Minor surge at start up.

[tomloans]

1B737378
FEB 2009
PRO XS L

Minor surging at idle neutral. Any ideas would be great. Want to nip this at the bud. Thanks guys.

[EuropeanAM]

Does it seem to rev and buck for a couple moments on a cold start, and then settle into an idle, or??

One reason might be a tracker valve, but there are some other possibilities, also.

[tomloans]

Don this is after about 10 hours on the new fuel rail. It is mild. Only I would notice it and it is noticeable when I put it in gear as well. Again mild Rpm fluctuation/surge. After the morning it ran strong for the rest of the day.
I don't think heard it again.

[EuropeanAM]

If it does this again, see if you can take a short video showing the tach readings and sound of the engine.

Keep in mind that if the engine is COLD (not up to operating temp), it will not run nearly as smoothly as a warmed-up engine, as it's dumping large multipliers to the fuel delivery curve (based on air and engine temp). Essentially the PCM must perform the functions of a "choke" (though it's electronic, and automatic).

[tomloans]

Don,

Here it is. My fishing buddy thinks I am nuts and over the top with this engine. I don't blame him. I am, as it is one thing after another. Anyways, please listen to this start up mild surge. I have never had this before. Again the latest addition has been a new fuel rail and spark plugs and that is all. After the new fuel rail I have put about 8 hours on the motor before this surging started last trip out. Thank you for any feedback guys. 580 hours on it...



Thanks again.

[EuropeanAM]

May I ask how much water pressure you happen to have at IDLE? That telltale took like .002 seconds and looks very healthy.

Also wondering if BOTH banks of cylinders are coming up to at least 120 degrees F (check at thermostat cover with an infrared temp gun, or monitor on suitable diagnostic system).

[tomloans]

Water pressure on the water is usually about 3 to 4 PSI at idle. I didn't check at the moment of this video. But I will check and bring it up to temp and use the infrared gun on it. I just yesterday flushed the entire cooling system and cleaned the strainer and the pulled and cleaned both thermostats and pulled and clean the poppet valve as well. They all look clean but I will use the infrared gun and see if one is bad.

I pulled the fresh plug to double check the gaps, pulled the tracker valve and I didn't see anything ( I use a magnifying glass, LOL) that looked like a tear of any kind. It looked new and it should as it has about 8 hours on it. I did notice that the roller on part number 858851A03 at the throttle body was worn to one side so I ordered another one.

BUT what I found odd is that all the plugs were quite sooty - this is scary because I don't want build up in the pistons and then something breaks, like cylinder 6. I opened a new thread for this as well. Thanks Don.

[EuropeanAM]

Two threads running for a likely common problem.

[tomloans]

Regarding the surging and sooty plugs. Using the infrared gun, it looks like possibly the port side thermostat wasn't opening. I will test it on the water tomorrow with the new thermostat I put in. Not sure how this solves the 6 plugs that are all sooty but I hope it does.

Thank you and I will let you know if this solved the problem.

Tom

[EuropeanAM]

Wasn't opening, or was stuck open? What were the temps when taken in the center of the thermostat covers (at idle)?

[tomloans]

Wasn't opening, or was stuck open? What were the temps when taken in the center of the thermostat covers (at idle)?

Don,

I have no idea. Totally confused now. It looks like the one side is not warming up. So I changed it and went out yesterday. Started it up to the minor surging again. The rest of the day start up and running was excellent. So I have no idea. It really seems electronic or even mechanical. Let me know what you think.

[EuropeanAM]

If the engine was not warming up properly on one bank, THAT BANK will run RICH (and may even pass fuel to other cylinders as well).

Once the underlying problem (thermostat fault) has been rectified, it may take some run-time to clean up the spark plug fouling (or in extreme cases, may even require a plug change).

As state in Post# 10, really need to check each bank and confirm they are coming up to 120 degrees F (or better) with an Infrared Temp Gun (center of thermostat cover) OR a suitable diagnostic tool. This is AT IDLE, with no throttle applied whatsoever until engine reaches temp.