Author Topic: Hesitation just off idle (Read 4123 times)

myyota · « **on:** Dec 25, 2006, 06:07:27 PM »

I have an 85 carbed truck, the engine bogs or hesitates just off idle, once past this spot it accelerates normaly. ive checked all the vacuum lines and replaced the plugs and spark plug wires, cap and rotor. i rebuilt the carb a few months ago also, but i can`t seem to solve this hesitation problem. anybody have any ideas ?.

chaseheadrick · « **Reply #1 on:** Dec 25, 2006, 07:00:04 PM »

maybe fuel filter? or fuel pump?

myyota · « **Reply #2 on:** Dec 25, 2006, 07:02:59 PM »

Fuel pump is new (2 months old), havn`t changed the fuel filter yet, thats next.

chaseheadrick · « **Reply #3 on:** Dec 25, 2006, 07:50:50 PM »

i'd change that. just start with the basics, ya know. fuel, spark, compression, timing.

logan · « **Reply #4 on:** Dec 26, 2006, 01:36:13 AM »

couldnt that be that the carb needs rebuilt or somthing too?

myyota · « **Reply #5 on:** Dec 26, 2006, 08:44:08 PM »

The carb was rebuilt 2 months ago, along with a complete tune up, but i just can`t get this hesitation to go away. I will try replacing the fuel filter this weekend.

79coyotefrg · « **Reply #6 on:** Dec 26, 2006, 08:54:09 PM »

check the timing

kneedownnate · « **Reply #7 on:** Dec 26, 2006, 09:24:49 PM »

Did it hesitate prior to rebuilding the carb? If so, have you checked the timing?

myyota · « **Reply #8 on:** Dec 27, 2006, 06:48:39 AM »

Yes it did hesitate before i rebuilt the carb, and i have played with the timing a little and it made no difference.

Wermz84 · « **Reply #9 on:** Dec 27, 2006, 07:32:38 AM »

I would replace the fuel filter and see if that helps. Maybee makesure the lines arent cloged.

myyota · « **Reply #10 on:** Dec 30, 2006, 08:58:14 PM »

I replaced the fuel filter and the ruber fuel lines between the gas tank and the hard lines under the cab. it might have helped a little, but the off idle hesitation is still there, im thinking that it has to be the carb because everything else in the fuel system is new. im open to any and all ideas at this point.

chaseheadrick · « **Reply #11 on:** Dec 30, 2006, 09:15:04 PM »

here is what the FSM suggests to check:

Float level too low
Accelerator pump faulty
Power valve faulty
Choke valve closed (hot engine)
Choke system

Download a FSM from the FAQ at www.pirate4x4.com and see if you need to repair/replaice any of these items. you should have one anyway, they are a great help in diagnosing and solving many problems. much more so that a chiltons or haynes manual.

P.S. if you already have one then never mind

myyota · « **Reply #12 on:** Dec 30, 2006, 09:35:56 PM »

I do have a FSM. when i rebuilt the carb i didn`t touch the float setting, but that doesn`t mean its set right, both accelerator pumps are new, the power valve seemed ok but i will check it again, is there any way to tell if the power valve is bad ?. i didn`t take the choke a part when i rebuilt the carb, i was told it wasn`t a good idea.

chaseheadrick · « **Reply #13 on:** Dec 31, 2006, 08:16:22 AM »

i think you just blow air through it and make sure it is opening and closing ok. try all the suggestions in the fsm and see if it goes away. all my vehicles are efi, so im runnin out of ideas. if it was mine i'd probably just get a new carb, cause i don't know much about them

myyota · « **Reply #14 on:** Dec 31, 2006, 06:09:52 PM »

I have another carb thats off an 84 toyota truck, i think i will try it out on my truck and see what happens and if i still have the same problem, then i don`t know because im about out of ideas to.

tufsurf · « **Reply #15 on:** Dec 31, 2006, 06:35:58 PM »

replace O2 sensor?

myyota · « **Reply #16 on:** Dec 31, 2006, 08:16:24 PM »

Maybe im missing something, but how would the 02 sensor affect the carburetor ?, if it was EFI then i could how thats possible.

tufsurf · « **Reply #17 on:** Dec 31, 2006, 09:45:07 PM »

just throwing out there seems to be the first thing that pops out on the boards some times. good luck and happy new year!

toyrunner · « **Reply #18 on:** Dec 31, 2006, 10:21:37 PM »

The o2 could send a lean signal messing with the timing. These are computer controlled vehicles. Could be the emissions board is corroded. There is a known issue I have read about. I have EFI and don't know the exact fix for you. It would be right to follow the easiest issues first.

Danny

myyota · « **Reply #19 on:** Dec 31, 2006, 10:49:13 PM »

Well, like i said above i do have another carb, and i also have another computer that controls the emissions stuff so i will try those 2 things next.

mickeyfinn · « **Reply #20 on:** Jan 01, 2007, 08:10:20 PM »

the vacuum lines on that carb are critical. especially on the auxiliary accelerator pump. with the truck idling pull the vacuum line off and the truck should run rough for just a second and smooth out. an o2 sensor can cause a running problem with a carb. not usually at idle on those trucks. they are rpm dependent and are electronically controlled vacuum operated mixture solenoid. these systems usually are very sluggish throughout the whole power band when not working correctly. power valve problems usually causes hestation at part throttle. if this carb sat a while with gas in it it may need to be taken back apart and to be sure it is working.

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