random hesitation/cutting out at part throttle

[wv_lx450]

I have searched and searched and have tried everything that i could think of so far and no luck. here is my problem: a couple weeks ago my truck started sputtering/hesitating like it was running out of gas but only when i am pressing the throttle part way. it idles perfect and runs perfect when i am wot but wont run anywhere in between. the confusing part is that is does this almost everytime i drive it but sometimes it will just start running perfectly and run great for hours. no check engine lights. i searched here and found some issues that were similar to mine and this is what i have replaced so far-

fuel pump relay
fuel filter
spark plugs/wires
mass air flow sensor
intake tube

any other ideas?

 

[CJF]

No check engine light?

Curtis

 

[wv_lx450]

no. never has thrown any.

 

[wv_lx450]

anybody?

 

[IBCRUSN]

Do you have a Toyota service manual?

Injectors
cap & rotor - not likely the cause since it is intermittent but you've replaced all other consumables in the ignition system

Are the plug wires OEM? I ask because I had a similar issue with Beck Arnley wires about 10k miles after I purchased my truck.

The wires and injectors have been the two main causes of hesitation and cutting out on my truck.

 

[Beowulf]

Based on what you've already replaced, I would suspect the main engine wiring harness. Inspect the harness at the rear of the engine close to the EGR valve. Sometimes you can wiggle and move the harness in this area as the engine idles and see if anything changes.

PM me if you want to sell your "old" MAF sensor.

-B-

 

[wv_lx450]

Based on what you've already replaced, I would suspect the main engine wiring harness. Inspect the harness at the rear of the engine close to the EGR valve. Sometimes you can wiggle and move the harness in this area as the engine idles and see if anything changes.

PM me if you want to sell your "old" MAF sensor.

-B-

i will try that next. i put my old maf sensor back in because the new one didnt do anything for my problem. luckily i know the people where i got the new maf sensor and they let me send it back.

 

[wv_lx450]

Do you have a Toyota service manual?

Injectors
cap & rotor - not likely the cause since it is intermittent but you've replaced all other consumables in the ignition system

Are the plug wires OEM? I ask because I had a similar issue with Beck Arnley wires about 10k miles after I purchased my truck.

The wires and injectors have been the two main causes of hesitation and cutting out on my truck.

the wires arent oem but the problem was there before i replaced them and the plugs.

 

[IBCRUSN]

How many miles do you have on your truck? Stick the pertinent info on your rig in a signature.

I still say the injectors and secondarily the wire harness as Beowolf mentioned.

 

[Beowulf]

I'm not suggesting the plug wires are your problem but we have had several guys try non-OEM plug wires and report very poor results. YMMV.

-B-

 

[Squash]

Have you tried the checks in Reverse?
Engine torque tends to make the hesitation really obvious in Forward gears, try reverse...if everything feels normal bust open the wiring harness.

 

[wv_lx450]

How many miles do you have on your truck? Stick the pertinent info on your rig in a signature.

I still say the injectors and secondarily the wire harness as Beowolf mentioned.

almost 150,000. havent tried the reverse idea yet. ill do that today and see what happens. also, it seems like the problem occurs more after the truck has been sitting for 20 to 30 min. It ran perfect almost all day yesterday while i was wheelin but everytime we stopped for a bit it would run bad again for a min or so then start running good again. didnt matter whether i shut it off or left it running while we were stopped.

 

[wv_lx450]

Have you tried the checks in Reverse?
Engine torque tends to make the hesitation really obvious in Forward gears, try reverse...if everything feels normal bust open the wiring harness.

does the same in reverse. i have driven it twice today and both times it would run badly for the first few minutes then run good for the rest of the time. but i also noticed that it doesnt have anything to do with whether it is warmed up or not because i can leave it parked and running for a bit and it will run badly for the first few minutes then smooth out.

 

[wv_lx450]

i have been driving my truck everyday for a while now and i have found that it only runs badly after it sits for a few minutes (whether its running or turned off). it will sputter and act like its running out of gas for a few minutes but then it clears up and runs fine as long i keep moving/driving but as soon as i sit for while it starts running badly again. even if i am sitting for a short period like going through a drive-thru. and other ideas?

 

[Beowulf]

... and other ideas?

You were given a couple of suggestions in this thread and it is not clear to me if you have addressed those and reported back what you did to test and what results you found.

Start there.
-B-

 

[wv_lx450]

havent gotten around to doing anything with the injectors. i checked out the wiring harness and couldnt find anything that looked bad. i messed with it while the truck was running also and didnt notice anything changing. i tried putting the truck in reverse while it was running badly and it did the same thing in reverse. i just got back from a small trip that was a little over an hour each way and it ran badly when i pulled out of my driveway then ran perfect the whole way even stopping a couple toll booths. then it ran poorly when i started home but cleared up and ran perfect all the way back.

 

[Beowulf]

As I understand it, you have eliminated the intake tube, the fuel filter, the MAF, the fuel pump relay, the wiring harness, and have a recent full tune-up. Those are the usual suspects for your symptoms so I am at a loss to suggest much more.

My next step would be looking for an electrical problem... maybe the igniter or the coil? Maybe the fusible links? I really don't see how those would fail intermittently and only after the vehicle was stopped but we are running out of things to test.

Wish I had more for you... maybe someone else will chime in with suggestions.

-B-

 

[wv_lx450]

it was suggested to me that i might have gotten some bad gas or got some water in the gas but i have run 3 full tanks through it now and put some gas dryer in also with no change.

 

[wv_lx450]

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?

 

[MB4wd]

I have been having similar issues on my 96. I found the wiring harness to be singed and sitting on the EGR intake tube. I took the hood off, and did my best to repair the burned area. I re-wrapped the harness with header wrap, as well as the section of EGR intake tube closest to the harness. I had two codes stored, they were misfire on #5 cyl, and insufficientcat flow. I cleared the codes (I love the scangaugeII), and started it up. No miss, or hesitation. I took it out for a drive, and the miss is back. I haven't had a CEL thrown yet, but I'm thinking the wiring herness may be a candidate for replacement. It has 186K on it, so I imagine it's service life has been used up. Time to give CDan a call I guess.

Matt