Hello. I am looking for some help with a few isues on my truck. It is an '89 F150 with the 4.9L six, 5 speed manual, 2WD, with approximately 153,500 miles on it. I have two concerns.
First, at approximately 1700 rpms the truck runs very rough and surges like it is out of fuel or has too much fuel. Once I accelerate a little more it gets past the surge and seems to smooth out. It does not matter what gear I am in, it just seems to surge at that 1700 rpm mark.
Secondly, the fuel guage jumps around quite a bit and will read full until I get down to a 1/4 tank or so, regardless of how much fuel is in the tank or what tank I am running. I also noticed that the teperature gauge and the oil pressure gauge seem to be both on the low side. I have good pressure and had the radiator, water pump and power sterring pump replace about 20,000 miles ago. I am thinking this is an electrical issue, but I have no idea on where to start.
I am new to this forum (today in fact) and would appreciate and help or advise. I like the truck but this issue has me thinking about an upgrade.
Thank you and I look forward to any response I will receive.

 

The surge sounds to me like a timing chain. They'll stretch and when there's no load on them they will cause a corrolation problem. The oil pressure/temp sensor is located in behind the idler pulley or air conditioning compressor and it could be going bad.

 

I have a mechanic who is going to look at the timing chain as you suggest. Thank you. I am still trying to find the reason all the gauges do not read accurately. I am thinking some sort of short or other electrical issue. Thanks again and if anyone else has any ideas I am open to suggestions.