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2G Engine issues?

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97gsxmod

Proven Member
99
27
Dec 30, 2023
New haven, Connecticut
(Continued from https://www.dsmtuners.com/threads/starting-issues-with-new-to-me-modded-gsx.545572/)

Had a blown turbo that was burning oil. Replaced it and then on startup oil filter popped loose and drained all the oil while I was trying to rev the car to keep it at running (would turn off if I didn’t rev it a little on start up).

Assume the loss of oil and pressure blew f***ed my freshly built turbo but was having trouble starting the engine as well.

So I just did compression tests. Number are 130-140-140-150 on a dry test with a cold engine. These numbers don’t seem great but don’t seem bad enough to explain the engine not starting. However when pulling plugs for the test I noticed they are all black and I just put fresh ones in a month ago and only moved the car to the road then back to the drive way. Must be from the old turbo?

Had trouble starting before and I replaced the plugs and it started right up, so I’m going to try to clean these and see if it will start. But the last factor my brain in considering is the build sheet for this car said it had 1200cc injectors, this seems crazy big? Maybe that’s part of the reason I’m destroying spark plugs so quick and even with fresh ones I have to get it reving a little before it will stay at idle. Any information is greatly appreciated.

Also forgot to mention I spun the new but most likely destroyed turbo by hand to make sure this wasn’t causing the no start. It spins though, so I'm assuming its not related to my starting issues but maybe I should try cracking the intercooler to intake tube to insure it’s able to breath with the turbo?

It still spun but seemed to spin slower then when it was freshly built prior to lose of oil after install.
 
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Are bigger turbo 4g63t’s with big injectors known for fouling plugs and flooding engines easily? Does anyone know an ideal plug for my car or should I just go with oem? Threads here said oem was the way to go but they were pretty old, didn’t know if there was a knew type out that was better for my set up

Get a couple of sets. If you don't used them near term you will later and it is better to save a trip when you need them.

So guessing fouling plugs is common and just something you gotta change often in this type of car?

I’m coming from a life a stock cars, so replacing plugs twice in a month makes me concerned about deeper issues (even tho I did have the no start issues flooding the engine with old gas). But maybe that’s just how it goes with these?

Plugs are cheap enough and couldn’t be easier to change so that wouldn’t be bad news
 
So guessing fouling plugs is common and just something you gotta change often in this type of car? I’m coming from a life a stock cars, so replacing plugs twice in a month makes me concerned about deeper issues (even tho I did have the no start issues flooding the engine with old gas). But maybe that’s just how it goes with these? Plugs are cheap enough and couldn’t be easier to change so that wouldn’t be bad knews
It's not common on an engine that is running well. I've been running the same plugs with 1000cc injectors for months. Fouling is a result of incorrect burn. Glad you are changing out the gas. If the Gas is in this bad shape, I can only guess what the condition of your Fuel filter and Injectors are at this point.
 
Spark plug purchase questions

Ideal Ohms resistance- gap size - ignition style- bore depth ?

I was thinking of going with a high ignitability sprak plug, anyone familiar with how they perform in a modified 2g dsm?
 
img_0466-jpeg.717290
Refering you to your prior thread. Here's what you had which is one range colder than stock. NGK bpr7es spark plugs.

img_0467-jpeg.717291


For cold starts and idling, the bpr6es plugs are hotter and work better. Swap to 7’s when you get it running better.

It's not normal to be fouling your plugs but when you keep flooding the engine it takes it toll on them. Bad tunes don't help either.

Stick with NGK copper plugs, they have been proven over and over in this engine and plan on changing them every 20k miles or so.
 
img_0466-jpeg.717290
Refering you to your prior thread. Here's what you had which is one range colder than stock. NGK bpr7es spark plugs.

img_0467-jpeg.717291




It's not normal to be fouling your plugs but when you keep flooding the engine it takes it toll on them. Bad tunes don't help either.

Stick with NGK copper plugs, they have been proven over and over in this engine and plan on changing them every 20k miles or so.
Thanks! 🙏
 
just got it started again but it wouldnt stay running and was running really rough, pretty sure my turbo sounded like it was destroyed to. Does this log show any clues to whats wrong with it?
 

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  • starting log #2.elg
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Nothing obvious. - I see you went back to the original ECU settings. Now that you got it started again, try changing one thing at a time - starting with non 95/96 cam sensor. You really do want that sequence correct - especially for idle performance.

Next zero out the Timing curve. -1 deg of timing across the board will make little difference starting, the ECU generally runs 20-30deg timing on cold start.

What was the outcome of the MAF inspection? - Have any of the honeycomb been removed? Do you have the coolant lines plumed to the FIAV (fast idle air valve) on the bottom of the throttle body? 2000rpm is typical cold start result.

Your front 02 sensor is giving a continuous voltage - and it should be cycling up and down. It may just need to heat up some more.
 
Nothing obvious. - I see you went back to the original ECU settings. Now that you got it started again, try changing one thing at a time - starting with non 95/96 cam sensor. You really do want that sequence correct - especially for idle performance.

Next zero out the Timing curve. -1 deg of timing across the board will make little difference starting, the ECU generally runs 20-30deg timing on cold start.

What was the outcome of the MAF inspection? - Have any of the honeycomb been removed? Do you have the coolant lines plumed to the FIAV (fast idle air valve) on the bottom of the throttle body? 2000rpm is typical cold start result.

Your front 02 sensor is giving a continuous voltage - and it should be cycling up and down. It may just need to heat up some more.
Thanks man. Let me try to figure some of that out. I had two 02 sensors plugged into my straight pipe originally, but only have one in know and I’m not exactly sure witch ones o2 and witch ones wide band and witch one the ecu is actually reading. I’ll try to get some of that figured out. Thanks for the help!

I also had alot of black smoke when reving and it felt like a misfire they way it was sounding and vibrating. I’m just curious if this could be from the turbo I rebuilt? It sounds pretty shot after the oil loss. Maybe it’s messing with the air flow?
 
set injectors to 1200cc. seemed to end the black smoke and misfiring problems, must have been causing it to run rich. but it still wont hold idle?
 

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  • start log 1200ccinjectorchange.elg
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set injectors to 1200cc. seemed to end the black smoke and misfiring problems, must have been causing it to run rich. but it still wont hold idle?
i started this one without clicking the non 95-96 style cam angle sensor setting, then engaged the non 95-96 style cam angle sensor , then disengaged the setting, but i couldnt tell a difference from the feel of the car and wasnt able to deduce from the live log witch way worked better?
 

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  • camanglesnesor testing.elg
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and this one i set some more tables and settings to stock. didnt seem to hurt or help much by the sound of things, but again im not able to deduce from the log if they helped or hurt?
 

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  • ecu adjustments to stock.elg
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My latest theory is that the car previously had some mechanical or ecu issue that won’t allow it to idle in open loop. This would explain why previously I needed to rev the car for about 5ish seconds before it would hold idol. When I put an exhaust in my down pipe I had two 02( or wide band) sensors that I removed. I only had a spot to put in one sensor on the new exhaust set up. My log shows the o2 sensor acting like it’s not installed … ( Assuming I should switch the one currently installed with the one I currently have dangling) . Hoping this will allow the car to go into closed loop where it should be able to hold its idle ?!
 
My latest theory is that the car previously had some mechanical or ecu issue that won’t allow it to idle in open loop. This would explain why previously I needed to rev the car for about 5ish seconds before it would hold idol. When I put an exhaust in my down pipe I had two 02( or wide band) sensors that I removed. I only had a spot to put in one sensor on the new exhaust set up. My log shows the o2 sensor acting like it’s not installed … ( Assuming I should switch the one currently installed with the one I currently have dangling) . Hoping this will allow the car to go into closed loop where it should be able to hold its idle ?!
And my car actually currently has two dangling un Installed but plugged in 02 sensors . One hanging in the rear, one hanging in the front, and then the one that’s actually installed in the front , so just wanted to clarify the dangling o2 censor in the back is not what I’m referring to when I mention the dangling 02 sensor in the message above. ( the back 02 sensor is has the voltages locked in the ecu)
 
The stock 02 sensors are 4 wire sensors. Two wires for the heater circuit and two wires for the sensor signal. - blue, white, and black wires.

The front sensor is usually found very close to the turbo in the "o2 housing", but you can also run it a little farther down stream if you have a custom setup, and it plugs into the harness under the the water neck / thermostat housing here:

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The rear o2 connects with a different 4 wire plug under the driver seat, and goes through the floor so that it can be in the exhaust stream AFTER the CAT/test pipe.

If you still have an inj#4 circuit malfunction - and you have tested good the wiring, injector coils, and resistor pack - then the only thing left to resolve that issue is a trip to the ECU doctor.
 
It is easier to adjust the global dead time with a working front o2 sensor, but if that is not working, you can still try altering the global dead time and see how the idle is affected. Try getting it running, and then slowly increase or decrease the dead time 10 units at a time, and see what happens. Try adjustments in a -200 to + 200 range.

What about the MAF honycombs? If it is stock - try lowering the MAF Comp values back towards 0. Right now the low idle airflow numbers are being amplified - which will make it richer.

What about the coolant lines to the FIAV on the throttle body? If you don't have any - maybe your throttle body has a blockoff plate?

Justin
 
It is easier to adjust the global dead time with a working front o2 sensor, but if that is not working, you can still try altering the global dead time and see how the idle is affected. Try getting it running, and then slowly increase or decrease the dead time 10 units at a time, and see what happens. Try adjustments in a -200 to + 200 range.

What about the MAF honycombs? If it is stock - try lowering the MAF Comp values back towards 0. Right now the low idle airflow numbers are being amplified - which will make it richer.

What about the coolant lines to the FIAV on the throttle body? If you don't have any - maybe your throttle body has a blockoff plate?

Justin
Going to look into the throttle body being blocked off. Would this cause the car to not idol? It’s just confusing me because the only thing that’s really changed besides the built turbo is the fact that on of the o2 sensors in the front was uninstalled. It looks like by ur description that I have the stock o2 censor currently installed, I guess the other one in the front I uninstalled is a aftermarket thing previous owner installed? I’ll take some pictures and try installing it and uninstalling the stock one tomorrow. And as a temporary fix I was thinking maybe I can adjust the throttle position sensor to to plus percentage to keep it idoling?
 
Going to look into the throttle body being blocked off. Would this cause the car to not idol? It’s just confusing me because the only thing that’s really changed besides the built turbo is the fact that on of the o2 sensors in the front was uninstalled. It looks like by ur description that I have the stock o2 censor currently installed, I guess the other one in the front I uninstalled is a aftermarket thing previous owner installed? I’ll take some pictures and try installing it and uninstalling the stock one tomorrow. And as a temporary fix I was thinking maybe I can adjust the throttle position sensor to to plus percentage to keep it idoling?
Adjusting the TPS won’t increase the air needed to hold idle when cold, so scratch that.

You could try opening the BISS to let more air in, similar to cracking the throttle plate by hand, but when things get to operating temps, the idle will be too high.

I’m asking about the FIAV because its purpose on the throttle body is to be open when cold to hold idle around 2K, and then slowly close as the coolant temps warm up.

The FIAV has a reputation of failing and leaking to much air, or worse leaking coolant into the intake if the seals break down. Instead of fixing it or replacing it, some block it off. Unfortunately the ISC motor that is actively adjusted in closed loop mode to hold idle does not have a wide enough range to manage the cold start.

So…. If you use a FIAV BlockOff plate - you are kind of expected to hold the throttle open manually until the coolant temps get into the 160deg range where the ISC can take over.
 
thanks! i think thats most likely the culprit. i probably just noticed this issue less because it was warmer out.

been waiting for the rain to stop to jb weld in this wideband bung that i just drilled a whole for. its 1000 degree heat resistant jb weld so i think it probably wont fly out on the highway? back end exhaust pressure is what like 5 psi, should be good right LOL... but yea i know, i need to buy a welder

i did a log and turned on and if the non 95-96 style came angle sensor and it looked like i should click the tab and use the non 95-96 style. my graph was more similar to yours with the non 95-96 function. squiggly up and down heart beat type of pattern instead of a slow staircase pattern... i know thats a horrible explanation so heres the log
 

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  • camanglesnesor testing.elg
    91.9 KB · Views: 10
Depending on where you are putting the bung it's not likely to last. In the exhaust manifold the temps can normally exceed 1200F. It's gets cooler the farther you get from there but it still plenty hot when it reaches the Cat.
 
been waiting for the rain to stop to jb weld in this wideband bung that i just drilled a whole for. its 1000 degree heat resistant jb weld so i think it probably wont fly out on the highway?
JB weld is going to burn off (even if it claims to be heat resistant to 1000 degrees). If you can't weld the bung, you can get one that clamps on.

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Ok thought I tried this before but I guess the ecu wasn’t on auto save. Raised target idle to 1100 rpm and she started and held idol just fine! But I also installed the wideband that’s in between my front and rear o2 sensor but it’s not giving me a reading on my air fuel ratio gauge that I have hooked up in the car. It just reads at 10.0 the whole time and doesn’t fluctuate. Still trying the figure what’s going on with this “middle” wideband?
 
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