Need Help, 92 XJ Sport Hard to Start; Rough Idle

[rumncoke2004]

First of all, here's the specs:

92 XJ Sport
78,000 miles
4.0 I6 Auto

I've had it for about a year and half now. Always ran fine, then in the last 30 days, it has become hard to start, requiring to crank it for at least 10 seconds before the engine turns. I can hear the starter turning and the fuel pump priming when I turn the key. Usually I turn the key more than once to prime the fuel pump even more; seems to start better when I do. Have recently replaced spark plugs, plug wires, and battery, but these problems were beginning before all that. Have checked the electrical connections to the starter, ignition coil, and starter relay, all seem fine. Have also replaced the fuel filter within the last 10 days, and it made no impact.

Also, now it runs like crap, idles rough. While at idle, the RPM's drop below a 1000, and the roughness begins. After a few seconds, it will rise to 1000 or a little above, stay there for about ten seconds then drop below 1000 again.
While driving, it feels like I've lost a lot of power. Upon accelerating, the RPM's rise real high (4000-5000), and then the engine stumbles, I loose acceleration and the RPM's drop; even if I gas the pedal hard, If I gas the pedal to the floor, the engine jerks and just scares the sh** out of me, so I back off.

I have limited experience and knowledge on my XJ, but I want to get it running right before the end of next month, without blowing a lot of money replacing parts that aren't necessarily the problem. I am moving at the end of May, because the Marine Corps is telling me to ship out to North Carolina.
Need to get it running right for the trip cross country. The wife wants me to get rid of it, but what she doesn't know is I would get rid of her because I sell my XJ.

Any of you in the Omaha/Bellevue, NE area that can offer any assistance, your help is greatly appreciated.

[Aziraphale]

Mine did something similar recently. I thought it was the Cat clogged but a muffler shop said it was fine. I ended up putting fuel injector cleaner in the gas tank 2 fill ups in a row and now it runs great. Give it a shot ... if it doesn't work, you are only out a few bucks.

[Dirt]

yeah i think its a clogged CAT or mabey an EGR malfunction probably the convertor though. can take the exaust loose from the manifold and drive it around the block to see. It may set the check engine light but you can disconnect the battery for a couple a minutes to remedy that. If the problem persist check your fuel pres. The fuel pump running does not constitute proper fuel pres. And Egr malfunctions usually only make the vehicle act up at idle if the valve is sticking. Good luck DIRT

[Matthew Currie]

Originally Posted by dirt714

yeah i think its a clogged CAT or mabey an EGR malfunction probably the convertor though. can take the exaust loose from the manifold and drive it around the block to see. It may set the check engine light but you can disconnect the battery for a couple a minutes to remedy that. If the problem persist check your fuel pres. The fuel pump running does not constitute proper fuel pres. And Egr malfunctions usually only make the vehicle act up at idle if the valve is sticking. Good luck DIRT

It isn't an EGR malfunction because a 92 does not have an EGR.

[rianardo]

No EGR, yes...but I would still check the hoses coming off the valve cover to make sure they're clear and free-flowing. Also, I'm just shooting in the dark but does the 4.0 have an oxygen sensor that can wear out and cause these problems? I know a bad one on a Nissan I owned really made the engine run like crap.

Cheers,
R.

[Matthew Currie]

Originally Posted by rianardo

No EGR, yes...but I would still check the hoses coming off the valve cover to make sure they're clear and free-flowing. Also, I'm just shooting in the dark but does the 4.0 have an oxygen sensor that can wear out and cause these problems? I know a bad one on a Nissan I owned really made the engine run like crap.

Cheers,
R.

There is indeed an O2 sensor and it could be one problem. So might the MAP sensor. If they fail outright they should set a code, but if they just go out of tune they may not. I had a MAP sensor problem that did not set a code, but caused missing at low vacuum under load. I don't think bad crankcase vent hoses would cause that much problem, but they should be checked anyway, as should the little rubber elbows that connect them. So should all other vacuum lines.