03 v6 bogging down, can punch through it

Lucabrazi · Apr 8, 2018

Begin running poorly, was throwing misfire cylinder 1 code. Began basic tuneup: I have replaced spark plugs, ignition coil pack, fuel injectors, intake Plenum gasket, fuel filter. (Plug wires are 1 year old and look fine) Now it is not throwing any codes, however under acceleration, and especially at lower RPMs, it's bogging down. I can give it WOT and it will punch through.

Based on my reading next things to replace would include: o2 sensors, egr, maf. Before I blindly start replacing parts, any ideas, tips, or diagnostic ideas to determine where to go next?

Thanks!

Noobz347 · Apr 8, 2018

Check your TPS with an ohm meter and make sure there are no "jumps" and that you get a full and smooth sweep.

O2 sensors, maf, and and egr should all all throw codes if malfunctioning.

I wonder if anyone has a surging idle checklist for the SN V6? Maybe @wmburns ?

wmburns · Apr 8, 2018

A common cause for "surging" is timing related. Think cam sensor or CKP sensor. For the V6 the cam sensor is more important than for the V8. So anything that could cause and unstable CKP or cam sensor signal might cause "surging" or bucking.

If looking for "pattern" failures remember that the V6 is prone to:

cam syncro wear
leaking head gaskets (base motor health)
cracked crank damper hub.

HOWEVER. Before replacing any parts always rule out:

Excessive AC ripple from the alternator. This can cause false cam sensor signal "issues".
Excessive EGR flow
incorrect fuel pressure. Double check the intake vacuum reference line is connected and leak free.
correct spark plug gap
Dirty MAF. A dirty MAF will often over report air flow at idle and under report at load. The give away is to note LTFT that change negative/positive from idle to load.

If looking to avoid loading up the "parts cannon", recommend more testing before replacing parts. Consider getting an ODB2 scanner. Often it's possible to pay for an ODB2 scanner from the $$'s saved by not replacing an expensive "good" part.

An ODB2 scanner that is capable of monitoring (graphing even better) can answer some of the key questions about EGR, MAF, O2, fuel pressure and much more without having to turn a single wrench or buy a single part.

Here's some information on an affordable Windows based unit.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

rancorkeeper · Apr 10, 2018

Cam sensor would be the first culprit on my list, too.

Lucabrazi · Apr 14, 2018

Noobz347 said:
Check your TPS with an ohm meter and make sure there are no "jumps" and that you get a full and smooth sweep.

O2 sensors, maf, and and egr should all all throw codes if malfunctioning.

I wonder if anyone has a surging idle checklist for the SN V6? Maybe @wmburns ?

Thanks Noobz347, just ran through some testing on the TPS with a multi meter and it looks good. Nice smooth voltage up and down. I'm going to take a look at the cam sensor as @wmburns suggested next.

Lucabrazi · May 5, 2018

wmburns said:
A common cause for "surging" is timing related. Think cam sensor or CKP sensor. For the V6 the cam sensor is more important than for the V8. So anything that could cause and unstable CKP or cam sensor signal might cause "surging" or bucking.

If looking for "pattern" failures remember that the V6 is prone to:

cam syncro wear

leaking head gaskets (base motor health)

cracked crank damper hub.

HOWEVER. Before replacing any parts always rule out:

Excessive AC ripple from the alternator. This can cause false cam sensor signal "issues".

Excessive EGR flow

incorrect fuel pressure. Double check the intake vacuum reference line is connected and leak free.

correct spark plug gap

Dirty MAF. A dirty MAF will often over report air flow at idle and under report at load. The give away is to note LTFT that change negative/positive from idle to load.

If looking to avoid loading up the "parts cannon", recommend more testing before replacing parts. Consider getting an ODB2 scanner. Often it's possible to pay for an ODB2 scanner from the $$'s saved by not replacing an expensive "good" part.

An ODB2 scanner that is capable of monitoring (graphing even better) can answer some of the key questions about EGR, MAF, O2, fuel pressure and much more without having to turn a single wrench or buy a single part.

Here's some information on an affordable Windows based unit.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

I picked up a scanner and the FORscan software. I now have access to lots of data, but not sure what are appropriate limits for my make and model. What is excessive AC ripple, EGR flow, or incorrect fuel pressure? Thanks for pointing me in the right direction. Any tips on getting started with the FORscan software for an amateur would be appreciated as well.

Matt

wmburns · May 5, 2018

Let's start by looking at fuel pressure. For the Mustang it should be around 40 PSI almost all of the time (as measured by the FRPS).

Lucabrazi · May 6, 2018

wmburns said:
Let's start by looking at fuel pressure. For the Mustang it should be around 40 PSI almost all of the time (as measured by the FRPS).

Thanks for your help.

Fuel Pressure is holding steady between 29-30%. That's lower than the 40% you referenced, but not sure if low enough to suggest malfunction?

Also I looked at Fuel System Status (open/closed loop) and it reads: Bank 1: Closed. Bank 2: Error. Not sure if that indicates anything, but the error indication caught my eye.

Thanks again

wmburns · May 6, 2018

30 PSI as reported by the PCM is too low and should be looked into.

The Mustang only has one fuel system. So it's not a problem that the fuel system 2 shows an error is not a problem.

Lucabrazi · May 29, 2018

wmburns said:
30 PSI as reported by the PCM is too low and should be looked into.

The Mustang only has one fuel system. So it's not a problem that the fuel system 2 shows an error is not a problem.

From my reading seems the likely culprits for the low fuel pressure are a fuel pressure sensor or the fuel pump (fuel filter has been replaced with no change in performance). Should I try replacing the sensor first, since that is a simpler job, or are there further diagnostics I should try?

Thank you for the guidance @wmburns

Matt

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