EJ22 Surging at Idle

[SaltyMike]

Hey everyone,

I have an EJ22 from a '98 Legacy now in an '82 Brat. I've found that once at operating temperature, the idle begins surging. It is running rich at idle and at 2k rpm. After hooking it up to a diagnostic scanner, it was discovered that the ECM is fluctuating between a closed loop and an open loop when the idle surges. When in a closed loop, the engine wants to stall.

I hope I put this post in the right place rather than the Retrofitting forum. I figured that since this question pertains more to the operation of the engine rather than how to put this engine in an older Subaru, then its best place is here. Thank you!

[el_freddo]

Got any codes associated with the idling issue? Or any codes at all? 

No vacuum leaks present? 

They’re a couple of things to start with  

Cheers 

Bennie

[Steptoe's photos]

open loop/closed loop stuff is generally O2 sensor related ? If the ECU gets no or not happy with O2 sensor input - ECU goes to a fail safe rich condition.

I would disconnect O2 input and see if you get a change there ....

[el_freddo]

@SaltyMike- is this surging also associated with difficulty starting the EJ22? 

Asking as another thread about a hunting idle issue reminded me of a hard starting a fluctuating idle issue I had with my EJ22 many years ago. 

I had several codes show up, CTS, TPS, knock and I think an O2 sensor issue. 

It was an absolute dog to start, idle was poor at best and it ran like a dying dog under load. I’ll give it this though, I was still able to reliably drive places once it started, just it was missing a few ponies in this situation. 

I changed all the sensors at once rather than chasing down what the real culprit was. At the time I was living in our alpine area and working outside in the snow at the remote staff carpark wasn’t a time I was going to individually swap and test which sensor change made the engine operation return to normal. Once they were all swapped, the TPS “gapped” and an ECU reset all was well once again! 

Cheers 

Bennie

[SaltyMike]

5 hours ago, el_freddo said:

@SaltyMike- is this surging also associated with difficulty starting the EJ22? 

Asking as another thread about a hunting idle issue reminded me of a hard starting a fluctuating idle issue I had with my EJ22 many years ago. 

I had several codes show up, CTS, TPS, knock and I think an O2 sensor issue. 

It was an absolute dog to start, idle was poor at best and it ran like a dying dog under load. I’ll give it this though, I was still able to reliably drive places once it started, just it was missing a few ponies in this situation. 

I changed all the sensors at once rather than chasing down what the real culprit was. At the time I was living in our alpine area and working outside in the snow at the remote staff carpark wasn’t a time I was going to individually swap and test which sensor change made the engine operation return to normal. Once they were all swapped, the TPS “gapped” and an ECU reset all was well once again! 

Cheers 

Bennie

Apologies for the late reply! Got busy with work and couldn't check the forums.

Anyways, the scanner wasn't throwing any codes specifically related to a bad idle. However, there were multiple EVAP codes thrown as well as two other codes: P0172 (Bank 1 Too Rich) & P0301 (Cylinder 1 Misfire). Besides the surging idle, the engine feels as though it is running pretty well. The surging idle makes itself known once it has had a few minutes to warm up. While driving, it runs pretty smooth but there's probably a 20%-25% chance that when I coast to a stop in neutral, the car will die on me. That being said, I'm assuming that the cylinder misfire is a result of the rich environment it's in (fouled plug maybe, but I haven't gotten the chance to check it). 

From a cold start, the EJ22 does take a few seconds to start, and it actually sounds like it's struggling a bit. Once it's warmed up and then shut off, it doesn't have a problem starting up again. That may be a contributing factor, I will look into this, thank you!

[1 Lucky Texan]

see if the vacuum line from the fuel pressure regulator is wet with fuel. maybe the FPR's diaphragm is leaking.

[SaltyMike]

On 7/9/2023 at 7:21 AM, el_freddo said:

@SaltyMike- is this surging also associated with difficulty starting the EJ22? 

Asking as another thread about a hunting idle issue reminded me of a hard starting a fluctuating idle issue I had with my EJ22 many years ago. 

I had several codes show up, CTS, TPS, knock and I think an O2 sensor issue. 

It was an absolute dog to start, idle was poor at best and it ran like a dying dog under load. I’ll give it this though, I was still able to reliably drive places once it started, just it was missing a few ponies in this situation. 

I changed all the sensors at once rather than chasing down what the real culprit was. At the time I was living in our alpine area and working outside in the snow at the remote staff carpark wasn’t a time I was going to individually swap and test which sensor change made the engine operation return to normal. Once they were all swapped, the TPS “gapped” and an ECU reset all was well once again! 

Cheers 

Bennie

Update: Got a fuel pressure gauge on the Brat recently, and discovered the source of the rough idle: high fuel pressure. I believe that the 2.2 is supposed to run around 30ish psi. My fuel pressure gauge gave me a rating of 65 psi 😬
 

Now I'm trying to figure out why I'm getting such a high fuel pressure rating. I disconnected what I am 99% sure is the fuel return line coming from the firewall (next to throttle cable coming through firewall) and I got a way more normal fuel pressure of around 30ish psi. I blew into a piece of fuel hose connected to the return line to see if there was any resistance that would indicate a clog. I could easily hear bubbling in the tank when I did so. Just in case the power of my lungs wasn't enough, I blew some compressed air through the line with the same result. I hooked the line back up and got the same pressure reading of 65 psi. 

I am using the stock return line that came with the Brat. May be common sense, but could the change in diameter between the fuel return port on the EJ and the fuel return line on the Brat cause such a drastic increase in fuel pressure? Out of all of the write ups I researched while doing my swap I don't remember seeing anything saying that I need to run a completely new return line of larger diameter, just that I would need to upgrade all of the rubber fuel lines to be EFI grade. 

[SaltyMike]

On 7/10/2023 at 12:05 PM, 1 Lucky Texan said:

see if the vacuum line from the fuel pressure regulator is wet with fuel. maybe the FPR's diaphragm is leaking.

Vacuum line seems to be completely dry, I can probably eliminate that as a possibility unless there is another way to diagnose a bad FPR. 

[el_freddo]

You’ve got three lines from the tank correct? 

If so the general practice is to swap the vent line and the fuel return line with EJ conversions. You also need to swap it all at the back end before the tank too, otherwise you’re still down to small diametre return line. 

Cheers 

Bennie

[SaltyMike]

16 hours ago, el_freddo said:

You’ve got three lines from the tank correct? 

If so the general practice is to swap the vent line and the fuel return line with EJ conversions. You also need to swap it all at the back end before the tank too, otherwise you’re still down to small diametre return line. 

Cheers 

Bennie

On the front of the tank, there are two lines directly next to one another. I know that the larger of the two is the feed, and I assumed that the one directly next to it was the return. (This post shows what I am talking about: 

There's another line that wraps around the tank (evap I'm assuming) which leads to a canister located in the right rear fender. There's two other lines that come out of the tank right above where the fuel fill port is. These two lines also lead into that canister located in the right rear fender. 

I tried to switch how I hooked up the return and evap firewall lines, guessing that maybe I had swithced them accidentally and that this was causing the high fuel pressure. This just lead to increased pressure in the fuel tank and purging of fuel through the return line. Is there a write up on the forums here on how people have swapped the lines so the return line will have a larger diameter or do I need to run an entirely new return line?

[el_freddo]

No need to run a new line. 

Just ensure that what you swap up the front is also what you swap at the back of the cab under the tray area or for sedans/wagons etc, under the back seat. 

It could be worth removing the fuel tank filler cap and blowing some compressed air through the small return line to ensure there’s no crud blocking it or reducing the flow.

Worst case scenario is to run a line from the old vent (swapped to return) line up to the breather line at the filler pipe, tap into that line as the return line. And ensure you seal up the factory return point on the front of the fuel tank! 

Keep us updated! 

Cheers 

Bennie

[SaltyMike]

On 7/27/2023 at 7:00 AM, el_freddo said:

No need to run a new line. 

Just ensure that what you swap up the front is also what you swap at the back of the cab under the tray area or for sedans/wagons etc, under the back seat. 

It could be worth removing the fuel tank filler cap and blowing some compressed air through the small return line to ensure there’s no crud blocking it or reducing the flow.

Worst case scenario is to run a line from the old vent (swapped to return) line up to the breather line at the filler pipe, tap into that line as the return line. And ensure you seal up the factory return point on the front of the fuel tank! 

Keep us updated! 

Cheers 

Bennie

Just last night I swapped the evap and return lines coming through the firewall, as well as back at the tank. Unfortunately, it doesn't seem to have made a difference. Upon inspection though, it seems as though the evap and return lines are approximately the same diameter. I measured both of these lines at roughly 4mm. Seems strange to me, because when I read a write up about converting the fuel system for an EJ22 swap from Phizinza, it says that the return line is 3.2mm and the vent line is 6.3mm. 

My Brat is an '82 DL. From my understanding, this was a bit of a strange year for the Brat (only 2nd gen body with a hardtop option, single range 4 speed, Carter-Weber carburetor instead of a Hitachi carburetor). Maybe this uniqueness has something to do with why these lines are the same diameter? Not sure, I may be missing something here. If not, it sounds like I'll have to run a new line to resolve this. 

[el_freddo]

I reckon you’re on the money about your model year and the same diametre return and vent lines. That’s plausible to me. 

Our Brumby/BRATs were in production until 1991/1992 and I’ve heard sales still occurring in 1994 but I can’t verify that. 
So our models ran a lot longer and they may have change the fuel lines to be the same setup as the L series. 

Cheers 

Bennie