Simple power increase?

[Outlaw]

Ok, the motor in question is an 88' with 284K+ miles on it. The vacuum leaks have been found and fixed, and the EGR was replaced today along with removing the solid carbon wall from the top hole in the intake manifold. So heres my question. The motor is tired, it has an overall lack of power, driving it around after getting it to idle and stop misfiring it is slow to accelerate. But in park it will rev through the entire RPM range smoothly and quickly. I was wondering if there are some small things that can be done to help improve this aside from a complete tear down and rebuild. Thanks in advance!

[bigjim350]

How long has it been since you did an ignition tune up. And is it still the original cat converter on it, the tend to get stopped up

[Outlaw]

How long has it been since you did an ignition tune up. And is it still the original cat converter on it, the tend to get stopped up

The Cap & Rotor, plugs, wires, and air filter are all new. I am taking out the Cat****** converter out tomorrow and putting in a cherry bomb type muffler.
(censorship just for you Jim:smiley-laughing021:)

[bigjim350]

Well that should help :thumbsup:

[Thomass]

And is it still the original cat converter on it, the tend to get stopped up

Hmm, I never replaced the thing because they are expensive,
i do hear (read a lot about "cherrybombs") is there a big difference, in output power ? not considering more sound, just for the knowledge...
by law I may remove the cat and replace it even with a pipe if i want to, if the rig is from before 1992 and running on petrol.

[Outlaw]

Ok so I took the exhaust off from the cat back, now it sounds like a damn stock car. But it doesnt have any more get up and go... :( Tomorrow I am going to be doing a compression and leak down test... I guess we will go from there. I am completely stumped though. Everything I know about mechanics tells me if the rings are bad or have a problem with leak down it should be burning oil and smoke at least a little. I guess we will find out.

[bigjim350]

Well ive seen timing chains get enough slack in em that it makes the timing off, but you can usually hear em slapping around in there by then. But if worse comes to worse, a nice Universal Wet shot system works great :thumbsup:
http://www.myhotbimmer.com/productImages_thumbBIG/c2888f67_1147.jpeg

[steph74]

Did you try to seafoam it ?
There are pro and cons especially on an older engine
But I have heard people saying that seafoam in the gas can clean up the injectors and lines and lubricate top of cylinders
Seafoam in the intake system clean up more crap
I don;t advice seafoam in the oil for old engine

[Tural]

just my 2 cents.
freshen it up, but don't add too much power. you have a lot of miles on that motor, and adding more power will add more stress.
i have realized that a lot of renix XJs run 300-400k miles. but most of em are kept stock, that means more than likely they haven't seen much hard abuse.

[4.3LXJ]

Ok so I took the exhaust off from the cat back, now it sounds like a damn stock car. But it doesnt have any more get up and go... :( Tomorrow I am going to be doing a compression and leak down test... I guess we will go from there. I am completely stumped though. Everything I know about mechanics tells me if the rings are bad or have a problem with leak down it should be burning oil and smoke at least a little. I guess we will find out.

How long since you replaced the O2 sensor? They are critical for proper power. Also, if you pull the cat and not have some back pressure there, you will loose power because the ECM is calibrated to have some back pressure there. It is not quite like a carburetor in that area.

[Outlaw]

How long since you replaced the O2 sensor? They are critical for proper power. Also, if you pull the cat and not have some back pressure there, you will loose power because the ECM is calibrated to have some back pressure there. It is not quite like a carburetor in that area.

The O2 sensor hasnt been changed since 88 by the looks of it. I may try that next depending on what the leak down test tells me. My tax money that was gonna by my lift and tires may be going towards a Titan 4.6 stroker.... Hopefully I can do something with the stock motor, I really wanna lift it but the engine needs to be running A LOT better. As it is right now I can barely get the thing to do 55 and that is foot in the floor and manually shifting from low to drive.

[Outlaw]

As far as the back pressure, it wont stay that way. I am putting straight pipe to a "cherrybomb" type muffler. much like jims set up.

[4.3LXJ]

The O2 sensor hasnt been changed since 88 by the looks of it. I may try that next depending on what the leak down test tells me. My tax money that was gonna by my lift and tires may be going towards a Titan 4.6 stroker.... Hopefully I can do something with the stock motor, I really wanna lift it but the engine needs to be running A LOT better. As it is right now I can barely get the thing to do 55 and that is foot in the floor and manually shifting from low to drive.

If that sensor has been there that long, it is almost guaranteed that it is robbing you of power from being too rich or lean. Either way, you will be better off if you change it. They wear out and can do this without giving you a CEL. That happens only if the heater in it goes bad.

[Outlaw]

If that sensor has been there that long, it is almost guaranteed that it is robbing you of power from being too rich or lean. Either way, you will be better off if you change it. They wear out and can do this without giving you a CEL. That happens only if the heater in it goes bad.

I know anything is possible when it comes to ECU's and engine power, I wish everyone could drive it to understand the magnitude of sluggishness I am talking about, but I pulled the plugs today and they are all tan, meaning a good air/fuel mix for those that dont know, so I am perplexed as to what else to do besides yank the darn thing and start from scratch.

[bobt]

Take the cat out of the system. They do plug up and restrict exhaust flow. You will notice the most when you are taxing the engine.No load means low exhaust flow.Thus it may not be noticed.

[XJ4IV]

I concur with JIm, you ought to do an exhaust tune up ... Though I dont condone his ill mannered ILLEGAL ways of having NO CAT...:eek: Just kidding man, If I could get mine to pass state inspection Id be the same gig. as far as the 02 sensor, I nver knew the thing could have THAT bad of an issue as far as robbing of power... I have a regulator on my jeeps injectors so I can run it however I tune it rich, lean of right on... my power is SUBSTANTIALLY higher than it was PRIOR to the 24# injector upgrade, thats a reasonably cheap mod but it wont fixt the issue you have unless your issues are WITH the injectors... which it COULD be!

[bigjim350]

Ohh and after ya get it running right, this is a good upgrade for Renix motors http://www.rockmodified.com/Tech/TB/tb_perf.htm

[easttxhunter]

Did you do the leak down yet? you could have bad valve seats or valve springs may have given up on you and you wont have blow by (burning oil).

[LizardRunner]

If the plugs are good, as you say. The compression and leak down will tell you a lot, as will replacing your worn out O2 sensor. If the compression is ok, then it will likely be the O2 sensor. If that doesn't do it, then the cat could be part of it, but not all of it. It could be a combination of things being wrong at the same time. Like weak valve springs, bad O2 sensor, and plugged up cat. If, the engine sounds strong but doesn't pull it could also be a transmission problem.

[easttxhunter]

If the plugs are good, as you say. The compression and leak down will tell you a lot, as will replacing your worn out O2 sensor. If the compression is ok, then it will likely be the O2 sensor. If that doesn't do it, then the cat could be part of it, but not all of it. It could be a combination of things being wrong at the same time. Like weak valve springs, bad O2 sensor, and plugged up cat. If, the engine sounds strong but doesn't pull it could also be a transmission problem.

good point

[easttxhunter]

I concur with JIm, you ought to do an exhaust tune up ... Though I dont condone his ill mannered ILLEGAL ways of having NO CAT...:eek: Just kidding man, If I could get mine to pass state inspection Id be the same gig. as far as the 02 sensor, I nver knew the thing could have THAT bad of an issue as far as robbing of power... I have a regulator on my jeeps injectors so I can run it however I tune it rich, lean of right on... my power is SUBSTANTIALLY higher than it was PRIOR to the 24# injector upgrade, thats a reasonably cheap mod but it wont fixt the issue you have unless your issues are WITH the injectors... which it COULD be!

Jim just uses mud to pass state inspection. :D