limp mode

M

mikem

Member

• Jul 22, 2004

• #1

I've had two factory fuel pumps go out in the last 4,000 miles. Last night I installed the walbro gss342 in tank fuel pump. BTW, all this was going on before the fuel pump swap and I thought it was the culprit. Here's a few questions, My car is stuck in limp mode when cold(first thing in the morning, etc.). My primary o2 sensor is reading 5.111 volts. I know that is ungodly rich more than likely even impossible. The reading used to be .030 upon just starting up and would work it's way through the A/F spectrum up to .990. The 5.111 volt reading is throwing me off. I hoped it was the fuel pump, but it's not. Now on cold starts the A/F will work it's way down to normal readings faster with walbro installed, but it's still not normal. I've replaced the primary o2 sensor, it was not the problem. I've checked the engine coolant temperature sensor voltage and it's correct. I've checked the MAF sensor voltage, it's correct. I know some of you are wondering why I haven't hooked it up to an obd-ll scanner, my car will not read on it, I've tried 4 times. I am boosted, and I need some help to figure this thing out. All suggestions are greatly appreciated.
mike

 

M

Matthew

Member

Contributor

:

CX9, CX5, i8

• Jul 22, 2004

• #2

what is actually wrong? i see your voltages, but im asking for symptoms. like, how did you know something was wrong? you say it is stuck in limp mode, yet how do you know that?

 

M

Mr. Win

Member

Contributor

• Jul 22, 2004

• #3

are you knockin?

 

M

mikem

Member

• Jul 23, 2004

• #4

Here's the symptoms.
Upon cold start A/F is pegged rich. primary o2 sensor is actually reading 5.115 volts. Normal readings on cold start would be lean and voltage would read .030 or so.
Since the fuel pump upgrade, the above is still a factor, now once warmed up the A/F will read a little above normal voltage for rich conditions.(1.020-1.200) It really should not get over 1.000 volts.

Once warmed up the A/F will run lean under some engine load and I have to feather the gas to get A/F to oscillate. This condition lasts for about 3-5 minutes. After that, minor engine load will get a pegged rich condition(I'm not really complaining about this), and my egt temps do not really exceed 1200F(probe mounted in manifold). These temps are colder than my normal flame breathing beast, so I'm not really complaining here either.

One other question, does the higher flowing fuel pump account for my rich condition without a fuel pressure regulator? (I'd like to think so, please inform me though)

I'm not knocking.

 

B

blynzoo

Member

Contributor

:

'02 Red P5...BUT AS OF 1/31/08 an '08 Silver SPEED3!!!

• Jul 23, 2004

• #5

What CPU are you running? Stock, or aftermarket? Also, have you had the "cold chatter" fix completed on your car?

 

Y

YP5 Toronto

Member

Contributor

• Jul 23, 2004

• #6

The STOCK FPR "should" still be managing the correct Fuel Pressure...but most likely it is not.

Do you have a FP gauge? I am assuming no....

I would look into getting an aftermarket FPR and insuring you are running correctly.

Wait...are you running an FMU? or an aftermarket ECU piggy back, etc..

More info please..

 

N

napmsp

Member

:

03.5 mazdaspeed

• Jul 23, 2004

• #7

I am running the stock ecu and no re-flashes were ever done to it.

 

N

napmsp

Member

:

03.5 mazdaspeed

• Jul 23, 2004

• #8

I am also running a FMU

 

Y

YP5 Toronto

Member

Contributor

• Jul 23, 2004

• #9

my guess...is that the new fuel pump has altered the base Fuel Pressure settings... it would explain the starting and the colder EGT....

 

M

mikem

Member

• Jul 23, 2004

• #10

sorry for any confusion, napmsp is a coworker and had his login remembered.

 

M

mikem

Member

• Jul 23, 2004

• #11

yp5, my only guess with that is it was in limp mode before the fuel pump replacement. Maybe something else fuel related went awnry with the factory fuel pump, or maybe it was that pos fmu

 

Y

YP5 Toronto

Member

Contributor

• Jul 23, 2004

• #12

so wait...running and FMU + the stock FPR? You will still need to adjust the BASE Fuel Pressure Settings.... I am confident that the stock (idle) fuel pressure level is running higher than stock.

 

Y

YP5 Toronto

Member

Contributor

• Jul 23, 2004

• #13

check engine light on?

also...did you reset the stock ECU?

 

M

mikem

Member

• Jul 23, 2004

• #14

I'll try that, just need to scrounge some dough for the FPR. Any suggestions, I was thinking about the AEM FPR, but have not decided as of yet.

 

M

mikem

Member

• Jul 23, 2004

• #15

cel is on, I've reset this numerous times. It comes on when the blow off valve is open at idle, which in turn causes poor idle when engine is warm. I've yet to recirculate the BOV, I guess I'm somewhat lazy even though I hate to admit it. It has come on now because of the poor fuel conditions.

 

M

Mr. Win

Member

Contributor

• Jul 23, 2004

• #16

what code do you have? do you have a voltage clamp?

 

M

mikem

Member

• Jul 23, 2004

• #17

I can't hook up my car on an obd-ll scanner. Something got screwy when the turbo was put on. I do have an o2 signal modifier and that could have screwed with the ecu or could very well be the problem(uhm)????? I'm a bit lost at this point, I probably need to take another look at it tomorrow when my thoughts have cleared.

 

M

Mr. Win

Member

Contributor

• Jul 23, 2004

• #18

explain what you kit is here i think youve tapped into the wrong wires on your ecu i dont know why you obd scanner wouldnt work pull the ecu check it out. lets us kno what you have set up

 

M

mikem

Member

• Jul 23, 2004

• #19

I'll have to pull the ecu and figure out what's going on. This has been on my car for about 15 months and I've put on about 18,000 boosted miles. The obd-ll problem has been a problem since day one. Very well could be part of the issue. I'll post back tomorrow. Thanks for the reply's so far

 

P

Protege2K

Member

:

2010 MAZDASPEED3

• Jul 24, 2004

• #20

*subscribes*