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YotaFun
09-19-2008, 03:38 PM
Here is a fun one for you all.

About a month ago, just before my trip to Florida on the last week of August(didn't drive the truck there just trying to give you a time perspective) Tess started to do something to me that seems very out of the ordinary for use 3.4l guys.

During cold start up, no matter what time of day it was whether it be early in the morning, late afternoon after sitting all day, or at night, about 30seconds to a min after start up I would start to get a nice engine rumble at idle.
Talking like a nice V8 idle that we all dream we could have with nice deep strokes that you could here with ever revolution of the pistons and you can feel as the whole vehicle vibrates from the power (something that 3.4l while being large enough is still no V8) and she would proceed to do this for the next 30 seconds or so before going back to high idle to warm up.

Interestingly enough, the RPM gauge does not budge the entire time when doing this and stays at a steady 1000-1200 range (can't really remember exactly at the moment if it was 1000 or 1200 but it was in that range.)
No CEL is being thrown either.
Today I was leaving work and was in a bit of a rush, so I started her, put her in gear, and went, got to the light and idled for about 15 seconds then it changed, let my foot off the gas and she started to do it, this time you could feel the engine was doing something since she jolted a little and still NO CHANGE on the RPM gauge and still no CEL.

I know I am do for an oil change but that never seemed to be a problem and this little symptom goes away after the 30 second period it does it.

I will tell you a little about the truck and then you all can help me go from there.
97 3.4l SR5 4WD Runner (for those who don't know)
135K+ on the OD
Auto Trans
The oil I am running is that Mobile One 0W-30 Full Synthetic Advance Fuel Formula.
Every oil change I clean out the TB and the MAF.
Every other oil change I run Seafom through the gas tank.
Every 4th oil change I run Seafoam through the gas tank and the TB

At the 130K interval the following was done:
Spark Plugs
Wires
Air Filter
Oil (switched to the 0W-30)
Oil Filter
Clean MAF, TB
Seafoam

That's about it.
What I thought it could possibly be was the fuel filter which is original (either from the factory or the previous owner playing around, some how the nut that attaches to the filter on the line heading to the engine got cross threaded making it difficult to change to a new filter, I need to re-tap the nut and get a new filter in...)
But since this only happens on a cold start up I ruled out the filter as a possibility.

So Gang?
Any thoughts?

4runnerchevy
09-20-2008, 08:21 AM
Does a 3.4 have a cold start injector ? I know if a 22RE cold start injector, is left open to long the motor rumbles, and starts to die. Yours isn't dying so this might not be the case.

thook
09-20-2008, 03:39 PM
How does it act on throttle return during that 30sec-1min window?

YotaFun
09-20-2008, 03:42 PM
What ca mean?
Kinda of a confused.

YotaFun
09-20-2008, 04:03 PM
If you mean how does it act if I hit the gas during this period, the throttle does responmd and then when it come back to idle it acts normally.

CJM
09-20-2008, 09:27 PM
Put truck into gear and powerbrake it, if it does it then hello dead miss.

YotaFun
09-20-2008, 09:30 PM
Put truck into gear and powerbrake it, if it does it then hello dead miss.


huh?

YotaFun
09-20-2008, 09:35 PM
Also update.

I got done work at midnight tonight nice 54 degrees here in Chadds Ford.

Went to start it and watched the RPM gauge carefully this time, when it begin to do this the truck is idling between 1200-1300 RPM, when the rumble starts you can see the RPM needle slowly drop to 1k flat, it doesn't bounce down or dip below 1k it just falls steadily and then after reaching the 1k mark for about 3 seconds begins to rise back to the 1200-1300 mark for warming up.

corax
09-21-2008, 08:06 AM
Check your Coolant Temp Sensor - make sure the connector is on tight and that the sensor's resistance is what it should be (find an FSM). The CTS is responsible for cold start fuel enrichment (like the choke used to do for a carbureted car).

thook
09-21-2008, 11:16 AM
What ca mean?
Kinda of a confused.


It rumbles between 30 sec's to 1 min after initial cold start. So, during that time I was wondering how the throttle release response was. Trying to determine if it may have something to do with the air sensor, throttle sensor, tb linkage, etc.

Corax has a good pointer. If not that, then I'd look at the cold idle air valve. Not real familiar with 3.4's, though.

YotaFun
09-21-2008, 11:25 AM
Again throttle response is good.
so I don't know. I might check in to Corax's idea though.
Of course I go to make a video of it and it doesn't do it this afternoon...
So I will try later tonight after I have done my errands and it has been driven a bit.