Hi all great site. i have a xj with 160000 miles on it. It is hard to start and recently started to backfire and has no power when accelerating. i changed the cps still runs the same checked all the air lines i tested the tps and the cam position sensor and they seem to be fine any ideas. thanks again

 

help please

 

First off welcome to CF. One bit of advise is we have no clue what you have. What year what kind of motor and what not. More info is needed. Thanks.

EDIT: well from your sig I take it you have a 89 which is a renix is it the 4.0L

 

I would check your spark plugs and make sure their gapped properly. Wire order or timing as well, have you taken out the distributor lately?

 

Dunno if the 89 Renix era has O2 sensors or not but if so might check that as well..

 

thanks sorry for the lack of info. it is an 89 with a 4.0L was running fine tell the other night about half way home from work (only about 6 miles) then it started to backfire when accelerating had to floor it to get it to go then it would but even then it would only go a little then it was i=klike i was just coasting had to keep pumping the peddel to get it home. it had a tune up 10k ago and the o2 sensor was replaced at the same time

 

i forgot to add its an auto and runs fine in park it just runs like @#$% when in gear

 

Maybe a fuel pump? When in park the engine has little to no load on it, however in gear there is a load and something can't keep up.

I have a similar problem with my 93 4.0 when it gets warm.. it doesn't die but won't hardly get out of its own way. Still havent tracked down the problem and have changed the CPS as well..I am leaning to the fuel pump...

Is yours noisy? Mine is.

 

Check spark plugs, wires and pop off dist. cap and look at contacts.

Also, check your rotor's contacts.

These are cheap and very easy things to check first.

If contacts are nasty looking, they can be cleaned with a flap-sander wheel (1 1/4"dia.) on a cordless drill. Just enough to make em shiny. No more than that otherwise you will be creating more of a gap for the spark to arc across.

I check mine everytime I change oil.


This message has been certified "Non-abrasive"

 

I had the same problem pull the valve cover off and push down on the push rods to see if you can push any of them down.If so you need to change out the cam and lifters.

 

thanks for all the help everyone. prerunner the pump seams quiet to me. that got me thinking so i checked the fuel pressure and its only at 10 psi even of your pressing on the gas i think the book said it needs to be at 30 psi. thanks again for all the help.

 

if your backfire is coming from under the hood and not the exhaust it is definitely running too lean. (not enough gas) so the fuel pump is probably your issue. if you replace that and still have problems i would look into fuel pressure regulator. that was the problem when my car was running lean.

 

I can tell you a bad fuel pressure regulator will cause backfire but it's gotta be leaking aswell...

 

1-Fuel pump
2-Fuel Filter
3-Fuel regulator
4-dirty TB
5-ignition components

This is the order I would approach your problem in.
HTH
Blue

 

Don't forget to run some seafoam through it when you are done