Fuel trims stuck at 100%? Lots Of issues, MMCD on a GVR4 Help.

[imdrax]

First off I would like to know if anyone on here is running MMCD on their GVR4 and if so is it fully compatible? From what I know the ecu's between a 1g DSm and a GVR4 so I'm assuming the information I am seeing on the logger is accurate. This brings up some major issues.

So after a quick log I found some interesting things.

1. MMCD shows my tps to be at 12.8% at idle ALL THE TIME. whether hot or cold its reading 12.8% at idle. My afc shows a TPS voltage of .65v at idle. Not sure whats going on here

2. For some reason MMCD shows voltage for F & R O2 sensors even though the GVR4 has only the front. The weird thing is they both provide a constant voltage signal to the logger. The "front" O2 is sending 2.5v and the "rear" O2 is showing .5v, neither of which are cycling. This leads to my next problem.....

3. My fuel trims are all at 100%, L M & H. Even the o2 trim is stuck at 100% and is not cycling, I believe this is due to a faulty O2 sensor. Confirmation?

4. I am getting an intermittent CEL, it comes and goes sometimes more thn once during one short drive. I looked up codes on MMCD and I BELIEVE( if i read the logger right because I am using v1.8 which is new to me, im used to the old MMCD) that I am storing codes 21 & 31 which are ECT sensor and Detonation sensor, respectively. This leads once more to my next question....

5. I logged a small acceleration in 2nd gear from about 2000rpms to about 3500rpms(let off due to stuttering really bad) and got anywhere from 5-10 up to 25 counts of knock. No bueno. I will be checking the knock sensor tomorrow for goo.

To sum up, the car idles fine, drives ok, coasts at 2krpms until stopped, the tps is supposedly stuck at 12.8% throttle when the accelerator pedal is not depressed, stutters under heavy acceleration, provides no O2 signal, fuel trims are stuck, knocks under almost any boost, and throws codes 21 & 31. Phew what did i get myself into this time.

What is everyones opinions on some or all of the issues presented, and their ideas of possible causes and solutions.

 

[steve]

Log the ECT when the engine isn't running and the car is cold. If it isn't withing a couple of degrees from the IAT temp it or it's wiring is bad. The O2 sensor sounds like it's toast if it's stuck at 0.5v.

Ignore O2-F it's for 6 cylinder cars that have a O2 sensor per bank.

The TPS should read 10% (0.5v) when the throttle is closed. 12.5 isn't too far off but you can reset it by turning the TPS.

 

[imdrax]

Thanks, I was wondering about the 12.8%.

I went out and checked. The coolant temp and air temp were both around 25*c. I started the car and the coolant temp started rising so there seems to be no issues there. Im curious as to why I had a stored fault for that sensor(21).

For some reason there is a 1-wire O2 sensor installed. I'm not sure what kind of problems that can create but I am going to replace it with a 4-wire universal anyways.

Tomorrow I will run some tests on the TPS, O2, test the knock sensor, Coolant sensor, and closed throttle switch and then report back.

Any insight on how to test the parameters for the closed throttle switch?

 

[forcefed86]

U need to take a few steps back before driving/boosting.

First off U have to have all codes cleared. Take the neg term off the battery for around a min and reinstall. This shoudl clear it. If the code comes back U know this is an issue you need to fix. Before it will run correctly you need all those codes cleared.

Closed throttle switch wouldn't be an issue. But can be tested with a meter very simply. It's just an on off switch.

Lastly assuming your not in open loop mode the fuel trims should be at 100%. This means the ECU is not taking away or adding any fuel. I believe it has teh ability to add or subtract around 20%. So if you see a 90 in the trim field it means the ECU is leaning out the mixture. If you see 110, it is enrichening the mixture.

Good luck... I just went through learning the DSM MMcd stuff as well. It's pretty awesome tool for the money once you get it down!

 

[imdrax]

Thanks, but i understand how fuel trims work, I've been around the block. Although yes, like you say, fuel trims ideally SHOULD be at 100% the O2 trim should be cycling,it is not. My question is besides a faulty O2 sensor can anything else prevent the O2 trim from cycling? I am not sure what you are refering to as far as taking steps back, I have taken no steps forward. I bought the car in the exact condition it sits in my driveway. The codes have already been cleared through MMCD, that is not issue, the issue is what is CAUSING the codes.

PIC: My guess is that RTV does not work very well in this application->

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[steve]

I don't think filling the knock sensor up with RTV is going to help once the original potting has failed.

There are several things that can cause the ECU not to enter closed loop including active CEL's. Your O2 sensor reading 0.5v and not changing is a 100% factor. Even if you have other problems you should see the O2 sensor changing in value as it heats up during initial startup.

fueltrimupdatepoints [ECMTuning - wiki]

 

[forcefed86]

Thanks, but i understand how fuel trims work, I've been around the block. Although yes, like you say, fuel trims ideally SHOULD be at 100% the O2 trim should be cycling,it is not. My question is besides a faulty O2 sensor can anything else prevent the O2 trim from cycling? I am not sure what you are refering to as far as taking steps back, I have taken no steps forward. I bought the car in the exact condition it sits in my driveway. The codes have already been cleared through MMCD, that is not issue, the issue is what is CAUSING the codes.

Not trying to "dumb things down" for you. I'm just saying that if the ECU sees the 02 sensor isn't cycling it will throw a code and lock you in open loop. So clearing the codes in the MMCD isn't going to fix this issue. First U need to fix the 02 sensor. Nothing else in the system will prevent the o2 information from cycling aside from a faulty sensor or ECU. I'd get a multi-meter and probe the 02 sensor voltage wire at the back of the ecm. If it's fluctuating on your meter then there is a fault in the ecu.

Then obviously buy a new knock sensor. Filling them with RTV is an old school trick to make the less sensitive too. Great for selling an unsuspecting person a car that knocks to bah-jesus...

Your fuel trims usually take a good 20-30 min of driving before they will change.

As far as taking a step back.

5. I logged a small acceleration in 2nd gear from about 2000rpms to about 3500rpms(let off due to stuttering really bad) and got anywhere from 5-10 up to 25 counts of knock. No bueno. I will be checking the knock sensor tomorrow for goo.

This is what I mean. The above is how engines are broken. Before you leave the driveway, you need all sensors working properly. Those 5-25 counts of knock,if real, are enough to damage a motor. Now in your case it may be false knock. But what is the point of chancing it.

 

[imdrax]

Im curious as to how the RTV makes it less sensitve? From what I have experienced it makes it MORE sensitive. There is no way I am knocking that bad at 5-10lbs on a baseline MAFT tune.

As for the codes, they were not active codes, they were stored faults.

I am going to chop off one of my unused 4w oxygen sensors from my IS300 and throw it on Ill update.

 

[forcefed86]

Im curious as to how the RTV makes it less sensitve? From what I have experienced it makes it MORE sensitive. There is no way I am knocking that bad at 5-10lbs on a baseline MAFT tune.

As for the codes, they were not active codes, they were stored faults.

I am going to chop off one of my unused 4w oxygen sensors from my IS300 and throw it on Ill update.

If the 02 sensor isn't cycling the ecu won't operate in closed loop period. The MMcd may let u bypass the fault but it's not gone and the car won't run right until you fix the issue.

RTV absorbs some of the vibration... Lots of people put it on the threads as well.

Your probably experiancing a bad sensor to start with. Has nothign to do with the RTV. Tons of things other than boost can cause knock. Noisey lifters, spun bearings, bent rods solid motor mounts, excessive rpm...etc.

And yes, you can detonate on 5-10psi if you don't know what your doing.

Before going all "willie-bubba"... cutting off parts U don't know are bad. Why not check the part you have. Multimeter is $2.99 if you don't already have one.

 

[imdrax]

Willie bubba? The o2 im pulling from my IS300 is not being used so it makes no difference. You obviously missed the part where I said the previous owner had a single wire oxygen sensor installed so I am replacing it with a 4wire in either case. I have a couple DVOM's actually.

BTW I DO know what im doing, this is my 7th DSM and I've been working on these POS cars for way too many years to count. And no I do not believe this car is actually knocking at these boost levels with how I have the fuel supply and MAF setup.

If you reread my original post I was merely stating my observations and asking for input on my findings. I do not need you to tell me about how fuel trims work, what an o2 sensor does, or how to put oil in my car.

 

[forcefed86]

Willie bubba? The o2 im pulling from my IS300 is not being used so it makes no difference. You obviously missed the part where I said the previous owner had a single wire oxygen sensor installed so I am replacing it with a 4wire in either case. I have a couple DVOM's actually.

BTW I DO know what im doing, this is my 7th DSM and I've been working on these POS cars for way too many years to count. And no I do not believe this car is actually knocking at these boost levels with how I have the fuel supply and MAF setup.

If you reread my original post I was merely stating my observations and asking for input on my findings. I do not need you to tell me about how fuel trims work, what an o2 sensor does, or how to put oil in my car.

Really because you sound like someone who hasn't touched a turbo car in his life. There is nothing wrong with a 1 wire 02. They will work just fine. Just takes a little bit longer to "warm up". I'd think someone who had been working on cars for 7+ years would know that.

Obviously you don't know what your doing or your car would run correctly.

Might want to learn how to handle constructive criticism. To come on here asking for help and then whine about the help received it pretty lame.

If you don't give us all the details, and ask obvious questions we will assume you don't know what your doing. There's nothing wrong with not knowing, we've all had our fair share of questions. But don't get pissy when someone tries to help you.

...I'm done with you now. Good luck, your gonna need it.

 

[imdrax]

I appreciate that you are done, not one of your comments has helped anyone who may have looked at thread with any problems similar to mine, which is the purpose of these forums.

Take a look at steve's posts and you will see what a contructive response is. I am not trying to have a pissing match here. I merely started the thread to have some input And discussion on the situation at hand.

Lastly I have had the car a total of about 5 days so the car not running correctly has nothing to do with my mechanical capabilities it is a representation of the previous owners backyard Billy bob swap.

 

[jeffo]

0.65 volts is 13% TPS. The factory spec is 0.45 to 0.55 volts, or 9-11%. You just need to loosen the TPS and adjust it slightly, until its between 0.45 and 0.55 volts.

 

[imdrax]

O2 are cycling MOST of the time. However I am still not entering closed loop and the only trim changing is the O2.

I realized when my car is FULLY warmed up the logger shows 79*C which equates to ~175*F, according to the link< http://www.dsmlink.com/wiki/fueltrimupdatepoints > earlier in the post i need to reach 190*F. Now either my sensor is somehow reading low OR my thermo is dead(although my gauge sits dead in the center when warmed up so I dont think so). I will figure this out soon enough.

One item from the link above that is not sinking in is the condition of baro being between 22inhg-31.6inhg in order to enter learn mode. My baro is at a constant .97 bar due to the maft.

My fast decel idle is still present as well. I'm not sure where I should be looking next to address this issue. There is obviously something in the loop I am missing as far as idle controls are concerned.

BOOST LEAK at my GM MAF, great. Now I must rip that apart and seal it up. Mid terms this week so progress will be slow.