Engine 1990 LX 5.0L EFI Mustang Fuel Management Problems - HELP!

[5.0LXStanger]

I bought this car with all the go-fast parts installed by a shop from the previous owner in Pennsylvania. When I bought it, it ran great with no idle or other misfire or rough idle issues. I moved back home to California and needed the car to pass smog certifications. I had to do the following to make it legal and register the car:

• Removed full-length headers & Shorty H-pipe
• Installed (used) 4-cat stock exhaust
• Installed shorty equal length CARB-legal headers
• Swapped out Edlebrock intake for a CARB-legal Trick-Flow Street Heat intake manifold

Aftermarket Parts:

• Vortech V-1 Blower kit w/upgraded fan & rebuild
• Trick Flow Twisted Wedge Aluminum Heads - Rebuilt
• Trick Flow Street-heat intake manifold
• 24lb Injectors
• Phenolic upper intake spacer

Stock Parts:

• Stock EEC
• Stock Distributer

Test Drive Observations:

• Lean Pop under load (not WOT)
• Runs like when cold - Doesn't want to idle
• Stalls when coming to a stop even when warm
• When warm it runs better, but still has lean-pop in intake under load at lower RPM
• Under WOT it seems to run strong
• Fuel pressure sits about 28 when primed and at start-up
  • Driving fuel pressure drops to about 22 when cruising / not under acceleration - This seems low! Shouldn't FP be around 32psi and go up on acceleration?
  • Under hard acceleration I see fuel pressure pushing 40psi (There is a T-Rex boost pump that came with the Blower)
• Ran KOEO and it passed with no codes: 11 then 10
• I did find two codes in storage:
  • 66 - Low MAF Voltage - Just tested the MAF with the following observations:
    • At idle: .82 Volts
    • Moves smoothly under acceleration up to a max ~ 1.80 Volts
  • 95 - Fuel Pump Secondary Circuit our of range - Haven't investigated this yet...
• Smog Test Results:
  • Idle Smog Test: I fail this test!
    • I have high HCs (PPM) - I am considered a gross polluter (Is this due to running lean, or running rich? I think it's from running lean and not igniting the fuel.
    • I have elevated CO - I am over max, but not over gross polluter level also likely from unburnt fuel
  • Test at 2,500 RPM
    • The car is super clean with HCs & CO - Passes on this test!

Here is a summary of my thinking:

• When cold the car is supposed to run in a Closed-loop with minimal EEC control from sensors - Runs like crap smells like unburnt fuel
• According to Smog test, I have unburnt fuel at idle - I believe this is due to a lean condition not igniting the fuel in the cylinders.
• Under load, even after warming up, I have lean-pop under load and mild acceleration - This too is typically due to lean condition - Vacuum leak?
• WOT it runs strong & above 2,500 RPMs it runs clean! 2nd gear is like a time-warp!

Here is a list of all the things I have done on my '90 LX to try to solve this problem:

Completed Tests & Replaced Parts:

• Rebuilt heads
• Rebuilt Blower
• New 8mm Spark Plug wires
• New Spark Plugs
• New Cap & Rotor
• Tested & Cleaned MAF
• Replaced ECT
• Replaced IAC
• OBD1 Tests – No codes!
  • KOEO
  • EEC Advance Test
  • KOER Test
  • Cyl Balance Test
• Cleaned Salt & Pepper connections
• Set base idle w/TPS
• Set base timing – 10 Degrees BTDC w/Spout removed
• Tested TFI module
• Install coolant line to overflow
• Installed new Spark Plugs
• Clean IAC
• Clean throttle body
• Re-torque lower intake
• Tested & rebuilt fuel injectors
  • One was leaking – Replaced w/New
• Run compression check on Stang – All cylinders ~ 160psi
• Test Injector wires with Noid Light - Pass
• Retorqued Upper intake
• Smoke tested both Intake and Engine for leaks

Next Steps:

• Validate and clean all grounds
• Validate all vacuum line routings
  • Smog-pump & Actuators
  • EGR
• Replace Coil - Ensure strong spark!
• Replace O2 sensors - I have these already
• Consider replacing Fuel Pump - I have a 255lph Walbro that I can install

 

[nickyb]

I believe a way to tune what you have, is the way to go.
Warrning!..This is just my two cents.

 

[General karthief]

I don't see any fuel pump pressure readings, vac line off and on.

 

[5.0LXStanger]

@General karthief Happy Memorial Day!

Yesterday I tested the following:

• I have an electric fuel pressure gauge plumbed to the Schrader valve in the fuel rail.
• Fuel pressure measures about 28 psi when the key is turned to on and at start-up
  • Driving fuel pressure drops to about 22 psi when cruising / not under acceleration - This seems low! Shouldn't FP be around 32psi and go up on acceleration?
  • Under hard acceleration WOT (and boost) I see fuel pressure pushing 40psi (There is a T-Rex boost pump that came with the Blower)
• I will re-test with the Fuel regulator vacuum line on and removed and plugged today.

I also plan to test vacuum with a vacuum gauge - I suspected a vacuum leak, but all my investigation has turned up nothing. Yesterday I re-verified all my vacuum lines from the vacuum block and to the vacuum distribution connection were all correct and they are. I've sprayed lots of carb cleaner all over the engine and bay with no noticeable change in idle speed.

At the moment I suspect a failing primary fuel pump. Plan to drain and pull the tank and install a Walbro 255 lph high volume pump I already have...

It's interesting, I've seen a lot of posts on this forum with many of the same issues I am experiencing, but none that I have seen actually post a resolution to their issues. I guess it's human nature to only engage a forum when there is a need and once their problems are resolved, the need is gone??? Some resolution would be helpful!

 

[Noobz347]

Holler at us once the pump is in.

That's likely where I would start with that too.

I also saw that you also have a T-Rex external... Bad ju-ju IMO. When I initially did my KB kit, I used their external pump as a trash pump and went straight for the 255L high pressure.

It is possible that the T-Rex is going all of the remaining work after your in-tank, pooped-the-bed.

 

[JD1964]

If this car doesnt already have a wideband, it needs one.

 

[General karthief]

It's interesting, I've seen a lot of posts on this forum with many of the same issues I am experiencing, but none that I have seen actually post a resolution to their issues. I guess it's human nature to only engage a forum when there is a need and once their problems are resolved, the need is gone??? Some resolution would be helpful!

Yeah that's an uncontrollable fact on forums, most times the author finds some dumb, overlooked wire, vacuum hose or widget that is so simple they don't want to appear mechanically inept or they just don't care and never intended to be a regular member.
Another possibility that I believe in is that the author is looking for the 'magic bullet' and when the membership is not telling them what they want to hear they go elsewhere.
I admit and generally post up those antics and automotive shenanigans that I preform, most are drop-dead funny,
Like the 'first ride' my girlfriend took in the Junk Pyle, one mile from the house she smells smoke, we are stopped in traffic at a light and with a faint puff of white smoke from under hood, I looked at her, smiled and said " yes dear, we're on fire.......
Alternator wire, no biggie....
That's a standing joke with us now, as I leave the house.....'I'll call you if I catch fire'..

 

[Noobz347]

That's a standing joke with us now, as I leave the house.....'I'll call you if I catch fire'..

Her:

15 minutes should do it

 

[5.0LXStanger]

If this car doesnt already have a wideband, it needs one.

Hey there! Would the Wide-band sensor be plumbed back into the stock EEC, or would I need an aftermarket programable EEC?

I'm willing to go that route, but I was thinking that I needed to pass smog in California 1st to get it registered and tagged...

 

[gkomo]

Hey there! Would the Wide-band sensor be plumbed back into the stock EEC, or would I need an aftermarket programable EEC?

I'm willing to go that route, but I was thinking that I needed to pass smog in California 1st to get it registered and tagged...

The wide band will be like its own little 'system', not connected to the ECU. You'll need a gauge, wiring for power, wiring for a new additional O2 sensor, you'll have to have a bung welded into your midpipe for the new sensor. If you buy a wideband (i just purchased the AEM one from LMR, but there are many), it all comes in the 'kit'. Probably looking at around $200-300 for that, plus installation of the bung if you don't know how to weld.

 

[5.0LXStanger]

So how does the wide-band effect fuel management? Or maybe it is only used to read AF Ratios sent to a gauge? I assume I'd want to plumb the bung pre-cat - correct? Or maybe in the cross-over to get readings from both banks?

 

[gkomo]

So how does the wide-band effect fuel management? Or maybe it is only used to read AF Ratios sent to a gauge? I assume I'd want to plumb the bung pre-cat - correct? Or maybe in the cross-over to get readings from both banks?

It doesn't affect fuel management, only tells you what your AFR readings are, and then you can take that information and do what you need to do to get it right.

In the directions it will tell you where to put the sensor, if i recall (don't quote me) its like 15" downstream of the collector, after the first cat but before the second cat. It will only read one bank unless you get a kit that has two O2 sensors. Mine only has one, and i need to figure out which bank it goes on (or is preferred to go on, drivers or passengers). I've somewhat wired up my wideband (like the gauge lights up) but haven't installed the actual sensor yet so it just displays "SENSR" or something right now on the gauge.

 

[JD1964]

I have an x pipe. I’ve got my wideband sensor mounted just aft of the x. This way I’m sampling both banks with one sensor. Or, at least I think I am. It’s gotta be somewhat of a mix at that location. My wideband is PLX brand.

 

[5.0LXStanger]

Ok I dropped my tank today and pulled my fuel pump. Looked nice and clean inside. The current pump looks like a stock 95 lph unit. I’ll drop in a Walbro 255 lph unit I already had purchased. The Vortech blower kit in my car installed a 2ndary T-Rex booster pump.

Question: With the new Walbro 255 lph pump, will it still make sense to have the 2ndary booster pump? Also, with the new Walbro pump, will I need a new FPR? Currently there is a stock FPR on the fuel rail and a Vortech FPR plumbed in line.

 

[gkomo]

I have the Paxton Novi 1220sl which should be comparable to the V3, there was no inline secondary pump in the kit and it doesn’t call for it, I’m also running a walboro 255lph in tank pump and I plan on that being fine, so I don’t think you need the t-Rex.

The stock FPR should be fine… I didn’t go back and read if you had a ton of other mods and just the blower. I’m running my stock FPR, but I’ve also not driven my car since I installed my blower.

 

[5.0LXStanger]

I have the Paxton Novi 1220sl which should be comparable to the V3, there was no inline secondary pump in the kit and it doesn’t call for it, I’m also running a walboro 255lph in tank pump and I plan on that being fine, so I don’t think you need the t-Rex.

The stock FPR should be fine… I didn’t go back and read if you had a ton of other mods and just the blower. I’m running my stock FPR, but I’ve also not driven my car since I installed my blower.

Did you end up running a larger hot wire than stock to your Walbro pump? I understand the Walbro needs a larger wire to carry the current to the pump so it delivers fuel to spec. and for safety.

 

[gkomo]

Well I spliced in the wiring that comes with the pump but didn’t change any other wiring as far as the fuel system goes.

 

[5.0LXStanger]

Ok I'm starting to put my fuel pump hanger assembly back together and don't want to re-use the rubber "S" hose from the hanger assembly to the fuel pump. It was super hard and brittle - I had to cut it off. Anyone know where I can buy the rubber "S" hose, as well as a new hanger rubber gasket and jam-ring? I don't really want to try to bend straight rubber fuel line - I'd be worried it would bind and restrict fuel flow. The only one's I see on line come with the pump...

 

[gkomo]

LMR sells a fuel pump repair kit with all those parts but also the connector. It comes with a plastic flex hose instead of the rubber S hose

 

[5.0LXStanger]

I ended up buying a fuel pump rebuild kit from DeuschWorks with the rubber "S" line for the pump to the hanger. Also picked up a new fuel filter and new fuel gauge sending unit, as mine failed the resistance test. It was 35 years old ~ It was time! I should get my parts next week and have the Black Widow back on the road again sometime at the end of the week to run some more tests... I plan to test my fuel pressure regulator next, as well as look for any kink in my fuel line.