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gijohns_xj
October 23rd, 2006, 19:43
:repair: My son's 91 xj (stock I6 engine and auto tranny) has been really terrible running... from a stand still I can floor it and it will cough and backfire until I hit about 3600 rpm at which point it runs great... It has lost allot of power as well... I have replaced the fuel filter, cap, rotor, spark plugs and checked the plug wires (all good) but it still sputters under 3600 rpm...

Haynes manual said to check the o2 sensor of which I did and there is voltage fluxuating but the two white wires (heating element) are both open.... the motor ran when I had it disconnected and kind of smoothed out when I reconnected it...

what else am I missing? anyone had this problem before?
john
Slo-Sho
October 23rd, 2006, 20:00
Is there dark colored exhaust coming out of it? Maybe a plugged cat?
gijohns_xj
October 23rd, 2006, 20:02
:repair: The exhaust is colorless.. not a plugged cat... or a banana in the tailpipe!
j99xj
October 23rd, 2006, 21:52
Vacuum leaks maybe? Check your intake manifold gasket and throttle body gasket.
mcnamaag
October 24th, 2006, 07:09
Could be you timing chain. Check you harmonic balincer for play by putting a breaker bar on it and GENTLY turning it back and forth. You have to do this with the Dist.Cap off and watch your rotor button. It should turn with the engine with very little or no play.
old_man
October 24th, 2006, 07:39
Has the distributor been pulled for any reason? An indexing problem with the distributor can give you the same symptoms.
gijohns_xj
October 24th, 2006, 17:42
The distributor has not been taken off but I will check for the timing chain it probably hasn't been changed out ever... and it does have 155,000 miles on it...
thanks
2000xj4x4
October 24th, 2006, 18:52
when do you think it is time to change to timing chain?? i have 138,000 on a 2000 sport 4.0
gijohns_xj
October 25th, 2006, 06:02
The manual I have says that the timing chain should be replaced after 100,000 but I know that many go alot further on their chains then that...
mcnamaag
October 25th, 2006, 08:31
Mine has 240,000 and is on its second chain. I think the first chain was done about 90,000 and I just chainged it again at 200,000. I noticed more wear on the first chain than the last one. From what I can remember. I dont think the original chain was made as well as the new one. My tell tale sign was a small amount of hesitation and hard starts when hot then a BIG loss of power.
Risco
October 26th, 2006, 12:45
did you put plugs in wrong direction
gijohns_xj
October 28th, 2006, 19:57
Could be you timing chain. Check you harmonic balincer for play by putting a breaker bar on it and GENTLY turning it back and forth. You have to do this with the Dist.Cap off and watch your rotor button. It should turn with the engine with very little or no play.

And I tried this and guess what... it had almost an inch of play in the chain... so got it replaced.... but have to wait until tomorrow to get the gasket set so I can put it all back together to see if this takes care of the trouble...