Why does a 2.5L 4 cyl almost die when letting off the throttle?

Question

Standard transmission on a 91 Wrangler. When I let off the throttle to brake it almost dies. Seems to do it more when it is above 90 degrees. Kind of stumped here. Changed out the plugs, wires, and rotor 5 months ago. No other changes. Seems to have come on gradually. Any thoughts or web site ideas would be appreciated.

Answer 1

Sensor problem sounds like. From experience I would take it to a parts store and let them find the fault w/ thier dio computer. It's free at most places. Before you do that check your vacuum lines. The one more importantly then others would be the line from your intake-manifold to your brake booster. gl

Answer 2

im not sure if its on a 1991 or not.  the 2.5 liter is a general motors engine they put in your jeep.  you may want to replace the throttle positioning sensor to level out the idle when you push in the clutch.  it regulates the fuel flow and may fix your idle problem.  if its fuel injected by a throttle body or multiport fuel injection you may need a fuel injection cleaning service.  also you should always change out the distributor cap when you change out the rotor.  there are many times hidden cracks in the cap you cant see that can cause arcing and make it run rougher.  

Answer 3

all good suggestions. Run the codes.(self test:) Not all codes trigger the check engine lite. Im sure there is a code, by the symptoms. Id try injector cleaner like LUCUS too.Does it have a/c? if so, the engine should compesate for the load when u use it.  

Answer 4

Vacuum Leak Check the rubber hose that goes from the manifold to the break booster first and then the rest. you can do this by spraying the hoses with carb cleaner and when the rpm's go up you found the leak

Answer 5

bad fuel flow would do it so add a bottle of fuel treatment and change the fuel filter

Answer 6

Release the park brake!

Answer 7

Throttle position sensor, EGR valve, temp sender, MAP sensor, MAF sensor. Does it have a check engine light?

Answer 8

hmm, a few things, the EGR valve, if malfunctioning, it can over lean or over richen the engine after going at speeds above 45mph.

it can be the tps or throttle position sensor, and it shut the car down because it doesnt know where the peddle is.

or three, you need a new fuel pump relay, belive it or not, but when those relays get hot, either from the sun or from the engine, they loose magnatisim and shut off, no fuel pump, no fuel, no engine.

try the relay first and then get it tested by a good tech if that dont work good luck.