terrible running until about 3600 rpm?

G

gijohns_xj

NAXJA Forum User

Location

Layton, Utah

• Oct 24, 2006

• #1

: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

 

S

Slo-Sho

NAXJA Forum User

Location

The 2nd most regulated state.

• Oct 24, 2006

• #2

Is there dark colored exhaust coming out of it? Maybe a plugged cat?

 

G

gijohns_xj

NAXJA Forum User

Location

Layton, Utah

• Oct 24, 2006

• #3

:repair: The exhaust is colorless.. not a plugged cat... or a banana in the tailpipe!

 

J

j99xj

NAXJA Forum User

Location

Colorado Springs, CO, USA

• Oct 24, 2006

• #4

Vacuum leaks maybe? Check your intake manifold gasket and throttle body gasket.

 

mcnamaag

NAXJA Forum User

Location

Red Lion, PA

• Oct 24, 2006

• #5

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

NAXJA Forum User

Location

Loveland, Colorado

• Oct 24, 2006

• #6

Has the distributor been pulled for any reason? An indexing problem with the distributor can give you the same symptoms.

 

G

gijohns_xj

NAXJA Forum User

Location

Layton, Utah

• Oct 25, 2006

• #7

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

 

2

2000xj4x4

NAXJA Forum User

Location

mandeville,La

• Oct 25, 2006

• #8

when do you think it is time to change to timing chain?? i have 138,000 on a 2000 sport 4.0

 

G

gijohns_xj

NAXJA Forum User

Location

Layton, Utah

• Oct 25, 2006

• #9

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

NAXJA Forum User

Location

Red Lion, PA

• Oct 25, 2006

• #10

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.

 

R

Risco

NAXJA Forum User

Location

tampa fl

• Oct 26, 2006

• #11

did you put plugs in wrong direction

 

G

gijohns_xj

NAXJA Forum User

Location

Layton, Utah

• Oct 29, 2006

• #12

mcnamaag said:

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.

Click to expand...

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...