Went up to get a new project today. About a 200 mile round trip. Heading up, I heard a few thinks but couldn't figure out where they were coming from. They might have been road noise. (I'm hard of hearing.) Coming back loaded, I heard the occasional noise but coming down the interstate, they got constant and I lost power. I pulled over but couldn't see any anomalous movement of anything mechanical. I managed to finish the run by keeping it to 55-60 mph. The CEL blinked three times then stayed on.

I got three codes. Random misfire, misfire cylinder #1 and misfire cylinder #8. My heat kept cycling to defrost on the run. I'm going to pull some plugs and see what they look like. Does this sound like the plenum failing? It's going to be a bit before I can tear into the engine.

 

Might want to take a look into the plenum with the throttle blades opened to see if any oil is puddling on the plenum plate. When was the last time the spark plugs and/or plug wires have been changed?

 

The plugs and wires were on the truck when I got it about 1 1/2 years ago.Lately I've been thinking I might have some slop in the timing chain. I can't go by the odometer as it reads high. At 72 mph the speedometer reads 80. At 40, it reads 45. The odometer keeps pace with the speedometer.

I'll look for oil puddling when I get time to work on the truck. The first thing I'll do is pull plug #1 and see what it looks like. I had planned to wait until spring to pull the timing cover but I may check for slop by hand. I've had engines jump a tooth and keep running but be WAY down on power. I had planned to rebuild the new project first.

Now that I've gotten some sleep, I can look at it better. That last 100 miles with a sick engine worn me out.

 

What year truck? When I changed the gearing in my truck, I swapped out the speedo pinion to the proper gear count to address the speedometer issue, but that only works for '94 - '97 trucks, I believe.

Yes, slack timing chains can cause a motor to be sluggish. Changing out the existing timing chain and gear set to a new double roller timing chain and gear set (along with a timing chain tensioner, if desired) would certainly help if your timing chain set history is unknown.

 

I can't offer suggestions as to cause, but I at least wanted to extend my sympathies and moral support. Never a fun time when that sort of thing happens.

 

The speedometer is run off a sending unit on the transfer case.It's adjustable but even the transmission shop said it's a try and try and keep on trying to get it right if it isn't done right when the transmission is first replaced. The one in my truck is the third transmission and the PO said it read high after the first transmission puked its guts.

I'm leery of the chain anyway. Due to the height of the truck, I'm not looking forward to the tear down and replacement. I've done plenty of timing gears over the last 50+ years. I'm guessing but I think the actual miles are closer to 150,000 miles. It's showing 163,000. No telling when the first transmission was replaced. As soon as I get my new project running good, I'll use it and park the Ram until I can get into the engine.

 

What year truck do you have?

 

You need a different drive gear on the trans sender to fix the spedo. There was a pole on another forum: When did your plenum gasket start leaking? About the 150K mark is when most of them started to go. it's just a matter of time so do the plenum fix and not have to ever worry about it again. What is the new project? Hopefully not another Furd.

 

'97 Dakota Sport extended cab. It's a bit of a dichotomy. Ugly, rusty and the previous owners just put in gas and drove it.




On the other hand, it fired right up with old fuel in the tank, the cab mounts have NO rust (it came from north of me) and the frame doesn't have much. I was originally going to do a "Farmer Chic" paint job like the Ram but around here, red lights are a suggestion. I figure all the soccer moms who cut in and out of traffic all the time won't cut me off. I do always carry insurance, but they don't know that.

 

As was mentioned, since you have a '97 truck, you can fix the speedometer readout by swapping in the correct speedometer pinion gear in the VSS on the side of the transmission (2WD) or the transfer case (4WD). If you can determine the rear end gear ratio and the tire height, you can use this chart to determine the correct pinion gear needed to get the speedometer to read correctly - https://jeepey.com/media/workspace/f...ter-gear_3.pdf

I had to do this to fix my speedometer readout when I installed taller tires and 4.10 gears.