Running lean under boost

Post by **jasonkg** » Mon Dec 18, 2006 11:15 am

My engine is running lean as soon as I get into positive pressure. It starts sputtering and hesitating and makes a knocking sound. I am able to attain 7 psi. This started happening directly after I changed out the dump pipe gasket and I got a new intake filter (not the piping). I don't understand how this would give me a problem.

Here is the list of checks I have completed so far:

• Swapped out the mafs twice• Inspected the intake tube for cracks• Inspected all couplers for the intercooler • Inpected fuel pump connector• Did a FPR test• Checked timing• Changed spark plugs• Inspected fuel lines• Checked for vacuum leaks • Swapped out ECU• Checked turbo for shaft play (none)• Checked BOV for leaks none (none)

I thought it was a boost leak at first, but it does not appear to be since I checked all parts that would be associated with this problem.

Is there something I missed other than engine internals. It seems like I am having a fuel pressure problem, or a sensor issue. Help please!

Modified by jasonkg at 7:58 PM 12/18/2006
Modified by jasonkg at 8:09 PM 12/18/2006

Post by **Florida240sx** » Mon Dec 18, 2006 1:54 pm

What do you have for tuning? What size are your injectors? What is your spark plug gap? What is your fuel pressure at idle?

Post by **jasonkg** » Mon Dec 18, 2006 2:31 pm

Florida240sx wrote:What do you have for tuning? What size are your injectors? What is your spark plug gap? What is your fuel pressure at idle?

0 tuning, stock injectors, New NGK coppers pre-gapped BKR7E... I am going to get a fuel pressure test kit from the autoparts store tomorrow to check fuel pressure at idle and we'll see what its at under boost.

It seems kind of odd that prior to changing out the intake and dump pipe the car ran like a champ and now I'm having issues???

Post by **Florida240sx** » Mon Dec 18, 2006 5:03 pm

Wait a minute....Your driving around boosting on stock injectors, with no tuning??? You asking to crack a ringland, or fry your rings. What is your air fuel ratio? Do you have a real wideband?

Post by **Florida240sx** » Mon Dec 18, 2006 5:05 pm

Reason why the car sputters is because you don't have enough fuel dumping into the cylinders..... at least get 370cc injectors. What is the pre-set gap on the sparkplugs?

Post by **jasonkg** » Mon Dec 18, 2006 5:59 pm

Florida240sx wrote:Wait a minute....Your driving around boosting on stock injectors, with no tuning??? You asking to crack a ringland, or fry your rings. What is your air fuel ratio? Do you have a real wideband?

I have an SR20. Whats wrong with stock injectors they are 370cc. I have the walbro fuel pump. There should be no need for tuning at this point since I am only running on stock 7 psi, with no boost controller. Are you under the impression that this was a KA. No I don't have a wideband yet. I'm not sure what the spark plug gap is (their pregapped). I highly doubt this is the problem since #1 I changed them # 2 I changed them to the exact same plugs as I had on before this problem occured.

Post by **180fan** » Mon Dec 18, 2006 8:33 pm

It is possible that you've got a blockage in the fuel system. You should be able to take that SR stock fuel system to a little more than 7psi...

You should do a few other things to add to your list anyway. Recalibrate your TPS, change the cts, clean the mafs, add another ground for the mafs, run some fuel system cleaner AFTER changing your fuel filter. By the way, what kind of fuel pump are you using? Please don't tell me stock...

Post by **jasonkg** » Tue Dec 19, 2006 4:01 am

180fan wrote:It is possible that you've got a blockage in the fuel system. You should be able to take that SR stock fuel system to a little more than 7psi...

You should do a few other things to add to your list anyway. Recalibrate your TPS, change the cts, clean the mafs, add another ground for the mafs, run some fuel system cleaner AFTER changing your fuel filter. By the way, what kind of fuel pump are you using? Please don't tell me stock...

If I was having a TPS issue wouldn't that apply in all aspects of positive and negative pressure. I have cleaned the mafs and swapped it out twice with two different housings. The fuel filter (z32) has less then 2000 miles on it. The fuel pump is the Walbro 255lph as i stated in my previous reply. The cts, are you referring to the coolant temp sensor? What would this have to do with the fuel system or running lean? My engine temps are fine, unless you're saying that it might be faulty and not indicating the correct temps.

Post by **180fan** » Tue Dec 19, 2006 9:25 am

your cts reports to the ecu your temps. different temps will change the fuel mix. if your tps is off, your ecu will change the injector pulse accordingly.

Post by **jasonkg** » Tue Dec 19, 2006 10:19 am

If the tps was off wouldn't this create drivability issues--in and out of boost?

Post by **180fan** » Wed Dec 20, 2006 7:59 am

not always, but usually.

Post by **meangreens14** » Sat Dec 23, 2006 6:57 pm

not positive if this was mentioned or not, but are all vacum lines connected properly(not as inleaks, but proper routing)? i remember my sr ran fine up to 7psi and then after that started acting strange and doing close to what you are saying your is doing...it was a misconnected vacum line...wierd i know.

Post by **jasonkg** » Sun Dec 24, 2006 3:51 am

I did check the vacuum lines. They have to be routed correctly since it was running fine before I had this problem. I didn't change anything. Thanks for the reply.

Post by **jasonkg** » Sun Jan 14, 2007 12:57 pm

180fan wrote:your cts reports to the ecu your temps. different temps will change the fuel mix. if your tps is off, your ecu will change the injector pulse accordingly.

*Update*

• Installed a new coolant temp sensor• Did a fuel pressure check--fuel pressure was fine. I don't think it's running lean under boost• Pulled off the front bumper and inpected the intercooler thoroughly• Bypassed the intercooler by routing the hotpipe to the throttle body Ruling out the intercooler and couplers• Swapped out the hotpipe, BOV, and intake • Installed a new wastegate accuator• Oil change• Inspected the inside of the turbo on both the intake side and outlet side. I did not see any signs of shaft play or any problems. • Put a multimeter on the MAFS and did a voltage test and checked for shorts. All test were fine • Checked voltage on TPS. Tested good

Still bogging down, spuddering, hesitating, and some backfiring

I ordered a new O2 sensor since I was recently in this region replacing the turbo outlet gasket. Maybe, I damaged it. We'll see what happens...

I'm at a loss. Is there something I'm missing. Help a brother out.

Post by **rotorimp** » Sun Jan 14, 2007 3:00 pm

The O2 sensor will not solve this problem

are you absolutely sure that the line going to the Waste gate actuator is good--also is there any way you bumped the cas when you were first changing things?

Post by **jasonkg** » Sun Jan 14, 2007 4:50 pm

I'm going to replace that vacuum line tomorrow, just to rule it out. The actuator should be good. Then again I didn't install a new one, but the one I swapped it for was a known good actuator from a friends car. Where is the crank angle sensor located? Will this cause issues when under boost though? Thanks

Running lean under boost

Running lean under boost

Re: (Florida240sx)

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Re: (180fan)

Re: (180fan)

Re: Running lean under boost (jasonkg)

Re: Running lean under boost (meangreens14)

Re: (180fan)

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