Hesitation, stumbling; End of my rope.

[LukeDog3D]

Yeah, I never ragged the truck out or anything like that, so I guess you could say it resulted from normal driving. The electrode melted after I changed the head gaskets, so I didn't get a look inside. However, I've done numerous compression tests since then, and I can't see any significant compression difference between cylinders. Sometimes, the truck runs perfectly, so I'm assuming that it can't be something as bad as a hole in a pistion.

My dad thinks that it is something that is screwing up due to the way the motor torques to the side as you floor it, since this is the only time it happens.

edit: yeah, the shotgun approach hasn't paid off this time.

 

[LukeDog3D]

changed the vacuum modulator.

no help to the problem.

 

[Billy177]

only does it hot and muggy huh. do like three seafoam treatments and fill it up with premium fuel. if it dosent do it then it narrows it down significantly

 

[LukeDog3D]

I wouldn't say only when hot and muggy, but it seems like more consistantly.

whats a seafoam treatment?

 

[Billy177]

an engine decarbonizer www.seafoamsales.com

 

[IronIndian]

The check engine light never came on? If not, then I don't think it wouldn't throw a code. I just replaced my TPS and cleaned the MAF to solve a problem with hesitation/stumbling/surging on acceleration from idle. After each "fix" to the engine, you unhooked the battery for approx. 15 mins, correct? Did changing the modulator stop trans fluid from entering the intake?

 

[Billy177]

i would take it to a dealer or a shop and have them hook up this so called black box that monitors all the computers settings so you can see what happens when this occurs

 

[cecoen]

Just double check these items: Plug wires and plugs. Mine started stumbling like that when a plug wire was breaking down. I replaced it and got another 40K miles before it began to do it again. Was intermittent as hell. Really hard to diagnose. Did seem to be weather related, but more so, load related and even then it kept changing when it would miss.
Also, the reason I mention plugs is because on more than one occasion I have installed new out of the box plugs just to find out one or more is bad from the factory.
As far as the plug wire go, I got the 40K miles out of the auto Zone cheapies. I switched back to Motorcraft wires and have been good for almost another 90K miles. I have dealt with the missing problem three times now(230K miles on my truck) and it was always the plug wires. Hope this helps.

Chad

 

[MattPersman]

have you used a noid light on your injector harnesses to make sure they are pulsing?

you mentioned ebay injectors, how do you know they are good? 1 could be bad intermittantly

there is also a fuel injector tester that OTC makes that fires the injectors bypassing the computer to make sure they work correctly

could be fuel, could be ignition considering you base engine is sound with 180-190 compression

I assume your vacuum is steady at idle, 1800 RPMs and load?

also never assume parts are good just cause they are new, especially from Twilight, I mean Auto Zone. There stuff is subpar, sometimes you get something that is just great other times you may take that part back 10 times before you even get one that is good to start with, sure we have all bought crap there cause the price, well its hard to beat usually, but there is a reason for that too = quality

you need to do all your trouble shooting road maps for things. get out a vacuum pump, and multi meter and get busy.

it may end up being one of those things thats not worth all the time you put into it though, and if you are in the right situation it may be worth making it disappear and get something with less or no problems

there are tons of neat tools out there that can help you along the way, but most people do not have them or even access to them so it makes it harder thats why shops charge ya 80/hour cause all the cool tools they have to pay on each month when the tool man has his hand out for your payment

 

[hardeeharhar]

i had the exact same thing happen to me, lost the electrode, truck runs with a miss now, after a comp test, 150 in all 5 30 in the other. exaust valve is our best guess on my truck. good luck bud
ps i am looking for a stick of dynomite lol

 

[LukeDog3D]

Ok guys,


no, the check engine light never came on. I did reset the computer after each new item.

I "decarbonized" the engine using the "steam clean" technique described on this website. I also checked and re-gapped the plugs today, and they all looked perfect. I also tested the IAC valve at 9 ohms (supposed to be b/t 7-13).

I did find that there is gas (though not pure...its thicker than gas somehow) emmitting out of the vaccuum line from the Fuel pressure regulator, which is basically new. My current running hypothesis is now that I bought a ****ty FPR twice. --- I replaced the stocker a couple of years ago, looking for the solution to a different problem. Then when this problem arrived, and I replaced it again (i don't remember if there was gas in the vac line on the 1st one) , both times from autozone...so possibly i got two ****ty ones in a row??

The new vacuum modulator has stopped the flow of tranny fluid to the intake. That seems cool.

As for the Ebay injectors, the guy said that the truck ran great when he started parting it out (wreck), and i assumed that even if one or more were bad, the symptoms of the problem would change, at least somewhat. When i put the new injectors in, it ran the exact same, which i would find unlikely if the injectors were the actual problem. The injectors were clean, and I tested them all at around 15 ohms.

 

[dogfriend]

Did you check the secondary resistance of the coil pack? (Don't buy another one, just test it to see if its ok. I recall that you did replace it.)

I recently had a problem with misfiring and it never set a CEL, but I was able to find it by using a scan tool.

If you want to check the coil pack, there is a good section in the Haynes manual (Chap 5). Also see this thread: Coil Pack Testing

 

[LukeDog3D]

dogfriend,

i did the test, and the primary resistance was good, but the secondary resistance was 14.4k, 14.3k, 13.8k....out of spec according to the manual. replace it again?

 

[dogfriend]

Mine was 12.5k ohms on each coil and it was causing misfiring while trying to accelerate on the highway or climbing a hill. The new one from Napa ($120) read 11.5K on each coil. It fixed the problem.

I initially thought it was a tranny problem cause it wasn't obvious that it was a misfire and the plugs and wires were not very old. It never set a CEL even though the OBD II system on my truck should be monitoring for misfires.

 

[LukeDog3D]

I took the coil pack off of my brother's explorer and put it on mine; the resistance was around 11k ohms on each coil. It solved the problem! I haven't felt this much power in the truck in over a year. So, this APPARANTLY is the problem causing all of the trouble. (knock on wood)

I owe all of you guys a round of beers for helping me with this thing. I never would have guessed it was the coil pack after I replaced it the first time. Dogfriend, I owe you a 6 pack. Thanks, fellers.

I'll be going down to autozone a little later and throwing their defective coil pack through the window.

 

[dogfriend]