So, I am still trying to track down the stumble/hesitation problem my truck is having any time I tune it with my Superchips.

I have even been noticing a very slight stumble/hesitation at stock "death flash" tune in lower RPMs (usually around 1300-1400) at 1/4 to 1/2 throttle.

At idle, I noticed a little waver of about 50 RPMs or so, seemingly at random. Barely noticeable. Then I ran across an old thread on here from 2005 where RM_Indy states that at idle, an injector cutting out will drop the RPMs by about 50. So, I looked up the procedure for testing fuel injectors in the "Merry Christmas" manual. Piece of cake!

So I went out today and did that. The wiring harness on #8 does not clip on anymore, its harness plastic "lock" is broken. It sits just fine, but you can pull it straight off without having to depress the release. Thought maybe that was my problem, but continued on with the testing.

The manual states that all injectors should be 12 ohms +/- 1.2 ohms. All of them are somewhere between 12.3 ohms and 12.6 ohms, except #3. It registers at 13.2 ohms, barely within tolerance. #3's harness is also broken; the release tab is broken off, but it still clips into place, so its a major pain to take off of the injector.

My question for you guys is: could this injector be bad, and is partially/sometimes cutting out, maybe especially under increased load (like from a performance tune)? Thanks in advance for any opinions. I will be checking fuel pressure here soon as soon as I have a little more $$$ to buy the tools.

 

.3 ohm spread seems to be about the norm for oem injectors. That one thats off by .9 from the lowest reading, Id be swapping that one. Regardless of if its the stumble or not, probably hurting power & mpg being off that much from the rest.

Intermittant stumble probably related to the clips/connectors. Any that dont lock to the injector could have electrical contact broken for a split second as the motor shifts from torquing up. These are the injectors connectors I refered to in that old thread. http://store.summitracing.com/partde...5&autoview=sku

 

Thanks Indy, I appreciate the link and the help.

At first when I clicked on that link, I thought they were 23.95 per clip. I about had a heart attack. Then I realized that was for a whole set of 8, and I calmed down. I need to go grab another Coca Cola or head to bed. Thanks again Indy.

Anyone else that has any other theories related to the stumble, please voice up your opinions.

Timeline (approximates):
March 31: Switched the stock intake and plenum gasket with a modified intake ("kegger mod") and Hughes plenum kit. The truck had the Performance tune on it before the swap, didn't touch the tuner again until April 6.
April 6: Plugged tuner into PC, Superchips program reports an update and updates the tuner. I go out, plug the tuner in, program for 91 Performance tune. Everything is hunky dory, disconnect tuner, turn key... and severe stumbling and hesitation when you give it anymore than 5-10% throttle, almost like misfires. If you floor it (WOT), it will hestiate, stumble, hestitate, then you hear it pinging for a second, then stumble, hestiate. I immediately log onto the Superchips forums and initiate a discussion with their customer service about this.
April 7: Superchips CS forwards the issue onto the engineers, but tells me I am the only one to report this issue.
April 15: Engineers report back, files are good, no one else reported the issue, so it must be something wrong with my truck, and not the tuner.

Things I've done so far that did not solve the problem:
-Replaced pre-cat O2 sensor
-Replaced Autolite 3923 plugs (less than 5000 miles on them) with stock heat range NGK V-power plugs
-Replaced NGK V-power plugs with brand new Autolite 3923s
-Replaced MSD Blaster 2 coil with stock coil
-Made sure plug wires are routed properly
-Replaced TPS, helped a little but did not solve the problem


From research online and previous suggestions, the three biggest culprits I seem to find with an engine stumbling or hesitating (that I have not checked yet) are...
-MAP sensor
-Vacuum leak
-Fuel issue (injectors or pump)

 

Those clips that Indy posted won't work. Those are EV-1 clips and the '01s use an EV-6 connector.

I've been looking for EV-6 connectors as more of mine are broken than are connected correctly. I can't get over how cheap the plastic was that was used in the engine bay. All of it's brittle.

 

Thanks for the headsup squirrels.

I believe that they are also called USCAR or USCar connectors.

Here's the cheapest I've been able to find them with the wires. You can get them slightly cheaper if you just want just the connectors, rather than this "pigtail" style.
http://cgi.ebay.com/ebaymotors/EV6-E...419159010r6935

 

**** thats the clips I bought. I bought them months ago so its too late to return them now. god damn it i thought they looked different. Is there anyway to make them work? like if I need different injs could i get ones that need them plugs or do I still need the right ones?

 

Well that figures them ones cost more then the wrong ones I got. FML and my truck.

 

Yeah thats right, different clips, sorry was late, didnt look at what year you had,,,,

 

You can get EV1 to EV6 adapters, I've seen them while looking for EV6 pigtails. If you can get EV1 male to EV6 female adapters, that should work I'd think. Wire the EV1s in, plug in the adapters to it and to the injector, and presto.

EDIT: Not sure on the cost of the adapters, though. Might be cheaper to just buy the different pigtails (and tell me where you get them if you do, they are hard to find).

What is your guys' opinion on this fuel injector?
http://shop.advanceautoparts.com/web...S_567230225___

 

well i saw you replied to my similar post. found out my problem is there is an oil leak into cylinder 7 and it's pooling around the spark plug. i would check yours for this as well. i'm not sure whats causing it. could be bad piston ring but i'll let you know if i figure mine out. hopefully it's the only problem.