pingpong Posted March 24, 2008 Share Posted March 24, 2008 Well I have beat my head against the wall trying to figure this out. Ride is a 90 my with 2.5 and a 4 spd the issue is it will just cut off while driving. so far it has only happened when I let off the gas, but she runs fine at idle, so far I have done an ignition tune up. I really don't know much about the rig, but It appears to have had the intake and head off, for what reason I do not know. She does burn oil ( know this by she smokes a lil, and has a anti fouling plug thing on it) any help would be appreciated... the wife likes this ride, and if I don't figure it out soon.. I will be selling it Link to comment Share on other sites More sharing options...
Geonovast Posted March 24, 2008 Share Posted March 24, 2008 It can't run without a head or intake on it... Link to comment Share on other sites More sharing options...
brigarpeon Posted March 24, 2008 Share Posted March 24, 2008 Did you check Fuel pump pressure and/or replace the fuel filter? My Comanche had a severely clogged filter that did the same thing, stalled off load. Later the fuel pump when bad, we deduced from trying to push through the clogged filter. Less than 15 psi on the pump at the maximum adjustment of the regulator could be the problem. The only other thing that comes to mind would be a possible vaccum leak. Link to comment Share on other sites More sharing options...
Eagle Posted March 24, 2008 Share Posted March 24, 2008 Got a better description of the symptoms? Does "cuts off" mean the ignition stops firing completely? If it cuts off when your foot is off the gas, does it cut back on when you step on the gas? Link to comment Share on other sites More sharing options...
Geonovast Posted March 24, 2008 Share Posted March 24, 2008 Both my 88 and 89 4.0 XJs had problems with the engine dying when you'd push in the clutch and not feather the gas. Never figured it out. Some suggestions that had been made to me were a bad IAC. Link to comment Share on other sites More sharing options...
pingpong Posted March 25, 2008 Author Share Posted March 25, 2008 Got a better description of the symptoms? Does "cuts off" mean the ignition stops firing completely? If it cuts off when your foot is off the gas, does it cut back on when you step on the gas? BY cut off I mean engine stops running, then I pop the clutch and she starts right back up. So far it seems that it could be either the IAC, or he fuel pump.... at least that is what I kinda figured before too, just don't want to through parts at a problem if I am not sure what it is. Time to go buy a new tool .... fuel pressure tester :D Link to comment Share on other sites More sharing options...
tjbliley Posted March 26, 2008 Share Posted March 26, 2008 I have one here but I won't be in D'ville for a week or two minimum. My buddy might be there at Bushc park later in the week. I will see and send it if you want. Link to comment Share on other sites More sharing options...
aemsee Posted March 26, 2008 Share Posted March 26, 2008 highly doubt fuel pump. Fuel pressure issues will usually have a stumble or stutter before die out. And don't normally start right back up. Sounds as though could be more of an electrical thing, or IAC issue. Is 90 2.5 still TBI, or was it switched to multiport by then? If still TBI, then you don't have an airflow type IAC, but a stepper motor. These were very problematic and would cause a off the gas stall out like you describe. Link to comment Share on other sites More sharing options...
pingpong Posted March 26, 2008 Author Share Posted March 26, 2008 is there any way to test the IAC? Yes it is a tbi setup. TJ do you have a fuel pump.. or a spare IAC.. if you have a spare IAC I will try that :brows: Link to comment Share on other sites More sharing options...
mjeff87 Posted March 26, 2008 Share Posted March 26, 2008 Pat, you can have my IAC, but it'll be attached to the engine.....in about a month :D Jeff Link to comment Share on other sites More sharing options...
brigarpeon Posted March 26, 2008 Share Posted March 26, 2008 Here ya go for the tests, failure in any part of the process is a replace. IDLE SPEED ACTUATOR (ISA) MOTOR 1) Adjust ISA motor plunger to establish initial position of plunger only if motor has been removed or replaced. Remove air filter elbow and start engine. Run engine until engine reaches normal operating temperature. Turn A/C off (if equipped). 2) Connect tachometer leads to diagnostic connector D1, attaching negative lead to terminal D1-3 and positive lead to terminal D1-1. Turn ignition off. ISA motor plunger should move to fully extended position. 3) When ISA motor plunger is fully extended, disconnect ISA motor wiring connector and start engine. Engine speed should be 3300-3700 RPM. If incorrect, turn hex head screw at end of plunger to provide engine speed of 3500 RPM. 4) Fully retract ISA motor by holding closed throttle (idle) switch plunger inward as throttle is opened. Closed throttle switch plunger should not touch throttle lever in closed position. If contact is made, check linkage and/or cable for binding or damage. Repair as necessary. 5) Connect ISA motor wiring harness connector and turn ignition off for 10 seconds. ISA motor should move to fully extended position. Start engine. Engine speed should be 3500 RPM for short period of time and then decrease to normal idle speed. 6) Turn ignition off. Disconnect tachometer. After final adjustment of ISA motor, use thread penetrating sealant (Loctite 290) on adjustment screw to prevent movement and maintain adjustment. NOTE: If adjustment screw must be moved after thread sealant hardens, loosen threads by heating screw with flameless heat such as soldering gun. DO NOT use flame or torch type of heat as damage to ISA motor will result. FUEL PRESSURE REGULATOR WARNING: Always relieve residual fuel pressure in fuel delivery system before opening system. To prevent chance of personal injury, cover fittings with shop towel while disconnecting fittings. 1) Replacement fuel pressure regulator must be adjusted to establish correct pressure. Remove air filter elbow and hose. Connect tachometer leads to diagnostic connector D1, attaching negative lead to terminal D1-3 and positive lead to terminal D1-1. Remove screw plug and install fuel pressure test fitting. NOTE: Fuel pressure test fitting is not included with throttle body. Fitting (8983 501 572) must be obtained separately. 2) Connect fuel pressure gauge to test fitting. Start engine and increase speed to approximately 2000 RPM. Turn Torx head screw at bottom of regulator to set correct pressure. Turning screw inward increases pressure and turning screw outward decreases pressure. 3) All models require fuel pressure of 14.5 psi Install lead sealing ball to cover regulator adjustment screw after adjusting fuel pressure. Turn ignition off. Remove measuring equipment and test fitting. Install original plug screw and air filter assembly. Funny but when my filter clogged it stalled outta the gas, when the fuel pump went it stuttered under load or pulling out. When the IAC/ISA motor went out the throttle wouldn't respond to being pushed normally but you could get it moving by revving the crap out of it. Lotsa info here http://jeepgarage.free.fr/OWN/fuel%20injection%20system%20tbi.pdf Link to comment Share on other sites More sharing options...
tjbliley Posted March 26, 2008 Share Posted March 26, 2008 is there any way to test the IAC? Yes it is a tbi setup. TJ do you have a fuel pump.. or a spare IAC.. if you have a spare IAC I will try that :brows: Don't have either. I had some of the same issues on mine and the problem was in the connector for the injector. Also the CPS was an additional contributor. Jeff also said his acted up due to bad O2 sensor. so you might check those. Jeff just unplugged the O2 sensor and ran that way for about 6-9 months until he could get around to replacing it. Just a few thoughts for you. Link to comment Share on other sites More sharing options...
pingpong Posted March 27, 2008 Author Share Posted March 27, 2008 I shall try the IAc test.. once I get a fffew more winks of sleeps Link to comment Share on other sites More sharing options...
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