Engine Codes

Adam

Administrator
Staff member
Nothing stands out to me in the photos.

Besides a lack of boost, does the engine show any other signs of running poorly at idle or or any other RPM?
 

Briann1177

Goblin Guru
Engine runs good. The only other codes I have are P0449, P0452, and P0036. The first two are EVAP related and the other is for the post-cat O2 sensor. All those codes make sense to me. Every once in awhile I'll get an P0650 code which has to do with the MIL lamp. It doesn't seem to be very persistent though after clearing things out.

I'm going to swap out the MAF tonight and take it for a test drive. Just another random thought. I noticed that the tube after the MAF looks to be 2.75" while the MAF tube is 3" in diameter. I know you guys have built turbo cars before using these pipe sizes, but is there any chance that the smaller diameter could cause velocity issues? I know that section is post MAF so it doesn't make sense to why it would.
 

Briann1177

Goblin Guru
You could very well be right. I don't believe this code popped until I started driving it. If the new MAF doesn't fix it, the next step is to take it to the dealer and have them run a smoke test to see if there are any leaks.
 

ctuinstra

Goblin Guru
My understanding is that the difference in the tube sizes can cause velocity issues, but I would think it would be consistent across the board.
 

Briann1177

Goblin Guru
I replaced the MAF sensor this evening and drove my usual 7 mile or so round trip. About half way through on my way back, I noticed the boost decided to turn off again. It won't go past 5 PSI. I got home and checked for codes and got most of the usual ones. However, this time I couldn't find the typical P0101 code. So I think that particular code might be fixed. I'll do some more testing tomorrow, though.

Here are my current codes:

P0036 HO2S Heater Control Circuit (Bank 1 Sensor 2)
P0449 Evaporitive Emission Control System Vent Valve/Solenoid Circuit
P0452 Evaporitive Emmission Control System Pressure Sensor Low Input
P2178 System Too Rich Off Idle Bank 1

None of these codes that as far as I can tell should disable boost like that. It's almost as if the turbo got tired and decided to go home for the day. It's like the hell with this guy. He's going to run me in the ground. I quit. LOL.
 

Briann1177

Goblin Guru
Been doing some research and people have been talking about the evap purge solenoid on the intake. I believe it uses a vacuum to suck fumes from the canister. The empty line looks to be capped so I'm not real sure yet.
 

Briann1177

Goblin Guru
Well, the brand new MAF did not fix my issue. It looked promising for a bit, but no dice. Here are a couple other things I tried:

1. Thought maybe the check valve and/or vacuum canister (TCs only) was leaking. I completely disconnected the canister, and hooked up a line directly from intake manifold to the compressor bypass solenoid. No luck.
2. Found a suspiciously loose line on my waste gate. No luck.
3. Ensured the evap purge solenoid was capped. No luck.

At this point I'm completely stumped. It looks like I'm going to have to take it to the dealer and pay them who knows how much to diagnose the issue. Man, this will drive a guy crazy.
 

Brian74

Goblin Guru
I would carefully and slowly look the entire intake over from top to bottom, ensuring there is not a single, solitary place anywhere that is creating or allowing a vacuum/ boost leak. Take it apart. Pressurize each section and listen for air, look for soap bubbles, smoke machine ect. Also check all intake manifold gaskets.

Does your scanner pull data? What data changes when boost is cutting? Is your ECM going into closed loop? Are your air & coolant temp sensors reading properly? Is it dropping boost at part throttle as well? Take data snapshots and compare the data before and after. Can you get some fuel trims, pressure, temp and vaccuum numbers perhaps to compare with someone else’s?

An ECM does not always spit out a code if it thinks all analog sensors are within range. It will cut boost and retard ignition timing as a failsafe if certain conditions are not met, for something as simple as a knock sensor picking up false knock or temp sensor reading bad temps. It wont throw a code because it thinks its only making a timing, air or fuel adjustment to compensate.

I would not take it to the dealer. They will $$$ rape you and its a gamble if they even have a knowledgeable tech. Most of them just go by troubleshooting charts and replace parts until it works ($$$$$).

Don’t you have any reputable diagnostic/driveability based local shops where you live? Those types of shops live to troubleshoot problems like this.
 
Last edited:

Briann1177

Goblin Guru
Those are all great questions and suggestions. With only my Torque app and an OBD-II scanner, there's only so much I can look at. All sensors appear to giving normal readings at least on the surface. MAF, coolant, IAT, IAT2, manifold pressure, boost gauge, are all giving me readings that are consistent with what I'd expect to see. That doesn't mean there's not something wrong down deeper, but they look good up front.

I'm listening to every piece of advice you guys are giving me. I think I found a reputable ASE mechanic in my local area. I'm going to give them a call on Monday see if they would be willing to work on it and if they can do something like boost/vacuum leak tests using smoke, pressure or whatever.

Whatever the issue is, it's very consistent. The boost will just suddenly disappear without any warning after about a 5-10 mile drive. This is after clearing the codes before the drive. What I thought was odd, and thank you for clearing that up, is when I get back home, there may or may not be any codes that are set in stone to trigger the CEL. The pending codes and even the ones that are not pending are very consistent with P0036, P0449, P0452, and P0101. And maybe a P2178 code every now and then.
 

Brian74

Goblin Guru
Those are all great questions and suggestions. With only my Torque app and an OBD-II scanner, there's only so much I can look at. All sensors appear to giving normal readings at least on the surface. MAF, coolant, IAT, IAT2, manifold pressure, boost gauge, are all giving me readings that are consistent with what I'd expect to see. That doesn't mean there's not something wrong down deeper, but they look good up front.

I'm listening to every piece of advice you guys are giving me. I think I found a reputable ASE mechanic in my local area. I'm going to give them a call on Monday see if they would be willing to work on it and if they can do something like boost/vacuum leak tests using smoke, pressure or whatever.

Whatever the issue is, it's very consistent. The boost will just suddenly disappear without any warning after about a 5-10 mile drive. This is after clearing the codes before the drive. What I thought was odd, and thank you for clearing that up, is when I get back home, there may or may not be any codes that are set in stone to trigger the CEL. The pending codes and even the ones that are not pending are very consistent with P0036, P0449, P0452, and P0101. And maybe a P2178 code every now and then.
This is why I asked you if the ECM is going into closed loop. It may be running ok on an open loop fuel map for first 5 minutes then warming up & going closed loop and seeing a parameter that is shutting off boost. I’m no expert at these systems; just a guess but that is an easy check with a scanner.
 

Briann1177

Goblin Guru
The only other consistent code I get that could cause an issue is the P0036 which is the post-cat O2 sensor. From my understanding, that sensor isn't really used for anything other than cat health.

I'm assuming builders in non-emission caring states are just simply leaving that sensor unplugged and not running any kind of simulator or anything like that.
 

ctuinstra

Goblin Guru
The only other consistent code I get that could cause an issue is the P0036 which is the post-cat O2 sensor. From my understanding, that sensor isn't really used for anything other than cat health.

I'm assuming builders in non-emission caring states are just simply leaving that sensor unplugged and not running any kind of simulator or anything like that.
Agreed. None of us are running the second O2, no problems.
 

ctuinstra

Goblin Guru
This is why I asked you if the ECM is going into closed loop. It may be running ok on an open loop fuel map for first 5 minutes then warming up & going closed loop and seeing a parameter that is shutting off boost. I’m no expert at these systems; just a guess but that is an easy check with a scanner.
That's the first thing that crossed my mind also when he said it was consistent at 5-10 miles. This could be proven by taking taking it for another trip immediately after again with the engine warm and it should do it right off the bat. Doesn't help a lot but does prove that it's a closed loop issue.
 

Brian74

Goblin Guru
The only other consistent code I get that could cause an issue is the P0036 which is the post-cat O2 sensor. From my understanding, that sensor isn't really used for anything other than cat health.

I'm assuming builders in non-emission caring states are just simply leaving that sensor unplugged and not running any kind of simulator or anything like that.
Yes. It just monitors cat efficiency and serves as a tattletale to the emmissions inspector when the cat fails.
 

Brian74

Goblin Guru
That's the first thing that crossed my mind also when he said it was consistent at 5-10 miles. This could be proven by taking taking it for another trip immediately after again with the engine warm and it should do it right off the bat. Doesn't help a lot but does prove that it's a closed loop issue.
Any scanner should indicate closed or open loop. If the issue is happening once it hits closed loop, then its due to a parameter that is monitored in closed loop. (If the car is running fine in open loop under fixed parameters then the ECM is seeing no major failures.) Still not an immediate answer, but certainly a means to narrow down. A common misconception is that there are always codes thrown when something goes wrong. Not the case at all. There are always codes when it is emission- related equipment or emission equipment monitoring failure. Otherwise its due to sensor signals that are either at extreme reference ranges or providing no return reference signal at all.

Other times it could be a sensor out of range enough that the ECM is merely trying to compensate for by making drastic timing, fuel or boost adjustments. The ECM cannot differentiate a garbage signal if it is in an acceptable range. It will just adjust control outputs accordingly to run the engine efficiently.

If the car is hitting boost upon startup but losing it shortly after, then either a closed loop parameter is telling the ECM to cut boost, or something is getting warm enough to either expand and create a vacuum leak or a lack of electrical continuity at a sensor.

A big plus here is Brian has it nailed down to particular conditions. Its the intermittent issues that happen with no rhyme or reason that are the hardest to track down, and 99% of the time those are electrical/wiring issues.
 
Last edited:

Briann1177

Goblin Guru
First off, thank you guys for all the advice and getting me thinking. I think I am getting somewhere, possibly. I decided to pressure test the turbo plumbing. After spending $60 on a variety of brass fittings and a PVC cap, I was able to get something going.

Unfortunately, it appears that you can't pressurize the turbo inlet because there is another PCV hose that runs to the valve cover. So I had to disconnect that portion, reconfigure, and pressure test from there. When I first hooked it up, the two silicone boots on the aluminum pipe portion had massive leaks. I really had to play with them to get them to finally stop leaking. Come to find out, they had to be tightened down by more than just hand. I checked all of my other connections on the TB side and they look good.

This section of pipe is a bear to hook up to the turbo. It's a very tight fit and a royal pain to get the pipes and the t-bolt clamps on straight. If I had to fiddle this much in a configuration that was easy to work with, I can't imagine how much they leaked when I first hooked them up.

20180819_125040.jpg
 
Top