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2G GHS GSX Shop Project- Tuning/Idle Help

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gijoe985

15+ Year Contributor
562
20
Dec 13, 2007
Grandview, Washington
Hello all,

We wanted to start a new thread for our high school shop project that has been sitting for the last half year. You can see our old threads here and here.

We have the car turning on now. We've got our timing correct and we have good compression on all cylinders now. Today when we turned the engine on it ran smoothly, but at 1600rpms. It ran well for a couple minutes, but then began to have some hiccups here and there. Eventually the idle lowered some and the idle became rough and then it just died. We tried restarting it and it idled ok and then again eventually died. Wideband originally showed us right around 14. The last time we ran it it was idling at 15:1.

We did a boost leak test and thought things looked ok. Though the psi gauge we had (attached to air gun) may not have been working well. How long does it take to pressurize the system normally? We were pumping in 50psi for 10 seconds or so and that seemed like overkill. It would hold some pressure, but again, I'm not questioning how well that gauge is reading. Sadly maintenance just came to service our compressor, so we may not have air for a few days. But we didn't hear any leaks when we pressurized it as high as we felt comfortable.

I know that the BISS will need to get adjusted, but I was waiting until it seemed to be running better.

Thoughts?
 
PROGRESS (but not the kind I wanted)

So, after adjusting the MAF adjustment, I felt like there as some improvement, but then I started thinking... We are inside and hooked up to a vehicle ventilation system. I unhooked our exhaust tube and lo and behold, white smoke. Not horrifically bad, but enough to warrant a worry.

I went to pull the spark plugs again and found that the #2 was a bit wet and there was some steam coming from the cylinder...

Now I have to determine how to fix this and WHY is it like this. We did the head gasket not long ago because we had lower compression on #4. We used a permatorque gasket and followed all of the procedures correctly. So I'm stumped as to why it didn't seal. And we got good compression on that cylinder when doing our compression test, but who knows... Maybe I could start by just torquing the bolts again? Dare I suggest head gasket in a bottle? (I think I'm just feeling lazy because of how much time we have sunk into this.)

Looking for ideas.
 
One problem we may have had was that we used moly assembly lube with our arp head studs. I don' even remember what torque we put them to, but I remember that I did a lot of research so that we had hopefully done it correctly.
 
Pull the valve cover and retorque. See if it still smokes. I torqued my head to 90 ft lbs, let it go through a heat cycle and retorqued them. A couple studs did need the retorque. Don't use the bottle to seal the leak. It can cause build up in the radiator.
 
I would go back over them Joe. When I bought my 92, it had headstuds put in it by the PO. I drove it for a a couple months and thought about those studs and man were they loose. Probably only 50 ft/lbs. I have them in at 85 now. IDK if the PO just didn't tighten them down good or if they worked loose.
 
Check the oil to make sure it's not milk shake because that'll bring all the boys to the yard:nono:
Thanfully we have 0% milkshake... no boys in this yard.

And yes, a couple studs were loose. I do have a bottle of the Blue Devil sealer on the shelf. And IMHO, I'd rather swap a radiator (we have an extra) than do the head gasket again... but this is shop class. The kids are learning.
 
So after all this, we tried the Blue Devil head gasket fix.... and now we have fine compression on cylinder 2, but low compression on cylinder 4?!?!?! That was the cylinder that we previously had low compression on. We did new rings and a head gasket and we bought the best gasket we could, followed all the steps, and it had 165psi the last time I checked it, now 130. All the rest are registering 165...

I'm kinda dumbfounded over this. This is the 4th year we've been working on this car. It'll be a classic by the time we get done.
 
How are you testing compression? let the tester max out dont be concerned about "X" amount of puffs etc, and hold the throttle open while cranking.
 
Yeah, we did a leak test with the head off. Put fluid in the combustion chamber and it held fine. I may have the kids to a leakdown test before disassembly.
Joe, put lacquer thinner in the runners on the head and look for leaks on the valve/combustion chamber side. My machinist and I do that with my heads. You probably already knew that or have done it though.
 
Joe, put lacquer thinner in the runners on the head and look for leaks on the valve/combustion chamber side. My machinist and I do that with my heads. You probably already knew that or have done it though.
Yup, that's what we did last time. Everything sealed fine. So, we'll pull the head, check for warpage again, last time we even replaced the rings because we didn't want to pull the head and not know why we had low compression. I have more rings, we could do it again, but I don't see why we'd need to...

A wet compression test yielded almost no change in compression. We still get 165 on cylinders 1-3 and 135 on cylinder 4.
 
Put fluid in cylinder 4 runners and blow compressed air around the valves and look for bubbles in the fluid in the runner? Just trying to help.
Ring gaps within tolerance?
 
Head gasket replacement in progress. No visual sign of issues. Chambers held fluid tightly. Hoping for the best. Bought ANOTHER felpro permatorque gasket. (Those are expensive!).

Stay tuned. Only 2 weeks left with my seniors. 3 weeks total...
 
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