1999 Mustang Gt Misfire/hesitation {help}

Andrewmklo30

New Member
Oct 16, 2017
1
0
1
20
Hello I have a 1999 mustang gt that I have been working on for well over a year and still haven't found the problem. I originally bought the car off of craigslist for 3900 with 130,000 miles at the time it seemed like a good car ran fine no problems. after two weeks of daily driving it the motor went bad. the car sat for about 3 months till I then decided to take out the motor myself and take it to a shop to get it rebuilt. I then put the motor back and went for a first test drive and ran like :poo:, had no power at all. The car hesitates when I step on the throttle and when it gets to about 3 thousand rpms it suddenly grabs and has all its power back. I took it to a shop and they told me to get all 8 new ignition coils I put them in and it ran fine like when I first bought the car for about 10 miles and then started to hesitate again. After that I took out the spark plugs and noticed that the 4 spark plugs on the passenger side were running lean and the 4 on the driver side were running rich. I recently had the check engine light tester plugged in and the codes are p0301,p1130,p1150

this is what I've tried to the car since I've rebuilt the engine
-ford motorcraft coils
-ford motorcraft spark plugs
-brand new egr valve
-TPS sensor
-cleaned MAF sensor
-brand new flywheel and clutch
-rebuilt transmission
-1 new fuel injector for the code P0301
-checked if all the wiring harness connectors were plugged in properly and they were
NONE of this worked
 
  • Sponsors(?)


imp

Mustang Master
Jul 13, 2017
531
104
83
68
Have any modification(s) been done to the engine: inlet air modifications like bigger MAF, ducts, filters, etc? Bigger injectors?

Many of the replacement items you show are irrelevant to your symptoms, IMO.
 

wmburns

SN Certified Technician
Aug 14, 2009
5,364
417
164
Houston Texas
After that I took out the spark plugs and noticed that the 4 spark plugs on the passenger side were running lean and the 4 on the driver side were running rich. I recently had the check engine light tester plugged in and the codes are p0301,p1130,p1150
There are a couple of things that need to be ruled out.
  • Swapped left/right front O2 sensors body harness wires.
  • Left hand cam 180 degrees out of time relative to the right hand cam. Yes this CAN happen and compression will test OK without PTV contract.
  • Electrical wiring faults to each O2 sensor.
  • poor compression in cylinder #1. Note, this is not the cause of the main problem but IMO a possible additional problem.
  • Exhaust leaks on the left side.
Do you have an scanning infrared thermometer? If so, measure and compare the temperature of the exhaust manifold between the right and left sides. What we are looking for is a big difference between the sides. IF one side is cold suspect cam timing 180 degrees out of time.

Another 4.6 rebuilding mistake I have seen is the cam sensor bump on the left hand cam being mistaken for a timing mark. This results in the left hand bank being out of time by a large amount.

The list of "possible causes" is long.

>>From Ford manual
P1130 - Lack of HO2S-11 Switch, Fuel Trim at Limit
P1150 - Lack of HO2S-21 Switch, Fuel Trim at Limit


  • Electrical:
    • Short to VPWR in harness or HO2S
    • Water in harness connector
    • Open/Shorted HO2S circuit
    • Corrosion or poor mating terminals and wiring
    • Damaged HO2S
    • Damaged PCM
  • Fuel System:
    • Excessive fuel pressure
    • Leaking/contaminated fuel injectors
    • Leaking fuel pressure regulator
    • Low fuel pressure or running out of fuel
    • Vapor recovery system
  • Induction System:
    • Air leaks after the MAF
    • Vacuum Leaks
    • PCV system
    • Improperly seated engine oil dipstick
  • EGR System:
    • Leaking gasket
    • Stuck EGR valve
    • Leaking diaphragm or EVR
  • Base Engine:
    • Oil overfill
    • Cam timing
    • Cylinder compression
    • Exhaust leaks before or near the HO2S(s)
 
Last edited:

Sluggie24

Member
Apr 8, 2017
92
15
18
44
I'm confused why you didn't bring the car and engine right back to the shop that re-built it to have them look at it? Unless you did something wrong on your install they are responsible for their work.