In my case, the answer is no. I didn't let it settle in. I removed it immediately for it was bad.

In your case specifically, we have a cold start idle condition and, I am assuming that it is consistent 100% meaning, every time you start your truck, the results are identical correct?

If this is true, it could be a number of things including the following:

Sensors

- IAC: motor is not working either due to motor failure or, there's no voltage going to it at idle. Elec check: remove the IAC connector and turn the key to <ON> and note voltage present. If no voltage is witnessed, the problem lies within the circuit the controls it. Mech Check This can be done by removing it and powering to <ON>. Note movement. If there's no movement- it is faulty. R&R

NOTE:I have gone through three IACs so, from past experience, they don't all work out of the box.

-TPS sensor: may be faulty while at idle on cold startup conditions. To check: you will have to back probe it (at the connector) and, with the engine OFF and the key to <ON>, as the throttle is increased, you will see an increase of voltage. IF it's not reading, or, it jumps voltages or, it has a dead spot- no voltage- R&R.

-Camshaft sensor: may be intermittent at cold. To check, back probe the connector and check the output voltage against OEM specs.

-Crank sensor: may be intermittent at cold starts. Like I said, on mine, it was really bad- up and down and finally trying to settle in but, I didn't give it any time to settle in and removed it immediately as it was faulty. Again, back probing will tell you what it's doing while it's running.

Air Flow Rate Mismatch you may have a mismatch due to your intake that your using or, it may be leaking at the TB / CAI gasket. If you have the OEM intake, place it back on and retest. If problem clears up, it's your intake. If problem persists continue to check for vacuum leak at the gasket.

NOTE
I can't tell you the number of times I have heard this same complaint come up The only intake that I found to work was the Volant CAI setup. I had tried round air hats only to find out of balance air flow rates. I have tried a K&N setup with a heat shield and that didn't work either.

Vacuum leaks:

- Injector leak: You may have a vac leak at the injector. Did you change injectors in the past or, did you remove them at any time? If so, I would remove all the injectors and check all your O-rings at the manifold level. Remember, tops leak gas while the bottoms leak vacuum.

This is one place that lots of people fail to check for vac leaks. Everyone is checking the hoses and check valves but, I don't see anyone checking it at the injector level. This is very common after changing injectors. If any of the O-rings were nicked or cut, there's a very good chance of it leaking.

-PCV valve: check that for leaks around both hose connections at the PCV and at the manifold. IF unsure, plug this port and perform cold start. If problem persists, it's not the PCV system. Next.

-Leak at the TB: check all bolts and tighten those to 19 ft lbs. Check the gasket for tell tail signs of a vac leak. Torque as needed and retest. If problem persists it's not a TB gasket leak.

-Leak at the Purge Solenoid / Evap canister system: to check, plug that port and retest cold. If problem persists, it's not related to this system.

-Leak at the Brake Booster level: to check: plug this port and retest cold start. If problem persists, it's not related to this system.

NOTE:
Someone mentioned a vac line that runs under the battery area. I don't have a line on mine but, you may have some lines that run under that area. Don't confuse the washer, fluid delivery line for a vac line.

-Vac leak inside the dash area: to check, plug this port on the passenger side of the manifold. This is the one that has the check valve. If the problem persists: it's not related to this system.

There may be other vac systems on your truck. I don't have an EGR system on my truck and, mine is very simple. Not sure about yours and what set of schematics go with yours. Look under the hood or, on the radiator area for a sticker. This will show you your vac schematic.

Faulty Fuel System

-Faulty pump: you may have insufficient pressure at startup thus not delivering the right amount of fuel and, once it's primed and expelled the air in the lines (if any), it runs fine. To check: place a pressure gage into the Schrader valve. Turn the key to <ON> and go look at the gage. It should read full operating pressure on one click. If it falls below that where, you need two key <ON> sequences- the pump is on it's way out and needs to be replaced. You will need to verify the correct psi rating for your truck and compare that to the reading on the gage. For example, for a 96, the correct psi rating is 45 psi according to OEM specs. When I turn my key to <ON>, the pressure reads 45 psi.

I should note that I did have a bad pump and, for what it's worth, it didn't cause a loping idle condition. I was getting erratic output readings at cold startups thus inducing a low idle condition. It did not ramp up. However, if your pump ouput is low- you get a low idle and when it's putting out too much fuel- you can get an increase in idle as the A/F mixture changes which will induce an idle loping affect.

Head Gasket Leak

-head gasket leak: you may also have a leak there and, after it warms up, the PCM adjusts the A/F mixture. To check: run a compression test.

NOTE:
You would also be able to tell if your losing coolant or, oil is mixing in with the coolants and vice versa- coolant in your oil.

That abouts all I can think of for your symptoms. I would get a Haynes manual and a nice DMM- Fluke, (if you don't already have one) and start looking into everything above.

Other than that, I don't know what else to tell you. Good luck.

Chris McKenna

 

no the problem only occurs the first start of the day once it has gotten up to temp its fine the rest of the day, once we get into winter as it cools faster this may change but as of now its only the first start.

 

Ok, so, let's say that after you drive it, let the truck sit for 8 hours or more, and you restart it, it's fine? This is leaning more towards a fuel related issue now.

Q: Does the truck do this when it has been off for more than 4 to 8 hours? If so, I want you to run a test. Start it. Drive it. Get it up to temp. Shut it off and let it sit for 4 hours. Restart. Repeat the test and this time, let it sit for 8 hours. Let me know what happens.

 

Do you have the means to test your fuel pressure? Without doing any of the tests, you will never know what the problem is. See about running those tests I listed above. The time test may provide some information that will help to narrow it down to your fuel system.

 

The fuel pressure is within the specs in the workshop manual and it does hold pressure overnight.

 

What exactly is the pressure that your seeing in the am at time of startup? I would like to know what the psi is. Give me a number. Do you have a pressure gage on it? What is the specs for your truck and, what type of injectors are you running in that truck. Within specs is huge for my 96- from 35 psi to 45 psi and, that covers quite a few different models and does not account for different injectors. Not all makes and models work in that range nor do all injectors work at those ranges.

Injectors have specs too. What injectors are you running? I would like to look them up to compare your injector requirements against your pump output and see if there's a mismatch.

Also, you never answered my question so, in case you forgot, I am going to ask you one more time:

Q: let's say that after a drive it early morning and you let the truck sit from 9 am until 9 pm and you restart it, is it fine or is it not fine?

How about in the summer- it's really hot out, do you have any issues starting it in the early am?

 

I tested a few times and it was always within 43-45, as for the injectors they're stock as far I know I doubt they've been changed.

 

Have you tested it before startup to see what the pressure reads? Did you test it recently? 43 is a tad low. What year is your truck again?

See, we really don't have all the information that we need to troubleshoot 100%. Are you the original owner? What color are the injector tops- blue, black, red or orange? On the side of the connector on the injector, there's raised lettering. I would like to see that.

Also, I would like to check the pump output from zero psi up to 45 psi. How did you check your fuel pressure in the past?

 

I am not the original owner of the truck, the pressure is the same or mayb a little higher before start id have to check it again, the truck is an 01 and ill have to post the rest of the info tomorrow when its light out.

 

There's no way the fuel pressure is going to be higher when the pump is not running. The pump pressurizes the lines to full psi. While it's off, it drops down to a lower psi value after the pump has ceased and continues to drop over time.

I am going to look into your year to find out the PSI spec along with what kind of system they are running in the 2001s. I will see what I can find out. My gut feeling is going with a fuel related issue on this one as it's not happening every time and, when it does happen, it's after a long period of time such as when the pressure drops.

I believe this is why the vehicle starts fine all day as it's holding pressure and starts fine over short periods of time. However, over long periods of time, it does not start fine.

This was why I was hoping you would have answered the question about time. This is information that is important to note. The time between bad starts is very important because you can time your fuel pressure drop and see if the two coincide. That means, if your pressure is dropping to zero in 12 hours and your encountering bad starts in 12 hours, you now have strong evidence that points to your fuel pump.

Then, to support that theory, you put a gage on in the morning, hit the key to <ON> ONCE and turn it <OFF>. You then look at the gage and note the psi reading. If it's not up to full psi (going to find out what that is for 01) you now know with absolute certainty that it's your fuel pump that is malfunctioning.

It takes one click of the key to pump it up to full psi. If you have to use two or more clicks to <ON>, you have an issue with your pump and, thus the reason for erratic idle condition at cold startup only.

That's what I believe it to be based on your feedback so far but, without the answers to those questions that I had asked, I don't have enough information to be 100% sure.

Good luck.