secretshark

Hey so I have a 1997 Jeep Cherokee in-line 6 4.0. It has almost 113k miles on it and recently it’s been having trouble accelerating. The check engine light is on, I checked it right away and it ran 0138. The downstream 02 sensor, I figured no big deal and don’t deal with it till about a week went by and the Jeep started to lag in a way when I went to accelerate. At first it only did this once every time I turned on the Jeep, about a minute or even a few seconds after starting it. I would Push the gas and it would go for a little but then the Jeep wouldn’t accelerate however the rpm would still act as I was accelerating. I then heard a knocking that seemed to be right in front of me when ever it would happen and the Jeep wouldn’t accelerate. I thought it was the transmission until later the Jeep would ideal rough when I would come to a stop for a short period of time. This has became more frequent as almost every time I go to accelerate instead of the first time right after starting the Jeep. I ran the codes again, both 02 sensor codes came up as well as the map sensor code. So now for what I’ve done to try and fix this issue.

Both O2 sensors have been changed.
All three sensors on the throttle body have been replaced
a new catalytic converters has gone in
I swapped out the fuel pump
Pulled and cleaned the fuel injectors and their holes ( none have a crack)
checked my spark plugs and the coil.

If anyone has any idea what could be causing this I would greatly appreciate any information I would like to ovoid taking it to a garage as long as I can if it’s something I can do myself.

fb97xj1

When was its last tuneup? Clean the engine grounds lately? Other things you can do are check for any vacuum leaks, and check the fuel pressure. And what brand sensors did you use? Another thought would be water in the fuel, or even a cracked exhasut manifold, which the O2 sensor could be picking up on. Not sure about the knocking up front. could be the engine, or in the suspension, etc.. Crawl under and see if anything is loose, or rubbing something it shouldnt.

secretshark

Last tune up was at 96k miles I’ll check the grounds, fixed a vacuum leak when I replaced the throttle body sensors. I’ll have to check for the exhaust manifold crack. I did run two things of dry gas through the car to clear up any water that could have been in the fuel.

third coast

* Has any other engine related work been done before current problems developed?
* Did any of the spark plugs look much different than the others?
* Does it idle and rev up normally in park?
* No critters have moved into the air box, restricting air flow?
* Check the distributor cap, rotor, etc?
* Ground connections, sensor wires
* As mentioned in previous post investigate for significant vacuum leaks, including around the intake manifold gasket and from the brake booster. Visually compare what you see to the vacuum diagram, looking for anything missing.
* Do a combustion gas test of the cooling system. This will help determine if you might have a bad head gasket. You can loan one from major auto parts stores and it is a quick and easy check. You will need to buy the test fluid for arout $13. Napa has it if others do not.
* Do a compression test. You can get a loaner from major auto parts stores.
* Intermittent or weak crank position sensor is a maybe but usually they show up as a complete shutdown or no start.

gat

I would check for cracks or holes in the intake boot. If too much air is coming into the system then it throws that fuel to air ratio. Ensure that the intake manifold is secure and without cracks. Ensure that the housing for the air box is the same. Also, verify that the throttle body is well seated so that no air is rushing past it. Check all clamps for tightness.

Dave51

Reboot the ECU.

jordan96xj

When was the last time you checked your transmission fluid for level and condition?

Dave51

What was the condition of the cats? Were the insides disintegrating? Check the length of the exhaust system for clogs and/or measure vacuum during rev.

secretshark

Transmission fluid was one of the first things I checked, the levels were fine. The old cat had no more screen inside of it when I took it off. The whole exhaust is now new besides for the exhaust manifold. I’ve disconnected the battery plenty of times and cleared the codes as well with a code reader. Still having issues accelerating.

Dave51

Got a scanner? Measure the fuel trims when it's acting out. Perhaps we can at least cut the search area by half (if it really is the engine). Get some noids and check electricity for the fuel injectors. What's the timing doing while this is going on? What brand of O2 sensors are you using?

BillyBoy

Distribute cap and rotor = 5bucks and 10 minutes...

BlueRidgeMark

Good thing to check. Also the dizzy bushing can go bye-bye, leading to lots of running problems. There is a Cam Positioning Sensor in there that can get wiped out by the rotor if the bushing has too much slop in it.

secretshark

I replaced the cap and rotor that wasn’t the problem still having issues. The cam shaft sensor I replaced as of two months ago. I know that isn’t the problem because I got a code for it last time and the car had issues starting when that went. The car starts with no problem. The fuel pressure is 44 with key turned and engine off. Then with engine on the gauge fluctuates between 30-50 pretty fast.

gat

"Fuel pressure should be 44.2-54.2 psi" - https://www.2carpros.com/questions/j...pressure-specs

That was for a 1998, but I believe that it also applies to your year. Your pump and pressure regulator should all be one assembly to replace. The filter sock may only come separately.

rgs80074

ok,

not sure this applies and is kinda out in left field but this is kinda what happened to my jeep.

i have a 1996 grand cherokee, the ac compressor bearings are going bad. if you accidentally turned on the ac even if you turned it off really quick the vehicle had very poor acceleration. seemed like if you disconnected the battery for a while it would go back to normal.

it went this way on and off for months where it would do this periodically, most times i swore i had not turned on the ac.

turned out i had a caliper sticking, this caused the vehicle to have poor acceleration due to the brakes not being released, but in the beginning it was not a major sticking so nothing with brakes came to mind, no real pulling, no burning smell, etc. a few weeks ago it froze up completely and i had to replace the caliper. i did both front calipers, new pads, etc. the drivers side really was sticking, then it would be fine then stick hard again.

it just made me wonder how many of those other times i assumed it was the ac bearings causing some issue that it was the calipers starting to bind up.

this might be something you want to check if you've got the time, it should be easy to see if this is the problem and other than time there is no cost to check if you do it yourself.