Air Intake causing surge at cold start

[lostboykev]

Hey everyone! I just first like to say that having a forum on ericthecarguy is a narly idea! I’m sure it will help eric with the over load of emails he gets from persons like us 😛

So now onto my question..

I have a 04 Grand Marquis that in recent, I’ve decided to install an air intake system on. It’s the same size as the throttle body being 3″ in diameter. With an appropriately sized cone. You will also see in the picture below that the MAF sensor is positioned on the intake. This was an add-on from the same manufacture Spectre.

What I’ve noticed is when you start this car at COLD it will surge back and forth and sometime even cut off until it reaches a certain temperature. I find that holding the gas a little bit will prevent all this and allow it to reach what ever temp it needs to.

Topic

[lostboykev]

@pcmdjason

I actually have a bluetooth OBD adapter that I use in conjunction with my android phone. I remember it supported realtime MAF and fuel trim readouts. What exactly should I be looking at when I’m viewing those readouts?

[pcmdjason]

I’ve never used Torque before on my phone since I just have a cable, but if you’re starting from a cold engine, I’d go anything MAF related, O2 sensor related, and short term fuel trim. If the car has the ability to monitor intake temperatures I’d check that as well.

?Until heated up the O2 sensor will read .5V because the computer is substituting data until real data is available. At this time the air flow readings from the MAF are helping the computer determine the amount of fuel for the injectors to fire.

Watch the short term fuel trim at this time, if the MAF is reading too much air the fuel trim may go up into the high single digits or even double digits and stay around in that area.

Once the O2 sensor heats up to operating temperature and the O2 readings start bouncing up and down, notice if the engine smooths out.
Fuel trim will probably stay in low single digits at this time as the computer is only having to make minor corrections.

Positive fuel trim means more fuel is being told by the computer to be sent into the cylinders, Negative fuel trim means the computer is telling the injectors to cut back on fuel.

Now these are done in correction to maintain a 14.7:1 air fuel ratio. Which is why if you rev the engine the fuel trim may spike but then level out again in the low single digits since the computer has compensated and is now maintaining 14.7:1 again despite the increased consumption of both.

A coworker of mine had a mid 90’s Mustang GT that he put long tube headers on. The car would barely run until the O2 sensor heated up since it was so far down the line from the engine.

Quoted From lostboykev:

@pcmdjason

I actually have a bluetooth OBD adapter that I use in conjunction with my android phone. I remember it supported realtime MAF and fuel trim readouts. What exactly should I be looking at when I’m viewing those readouts?

Also this intake is composed of multiple pieces, I should be able to move it up another 5 inches if need be. But then I’d need to extended the length of cable for the MAF sensor.

[EricTheCarGuy]

Given the the problem seems to be related to the intake you might try looking up the manufacturers website and see if they have an FAQ or support that may have information on solving this issue.

[pcmdjason]

How does it do without the filter on it at all? I’m wondering if having the MAF so close to the cone it isn’t picking up a leak or a spot in the cone where air is coming through faster.

Think of it like a like having pulling the release pin on an air compressor where all the air comes out one hole at extreme velocity and that is hitting the MAF and skewing the results.

If you have access to a OBDII cable and Scantool.NET you could check the readings for MAF and maybe fuel trim. When the car heats up the O2 sensor takes over a large portion of monitoring the air/fuel balance. If this car does not have a heated O2 sensor it may take longer for this to smooth out.

Another idea is see if you could put something to slightly diffuse the air coming towards the sensor element. Or if you could somehow re-engineer this so the MAF is closer to the intake manifold but not in the way of the oncoming vent gases coming from the valve cover since that could deposit on the MAF element and damage it.

[Third Gear]

I think the MAF is a little too close to the air filter. Most other intakes give the MAF at least an inch or two of straight piping to allow the air flow to even out a little bit. older GM MAFs have a honey comb shaped screen to try to create a laminar flow. So, there might be too much turbulence where it is at right now.

Also, if the inner diameter of the pipe where the MAF sensor goes into is different than the factory ID that will mess up the MAF because the ECM is calibrated to that MAF with a specific diameter pipe surrounding it. Changing the diameter of the pipe around the MAF alters the flow characteristics.

So ditch that MAF housing if it is not the same diameter as stock. If that isn’t the problem, try getting some pipe and maybe a few more silicone couplers and clamps to add some inches between the MAF housing and the air filter.

[Author]

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