Rough idle and acts like it is surging

Hi,

If the computer is for an automatic, yes it could be causing trouble. Code 89 is related to the torque converter clutch, so I understand why that one is on.

The one that I feel is most likely related to the issue with idle, is the 42. Code 42 indicates there is an issue with injector balance.

What I have done is attach specific tests below for each of the four codes I listed below. The only one I don't have is the 86. I thought maybe the numbers could have been transposed. Let me know.

Listed below I have the code and which pic is specific to that code. The pics are the diagnostics.

42 pic 1
74 pic 2
77 pic 3
89 pic 4

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Please keep in mind, an engine vacuum leak or weak ignition component can also cause these problems. If you haven't already checked, here is a link that explains how to find an engine vacuum leak.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know if this helps or if you have other questions.

Take care,
Joe

Hi,

Don't get the injectors or computer yet. I want you to check fuel pressure. The fuel pressure regulator, (pic 1 below) is located on the fuel supply manifold and regulates fuel pressure supplied to the injectors. One side of the diaphragm in the regulator senses fuel pressure, while intake manifold pressure is applied to the other side. Nominal fuel pressure is established by spring tension applied to the diaphragm. A constant fuel pressure drop across the injectors is maintained by balancing one side of the diaphragm with manifold pressure.

With that, the regulator could be bad. Check pressure first. Also, remove the vacuum hose to the regulator and make sure there is vacuum to it when the engine is running and make sure there is no evidence of fuel in the vacuum hose.

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Here is a link that explains in general how to check the pressure and regulator:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Pic 2 below shows the manufacturer's specs are far as pressure.

Let me know what you find.

Joe

Hi,

If you are certain the pressure is within the manufacturer's specs, then here are the directions for fuel injector replacement. I'm adding this because it contains steps and torque specifications. I just thought it may be helpful.

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1987 Ford Truck Ranger 4WD V6-177 2.9L
Upper Intake Manifold and Throttle Body
Vehicle Engine, Cooling and Exhaust Engine Intake Manifold Service and Repair Procedures Upper Intake Manifold and Throttle Body
UPPER INTAKE MANIFOLD AND THROTTLE BODY
V6-177 Engine

1. Disconnect battery ground cable.
2. Disconnect electrical connectors from air bypass valve, throttle position sensor, EGR sensor and air charge temperature sensor.
2. Remove air inlet tube from air cleaner to throttle body.
3. Remove snow and ice shield to gain access to throttle linkage, then disconnect throttle cable from ball stud.
4. Disconnect all vacuum lines from upper intake manifold.
5. Disconnect PCV lines from beneath throttle body and manifold.
6. Remove canister purge line from fitting adjacent to power steering pump.
7. Remove flange nut and disconnect vacuum line from EGR valve.
8. Loosen A/C line retaining bolt on top rear of upper manifold and unfasten retainer.
9. Remove upper intake manifold attaching bolts, then the manifold and throttle body as an assembly.
10. Reverse procedure to install, noting the following:
a. Install new gasket on lower manifold mating surface.
B. Torque upper intake manifold attaching bolts to 11 - 15 ft. Lbs.

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1987 Ford Truck Ranger 4WD V6-177 2.9L
Fuel Supply Manifold
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Rail Service and Repair Procedures Fuel Supply Manifold
FUEL SUPPLY MANIFOLD
V6-177, 183 & V8-302 Engines

1. Remove upper intake manifold assembly as previously described.
2. Disconnect fuel crossover hose from fuel supply manifold using tool No. T81P-19623-G or G1 or equivalent.
3. Disconnect fuel supply and return line connections at fuel supply manifold, then remove two fuel supply manifold attaching bolts.
4. On 6-300 engines, remove injector cooling manifold.
5. On all engines, carefully remove manifold and fuel injectors.
6. Reverse procedure to install. Torque manifold attaching bolts to 6 - 8 ft. Lbs. On V6-177 and 183 engines or 15 - 22 ft. Lbs. On 6-300 and V8-302 engines.

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1987 Ford Truck Ranger 4WD V6-177 2.9L
Fuel Injector
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Injector Service and Repair Procedures Fuel Injector
FUEL INJECTOR
1. Remove fuel supply manifold, refer to ``Fuel Manifold, Replace'' procedure.
2. Disconnect fuel injector electrical connectors.
3. Remove injector from fuel manifold by gently rocking injector from side to side while pulling upward.
4. Reverse procedure to install, noting the following:
a. Install two new O-rings on each injector. Use suitable oil to facilitate installation.
B. Use a light twisting and pushing motion to install injectors into the fuel supply manifold.

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Let me know how things turn out for you.

Take care,
Joe