2G Tricky lean problem. Any ideas?

[Old man Neo]

Didn’t think I’d be asking for help so soon after joining, but here we are!

About 2 weeks ago car started idling poorly on cold starts. A couple days later I got a P0170 code (fuel trim malfunction). Hooked up the scanner and found it running lean under all conditions, by the time the weekend came it would die shortly after startup (if I started it 3 or 4 times I could get it to stay idling poorly long enough to get it into closed loop). Idle speed is around 750, and very rough.

Lucky for me, I had just bought a bunch of parts to get the car in like new condition before my planned turbo upgrade, so here’s what I’ve done so far:

-boost leak test: found slight leaks at seals on 2 injectors, biss o-ring, and leaking pcv valve. Replaced everything (also added a check valve inline with the pcv).
-Repeat boost leak test: No leaks found.

-Tested air intake temperature sensor and baro sensor: IAT sensor slightly out of spec, had a new MAF on hand, so swapped it out. New one tests as good.

-Tested coolant temperature sensor: found slightly out of spec, and replaced. New one is reading correctly.

-Turned off injectors one at a time: engine bogs equally on all four.
-Checked injector resistance: 2.5 ohms on all four (in spec)
-Checked injector resistor pack: 6.5 ohms on all four (in spec)

-Repeated boost leak test in case I missed something: No leaks found.

-Removed cleaned and tested EGR: all good.

A little confused at this point so I thought I’d go ahead with planned upgrade work and solve this after. So:

-Installed new Walbro 190, Fuel Lab filter, braided stainless line from filter to rail, new RTM fuel pressure gauge, and Fuel Lab FPR.

-Checked mechanical timing: timing marks all line up still (only 30,000km on timing belt, previous owner had it replaced by dealership)

-Replaced throttle position sensor and set per factory manual.

-Compression test: 175 on all four.

-Leakdown test: 7% on all four.

-Looked at the plugs while they were out, they all look just fine, plugs and wires were done last year.

With that done, back to the troubleshooting!
-Set the new FPR base pressure to 43: no improvement.
-Pulled off fuel return line and ran pump to verify flow: LOTS of flow!

-Checked for pre-o2 exhaust leaks (pressurized the whole exhaust): No leaks.
-Replace upstream o2 sensor just for the hell of it, I had a spare.

-Checked ECU power supply and ground: all good but I just picked up a spare ECU from Performance Partout, so I swapped it. The one I pulled out looks perfectly fine inside, and the new one made no difference.

-Checked injector harness with noid light: all good.

-had ordered a ISC, so, what the hell I’ll throw that in too! (FYI, I set the biss properly- 750rpm at operating temp with the ISC at 30)
-No change… getting really frustrated now

-Repeated boost leak test again!: found nothing.

Decided to go old school at this point …
-Cranked the fuel pressure up to 65psi: Starts and idles nicely in open and closed loop. Still reading lean in all conditions, but running much better. Obviously I can’t leave the pressure like that permanently, need to find the cause!

-I plan on pulling the injectors tomorrow and bench testing them… but they were cleaned 3 years ago, It would be weird if they were all clogged, and I would expect the idle to have a miss if 1 or 2 of them were clogged. If they test good, I’m officially stumped…

Can anyone see what I’m missing here?
Any suggestions wold be greatly appreciated! Thanks!

 

[steve]

That's a lot of information and a bunch of new parts that don't sound like they needed changing but I'm confused at this point as to what the problem is?

Did you fix your P0170 code?

 

[92AWDHX40]

Fix the code injectors size .

 

[Old man Neo]

That's a lot of information and a bunch of new parts that don't sound like they needed changing but I'm confused at this point as to what the problem is?

Did you fix your P0170 code?

The fuel system upgrades, TPS, and compression and leakdown tests were items I already planned to do for my upcoming turbo swap. I did the MAF and coolant temp sensor as part of the p0170 repair tree. Same with the electrical checks. The IAC I wouldn’t have changed, but I had one on hand, so for the 5 minutes it took to change it and rule it out, I did. Pulled the injectors today- 2 of them have a shitty looking spray pattern. Going to give them a good cleaning and see if that helps before I send them out or replace them. Will update when they’re back in… I’d be surprised if this fixes it, but I’m hoping it does because I’m all out of ideas after this.

 

[Old man Neo]

Fix the code injectors size .

Stock injectors. 2 of them have a bad spray pattern. Going to clean them up.

 

[chrysler kid]

Can you post a picture of your engine bay looking down at the valve cover from your radiator so I can see the entire engine bay and vacuum lines

Is the car bone stock?
Is your aftermarket bov recirculated?
Are all the vacuum nipples on the intake to the maf hooked up?

 

[Old man Neo]

Can you post a picture of your engine bay looking down at the valve cover from your radiator so I can see the entire engine bay and vacuum lines

Is the car bone stock?
Is your aftermarket bov recirculated?
Are all the vacuum nipples on the intake to the maf hooked up?

Sorry I didn’t reply sooner, been working 14 hour shifts all week. Here’s the pics you requested. The car is bone stock other than the (recirculated) bov and the fuel system upgrades (bov has been in there 3 years, and the problem started before the fuel upgrades) all vacuum lines are hooked up, and none are leaking. I would greatly appreciate any insights you might have. Thanks!

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[Old man Neo]

The fuel system upgrades, TPS, and compression and leakdown tests were items I already planned to do for my upcoming turbo swap. I did the MAF and coolant temp sensor as part of the p0170 repair tree. Same with the electrical checks. The IAC I wouldn’t have changed, but I had one on hand, so for the 5 minutes it took to change it and rule it out, I did. Pulled the injectors today- 2 of them have a shitty looking spray pattern. Going to give them a good cleaning and see if that helps before I send them out or replace them. Will update when they’re back in… I’d be surprised if this fixes it, but I’m hoping it does because I’m all out of ideas after this.

Update: cleaned the injectors, spray pattern looks good now, but it didn’t solve the problem

 

[1990TSIAWDTALON]

Biss screw hole isn't leaking is it? It wouldn't lean it out much but just put your finger over the hole to feel for suction.
Intake nice and tight and you said no boost leaks.
Stock ECU? Any tuning software?

 

[Old man Neo]

Biss screw hole isn't leaking is it? It wouldn't lean it out much but just put your finger over the hole to feel for suction.
Intake nice and tight and you said no boost leaks.
Stock ECU? Any tuning software?

Biss is good, was leaking on my first boost leak test, replaced o-ring. No suction. Stock ecu, no tuning software.

 

[1990TSIAWDTALON]

And did I read you replaced the fuel filter also?
I hate to say "try this" but when I am at a loss I will give anything a shot. Use some Carb spray or other flammible spray and see if the thing will stay running if you squirt it into a vacuum hose or the intake trac, in front of the turbo or anything at the intake manifold. If additional "fuel" keeps it running then we are going down the correct path. If it does nothing then it is something to "check off" the list of things tried.

 

[Old man Neo]

And did I read you replaced the fuel filter also?
I hate to say "try this" but when I am at a loss I will give anything a shot. Use some Carb spray or other flammible spray and see if the thing will stay running if you squirt it into a vacuum hose or the intake trac, in front of the turbo or anything at the intake manifold. If additional "fuel" keeps it running then we are going down the correct path. If it does nothing then it is something to "check off" the list of things tried.

Yup, brand new fuel lab filter. Just went outside and sprayed some carb cleaner in a vacuum line- that smoothes it out, same as adding fuel pressure. While I had the can in hand I sprayed everywhere there could be an air leak, none found.

 

[Old man Neo]

On cold startup up it actually runs fine for like 15 seconds, then goes to shit. I’m not familiar with the logic of this ecu- can anyone think of something the computer changes shortly after start up?

 

[1990TSIAWDTALON]

A lot of times it's the CTS but you replaced that. Do you have a different MAF to try? That would change airflow figures if one is different from the other.

 

[Old man Neo]

A lot of times it's the CTS but you replaced that. Do you have a different MAF to try? That would change airflow figures if one is different from the other.

Changed the MAF. It didn’t help

 

[99dsmer4g63]

I know you said you boost leaked tested it but my vote is on a boost leak some where. Sounds similar to a problem I experienced and it ended up being a leak at the throttle body. The leak was located near the bottom so soapy water wouldn’t reveal it. Also you didn’t say anything about throttle body shaft seals and if they are original I promise you that they leak. I had a set of seals that were fine at idle and if you would move the throttle plate it would leak very badly. I would triple check for leaks. I was tipped off to check for leaks because I had a wide band and as soon as the cold enrichment would go away the car would go full lean. Probably about 15 seconds after it would start. Kinda sounds like your problem. Good luck
-Daniel

 

[Old man Neo]

I know you said you boost leaked tested it but my vote is on a boost leak some where. Sounds similar to a problem I experienced and it ended up being a leak at the throttle body. The leak was located near the bottom so soapy water wouldn’t reveal it. Also you didn’t say anything about throttle body shaft seals and if they are original I promise you that they leak. I had a set of seals that were fine at idle and if you would move the throttle plate it would leak very badly. I would triple check for leaks. I was tipped off to check for leaks because I had a wide band and as soon as the cold enrichment would go away the car would go full lean. Probably about 15 seconds after it would start. Kinda sounds like your problem. Good luck
-Daniel

My gut said boost leak in the beginning, that’s why I checked it so many times. I’ve had the throttle body shaft seals leak in the past, checked them extra well. Appreciate the input though. Thanks.

 

[chrysler kid]

To me it looks like the fuel pressure solenoid vacuum lines arent hooked up correctly.

 

[99dsmer4g63]

I think he just has the fpr hooked directly to the manifold. Nothing wrong with that. You don’t even have to the solenoid hooked up and the car be fine maybe just an extra crank on hot starts.
-Daniel

 

[chrysler kid]

I think he just has the fpr hooked directly to the manifold. Nothing wrong with that. You don’t even have to the solenoid hooked up and the car be fine maybe just an extra crank on hot starts.
-Daniel

Yeah it kinda looked like that, but I cant tell if the vacuum line loops around it and has a T in it

Some of those aftermarket regulators can go bad and actually cause a vacuum leak. Do you have the stock one you can put back on the fuel rail?

 

[Old man Neo]

Do you have the stock one you can put back on the fuel rail?

Had the stock one on when the problems started. Stock one was holding correct pressure, I was upgrading the fuel system as part of a planned turbo upgrade.

I think he just has the fpr hooked directly to the manifold.\

FPR is going to solenoid, solenoid going to intake.

 

[99dsmer4g63]

That’s my fault then looks like you bypassed it in the picture you posted. I don’t have it hooked up my car just fpr straight to intake and you wouldn’t even know it was bypassed. Maybe something you could try just for giggles if the solenoid is for some reason stuck open or something.
-Daniel

 

[Old man Neo]

That’s my fault then looks like you bypassed it in the picture you posted. I don’t have it hooked up my car just fpr straight to intake and you wouldn’t even know it was bypassed. Maybe something you could try just for giggles if the solenoid is for some reason stuck open or something.
-Daniel

Just tried it bypassed- no change. Thanks for the suggestion though! That’s something else I can scratch off the list.

 

[chrysler kid]

Maf to turbo intake could have a crack or slit in the rubber

Vacuum lines to charcoal canister could be damaged. Cap the vacuum lines on the throttle body and the vacuum lines on the intake to the turbo

There's always a chance that the egr valve isnt holding vacuum and internally damaged, or the purge valve etc. Start by eliminating unknowns and work foreward. Im thinking its a vacuum leak, but I think you said you already replaced the fuel injector o rings, if not replace them now too

Cap all the vacuum lines on the throttle body.

Make sure the seal on the idle air control valve is good, and the idle air control valve isn't cracked itself.

The Fiav on the bottom of the throttle body could have a bad seal or be rusted enough to not function properly

Inspect the vacuum lines down to the egr valve to make sure one hasnt slipped off a vacuum port