High cold start idle issue

I need to ask our tech gurus a question, since I have been dealing with this issue for years now, and I am at a loss on what to do next. My truck is a 2005 2.7 2TR-FE for context.

My truck at a cold start (sitting overnight or sitting more than 3 hours after getting up to operating temperature) will rev up to 2,250-2,500 RPMs, surge down to 2,000 RPM, then go back up to 2,500 RPM and finally start to idle down when the secondary air injection pump turns off. I know these engines will rev to roughly 1,800 RPM for a few seconds when cold, then start to calm down after that. The engine starts and idles normally when warmed up (from 80-90 degrees F coolant temp up to operating temp of 185 degrees F).

I initially thought it might be a vacuum leak, so I checked (and replaced) the rubber hoses for the PCV, checked the hose for the brake booster (saw no cracks) and checked and replaced the throttle body gasket. The only other gasket I have not checked is the intake gasket (but was replaced when I replaced the coolant bypass pipe many years ago).

I have then checked the secondary air injection system, since the idle goes down after the pump turns off. But I have found no issues with that system; the pump works, the valve works and is not clogged with carbon and the MAP sensor is reading correctly according to the chart in the service manual. I just replaced the valve and MAP sensor, since I broke my original valve when I disassembled it to clean it, and I thought the original MAP sensor was reading out of range, but the new sensor reads in almost the same range (2.5 volts at 0 PSI to 4.7 volts at 8 PSI).

I have done many of the normal maintenance items a number of times (cleaned MAF, cleaned throttle body, disconnected the battery, etc.)

Hopefully someone has run into this problem as well and knows what is going on. Or if anyone has any input please share! I can upload a video of a cold start if needed.

 

Any codes?

Are coolant and intake air temp both reading within about 5 degrees of ambient temp after sitting overnight?

If all that's good I'd want to look at fuel trims on a cold start and see if they are way positive.

 

No codes ever.

I will have to report back on scan data when I can get my scan tool.

 

Okay, here is a link to a video of my scan tool showing the data you want of a cold start after sitting overnight. The ambient temperature at start up is 43 degrees F. In the video, the truck is started at the 50 frame mark, and the air injection pump turns off around the 284-285 mark (the voltage of B1S1 goes up to 4.17v and shoots back down to 2.4-2.5v and settles back to around 3.2v).

I included some of it idling up to 85 degrees of coolant temperature. To me everything seems normal, but I am far from an expert reading scan data!
20240406 112317 (youtube.com)

 

Everything looks good there, the AFR sensor is lean at startup until the SAIS shuts down because it's pumping air into the exhaust but the truck is still in open loop at this point so the PCM is ignoring it.

Did this issue start suddenly on it's own or after some work was done?

 

It has been doing this for years but I don't think it started after doing a repair. It has just been slowly getting worse over time (7-8 years). And during that time, alot has changed/been repaired, including a new frame.

 

Did you ever find a fix to this? I have the same truck with the exact same problem. I’ve done lots of work trying to figure out what the issue is but nothing will fix it. Never any CEL either

 

Unfortunately no, I have not solved this issue yet. I just replaced the head gasket in my truck, and in doing so, was hoping there was going to be a small vacuum leak from the throttle body gasket or intake gasket, but my truck still does it after the head gasket job. The only other vacuum hose that I found not tight was the hose coming from the intake going to the booster (even with the rusty clamp, it slides right off the nipple on the intake). I have it on order with my local dealer, and I will report back if that made any changes.

 

My truck is a 2005 as well, when its cold out it can idle between 2200-2500 at times, common sense tells me it cant be good for an engine to idle that hi on initial startup in 20 degree weather. Ive been dealing with it for years, ive done everything you have mentioned as well as other things. Ive learned to just deal with it at this point, get in it start it up, let it idle for a second or 2 let the clutch out shift in second gear to get the rpms down & go easy on it for a few minutes. When it warms up its fine. Other than that the truck has always ran great...it just keeps going. If anyone has a fix im all ears as well!

 

Just to update, replacing the vacuum line from the intake to the booster made no difference (I unfortunately didn't think it would change anything, but I wanted to try).

Does your truck idle that high when it is 20° outside? Mine goes up to 1500 rpm, then slowly creep up to 1900-2000 rpm then goes back down to a "normal" cold start idle of 1200 (it only last 10-15 seconds). I agree, I don't think it is good for the engine to rev that high on cold starts, but I am not sure what else to try. The only other thing I might try to replace is the throttle body, but according to scan data, it is acting normally.

 

Completely normal, all fuel injected engines idle high when cold. Even old engines with a carburetor did when they were cold and on the choke, not gona hurt anything.

 

Yep, it idles that high when its 20 degrees. Starts around 1500 for a second or so & jumps right to 2200-2500, it would stay there for 20-30 seconds or so if I let it & slowly works its way back down. I have a buddy with the same truck but his is a 2008 & never goes over 1500 no matter how cold it is.