I know diagnosing engine troubles is difficult if not impossible to do online. My hope is that someone here will be able to recognize the symptoms and steer me in the right direction.

When I start my truck, it cranks and starts properly. Usually, in the first few seconds the engine is running, the engine will seem to shudder and run a little rough like its going to stall. Very rarely, it does stall out. Most of the time a tap on the accelerator will correct the problem.

The battery is an almost new Optima red top. Nothing else in the starting/electrical/engine systems has ever been replaced.

In the life of my truck I have had a bad O2 sensor and, recently, a vacuum leak which was fixed. This problem developed several weeks after the vacuum leak was repairs so I don't think its related.

I am not savvy on engines. I am just looking for some guidance on possible causes and stuff so I know if the repair shop is trying to sell me a pile of manure when I take it in.

Oh yeah, I am at 93K miles.

 

man, my 1998 ranger did that at about 145,000 miles the idle control motor was going out on it, it would crank then stall, then crank and gas it and it was stay running, at 93k miles changin those front 02's wouldnt hurt any, hope this helps man,

 

Not sure if you have an IAC idle air controller on that model, but my 99 5.4 did the same thing. Cleaning the iac and reinstalling it solved the issue

 

IAC cleaning will temporarily help, just replace it with a new one. Check for vacuum leaks. You could try to get some codes out of it, next time it does the rough idle...let it continue, don't give it any gas.

 

Thanks for the replies guys, I appreciate it. Gives me a starting point.


Could this be just as simple as a lack of air? It dawned on me last night that I am significantly over due to clean my K&N filter.

 

Agreed - That's IAC all the way

Use my galleries - I think all the IAC pics are in gallery one ? -

https://www.f150online.com/galleries....cfm?gnum=7538

 

i'm thinking iac or coolant temp sensor.

 

O2's don't use one of those. They use the Cylinder Head Temp Sensor (CHT) to cipher. Unless that's what you meant

 

yeah thats what i meant i'm just use to pre-97 and other vehicles having coolant temp sensors.

 

Yea that changed in 99 in the 5fours - Not sure when the 4sixes eliminated that -00/01 prolly when PI's & COP Ignition systems were incorporated.

 

Well, as most of you said... IAC was bad.

Thanks for the advice, you were right on.