random hesitation/cutting out at part throttle

[ScottyDog]

well i have eliminated the water in the fuel. i drained the tank completely and have refilled twice since. i put a new dist. cap and rotor on and that didnt help. i also cut the wiring harness open and inspected the wires and all looks good. the wires look brand new. also, after this problem started i have been able to smell gas under the hood and the smell has gotten stronger lately (dont know if it has anything to do with my problem) so.... whats the best way to go about doing something about injectors?

I'm a newb here as well. This is my first 80 and don't have much to offer like some of these guys on here.. However I have had Jeeps and if your smelling fuel under the hood it could be the injectors, or the injector o-rings. My last jeep the o-rings became brittle and cracked on one of the injectors. Noticed a mild idle issue and could feel it missing at mid-throttle... Not sure if this is an issue with the 80's but thought I'd throw my $0.02 in... Good luck.

 

[wv_lx450]

looks like the fuel filter was leaking at one of the connections and it finally started leaking enough to see so i fixed that and no more fuel smell. i replaced the suction filter on the fuel pump today and that did nothing for the running issues. also, i have been driving my truck frequently and have noticed that when it is running badly and i go wot, it seemed like it was running right but i noticed that it doesnt have the power it should. it will be running through the rpms and out of nowhere it will just take off. no particular rpm causes it but i can get it running at a pretty high rpm ( 3.5k on up) and hold the thottle there for a couple seconds and its like someone just flipped a switch and it will take off and run perfectly from then on until i stop for a min. does that discription give anyone any better idea? lol

 

[k5ryannc]

do you have a fsm
you might see if there is a way the test the tps (throttle posistion sensor)
i had this problem on a tpi chevy that drove me nuts
same conditions you mention
heck i don't even know if your motor has one but if it does do a voltage test with the multimeter
hope it helps if not spit at me and call it good

 

[SUMOTOY]

looks like the fuel filter was leaking at one of the connections and it finally started leaking enough to see so i fixed that and no more fuel smell. i replaced the suction filter on the fuel pump today and that did nothing for the running issues. also, i have been driving my truck frequently and have noticed that when it is running badly and i go wot, it seemed like it was running right but i noticed that it doesnt have the power it should. it will be running through the rpms and out of nowhere it will just take off. no particular rpm causes it but i can get it running at a pretty high rpm ( 3.5k on up) and hold the thottle there for a couple seconds and its like someone just flipped a switch and it will take off and run perfectly from then on until i stop for a min. does that discription give anyone any better idea? lol

Couple things to check when there is no CEL

First, ck baseline timing. If the timing is not advanced enough, the cutout issues you speak of can happen, btdt.

Second, bypass the fuel pump resistor, and jumper it where it plugs in. If this solves the problem, you have a bad Fuel Pump resistor, and/or a bad relay activating it at idle, and/or a bad idle switch/wiring.

After that, you need to clean the contacts at the Ignitor, the coil (and test it), and do the measure test for the wheel gap in the distributor. Engine temp sender would be where I'd go after that.

HTH

Scott J
94 FZJ80 Supercharged

 

[wv_lx450]

where is the fuel pump resistor? i have a scanguageII hooked up and going by it my timing reads ok at idle. also, can i use the tps guage on the scanguage to tell whether the tps is working properly? the number on the scanguage tps at idle is 10 and climbs steadily as i press the throttle. iirc it goes to 75 at wot.

 

[SUMOTOY]

where is the fuel pump resistor? i have a scanguageII hooked up and going by it my timing reads ok at idle. also, can i use the tps guage on the scanguage to tell whether the tps is working properly? the number on the scanguage tps at idle is 10 and climbs steadily as i press the throttle. iirc it goes to 75 at wot.

The fuel pump resistor is on the DS firewall, looks like an aluminum heat sink, with 2 wires and a 2 pin plug about 4in from the resistor. I see no reason why you can't run some diagnostics with the scan guage. A better test for the fuel pump resistor circuit would be the diagnostic connector to the Fuel pump. Put a volt meter to that connector, it should show 9.3 volts at idle, and battery voltage based on MAF readings in the ECU. I would do some running tests of this circuit. Is the temp showing normal on the scan guage as well?

Scott J
94 FZJ 80 Supercharged

 

[wv_lx450]

the temp reads normal. i was just curious if the readings i was getting from the tps meant it was working properly? which connector is the fuel pump diagnostic connector?

 

[terryjmatthew]

Did you ever get this problem resolved? I am having a very similar issue and can't seem to narrow it down.

 

[Polar Bear]

I went through this same problem earlier this year- same mileage on the truck and tested/replaced most of the same items. My problem turned out to be a bad solder joint in the ECU. I picked up a used one on mud and saved myself 1600 bucks over new. Not a hiccup since I did it. Best of luck to you!