# 96-97' 4x4 Hardbody 4cyl Hard Starting Problem



## hardbody4x4 (Jul 20, 2016)

Hi All -

I have 96' 4x4 Hardbody 4cyl that I recently completed changing the timing chain and tensioner, oil pump, distributor, spark plugs and wires, and air filter. Put it all together and it has a hard time starting, but will fire up, run, and idle smoothly. No lose of power. Anyways, I have over a 1000 miles on her and she has not brokedown. When warm the truck will fire up just fine, no heistation. But when left for long periods of time 8+ hrs it has a hard time starting. There is no check engine light, no unusual noise, nothing when running. Just has a hard time starting when cold. Does anybody have any ideas? Thanks


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## jp2code (Jun 2, 2011)

Check the timing. That will make a big difference.

Afterwards, try pulling the codes.


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## rogoman (Dec 16, 2004)

There may be one or more injectors that are leaking ever so slightly, so over time of sitting shut off, the fuel tube gets emptied thus causing hard starting.


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## smj999smj (Jan 1, 2006)

IACV-AAC valves were sometimes known to go bad on these engines. Improper base idle setting will affect it's operation.


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## hardbody4x4 (Jul 20, 2016)

Checking timing - 10° BTDC. This was also checked and confirmed by a mechanic. Pulled codes. 5 long pauses 5 short pauses. I beleive this 055.


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## rogoman (Dec 16, 2004)

A code 55 indicates there's no malfunction. 10 degrees BTDC is standard spec.


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## smj999smj (Jan 1, 2006)

Cold start idle and idle control are controlled by the ECM through the IAC valve. It shuts an air passage to slightly richen the mixture to raise the idle when cold and opens it to lower the idle as the engine warms up. It is also used to help maintain the idle speed during loads, such as when the A/C is running or the power steering is putting a load on the engine. The 96 models had some problems with them and there was a voluntary recall around 1998 (if memory serves correct) to make some updates for emission reasons. One of them was replacing the IAC valve and another was installing an updated bracket for the IAT sensor, which commonly broke and cut the wires of the sensor...and there were a couple of other things that I can't remember. The IAC bolts to the top of the intake manifold and looks like this:

http://www.partsgeek.com/assets/dimage/full/1062980.jpg

As I mentioned earlier, base idle setting has to be correct in order for it to work properly and should be adjusted per the factory service manual instructions.


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## hardbody4x4 (Jul 20, 2016)

smj999smj said:


> Cold start idle and idle control are controlled by the ECM through the IAC valve. It shuts an air passage to slightly richen the mixture to raise the idle when cold and opens it to lower the idle as the engine warms up. It is also used to help maintain the idle speed during loads, such as when the A/C is running or the power steering is putting a load on the engine. The 96 models had some problems with them and there was a voluntary recall around 1998 (if memory serves correct) to make some updates for emission reasons. One of them was replacing the IAC valve and another was installing an updated bracket for the IAT sensor, which commonly broke and cut the wires of the sensor...and there were a couple of other things that I can't remember. The IAC bolts to the top of the intake manifold and looks like this:
> 
> http://www.partsgeek.com/assets/dimage/full/1062980.jpg
> 
> As I mentioned earlier, base idle setting has to be correct in order for it to work properly and should be adjusted per the factory service manual instructions.



Could you elaborate on base idle? I keep going to base timing, but I don't think that is right. How do check the base idle? And what is spec? Thanks for the help


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## smj999smj (Jan 1, 2006)

The base idle is the idle setting without correction input from the ECM. I don't have the idle spec, but it's probably around 650RPM for a manual trans and 750RPM for an auto trans, +/- 50RPM. You can set the base idle and base timing using a scantool work support function or do it without a scan tool, like this:

-Run the engine @ 2500 RPM for about 3 minutes and make sure the coolant is at normal operating temperature.
-Shut the engine off and unplug the throttle position sensor.
-Start the engine, rev it a few times and then let it idle.
-Adjust ignition timing to spec. 
-Adjust idle to spec using the idle adjust screw. It should look something like this:
https://www.2carpros.com/forum/automotive_pictures/115045_IdleSpeedAdjust_01_1.jpg
-Shut of engine and reconnect throttle position sensor harness connector.


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## hardbody4x4 (Jul 20, 2016)

So I followed your procedure. Base idle was between 630 and 650. Also, I notice that during start up there is liquid coming out of the tail pipe. Seems to smell rich too, but goes away after warming up.


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## smj999smj (Jan 1, 2006)

If it's an auto trans, I would raise the idle up a little to around 725-750 RPM. If it's a manual trans, that's probably pretty close to spec. Water should come out of the tailpipe; it's a by-product of the combustion process as well as condensation that may have built up in the exhaust. As long as the liquid is not fuel or coolant, it's fine.


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## hardbody4x4 (Jul 20, 2016)

It is a manual. In regards to a leaky injector wouldnt that have continous issue, sputtering, misfire, etc?


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## rogoman (Dec 16, 2004)

Minor injector leaks many times go unnoticed where the engine runs OK, however the MPG and hard starting with a cold engine are some of the symptoms. You could do something like this to test them:

To test them, unbolt the fuel rail from the intake manifold and pull off the entire assembly. Keep the fuel hoses still connected and don't remove any individual injectors. Also keep the electrical connectors on the injectors. With the assembly now away from the intake, turn the ignition key to the run position WITHOUT STARTING THE ENGINE. Now observe each injector to look for leaks. There should be no drips.


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## smj999smj (Jan 1, 2006)

You don't have to pull the fuel rail to verify leaking injectors. Just do a fuel pressure leakdown test. Install a fuel pressure gauge, pressurize the system and pinch off the fuel lines before the gauge and after the fuel rail. Monitor the amount of pressure drop over time and compare to specs.


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## hardbody4x4 (Jul 20, 2016)

Took the fuel rail off. No leaky injectors. Any other thoughts?


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## rogoman (Dec 16, 2004)

At this point you can test the fuel pressure regulator. Tee-in a temporary fuel pressure gauge at the output side of the fuel filter. The readings at idle should be as follows:
- with vacuum hose connected to the fuel pressure regulator: 34 psi
- with vacuum hose disconnected from the fuel pressure regulator: 43 psi

After shutting off the engine, the fuel pressure should hold for quite some time. If it drops off quickly, the regulator may be bad.


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