NewbJeep

Hey guys! This forum has been great to me in the past so I thought I'd try again after a failed internet-wide search.

98 Cherokee 4.0L: No codes
If I just bump the accelerator, it surges and moves the vehicle for about 5 seconds without me continuously pressing it, then lets go. Going down the road, same thing. Seems like it'll take awhile to release the accelerator after I let it go. High rpm surge at start up too (2k-3k).

Replaced IAC, TPS with OEM and cleaned the throttle body. Seems worse after replacing TPS today.

Also, using cruise control at 50mph and RPM at about 1900, the RPM will drop to about 1600 then return to 1900, back and forth.

Would a vacuum leak cause this?

HALP!

CCKen

See if the cruise control cable at the TB is binding the throttle linkage.

NewbJeep

If I'm staring at it from the driver side, it's the one all the way to the right, right? Seems to be fine. Butterfly closed

fb97xj1

Cruise cable is the one in the middle of the other two. Grab the clip and pull it towards the end of the cable and it should slide off. Dont pry it off. Disconnect it from the throttle body and give it a slow pull to feel for any binding. Should be nice and smooth. Start the engine with it disconnected and see if the idle holds steady. Should work for the throttle cable, too (engine off). I think that clip uses a ball and socket and pops off. Might be a bit tight.


And make sure the air tube is good and tight at the throttle body. I forgot to push mine back on all the way once (i just sat it over the opening and left it apparently) and idled high next startup. Tightened it back up and all was right again.

NewbJeep

Thanks, fb! I'll take a look. Which throttle body air tube?

fb97xj1

The tube from the air cleaner.

NewbJeep

Gotcha. I've had that off and on during this chase and I think it's seated properly.

Pulled off the cable and it slides pretty easily. No tension or binding at all.

Started engine without cable and seems to run a lot better. What am I looking at? A new cable or do I have to replace the whole asssembly?

NewbJeep

Update:

She was running great yesterday. Sat for two-three hours and when I went to start, nothing but crank and the smell of fuel. Left it sitting over night and got it started this morning but running terrible. Stalled at an intersection after a nice puff of black smoke came out the left side of the engine. Then ran ok once I got it started again. Still high idle.

Fuel regulator and clogged cat?

fb97xj1

Got a code reader? You need something that can read pending codes. Pending codes are faults the computer has detected, but have not happened enough to trigger the CEL. The ability to read live data is always nice as well. I use an Actron cp9670 for my 97.


Checking the cruise cable was easy enough, but there is something else going on. A code reader and a fuel pressure tester will come in handy here. An Actron cp7838, for example.

NewbJeep

Thanks for the reply, fb!

I checked fuel pressure. Dances at right around 45psi and after shutting it down for 5 minutes, it doesn't leak down beyond 35psi. Looks like I'm good there unless that needle dancing is a problem.

I'll check the codes, if there are any. Thanks for the recommendation on the reader.

The cat makes a hell of a rattle so maybe it and the O2 sensors are making her run rich?

I'll keep you posted.

NewbJeep

Measured the upstream O2 sensor and didn't go above .29 volts. I'll start by replacing that

NewbJeep

My cat has been steady rattling for years. Didn't realize they played such a huge role. Ordered a new one and hoping with some time and little aggravation, I can replace it myself. From my research it seems it's partially blocked or at worst, I needed a new one anyway.

Any of you guys think I'm headed in the right direction or am I way off?