99 jeep Cherokee XJ issue

jeep
cherokee

#1

Have a concern about my vehicle it doesn’t happen all the time and sometimes it’ll happen for a few days and then go weeks before it happens again. Upon hitting the Excelerator it will sometimes bogged down spit Potter and backfire and just kind of bogged down. I have to stomp the pedal to get it back up to throw in some fuel at it to get it going again but it’ll sometimes even while driving it will lack and spotter Too. But then it will go off a week or so without acting up at all . It typically seems to happen when it’s really hot out not so much when it’s cooler or in the winter . I know it’s not the fuel pump, I have replaced the map sensor but I’m getting tired of this little gremlin that wants to mess with me here and there LOL. Anyone’s help or suggestions would be appreciated thank you. I’m happy to be part of the this group


#2

When you stomp on the accelerator a lot of air goes into the engine. If you’ve got a vacuum leak too, all that air can lean out the mixture so much the injectors can’t keep up, and this symptom could result. There’s sort of a system mehcanics use to check for vacuum leaks. You’ve got to check all the lines and connections, but also the vacuum operated gadgets too. The power brake booster is one gadget that can really through the engine computer for a loop mixture-wise if the diaphragm leaks and allows unmetered air directly into the intake manifold.

If you have a way to measure the fuel trim, that would provide a clue if you if you have a vacuum leak going on.

The other thing that happens when you stomp on the gas, the EGR valve (if you have one) actuates. But it doesn’t usually open if the engine is cold. So since this happens when it is hot outside, but not so much when it is cold, that’s a possibility.

The next thing to look for, when you step on the gas the engine computer realizes this and compensates b/c of the throttle position sensor. But if TPS wasn’t working correctly, this symptom could result.

Make sure you’ve read out the diagnostic codes, that’s where to start of course.


#3

(it will lack and spotter Too ) I have no idea what that means.


#4

More information is needed. During what period of operation and for how long does the problem occur?

If this occurs only during the first two minutes of operation it is a common slow oxygen sensor input problem. The PCM switches to closed loop and the oxygen sensor is not functioning yet, this results in a lean condition for the moment.


#5

Vacuum leaks are decreased when the throttle is opened, there is less vacuum. Vacuum leaks are a greater problem during idle or cruise when the vacuum is high.


#6

Rough translation “Lag and sputter too”.


#7

I have to defer to J.K Rowling on this issue…

:smirk:


#8

Very true. When my Ford truck gets a vacuum leak, the problem is most noticeable at idle. But when it has a vacuum leak, it also exhibits the same symptom as the OP, when I step on the gas, it tends to stall out. In fact sometimes it does just that. Fixing the vacuum leak solves both both, the idle and the stall out during acceleration problem.