98 Wrangler bucking


#1

My Jeep intermittently bucks while driving and in some cases idles rough. The dilemma

is the check engine light is not triggered for any faults making it difficult to locate the problem. Sometimes it misses

at idle either warm or cold but not bad enough to stall. However,

driving down the road it looses power completely for 5-10sec sometimes

popping though the throttle body and could be described as “bucking”.



A new crank sensor and fuel pump have been installed. It also

has new plugs cap and wires. All these problems are

very intermittent and it runs perfect otherwise. I have had days go by where it ran perfectly with

no issues. The shop were I had the fuel pump installed could not experience the problem

long enough to figure out.



I was going to try changing out parts … and wanted to

get some advise here. I was thinking about starting with the

MAP sensor… but if that where defective the check engine light

would be on right?.. so maybe try the coil and ignition module? I suppose some ignition problems could be undetectable by the ECM?.. help!


#2

oh its the 2.5 4cyl


#3

Perhaps changing out the fuel pump relay will fix the trouble.