wiring. Test to see if that one injector is firing. Easy tests

Thanks, Paul. Good point - a little more history... before I replaced the injectors we were having the same issue with #2 - hard miss, not firing much if at all. Could pull the #2 plug boot while running and no change, where pulling 1, 3 or 4 was noticeable. Used a noid light to check to make sure the injectors were getting signal - they were. Figured since we had spark, compression and fuel pressure it was likely the injector, and since it had sat for many years I guessed that maybe the injector was stuck partially open or not opening enough, and probably should be replaced anyway. Replaced all the injectors and clip wiring and it was running pretty good for a couple weeks. Perhaps that was coincidence. Then would start and idle OK, but started loosing power as soon as the clutch was let out. Seemed like a fuel starvation problem and suspected that the fuel filter was clogged. When we first got the vehicle we had to replace the fuel pump and did so, but there was a lot of rust in the tank that we didn't take the time (or know better) to clean out. Really regret not doing that then, but water under the bridge for now... Anyway I wasn't too surprised that the filter could be clogged. Replaced that, and it was indeed running better (not acting like it's loosing power in a big way) but still missing. Followed up and checked the fuel pressure - stayed around 43 psi at idle and rev'd, and compression again (1: 182, 2: 195, 3: 167, 4: 180) but in doing that noticed what appeared to be steam from #2, the fouled wet plug, and the higher compression on that one. Trying harder to hone my diagnostic skills, but still feel like some of this was shotgun troubleshooting.

I'll see if I can come up with a leakdown gauge and give that a go to see what it reveals. My understanding is that it could/will show where/if the cylinder is leaking, yes?

 

[Chuck Boone]

Hey Chuck. As with any old car that runs a belt for timing, it is DEFINITELY time for those. I think putting new timing pulleys is always a good deal along with a OEM tensioner. I am not up on the 1.8's but its all a matter of maintenance on an old car. Check all hoses and fluids and R & R as you need to.
Glad you jumped on the board to trust good advice, thanks and Welcome!
Marty

Thanks, Marty - I appreciate the reply and thoughts. Have taken care of the hoses and fluids and will definitely do the timing belts and pulley once we get in to see what's going on with the misfire.

 

[Chuck Boone]

So finally got a free Saturday with decent weather to do some more tests. Did another compression test, and a leakdown test. Findings (engine warmed up)...

1 - 185 psi, 15%
2 - 200 psi, 20%
3 - 195 psi, 25%
4 - 188 psi, 15%

Only air leaking noise I could hear was from the oil fill in the valve cover and some from the oil dipstick tube (nothing from intake/exhaust). No bubbles in coolant at fill cap.

Definitely a solid miss on #2 - can pull the plug wire while running at idle and get no change in how it's running, but pulling 1,3,4 runs much rougher. However seems that when I pulled 3 it maybe ran a little bit rougher, but not as bad when 1 or 4 were pulled.

I appreciate any diagnostics help! Thanks.