mustangfactory

I need some inputs too see if I am missing anything. Running very lean, like a large vacuum leak. Here's what I have:

80s thunderbird 5.0L EFI motor with C-4
Camshaft changed to 5.0 HO
1989 Mustang computer with MAF
Painless EFI wiring harness
All sensors are new and has Reman. ECU
Shorty headers

Vehicle will start and die, after a while the engine will run but very rough and low vacuum. If I enrich the mixture with propane engine runs great and vacuum comes up.

It does not seem to mater if it is in closed or open loop

I have checked all the sensors and all are in specs. I have also checked for vacuum leaks with propane and found none

Things I have checked:
1) O2 sensor voltage very low 0.1v (lean) checked sensor wiring and EGO ground. With propane O2s come up to .5v and vary (O2s OK)

2) MAF voltage is within specs at idle around 1.2v. I have unplugged the MAF sensor (limp home mode) and the way it runs does not change

3) Found small leak at EGR, plugged port and no change.

4) Blocked off a all vacuum lines, no change

5) Fuel pressure is within specs and volume is great

6) Check Engine coolant and intake temp sensors. Read correct for temp. I have unplugged both sensors (goes rich by default) and no change in the way it runs. This puppy should be running super rich with these unplugged

7) Checked Baro and tried three know good sensors, no change

8) Replaced ECM with another new unit.

9) Checked ignition system (scope) and power balance test all cylinders ok (I did find #5 and #6 injector driver wires swapped. but still runs lean

10) I have check all ground circuits at the PCM and check out OK

11) Will not run at all past 10deg timing

12) Checked base idle speed and TPS voltage, I have even tried adjusting TPS voltage to richen it up but no change.

13) Hooked up scanner and performed KOEO test, nothing but TAB/TAD and NSS switch codes(deleted in painless wiring kit).

14) When trying to run KOER test, engine idles up for a second and then voids self test. This one has me baffled, does this with both PCMs, I have seen this with EGO grounds and bad sensors, but all check OK.

15) Pulled spark plug shows lean

OK I am starting to check the same things over and over so I need some fresh ideas, Am I missing anything??

Thanks Phil

aode08

why did you do all that, when a can of starting fluid or brake cleaner sprayed, would indicate the area of the vacum leak.?

Also check the ECM for codes, youll find your answer one way or another

brentloftis

The only thing I can think of that I did not see on your list is the ACT, Air Charge temperature sensor.
The ACT sensor,used on EFI models, provides the EFI system mixture (air/fuel) temperature information. The ACT is used as both as a density corrector to air flow calculation and to proportion the cold enrichment fuel flow. This sensor is mounted on an intake manifold runner or on the air cleaner.

Kudos on detailing all the steps info out.

mustangfactory

I think I found the problem, wrong injectors, 14lb vs 19lb
Phil

1990NOS!

yeah def a prob... those a factory sized injectors.... could step it up to 24's, get a FPR (fuel pressure regulator) and turn the fuel flow/volume down if need be. Runnin a lill on the rich side is safer then lean.... Especially if you plan on n20 down the road...
Then a pump, new maf, dif plugs, and timing come into play... Glad you got the prob solved...