Hey everyone, Added some Lucas fuel system cleaner to new tank of gas this morning trying to clean some stuff out. I have been prolonging getting the heads rebuilt as much as possible. After I got on the freeway I noticed what feels likea major misfire and a major loss of power. It was already having issues with a tapping lifter which is why I was going to rebuild at the same time. Is this a common thing when using fuel additives or am I experiencing something completely different?

I also have a lead on a used 3.9 for 1K with only 96K on it as a long block. Should I just scrap the current engine and go with one that I know is running right or could I just be experiancing a wierd fuel issue that can be fixed?

Thanks for all your help in advance.

 

Forgot to add, it is a 94 3.9 with 152K on it.

 

When did you last change your fuel filter, any gas additive on a dirty filter can help plug them up as junk in the tank is broken down.

 

I did the fuel filter about 1000 miles ago. I had also had some random dying issues that seemed like it was fuel related but then I thought more about it since I had good fuel pressure. I changed the O2 sensors and then that issue went away. I have changed to magnacores, Plat 4s, new cap and rotor, new coil and did another ATF flush in the past 2000 miles. I still have the tick that plagues me but when I drive on the freeway the engine seems to only run on about 6 cylinders. When I get off the freeway and drive it for about 20 minutes at around 35 then the miss seems to go away. I know I have a lot of build up in the heads, I took off the valve covers and just about had a heart attack, so I know the previous owner left oil in there a long time. I was going to do the heads but I am thinking that maybe this pother engine is a better deal for me, the guy who has it is pulling it out of his Defender to put in a 4.6.

I am beginning to think that the heads are causing my issues and cost for cost it may be more sensible for the other engine. Any other ideas though is greatly appreciated.

 

Well if you have water in your gas tank the fuel additive will "soak" it up and cause it to be burned and if you have a exsessive amount of water this can cause rough run issues.
Run this tank until the low fuel light comes on and then fill up again without additive and see what happens.

 

That is a possibility, I will run it down and then see what happens. I ran it down til the light right before I put it in and then it was within the first 10 miles it started. I guess time iwll tell. Thanks.