Lean at WOT issue

**Darth Maul** · 12-06-2018, 12:38 AM

Hey guys,

I read through the many threads and posts regarding this issue and haven’t been able to figure out this issue. I’m running lean at WOT around 16-17 afr. On idle, on cold start I start out about 15-16, then when warmed up come down to 14-14.7.

Cruising, I’m at 14’s and when accelerating I’m at 14—>12 depending on how much which seems normal. When I go WOT it goes lean.

I’ve replaced FPR, hardwired my 450 fuel pump with a relay, fixed a cracked sending unit which leaked a bunch of fuel, recalibrated my wideband, new wideband sensor, fuel filter, checked for leaks, epoxied icv hose, replaced vacuum line from fpr to intake manifold. New o2 sensor as well. I’m not really sure at this point what it could be. I thought for sure it was going to be this leaking sending unit.

My setup is:

S52 OBD1
BW S366
22rpd Tune
E85 fuel
44mm wg

Lately, I’ve had to crank the car about 4x before it starts. I know I ran E85 before on my old 335i and on cold start it was a bit tougher to start, took a few times. Tuner says it should not though, so I’m thinking maybe my fuel pump might be going out? Running out of ideas.

Thanks for the help, any input or suggestions appreciated.

**crazyyardie** · 12-06-2018, 07:15 AM

Maf sensor ??

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**Darth Maul** · 12-06-2018, 08:51 AM

I’ve cleaned my maf sensor a few times already. The wiring I did according to the directions.

**bmw328m52** · 12-06-2018, 08:55 AM

Fuel pressure at idle and WOT? I would think cold start would produce lower afr's and then creep up to around 14-15. Definitely seems like a fuel issue....

**Darth Maul** · 12-06-2018, 10:01 AM

Fuel pressure I have not checked. I was going to but the gauge broke. I did replace the FPR right after, still trying to diagnose the issue. Found the fuel sending unit was cracked and leaking.

It does seem like a fuel issue, but not sure what it could be. Fuel Pump is about 1.5 year old, FPR is new, Fuel Filter is new, fuel pump is hardwired with relay.

Anyone ever have the line hose inside the fuel pump leak?

**someguy2800** · 12-06-2018, 10:26 AM

Sure sound like the vacuum hose going to the FPR is cut or missing.

**bmw328m52** · 12-06-2018, 10:35 AM

Originally Posted by someguy2800

Sure sound like the vacuum hose going to the FPR is cut or missing.

Yup experienced similar issues when mine was torn. OP said he replaced it tho...

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**Darth Maul** · 12-06-2018, 10:41 AM

I can assure you my FPR is in tact and connected. I replaced it with a new vacuum hose too, I even went back and checked last night because I didn’t remember connecting it but sure enough it was connected :/. Is there supposed to be a resistor on the signal wire for my maf?

**IR M5** · 12-06-2018, 02:57 PM

I don't think 22RPD(Zach) uses a resistor on the MAF, but you should ask him.

**Darth Maul** · 12-06-2018, 03:17 PM

You’re right, I’m thinking it’s fuel related. Has anyone ever had a line inside the fuel pump assembly go bad?

**IR M5** · 12-06-2018, 06:32 PM

Originally Posted by Darth Maul

You’re right, I’m thinking it’s fuel related. Has anyone ever had a line inside the fuel pump assembly go bad?

You keep mentioning fuel yet you haven't checked the basics like fuel pressure. Gotta clear up the gray areas before you dive into deeper parts of the system.

**bmw328m52** · 12-06-2018, 06:37 PM

Originally Posted by IR M5

You keep mentioning fuel yet you haven't checked the basics like fuel pressure. Gotta clear up the gray areas before you dive into deeper parts of the system.

Correct...

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**Darth Maul** · 12-06-2018, 09:03 PM

I just assumed since I changed my FPR, I have a relatively new Fuel pump and filter that my pressure should be good but who knows. I can check sometime.

**m3boost** · 12-06-2018, 11:47 PM

check the small hose from the fuel pump to the fuel pump cradle..

**Darth Maul** · 12-07-2018, 01:10 AM

Originally Posted by m3boost

check the small hose from the fuel pump to the fuel pump cradle..

Have you had that give you trouble? I inspected it when I hardwired my pump, it gave me trouble trying to install the hose the first time a while ago and I had to use needle nose pliers which marred it up a bit wondering if it’s leaking from there under pressure

**someguy2800** · 12-07-2018, 09:15 AM

check the fuel pressure

**bmw328m52** · 12-07-2018, 09:17 AM

Originally Posted by someguy2800

check the fuel pressure

Yessss

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**chikinhed** · 12-07-2018, 09:44 AM

I have had the the small hose from the fuel pump to the fuel pump holder fail twice, once was the stock accordian type split and once from a loose clamp at that location. The car would go lean to the point of dying at any load above idle. Fuel pressure at the fuel rail was below what it should have been at idle. Check your fuel pressure, that is primary information for troubleshooting.

Fuel pressure at idle should read 51 psi with the vacuum line from the intake to the fpr disconnected. Plug the line to stop the vacuum leak while disconnecting the vacuum line.

It will be somewhere around 43 psi with the vacuum line from the intake to the fpr connected. This pressure ensures the integrity of the vacuum signal to the fpr and the integrity of the fpr diaphragm. But ensure that you have the disconnected pressure as that’s the one that counts for pump output and what the tune is counting on (unless the tune is bandaiding some hardware issue).

**Darth Maul** · 12-07-2018, 09:36 PM

Originally Posted by chikinhed

I have had the the small hose from the fuel pump to the fuel pump holder fail twice, once was the stock accordian type split and once from a loose clamp at that location. The car would go lean to the point of dying at any load above idle. Fuel pressure at the fuel rail was below what it should have been at idle. Check your fuel pressure, that is primary information for troubleshooting.

Fuel pressure at idle should read 52 psi with the vacuum line from the intake to the fpr disconnected. Plug the line to stop the vacuum leak while disconnecting the vacuum line.

It will be somewhere around 43 psi with the vacuum line from the intake to the fpr connected. This pressure ensures the integrity of the vacuum signal to the fpr and the integrity of the fpr diaphragm. But ensure that you have the disconnected pressure as that’s the one that counts for pump output and what the tune is counting on (unless the tune is bandaiding some hardware issue).

I’ll check fuel pressure tomorrow. I’m obd1 using the obd1fuel rail, should I check the pressure by using a T fitting at the front of the fuel rail by the oil filter housing hose or the back of the rail or fuel pump? I’ve seen and heard numerous ways to check.

**Darth Maul** · 12-10-2018, 11:02 PM

Fiel pressure at idle is 51 and with vacuum hose disconnected it’s 60

**Darth Maul** · 12-10-2018, 11:07 PM

Also, took my fuel pump out. The stock accordion looking hose in the fuel pump was cracked at the hose clamp. I ended up picking up some ptfe fuel tubing hose made for e85. Still didn’t solve the issue.

**crazyyardie** · 12-11-2018, 06:21 AM

Originally Posted by Darth Maul

Fiel pressure at idle is 51 and with vacuum hose disconnected it’s 60

Fuel pressure at idle without vacuum should be 52 psi not 60 psi

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**bmw328m52** · 12-11-2018, 08:23 AM

Originally Posted by Darth Maul

Fiel pressure at idle is 51 and with vacuum hose disconnected it’s 60

Too much pressure. As previously stated 43-44 psi at idle. If pressure is high, I wouldn't think you'd have a fuel leak. When my stock 3/2 valve was overpowered by fuel pump, I was also around 51psi at idle. It ran rich at WOT. Still seems vacuum related...

**IR M5** · 12-11-2018, 05:06 PM

How have you been checking for boost leaks?

**Darth Maul** · 12-13-2018, 12:42 AM

I found my Intercooler clamps when removed were a bit messed up and possibly pinched the hose. I am replacing those. I also thought I would get the injectors tested, they came back good but were clogged.

They said after cleaning them they produced 5 mL more in the same amount of time as before. Hopefully this helps out along with new clamps.