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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?
 
Agree with the biss screw, but I might recommend looking at the egr system as well if it's still hooked up.

Where are you hooking up to do the BLT: turbo inlet, outlet, TB, I/c piping? 50psi seems excessive but if you're not leaking at that pressure that's a good thing.

Setting up initial idle, timing etc. Isn't too bad, just follow procedure and it can take less than 5 min to get dialed in.

Have you set base timing?
 
Agree with the biss screw, but I might recommend looking at the egr system as well if it's still hooked up.

Where are you hooking up to do the BLT: turbo inlet, outlet, TB, I/c piping? 50psi seems excessive but if you're not leaking at that pressure that's a good thing.

Setting up initial idle, timing etc. Isn't too bad, just follow procedure and it can take less than 5 min to get dialed in.

Have you set base timing?
I didn't even think timing was adjustable with the 2ga sensor? Behind the intake cam gear?

I wasn't letting the air come in at full strength, but the regulator was set to 50psi. I can always lower it to 15-20 and let it run continually.

And call me a noob, but what does BLT stand for? I'm familiar with BOV....?

Are the coolant lines still connected to the throttle body? or do you have the fiav properly bypassed?
Coolant lines are attached. I do not believe that we've bypassed the FIAV. Though I'm drawing a blank. I know that I've done that before on a different dsm and since this is a 3 year long project that has never driven, it is beginning to be a blur.
 
BLT at 5psi above the pressure you intend to run at with the crank rotated 30 deg atdc i believe.

If your regulator is at 50 but youre throwing in tons of air and not making headway it is likely due to crank position not sealing valves. Or massive blowby if your exhaust valves are closed.

Stock valve springs i find hard to believe could hold back 50 without leaking.

15:1 afr solid would tell me a slight leak after o2 housing but before wideband IF you have it downstream.
 
I didn't even think timing was adjustable with the 2ga sensor? Behind the intake cam gear?
It isn't adjustable

I wasn't letting the air come in at full strength, but the regulator was set to 50psi. I can always lower it to 15-20 and let it run continually.

And call me a noob, but what does BLT stand for? I'm familiar with BOV....?
Boost leak test


Coolant lines are attached. I do not believe that we've bypassed the FIAV. Though I'm drawing a blank. I know that I've done that before on a different dsm and since this is a 3 year long project that has never driven, it is beginning to be a blur.
 
I didn't even think timing was adjustable with the 2ga sensor? Behind the intake cam gear?

I wasn't letting the air come in at full strength, but the regulator was set to 50psi. I can always lower it to 15-20 and let it run continually.

And call me a noob, but what does BLT stand for? I'm familiar with BOV....?


Coolant lines are attached. I do not believe that we've bypassed the FIAV. Though I'm drawing a blank. I know that I've done that before on a different dsm and since this is a 3 year long project that has never driven, it is beginning to be a blur.

BLT = Boost Leak Test.

I'm not familiar with 2g stuff per-se, but you're probably correct that timing isn't adjustable with the sensor behind the cam gear.

Compressor tank pressure doesn't matter, whatever pressure is in the boost tract is important, and typically 5psi over target pressure is a good test pressure.

It's possible that you have an exhaust leak, but I'm still curious if you have the egr system intact on this car?

Essentially you have some adjustment to get the idle dialed in and find any leaks on the intake and exhaust. Do you have a smoke tester? You could quickly test both intake and exhaust with that, otherwise you'll have to get your BLT sorted out and hunt for exhaust leaks the hard way.
 
So, we have a smoke machine, but it kinda sucks. I hooked it to the motor, but could not see any smoke coming out. The smoke that it makes isn't that thick. It's an old vacutech model.

So, I tried pumping 20psi in and sprayed soapy water all around. I did find some slight bubbling from the IC hose coming off of the turbo as well as some from the base of the BOV.

I double checked any it does look like we have an EGR blocking plate installed.

When I put a constant 20psi on the system I have not been able to find any other leaks for now, but once I turn off the air it seems to depressurize immediately. I should be at 30 degrees ATDC.
 
If it depressurizes immediately, you don't have a boost leak per se, you're just not getting a seal of any kind in your intact tract. Technically that's a boost leak, but much more extreme.. You would hear it out the BOV so I'm inclined more to think that air is going past the intake and out exhaust valves. Otherwise, with a "well enough" sealed system you should leak back down to zero in 45 seconds or so.

A cold engine will cause more air to escape but how much do you hear out the oil cap?
 
So, since I've got a BLT that fits where the MAF attaches, I'm going to block of the end of IC pipe running to the TB elbow. That way I can eliminate problems prior to the TB elbow. If those check out, then I can reconnect it and check from the TB elbow forward.

Sound good and systematic?
 
Sitrep-

BLT seems ok. Pressure slowly drops.

I ran the motor. Idles semi smoothly at 1600 when the kids first turned it on. When revving the motor we got some loud backfires out of the exhaust. I then had them pull injector harnesses off one at a time. If we pull cylinders 1 or 4 it will die. Cylinders 2 & 3 make very little difference. Hardly noticeable, if at all.

Again, we have confirmed that we have good compression on all cylinders.

This is kinda why I felt like I might have a timing order issue (which I posted on another thread, but was told that the regular order is what we want in this scenario.) I need to verify that the injector wires are in the correct order, though lengths of the wire seem pretty intuitive.
 
Good catch Joe. Sometimes the little things are very important. Glad you are posting up results and asking the questions that the kids need answers too.
I, for one, am following this, as I am teaching rebuilding at my house for 4g63's to anyone wanting to attend.
So far, I have one student....my 20 year old son.
I also am following the father/daughter duo that are on our board also. I love to teach kids motors as much as I can before I won't be able to remember it, LOL.

Here is our progress, so far....
2 six bolts at once!
You must be logged in to view this image or video.


Keep teaching those kids, I applaud you!!!
 
UPDATE- So, we've still got mostly dead middle cylinders. I'm going to have the kids swap the inner injectors to the outside and see if it is an injector issue. Again, we've never ran this car before, so all parts are condition unknown.
 
Swapped injectors, same problems. Was going to test the middle harnesses with a noid light, but then we started leaking gas back at the fuel pickup. So once we have that back together I hope to get it checked. Class just ended for today, so it may not be until tomorrow.
 
Ok, new problem. I replaced 2 fouled spark plugs. It appears that we now have 4 cylinders. That said, when we turned it on it now sits at 2500 rpm. Maybe I need to get dsmlink out and wipe the memory and start fresh. I did check the throttle cable adjustment and the BISS and those were ok. Or at least, not way off.
 
It's not possible to idle over 1500 once warmed up. ECU won't allow it UNLESS throttle isn't really closed which you said you check throttle cable or the ECU doesn't know throttle is closed. Funny I have a 2g dsm and I can't remember what controls idle switch. I want to say it's integrated into TPS on a 2g. Anybody care to chime in?
 
Joe, check the idle stop screw/switch on the throttle body. Loosen the jam jut and see if you can manually adjust the idle down with it.

Sorry Paul, was typing when you replied.
 
Joe, check the idle stop screw/switch on the throttle body. Loosen the jam jut and see if you can manually adjust the idle down with it.
Sorry Paul, was typing when you replied.

Yeah, I have not gotten that far yet. As always we are plagued with having short class times, and 20 other projects going on. I'll look at the ISS *(Idle set screw? I think that's right) on Monday probably.
 
Let the "FUN" begin! :thumb:
 
Ok, so we may need to go back and look at the SAS again, but currently we had the ISC position at 32, but the rpms were around 1600. I'll loosen the SAS and try again, but we did 1.25 turns past touching, as the instructions said.
 
It shouldn't idle that fast Joe. Go back now and check that the throttle cable isn't too tight, holding the plate open a bit. It should idle around 750-800 real good. Vacuum leaks or open vacuum nipple maybe? TPS adjusted correctly also? Sorry if I am redundant.
 
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