Rough running when cold
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Rough running when cold
Hey all... New guy here after getting referred to the forum by another user.
Having an issue with my '97 powerstroke that I've never seen before. This is the 3rd 7.3 I've owned and never encountered this. When the air temp is cold, 30ish or below, the truck seems to runs way worse. The truck will idle just fine, but when I start to go, it seems like something opens up, I get a noticeable noise coming through the airbox, truck looses power and exhaust gets loud. It will continue while trying to hold constant RPM's and will shut only when I get on it and increase speed/rpm's, but as soon as I let out and try to hold constant speed again, it opens up and again... Loss of power and noise coming through airbox. I only figured out yesterday that it was coming through airbox when having the wife ramp of the RPM's and hold it while setting still in the driveway. The only thing that's different on this truck from the others I've owned, is there is a K&N Air Raid system installed on the truck. (Was on there when I bought it). After the truck runs down the road for a while (30 min or so) it will stop. Also, If I drive the truck a little ways and then shut it off and restart, it won't do it. Almost like I'm resetting something by shutting it down. I thought maybe it was something to help the truck warm up and I wouldn't be that worried about it if I had seen/heard it on my other trucks I've owned. It's just extremely loud and burns a lot more fuel while this is going on and almost makes the turbo sound like nails on a chaulk board out of the exhaust. I do have straight open exhaust on the truck to, which makes it sound way worse I guess. I thought about finding a stock airbox and installing that to see if maybe it's getting to much air, but I'm really at a loss. Any suggestions would be greatly appreciatted.
Having an issue with my '97 powerstroke that I've never seen before. This is the 3rd 7.3 I've owned and never encountered this. When the air temp is cold, 30ish or below, the truck seems to runs way worse. The truck will idle just fine, but when I start to go, it seems like something opens up, I get a noticeable noise coming through the airbox, truck looses power and exhaust gets loud. It will continue while trying to hold constant RPM's and will shut only when I get on it and increase speed/rpm's, but as soon as I let out and try to hold constant speed again, it opens up and again... Loss of power and noise coming through airbox. I only figured out yesterday that it was coming through airbox when having the wife ramp of the RPM's and hold it while setting still in the driveway. The only thing that's different on this truck from the others I've owned, is there is a K&N Air Raid system installed on the truck. (Was on there when I bought it). After the truck runs down the road for a while (30 min or so) it will stop. Also, If I drive the truck a little ways and then shut it off and restart, it won't do it. Almost like I'm resetting something by shutting it down. I thought maybe it was something to help the truck warm up and I wouldn't be that worried about it if I had seen/heard it on my other trucks I've owned. It's just extremely loud and burns a lot more fuel while this is going on and almost makes the turbo sound like nails on a chaulk board out of the exhaust. I do have straight open exhaust on the truck to, which makes it sound way worse I guess. I thought about finding a stock airbox and installing that to see if maybe it's getting to much air, but I'm really at a loss. Any suggestions would be greatly appreciatted.
Postmaster
Joined: Sep 2007
Posts: 4,195
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From: Medford Oregon
First, Welcome to FTE ...
The sound and feel you are experiencing is indeed the EBPV (exhaust back pressure valve) closing to aid in rapid warm up. This valve is just after the turbo that closes on cold mornings. Both air and oil temp must be below a certain value before it is activated. Once it is activated the computer is pretty stubborn and insists on activating it until oil temp is at about 170 degrees. If you go a little ways and shut off the truck the oil temp is probably above 37 degrees so on restarting it does not activate.
As you mentioned it only activates on light throttle demand such as cruising. Give it a little power or brake and the valve opens. It can be a bit disturbing when it first occurs and you don't know what is happening. Bottom line is it's doing what is was designed to do and does indeed help in rapid warm up.
Some people just unplug it. There is a two wire plug at the base of the turbo. If you unplug that connector then the PCM will ignore the function and not close the valve. I like the function but to each his own. You may have noticed when you first start the truck the PCM cycles that valve and you can hear that noise briefly. It is a self check that it is working properly. Also if you plug in the block heater the oil temp will be above 37 degrees so it won't occur unless you live in really .. really cold climates.
The sound and feel you are experiencing is indeed the EBPV (exhaust back pressure valve) closing to aid in rapid warm up. This valve is just after the turbo that closes on cold mornings. Both air and oil temp must be below a certain value before it is activated. Once it is activated the computer is pretty stubborn and insists on activating it until oil temp is at about 170 degrees. If you go a little ways and shut off the truck the oil temp is probably above 37 degrees so on restarting it does not activate.
As you mentioned it only activates on light throttle demand such as cruising. Give it a little power or brake and the valve opens. It can be a bit disturbing when it first occurs and you don't know what is happening. Bottom line is it's doing what is was designed to do and does indeed help in rapid warm up.
Some people just unplug it. There is a two wire plug at the base of the turbo. If you unplug that connector then the PCM will ignore the function and not close the valve. I like the function but to each his own. You may have noticed when you first start the truck the PCM cycles that valve and you can hear that noise briefly. It is a self check that it is working properly. Also if you plug in the block heater the oil temp will be above 37 degrees so it won't occur unless you live in really .. really cold climates.
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Sweet.... Thanks for the quick response. I figured it was doing what it was suppose to, I just don't remember any of my other trucks doing it so I was a little curious as to what it was and wanted to make sure it was normal. I'll probably leave it hooked up so it can operate properly. I have been plugging the truck in, but we have already experienced negative temps and it still does it. I have an oil pan heater, trans heater and 2 battery heaters on order. Hopefully, heating up the oil directly will help. Thanks again for your reply.
