After I do any heavy hauling with my truck, its somewhat hard to start. This only happens when I'm pulling a trailer, or have a load in excess of about a ton and a half on it. In normal driving, this doesn't really occur.

Sometimes, when I start to crank it, it will start to fire, sputter, then drop down and stumble at 200-300rpm for a second or so, then stall. Other times, it will crank for a few seconds, then rev up close to redline, then drop back down and be fine. I'm always able to get it started after just a few seconds, and then it runs fine. Opening the throttle a little doesn't seem to help at all.

I have occasionally noticed a tapping from the exhaust at idle, like a bad valve. Maybe its just sticking or something, because it doesn't always happen. I doubt this would be related though. Also, I'm running a 180 degree thermostat.

Either way, an overview is: hard to start when overworked, still runs strong with no missing, and has occasional tapping noise from the exhaust.

Thanks for any ideas.

 

have you checked the plugs?

 

I just did after I posted that. They all look the same (edit: and good), except one was ever so slightly cleaner looking than the rest. Still toasted, but not as much. The exhaust pulse was constant. I stuck a rag in front of the pipe, and it was just blowing out. It never sucked it back like a stuck valve.

 

Engines can be hard to start when they over heat. Mine can be hard to start just after I work it extremely hard. I have never experienced the change in RPMs that you are. It sounds like something in the idle control circuit is having a problem with the extra heat generated by the heavy loads.

 

That sounds like a good explanation, and a comforting one. It didn't happen as much until it warmed up this spring. And I haven't really worked it this hard until recently. It always runs cool when I'm constantly moving over 15mph. I was delivering flyers in newspapers boxes a few weeks ago, and it did heat up, but not to where it was alarming. The temperature gauge also seems to go up when it sits. Thanks