Engine Turbo 5.0 Mustang bad misfire at WOT

AwxyMoron

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Hello,
I have been having persistent problems since before I replaced the lower intake(about 2 months ago) when flooring it in my turbo fox. The first drive out after replacing the intake I discovered my fuel pump was just hanging in the fuel tank, so I fixed that, and the car ran like a bat out of hell for literally one drive. Since then, it started losing power up top(again), at first it just started falling flat, but now it will also misfire and occasionally backfire through the intake, usually around 3500rpms it starts falling flat and by 4000 its backfiring and running so horribly I don't want to give it any more gas, lol. It seems to rev and build boost fine if I am less than 1/2 throttle but once I start getting into it the car stumbles. Sometimes after driving for a while it will start backfiring through the exhaust while idling and stumbling during light acceleration(less than 1/2) in the lower rpm range(1000-2500ish) and then it will clear up unless I give it more gas. Also since replacing the distributor and TFI module, the autometer tachometer has also started jumping around, which I've heard can be from a bad pip? Water temp always reads between 180 and 210 once its warm, boost is at wastegate right now which is 8psi. Battery voltage is good.

Engine Build:
302 bored to 306
Icon Forged Pistons, Ford Racing Z Aluminum Heads, Scorpion roller rockers, trickflow cam,
billet timing set, plasma moly rings, clevite rod and main bearings, pioneer hp street balancer,
arp main and head studs, arp engine bolt kit , mls head gaskets, heads port matched,
trickflow streetburner intake, aluminum fuel rails, 455lph walbro pump,
adjustable fuel regulator, 60lbs? injectors, msd 6al ignition and 2 step,
Hellion turbo kit w/ 61mm precision turbo.

Car was tuned and Dyno'd at 460hp on 11psi of boost

So far what I've done:
Retorqued the lower and upper intake, Gone through the fuel system from the fuel pump to the injectors, gone through the ignition, from the 6al box(also ran it with the stock ignition, didn't seem to help) to the spark plugs. I've also checked all charge pipes, they were all tight. Checked the engine grounds, all battery grounds, ground running to alternator, grounds for computer. Those were all good and the ones that were not on bare metal are now.

Checked timing, set to 10degrees with spout out, also tried it at 7 degrees(result was worse drivability) recently changed and then checked spark plugs(at about 250 miles), #3 plug was rich enough the insulator was black, every other plug was tan and looked good. Checked fuel pressure while revving, at 4k WOT(using 2 step), and at idle, holds steady at 40psi, sits around 33psi with vacuum at idle. Checked Spark plug wires for arcing using a water spray bottle, did not see anything.

The codes I dump:
at first I was dumping a code 64(ACT sensor) and 41(pass side o2 sensor). I replaced both of those and they went away
Now I am getting code 85(canister purge which is deleted) and 95(fuel pump circuit, car has standalone fuel pump wiring) during KOEO, and code 91(drivers side o2 sensor) during KOER. The driver side o2 sensor was replaced when I first got the car about a year ago.

I tried the Engine balance test but the car idles around 1000rpm and I've read it needs to idle around 600-700 to be accurate. Regardless here are the results:

1st time: cyl 6,7 fail 2nd time: cyl 8 fail 3rd time: cyl 8,5 fail

List of parts I have replaced in order since I got the car:
TPS Sensor, Driver side O2 sensor, Header Gasket replaced with copper Permatex, New 255lph fuel pump(switched back to original 455lph), New Cap, rotor, spark plugs x2, spark plug wires and boots, New Trickflow lower intake, new MSD Coil, new fuel tank, new ACT sensor, New starter solenoid, New Motorcraft TFI Module(ended up being dead on arrival), swapped MSD pro billet distributor with used Motorcraft distributor and TFI module, New passenger O2 sensor.

Also I ordered a A/F gauge and Fuel Pressure gauge for the interior so I can get some better data when its under boost. Any help would be greatly appreciated as I'm just about out of ideas on what to throw money at next lol. also I have a few videos of the problems if anyone wants to see them I can post them or send them.
 
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Noobz347

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My first guess would be you're blowing the park out.

Perhaps the gap is too large or the coil isn't being saturated, or some portion of your MSD components are malfunctioning.

My second guess would be a lean condition caused by a vacuum leak somewhere.
 

AwxyMoron

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My first guess would be you're blowing the park out.

Perhaps the gap is too large or the coil isn't being saturated, or some portion of your MSD components are malfunctioning.

My second guess would be a lean condition caused by a vacuum leak somewhere.
I gapped the plugs down from .030 to .022 and the problem persisted. What do you mean by the coil isnt being saturated?
There are only 4 vacuum lines from the intake, they goto the wastegate, to the fuel pressure regulator, the vacuum tree, and the PCV valve is blocked off. On the vacuum tree there is one to the brake booster and then on the B/R port there is one that goes through the firewall i assume its for boost gauge but i will check. The only other place a vacuum leak could occur would be a bad seal on the intake somewhere right?
 
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AwxyMoron

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Is it chipped?
I was told that it was tuned by Brian from dynotune motorsports in Columbus. The first fall I had the car it ran great, I only started running into problems about last springtime after I blew a fuel pump fuse and since then it has only ran with zero issues a few times
 

Noobz347

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What do you mean by the coil isnt being saturated?
It means that voltage can be dropping off at the coil as the engine spins up. Test voltage to the coil. Rig yourself up a way to read it when accelerating.

The only other place a vacuum leak could occur would be a bad seal on the intake somewhere right?
A vacuum leak is [any] source of air that gets in without being metered. This also brings to mind the possibility of a pegged or malfunctioning mass air meter.

Other leak sources off the tip of my head: The gap between the heads and block deck at the rear (this usually tells on itself with an oil drip down the bell housing). PCV system leak. Throttle Body gasket or spacer. etc... The leak you're looking for would be somewhere on the inlet side if it exists.

Do you have a way to measure Air/Fuel ratio? If it's lean when it breaks up then it's a leak. If it's pig rich, it's something else (likely ignition, tuning, other..).
 
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Noobz347

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Is it chipped?
This shouldn't be ignored either. Regardless of what chip or who tuned it, A9L feature ports are [notorious] for corrosion.

Def recommend carefully pulling the chip ([only] once supplies are on-hand), cleaning the pins on the chip and A9L side and reinstalling. Do the same with the harness connector.

Best stuff on the planet:
Amazon productView: https://www.amazon.com/Hosa-D5S6-Contact-F5S-H6-FaderLube/dp/B00HNV7WI2/ref=sr_1_3?dchild=1&keywords=deoxit&qid=1617575613&sr=8-3


Other tools: Toothbrush, Q-Tips
 

AwxyMoron

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It means that voltage can be dropping off at the coil as the engine spins up. Test voltage to the coil. Rig yourself up a way to read it when accelerating.


A vacuum leak is [any] source of air that gets in without being metered. This also brings to mind the possibility of a pegged or malfunctioning mass air meter.

Other leak sources off the tip of my head: The gap between the heads and block deck at the rear (this usually tells on itself with an oil drip down the bell housing). PCV system leak. Throttle Body gasket or spacer. etc... The leak you're looking for would be somewhere on the inlet side if it exists.

Do you have a way to measure Air/Fuel ratio? If it's lean when it breaks up then it's a leak. If it's pig rich, it's something else (likely ignition, tuning, other..).
Okay, thanks for all the info, going to test the coil and MAF sensor now and will take a look at some other possible locations for a vacuum leak. I also ordered an air fuel gauge as well as a fuel pressure gauge.

Oh, and should I stick the negative lead in the negative on the coil or to a ground?
 
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AwxyMoron

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Apr 3, 2021
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This shouldn't be ignored either. Regardless of what chip or who tuned it, A9L feature ports are [notorious] for corrosion.

Def recommend carefully pulling the chip ([only] once supplies are on-hand), cleaning the pins on the chip and A9L side and reinstalling. Do the same with the harness connector.

Best stuff on the planet:
Amazon productView: https://www.amazon.com/Hosa-D5S6-Contact-F5S-H6-FaderLube/dp/B00HNV7WI2/ref=sr_1_3?dchild=1&keywords=deoxit&qid=1617575613&sr=8-3


Other tools: Toothbrush, Q-Tips
I will also do this in a bit after i check the other stuff:nice:
 

Noobz347

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Okay, thanks for all the info, going to test the coil and MAF sensor now and will take a look at some other possible locations for a vacuum leak. I also ordered an air fuel gauge (not sure why they turbo'ed the car and didn't get a a/f gauge lol) as well as a fuel pressure gauge.

An "Air Fuel Gauge" will not do you any good unless you've got a wideband sensor and encoder to drive it.

You need a wideband "system" like one from AEM or Innovate:


 

AwxyMoron

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An "Air Fuel Gauge" will not do you any good unless you've got a wideband sensor and encoder to drive it.

You need a wideband "system" like one from AEM or Innovate:


Okay, was hoping to get by with just a cheap one for now but I suppose its a good investment right? lol
 

Noobz347

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Okay, was hoping to get by with just a cheap one for now but I suppose its a good investment right? lol
Yeah... and I'm going to ping @a91what because you've accumulated enough combo that the A9L is no longer the best way to tune it anymore IMO. If you're going to put money into a wideband, you should put money into one that is future compatible with a good tuning system.
 

AwxyMoron

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Yeah... and I'm going to ping @a91what because you've accumulated enough combo that the A9L is no longer the best way to tune it anymore IMO. If you're going to put money into a wideband, you should put money into one that is future compatible with a good tuning system.
okay, and the aem or innovate ones should work then?
 

Mstng93SSP

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He will say this one.

 
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AwxyMoron

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An "Air Fuel Gauge" will not do you any good unless you've got a wideband sensor and encoder to drive it.

You need a wideband "system" like one from AEM or Innovate:


Update on some of the tests: The Coil is holding voltage all the way through the RPM's. I've also found the vacuum line from the intake to the blow off valve was kinked and there was also a spot where it looked like it was getting rubbed pretty bad so I'm going to replace that. I tested the MAF using https://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/maf-sensor-tests-3 . It passed every test.