- Truck has been sitting at least 8 hours
- Turn truck on
- Engine idles high immediately, over 2000 rpm
- Check engine light CEL blinks, or flashes 4 times
- Engine then throttles down to almost complete choke
- Engine then goes back up to over 2000 rpm
- Engine finally and steadily lowers to normal idle RPM range
- Total time is around 20 or more seconds

This happens every time the truck sits for at least quite a few hours. Performance wise, it seems to run just fine. I always let it do its thing. But it is very annoying as I've never heard of or experienced this with any other fuel injection vehicle.

I assumed that the engine is just finding its optimal idle point but it does throw that blinking check engine light 4 times, every time.

I have searched all over and can't find what it means. Could anyone please shed some light on this for me please?

Thanks much folks.

 

The cold start operation you discribe is normal within the 30 second time frame in cool outside temps.
Your year was a change-over period to OBDII PCM engine control.
Look under the hood for the decal that tells what the engine onboard diagnostics is.
The flashing mill lamp is the first attempts to signal raw fuel is getting to the cats. Some fueling problem at that time is being detected but then goes away after the ox senosr takes control in closed loop and leans out the fuel..
All later versions of OBDII can give the same signal if there is a problem of raw fuel in the cats.
It could also be a code 44 indication air injection fault that could tie in with the cats not lighing up fast enough. Usually codes don't show up unless requested but you need to find out what system the engine has to be sure.

 

Sounds to me like someone left a jumper in the OBD-1 test plug under the hood or the STI (self test input) pin is shorted to ground.

The four flashes is the code for an 8 cylinder engine. The idle variations are the KOER self test....

Steve

 

Good call. It fits. I mssed the second idle raise in rpm for some reason..

 

Thanks to you both for the reply. As soon as daylight hits, I will check it out. Assuming it is a jumper left in or a short, I hope this will fix the issue.

Once again, thank you for the replies. I will reply once I check under the hood tomorrow.

 

Well, did a tune up today, you know, cleaned TB and associated parts, MAF, oil change, fluid checks, re greased plugs, checked torque on most bolts, changed brakes, detailed things around a bit, checked for shorting or corroded wires, injected seafoam. Everything seems good.

I don't know why but the problem isn't happening right now. I didn't find any shorts or jumper wires left in place to cause the 4 blink error code. I guess I will just have to wait.

By the way, I did a PCM reset. Will I not be able to pull those error codes? I wasn't sure if they were kept alive somewhere else.

I am going to check oil, fuel, coolant pressures tomorrow. Also need to investigate a ticking noise. Hope it isn't an exhaust stud!