4g61t.org

Hi,

I have a 1991 colt with a 1990 6 bolt 4g63t swapped motor. I have a wideband AFR gauge installed and I am reading full lean (above 18 AFR) when cruising. When at idle it reads 10.5 AFR. When under full boost it runs about 13-13.5 afr. I pulled the spark plugs and they look fine. Not white.

-Stock engine
-Stock DSM ECU
-2g maf
-DNP tubular exhaust header
-front mount intercooler
-full 3" exhaust
-stock 14b turbo running 10psi currently
-stock DSM injectors.
-stock DSM fuel pressure regulator
-stock fuel pump from the 1.5L 4g15
-stock 1990 DSM throttle body with fast idle air valve blocked off
-idle speed controller still hooked up. But unsure if working properly

Is anyone running the stock 1.5L fuel pump on a 4g63t swapped colt? I am curious what my fuel pressure is. I boost leak tested the intake system and I am confident that I have no air leaks.

Aside from buying a dsm link ECU, does anyone have any ideas as to what could be causing the lean condition under low engine load? I am thinking that highway AFR's should be about 15 or so.

Thanks for your help,

Matt

well 10.5 is really rich for idle.... and 13-13.5 is way to lean for under boost.... I would almost put money that its the small 1,5 fuel pump....its not pushing enough gas. I would say u need to upgrade it before buying any other parts.



Steve

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Steve 89 colt 2.3 stroker stock top end. evo3@20 psi 13.489@99.30mph 3/10 2012
On drag radials.auto trans.launching @ 5 psi and no traction thru 2nd.

Why are you running a 2G MAS without fuel compensation?

Which DSM ECU are you running? 1G 90 or 1G 91-94 or 2G; Part number?

4g15 pump will not work, at all.

Put in a 4g63t 1G MAF, 4g63t fuel pump of some sort and you will run fine for the designed parameters of the 1G platform.

Which company made your wideband ?

My Innovate MTX-L, allows the user to calibrate it. Remove it from the exhaust or allow a time period of not running, before performing the calibration.

If keeping the sensor in the exhaust, it could take over 24 hours to clean it out and allow ambient oxygen levels to be present without any additive to sway things.

Each manufacturer has their own style or calibration, and or procedures.

Stop driving the car, until you get this sorted out. A valid reading from the wideband, AND a valid reading via datalogger for the stock 02 sensor.

Trust the stock 02 sensor that is being logged.

Your reading are worse than mine, much worse. This is why I was waiting to diagnose my fuel/mapping system.

I hit boost and dip into the super lean 15-16:1 zone. REALLY not good. So, I don't boost much yet. Simple as that.

You will damage piston tops in short order, or worse if you continue to drive this way.

You're gong to kill your engine that way. Like Flying Eagle said, if you don't get an engine management system, you need a 1g MAF stat! You're not far from me, so hit me up if you need help with that. I have a couple turbo 1g MAFs laying around my shop too so I can hook you up cheap.

_________________
"A good day racing is better than a great day fishing!"

First, get at least a stock DSM Turbo fuel pump, but recommend a Wally 190. If you are going to continue the 2gMAF, then install some Evo 560 injectors. That will compensate for the fuel and be safe. But you need to do AT LEAST these two items.

If you are willing to move to a 1gMAF, then just get the new Fuel pump and the 1gMAF from ColtsFan above.

_________________
Thom
1991 GVR4 1025/2000 (PTE 1200's, 16g, DSMLink v3, gm-maf, eagle/ross, .020 over, 272's, EVO VIII Wheels)
1992 GVR4 866/1000 (getting everything from above)

Hi Thanks for the help. To answer your questions:

-ecu is from a 1991-1994
-my wideband is an AEM digital mounted about 18" from turbo
-I honestly do not know why I am running a 2g maf. I did the swap over thanksgiving at my friends house in Connecticut who has lots of DSM's. We rewired the harness to take the 2g maf.

I had a set of 550 injectors in it before I had a wideband but it seemed like it was running way to rich. So I bought a stock set from a junkyard and now its too lean.

I understand that I will damage the engine by continuing to drive it. So it has been parked and i am trying to sort this out.

I would like to continue using the stock ecu since my engine is stock. Some sore of engine management system like DSM link would be ideal of course but I am thinking a stock setup should be ok.

Thanks for clearing up the 1.5 fuel pump. I'll get the right pump in it. Why is it 8 degrees out!!! And I have no garage

Because women and there hair spray LOL..


Steve

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Steve 89 colt 2.3 stroker stock top end. evo3@20 psi 13.489@99.30mph 3/10 2012
On drag radials.auto trans.launching @ 5 psi and no traction thru 2nd.

Haha yeah I'm gonna move to LA for sure.

Also, I have an EGT gauge with the thermocouple mounted in the #1 cylinder exhaust header tube. About 6 inches from the head. I am reading very low temps. With the engine fully warm at idle I am getting about 300 degrees F. At cruise under vacuum it runs about 450 F.

I had my thermocouple checked with a calibrated instrument and it reads the same as my Autometer gauge. I am thinking the lean condition is causing the low exhaust temps. But wouldn't a lean condition cause the engine to run hot? I am thinking idle egt should be around 600 F?

Thanks,

Matt

Try to get a 2g fuel pump at least, If you can also a 2g fpr it may help a little bit but for sure get 550cc/560cc better safe than sorry

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91' Mitsubishi Colt 4G67T FWD "The Minion" - 12.26@118
94' Mitsubishi Galant GS 4g63 Swap "White Unicorn"
95' Eagle Talon Tsi FWD "Ernie's car" - 13.92@104 *Rest In Parts*

Match your fuel system, and ECU/MAF components as a set.

Stick with 1G stuff or 2G stuff. Makes it much easier to answer the 5 w's when quizzed about what parts your car is running.

Please elaborate on how the MAF was re-wired.

Was it a rewire on the chassis harness side to splice in a 2G MAF connector?

Or, was a MAF adapter used to keep the 1G style harness end and allow an intermediate cable to be installed to run the 2G MAF?

Running a 2G mas is not going to cause the car to run erratically. That was and is still an upgrade for 1G mas folks looking to not overrun the 1G mas. Myself and countless other members un the community have run a 2G mass air flow sensor to no ill effect.

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1985 Mitsubishi Cordia
Build in progress

The thermocouple is suppose to be 2-4" from the head. All four cylinder at idle right around 600* on mine with a warmed up engine. And depending on the terrain 800-1100* at cruise. Steady uphills cause the 1100* temps.

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1985 Mitsubishi Cordia
Build in progress

I run a 2G MAF as well but my chip is setup for this modification, just like DSMLink/ECMLink users would do. Or the workaround with "matching" 510 or 560 CC injectors with it. If you want fuel trims and such to be at factory thresholds, then I would assume a 2G MAF should be installed with a compensation factor. These cars run badly enough with the slightest of problems, I only suggest this for the reason of bone stock drive ability and ease of repair. If he keeps the motor stock, and overrun becomes an issue, he will be looking for a way to tune and upgrade.
I only suggest all this for ease of use and explanation upon the need for repair - like an shop unfamiliar with his car should it come to it. 2G MAF will be an upgrade in many ways as biglady stated.
I imagine 2G MAFs are easier to come by now that the price ceiling has fallen out on them, and with more link tuning options too. I remember when I paid $125 CDN for mine. Sigh. I picked up a pair from out part finding member here, as spares, and they came in around a tenth of what I paid for one. Haha.

Just an update on this. I got the 1g MAF from Coltsfan and wired it back up and it fixed the problem immediately. My wideband reads 14.5-15.5 on the highway now. Under full boost it reads full rich 10.0. Even with the stock 1.5 fuel pump.

My plan is to install a Walbro 255lph fuel pump. And then when I get DSM link put the 2g MAF back on.

Also my EGT's are up to about 1100 F on the highway and around 400-600 F idle. So looks like I'm OK now.

To answer your question on the way I wired the 2g MAF when it was installed:

I cut the 1g MAF square connector off the engine harness and then wired in the flat 2g MAF connector using the info from vfaq.com.

So when I got the 1g MAF from Coltsfan I just wired the 1g connector back on.

I noticed there is a small vacuum line port on the 1g MAF. If I leave it unhooked it seems to run fine but at idle it runs full rich. Where is the proper location to connect this vacuum line? The throttle body?

Thanks,
Matt

This is a DSM full emission system diagram. What you have referred to is likely the BCS boost control solenoid that helps back off boost when fueling/knock gets ugly per the ECU.



Decent primer thread on some cool stuff between NA and TC DSM's. Tuners thread.

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