The 97 started missing, so ran a buzz test, and came up with open circuit on 5 and 7 injectors. Thought it was a bad under cover harness so started there. When the cover was removed everything looked OK, but installed a new Ford gasket and under cover harness and ran another buzz test. Same result. Haven't found any chaffed wires yet, but was wondering if the IDM can fail on just 2 injectors? If it makes any difference, at first, there was no miss when first starting, but the miss would start after the engine was up to temp. Now the miss is present whether the engine is cold or up to temp.

 

I'm thinking you may have a couple weak injectors Tom. How many miles on that truck? Does it smoke at all?

 

The truck has about 228Kon the motor, the injectors were replaced at around 178K. They were said to have 71K on them when they were installed. After doing some research, I found the center pin on the plug is high voltage, not ground like I had thought. I'm going to dig into the wiring a little more to see if the wire to the center pin is damaged. Thanks for the reply Darin.

 

^^^ +1; I would check the continuity of all three terminals on that right rear UVCH, from the injectors all the way back to the IDM connector. Too much of a coincidence that it's two injectors on the same branch.

 

A buzz test isn't meant technically that way.

To truely do a buzz test you have to start the test and listen under the hood at the sounds the injectors make.

if they are not factory new injectors, they will fail often.

As for the UVCH's, you ahve to inspect them really close and all the connectors.

 

I'm thinking it is probably the pigtail on the engine harness side. I replaced it several years ago. I was in a hurry, and used the butt connectors that had heat shrink on them that came with the pigtail. I'm betting the common wire has corrosion in the butt connector. I usually solder the wires. Hopefully it is an easy fix. Thanks for the reply Mad.

 

I got the miss taken care of, I replaced the but connectors I used with solder. Took her out for a run, and all is good. Out of curiosity I ran another buzz test, and the high to low open is still showing on#5 and #7. A cylinder contribution test show all is good. WTH is up with this? Maybe it is what Darin said, those two injectors are getting weak.

 

^^^^^ The buzz test only fires/tests the solenoids. I suppose you could swap those solenoids with two other ones (IIRC, you can pull the injector solenoids without pulling the injectors themselves), see if the open fault "follows" the swap.

 

Read my post above.

Buzz test results dont mean anything.

 

Then why was the test programmed into the PCM?

 

If the audible sound on the buzz test is good and its running properly I don't know that I would worry with it.

 

Clear the codes the redo buzz test.

 

Thanks Jim, That is probably the problem. I didn't even think to clear them after the first buzz.

 

Buzz test is a test that everyone gets hooked on thinking it does something super special.

As I explained above, the buzz test is for your ears, not for the code readout.
Solenoids rarely go bad. and by rarely I think Jim told me he can count bad solenoids on his fingers still.

The buzz test is started so you can listen for weak injectors by ear while the test goes on under the hood.
What the actual error codes will tell you doesn't mean a damn thing unless you have bone stock injectors.

The only time a buzz test is useful code wise is if you are having really bad injector problems, it can just point you to the right injector quicker than pulling all 8, so if its a quick fix, you can pull one, or inspect one.

 

That's a far cry from saying the results "don't mean anything", esp. since most people run stock injectors.