1995/2.3 Cold weather starts

[jet_doctor]

Hello,
My cold start problem seems to be unique to some of the other ones I've read. As the outside temp decreases the problem shows itself and gets worse as the temp decreases further. Normally, when you start the engine the rpm runs over the 2500 rpm mark and then stabilizes at 1500. With mine as the temp gets down around the freezing mark the truck fires up and runs at a very low rpm (around 1000 or less) and then after 5-10 seconds the engine will surge to 2500 rpm and then stabilize at a normal idle rpm. As the temp drops further the engine goes into a surge/falter cycle decreasing in severity until it runs normally. When it gets really cold the engine will sometimes quit before it gets to that first initial surge, in which case a re-start gets me going. One clue is that having the block heater plugged in hides the problem when the weather is extremely cold. I have never experienced any power loss while driving. So far the fuel filter has been changed, its had a fuel system treatment and the ECM software was updated...No joy.

Any advice is appreciated. Thanks in advance

 

[TireIron]

what weight oil do you run in it? and how old is your battery?

 

[jet_doctor]

I run Mobil 1 5W30, have been since I got the truck in '96. Battery is less than two years old. The problem was a little annoying at first, but has been getting worse over the past two seasons

 

[TireIron]

the IAC valve may be sticking, it is a film canister sized valve with two wires attached to it bolted onto the throttle body with two bolts. You can try pulling it off and cleaning it out with some good carb cleaner and getting all the carbon out of it.

 

[shadetree]

Check the engine coolant temperature(ECT) sensor circuit. shady

 

[HAPPY_RANGER_GUY]

Hello,
... Normally, when you start the engine the rpm runs over the 2500 rpm mark and then stabilizes at 1500...

1500 is too high for a "normal" stabilizing rpm. Should see 650-1000 rpm normally.

T.

 

[TireIron]

when the engine is cold it will sit at 1500 for a few minutes while it starts to warm up then it will drop to its usual 800 or so if you don't touch the gas pedal.

 

[HAPPY_RANGER_GUY]

when the engine is cold it will sit at 1500 for a few minutes while it starts to warm up then it will drop to its usual 800 or so if you don't touch the gas pedal.

That's what i said...1500 is too high for normal stabilizing idle rpm.

T.

 

[jet_doctor]

Thanks for all of the prompt responces,

I apologize, my figures for the idle may have been a little inaccurate. I was more concerned about the delayed surging and faltering. Both of you are correct, 1500 is too high for a stabilized idle and the idle rpm does descend in stages. Mine seems to want to hang around the 900 to 1100 mark after a short warm up. Anyways, yesterday I changed the fuel pressure regulator, the ECT sensor, and the PCV valve(the old one was perfect). The engine seems to be running a bit better, both in the starting and it seems to have recovered some power I hadn't noticed was missing. Not sure yet if the problem is solved this morning wasn't cold enough to give me the warm and fuzzies. If I get the chance tonight, I'm going to clean out the IAC valve. I also noticed that the engine is pinging since the new parts have been installed. Do your engines ping on 87 octane fuel? I remember when I got the truck I had to run mid-grade to get rid of it. We are at a pretty high altitude here...about 3500'ASL. Stay tuned I'll let you guys know what happens over the next few days, the temperature is supposed to drop a bit.

Thanks again for all the advice.