2G stuck in limp mode

[tschuhly]

Hey all,

I am trying to figure out what steps I should go through to figure out what is causing my issue.

Some background is that the car has been put together and running since about mid April. Towards the middle or end of May it started to act like it had a misfire or something. I replaced the spark plugs with the higher horsepower ones but that didn't do anything.

I decided to check for codes and I got the knock detection circuit fault code. I found that my sensor was loose so I tightened it up and no luck. I then was driving it and as I took off from a light, it sputtered a little and when I gave it slightly more gas it bucked hard once and then turned off. I got it towed and later found that my ECU 20amp fuse had "blown" or broke (I'm not sure if it was just old and brittle or if it legit blew). I replaced it and my knock sensor with a new one jic and my car started up except now it won't go over 4500rpms.

It doesn't have any codes but is still running a little weird and is still in limp mode. I tried to go into my ECU pinout settings to tamper with them to see if it was because of my AEM boost sensor being pinned to my MDP pin, but it is still in limp. I will say that for a little bit I had forgot to unplug my stock MDP so there were probably 2 conflicting signals going to the ECU so maybe that did something? I haven't driven it yet because I worried it will leave me stranded again.

I attached a log of it starting, idling and revving a little. Any guidance would be appreciated!

 

[jdxnc]

Is this a stroker motor or something? LoadScale is set to 82% and usually this isn't done unless there's more than normal displacement.

I don't think these cars really have a "limp" mode per say, it's just idling stupidly rich, even though it's calling for 14.7 it's idling high 10's to low 11's, just dumping fuel.

Actually just noticed in the MAF comp tab it's not set to Speed Density, that could be the issue, all the values should be zeroed here.

 

[tschuhly]

I don't believe it's a stroker but I had it tuned prior for the setup that I have which does have a lot of aftermarket stuff including 2150cc fic, 272 hks cams, a walboro 255, and other goodies.

It's not setup for SD yet but that's what I'm working towards. The thing is, it ran fine after getting it tuned and then randomly started acting up.

Is it possible that something happened to the ECU that caused settings to get screwed up?

 

[jdxnc]

This doesn't look like an ecu issue to me.

 

[tschuhly]

An important piece of info that I forgot to mention is that my car is limiting itself to 4500rpms...

 

[1990TSIAWDTALON]

I see your launch control is set at exactly 4500, move that up to 5500, just as a test, to see if the car will rev higher.
ALSO, you have your Knock Sensor set to basically never come on. I did that ONCE and melted a piston when knock came in but the sensor didn't pull timing...... I see that as dangerous. You have yours set to come on only ABOVE 7950. Ideally, you don't want any knock but the sensor should be active starting around 3500-4000 rpm and anything more than 90% throttle (some start it even at less TPS).
Just a few things I notice.

 

[jdxnc]

I see your launch control is set at exactly 4500, move that up to 5500, just as a test, to see if the car will rev higher.

Good catch, clutch switch could be grounding out. Like I said, these cars don't really have a limp mode, it's being held back by too much fuel or a limiter like the launch limit. If I'm not mistaken you can log the clutch switch by added it to captured values.

 

[tschuhly]

Thank you guys so much!! We are currently in a heat wave so it may be a couple days before I get to it to test this stuff out, but please stay tuned because I am pretty lost at this point if I'm on my own .

 

[1990TSIAWDTALON]

If you are on here, you are NEVER alone. That's what this forum does, it tries to help. I will follow along and chip in when I think I can contribute. Hang in there, we'll figure this out.
AND, who isn't in this heat wave? We are predicted for 99 on the 4th of July.

 

[tschuhly]

If you are on here, you are NEVER alone. That's what this forum does, it tries to help. I will follow along and chip in when I think I can contribute. Hang in there, we'll figure this out.
AND, who isn't in this heat wave? We are predicted for 99 on the 4th of July.

I'm in PA and it was like 112 today! Lol it's crazy!!!

Also, that's one thing that I really like about DSM's, the community is awesome. I talk to a ton of ppl that say that their car forums are trash or super mean!

You have already helped me so much on my build!

 

[tschuhly]

I have an update for everybody! First let me say that I am completely new to, not only the DSM world, but the performance world as well. That being said, it turns out the rev limit seemed to be the issue. I didn't even realize that was a feature with ECMLink...That solved PART of the mystery, but the car is still definitely running weird. I took another longer log of it idling and then going for a short drive. you can see at 425.xxx, it stalled out when turning left back into the parking lot.

I also tried to double check grounding points which all look fine. I did find something that is now scaring the crap out of me...I saw a video by the man, the myth, the legend, Jafromobile, where he talks about his 7bolt going kablammy and he said the culprit was a hidden bolt on the back of the engine that holds the engine to the transmission. He called this the "crank walk bolt" and said that it is important because over time, if missing, it could cause extra strain on everything, cause the rest of the trans bolts to loosen, and put extra strain on the thrust bearing leading to crank walk. Well...mine is missing...so I am going to definitely get one and install it, then check the rest of the trans bolts as well to see if they have loosened up. Would this causing the issues seen in the log and the feeling of a misfire or stutter when trying to drive/take off? If this is the issue, did I just screw my engine? I don't feel like I hear any weird noise otherwise.

The only other thing that I noticed today was that my fuel psi seems to hold at a normal psi but then when I give it gas it drops slightly. I am assuming this is normal though since I would think that the pressure would slightly drop when the injectors open up to release some of the pressure.

Hope this helps get closer to the solution. I again am so thankful for you all and taking time to try to help a fellow, hopefully longterm, DSMer.

 

[jdxnc]

No the CW bolt won't kill your engine, it can however cause of a lot of clutch engagement issues.

From your log, the clutch switch shows -1 constantly, you did move the car and came to a stop but the clutch switch never changed, so something is definitely up there.

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[tschuhly]

No the CW bolt won't kill your engine, it can however cause of a lot of clutch engagement issues.

From your log, the clutch switch shows -1 constantly, you did move the car and came to a stop but the clutch switch never changed, so something is definitely up there.

Do you think this would cause my engine to stutter and maybe stall when taking off? Or is stall what you meant by kill?

 

[jdxnc]

Do you think this would cause my engine to stutter and maybe stall when taking off? Or is stall what you meant by kill?

I meant it's extremely unlikely to damage the engine itself.

Being the car is still running on the MAF, have you done a boost leak test? The stock MAF is very susceptible to air leakage issues which will cause sputtering/stalling etc.

 

[tschuhly]

I meant it's extremely unlikely to damage the engine itself.

Being the car is still running on the MAF, have you done a boost leak test? The stock MAF is very susceptible to air leakage issues which will cause sputtering/stalling etc.

I did before getting it tuned but not recently. I'll add that to the top of the list!

Thank you for the reassurance with my engine health too!

No the CW bolt won't kill your engine, it can however cause of a lot of clutch engagement issues.

From your log, the clutch switch shows -1 constantly, you did move the car and came to a stop but the clutch switch never changed, so something is definitely up there.

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Sorry I forgot to respond to this as well. I bypassed my clutch safety switch because I was trying to avoid crank walk overtime from having to press the clutch in upon start up. I just used a jumper wire with the relay. I thought that I read that this wouldn't cause any issues (unless this isn't the switch your talking about).

 

[tschuhly]

Alrighty, here is the update:
-I did a boost leak and got everything post MAF to seal up. There is a small leak at the adapter plate for the filter but that shouldn't matter.
-I tried unplugging the MAF with the car running and it didn't seem to affect anything, if anything the car ran worse after unplugging.
-I have tried plugging my AEM 3.5 bar in with the MDP, only the 3.5, and only he MDP. It seems to run best with the MDP unplugged.
-I did find that my vacuum hose going from my valve cover to my catch can was cracked and I replaced that.
-I opened up my ECU and didn't see anything alarming.
I will attach videos and pictures and am thinking the next step is replacing the fuel pump aside from scanning for DTC's one more time?

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[tschuhly]

Alright, I took it for a little drive today and found the following: No DTC's upon returning. It definitely starts to stall out when turning the steering wheel and not giving any throttle. I also noticed that when I give it any amount of throttle it seems that the AFR shoots up and the engine sputters and doesn't continue to increase in RPM's. I can't tell if it is being limited or if it just doesn't have the power to continue to speed up...

Would the next wad of money to throw at it be a bigger fuel pump or ISC? I do have a Walbro 255 with 2150CC injectors...

 

[steve]

That sounds like two different issues. The first is dropping RPMs under load like the PS pump. Does the same thing happen when you turn the lights on or hit the brakes? What about if you turn on the AC?

The second is the throttle response and since you have DSMLink another log of it doing this would be very useful. The last log shows a 7.8% global scalar on a stock MAF, Boost control turned on and a pile of DA changes including additional MAF load scale modification, ISC positioning and fuel trim feedback.

 

[1990TSIAWDTALON]

Is your PS wire attached to the sensor on the pump? It is there to help keep the engine going under a slight load, if it happens to dip down. Check that, its a single wire with a 90* round end. That is just for your dying issue when you turn the wheel.

 

[tschuhly]

Here is another bunch of updates:

First one, I caught a mouse. ugh!!! But I didn't see a ton of poop anywhere and no new electrical issues have been found so I don't think it has anything to do with it.

Second: The power only seems to drop during steering and not when turning lights on, hitting brakes, or turning the air on (I didn't try AC because it's not completely installed yet but I can try it needed).

Third: Power steering wire seems to be connected.

FOURTH: This one I think may be a big hint for someone who knows what to look for. It seemed like when I first started and drove my car around 12, it was significantly worse (which is when the log was taken). I went to the gym, and my car was parked in direct sunlight. When leaving the gym, a little after 1, it was significantly better.

Fifth: The engine code 0325 Knock Sensor 1 Circuit Malfunction is now on, but I am pretty sure this is the one that popped up before. I have already replaced my knock sensor with the EVO one from STMtuned (i think). And I believe I already tested to see if the pin was grounded when unplugged but didn't find that it was. Though maybe this has changed or maybe there is a short?

Sixth: I am not sure if I have my boost 3.5 sensor set up correctly. I do not currently have an aftermarket IAT sensor, so I still have the MAF hooked up, but I did unplug my stock MDP and wire my AEM 3.5 to that pin.

Here is a log from the drive to the gym and a video of what it is doing that made me think limp mode.

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[steve]

It doesn't look like you touched any of the things I mentioned before. Why is that?

 

[tschuhly]

It doesn't look like you touched any of the things I mentioned before. Why is that?

If you are referring to the tuning stuff, I have no idea what I am doing with that and do not trust myself with it. I sent the log to my tuner to have him take a look at it. It John Kerr in Carlisle PA who is really good. I also sent him this thread so then he can take a look at the stuff you mentioned.

 

[tschuhly]

Alrighty, another update. I went ahead and unplugged my 3.5 bar sensor and hooked up the stock MDP. I tried to revert the ecm pin/sensor settings to stock in regards to these (I am not of SD). I found that the PS seems to be acting normal but still seems to have difficulty under load.

I think I may try a new fuel pump since mines kinda small, old, and sat 12yrs with the car before I bought it.

Steve, I did send this forum and my log off to my guy to see if he could help me with what you said.

I did take another log, which is attached.

 

[steve]

I don't know what we are looking for. The things I pointed out are going to throw off any other "tuning". Sit down with your guy and go over everything. If the two of you can't explicitly justify each non-stock setting you should consider putting a log file aside to save where you are at right now and then start over.

It's good to fix all the mechanical issues but if it was my car I wouldn't be running around in it until you get a handle on the baseline that you know and understand.

 

[tschuhly]

Alright, I'm still searching while waiting for ppl to get back to me about my tune settings and I think my problem may actually be my knock sensor wiring.

My code from above came back and when I inspected my wire at the ECU it looked pretty rough. I ended up breaking the wire anyway when trying to depon the connector.
What would be the best way to go about running a new wire that doesn't involve having to take the entire harness out again...

Also, I will need a new pin end for the wire that goes into the ECU plug, does anyone know where to source these from?

Lastly, there is a black and bare wire spun together and then a plastic cap was stuck over it and taped. Is this factory and where would this go to? Ground?

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