Dead miss problem, How can i tell if my injectors/spark plugs are firing?

GS70350

Round Headlights.Like em?
Hey guys. Finished installing the TA61 the other day, as well as wrapping the headers and DP which made a noticeable difference in the coolant temperature. Its now always < 180 with the AC blowing.

But i ran into a different problem. While i was installing the turbo, i replaced the spark plugs. My old ones looked like crap and the #6 was gunked up with crud. I put in AC R43TS plugs and afte rdriving it, it would miss at 10 psi or more. I drove it the next day after regapping, and checking everything, and it was missing erratically at all RPMs. I replaced the spark plugs with autolite 23s and took it back out for a test run, and the miss was completely gone, so i figured it was the spark plugs. I just drove it 15 miles to a gas station, and the miss is back worse than ever. Its missing constantly, a dead miss and i dont know which cylinder it is. I tried pulling off the plug wires one at a time, but shocked myself in the process so there has to be a better way to do this.

I pulled the plugs, and #6 is again sooty, the rest look good, #4 is slightly dark colored with some gas on it so it might be that cyl.

Compression test revealed that all cylinders are in good working order with 160-170 psi.

What should i look for guys? This is the 3rd set of plugs, wires ohm out alright and dont fluctuate when wiggled, and the coil packs ohm out to 11K.

Any help is greatly appreciated. Thanks
 

GS70350

Round Headlights.Like em?
Also the 02 readings are very low while driving, like under 100mV.

At idle they are at 500+ which is normal to me, but as soon as you start moving, they bottom out and stay this way. no KR, MAF readings are correct. I never got over 2200 RPM because i was so worried about getting home. oil looks clean. The noise is more out of the exhaust than sounding like a miss for some reason, like a loud exhaust pop because of the miss. Its really loud, but then again, i do have open exhaust right now which could magnify the sound. but its alot louder than usual.
 

Black Car

Active Member
First thing I suspect is the ingition module.
If you don't have a Casper ign/coil tester, find out if any of your Buicks friends in your area does.
IMO this is the ONLY way to test the ign & coil pack.

To see if the injectors are working, with the engine running, place on end of a wooden stick (or anything that will transmit sound) on each injector and the other end to your ear. If you hear clicking , then the injector is work.
 

19gn87

New Member
I suspect the module also (as a guess and from recent experience). As mentioned, hopefully you could 'borrow' a known good one for testing. A lot of us don't bother to LEARN and take the time to make a proper diagnosis. With a sudden (loafing along at 35 mph) dead miss, I managed to nurse it home. I only had my trusty inductance timing light and a DVM. Embarrassing as this is, I 'decided' to replace the coil pack (one corroded terminal)...no change. Plug wire inspection showed a couple of small cracks and slight hardness. Why not do them AND the plugs? Fine, NO change. Module next, right? Installed a new one...now it won't fire AT ALL. Reinstalled original...fires right up, same miss. Go back to the parts guy and 'beg' for another new module...bingo, never ran better. Here's a tidbit you won't generally read...ANY 'weak link' in the iginition system may not noticeably affect performance for a period of time, but creates significant extra load on the other components. Example: 'marginal' plug wire(s), marginal plug(s), corroded coil pack terminal(s), poor ground(s). One or more of these, run long enough, can be a direct factor in killing a module. Just wanted to throw out these happy thoughts. :)
 

GS70350

Round Headlights.Like em?
Replaced the coil, drove it around a bit, then 10 mins later(after it warmed up) the miss started again just like usual, so something is breaking down under heat as i had suspected.

Replaced module with engine still hot, cranked it up, and it still has the miss. So its not the coil, or the module
 

GS70350

Round Headlights.Like em?
I took all my plug wires apart and shortened them up and installed new terminals. these are spiral core wires and are a year old or so, so i was giving them the benifit of the doubt.

Same miss.

Found another wire laying around somewhere from when i changed them out, so i swapped it around a bit to check and see if one wasnt firing. Nothing changed except the idle got a little rougher.

I took out my #4 and #6 spark plugs to check them again, since these were the only ones in question upon the last 6 inspections. #6 was again sooty and black, #4 was bone white, unlike last time. So i figure its not getting fuel. I check all the injectors with a ratchet extention in my ear and cannot hear #4 ticking. Must be the problem. I wiggled the wire around and it ticks slightly, and the engine smooths out a bit, then returns to its missing state.

I wiggle it alot and get a steady but quieter tick than all the other injectors. I took the injector harness connector apart and spray contact cleaner in all the terminals and that didnt help any.

The wire doesnt have any abrasions on it at all.

If it only begins to do this after it gets to operating temperature for about 5 minutes, im guessing that somehow the heat is messing up the signal to the #4 injector. Is this injector by any means influenced by the #3 injector wire? That wire had grounded to the EGR before and was a source of a no- run situation in the past. It was keeping all the injectors from firing.

Another thing that might help, is that if i raise my fuel pressure to about 45, the car will not start again because the injectors wont fire. if i lower it back down to 42 it will start every time and run fine, but the higher pressure i think is causing a load on the injector harness causing a short somewhere, which might be the cause of this problem as well.

Any ideas where to look? Thanks for the help
 

Lee Thompson

New Member
miss

This happened to me recently---Pull the harness wires of and look down into each inj. harness plug (especially # 4 ) . One of the spades was pushed almost out of the harness. Might explain why it smooths out when you wiggle it.
 

chevyII

Active Member
Can you make it miss powerbraking the engine? If so take your tool to pull the spark boots on 4 and 6. Run a jumper wire with clips to ground, to not get shocked. OHM injectors/check power and ground while under load. It sounds like either a hot or underload type problem. Just for kicks mix some hot water and dish soap in a spray bottle. wash your complete engine then put a load on it,watch for sparks. Also double and triple check all your previous work just in case.
 

WarpSpeed

Fade to blurr
In case you didn't notice, the injector fires from a (-) signal from the ecm,, 5v i think. The Positive side of the injector lead is constant 12v. You can check it with a voltmeter. Car idling, it should show about 3v on the negative side... this doesn't tell you much about pulsewidth but it'll tell you if you're getting a signal,,, also, the ecm gets it's ground from the back of the PS head.
Be careful ohming things, somethings don't like 9v battery operated ohm meters.
Maybe you fried an injector
 

turboclam

Well-Known Member
Noid Light

Go to Auto Zone or Pep Boys and buy a $4.00 Noid light. It plugs to your injector connector and has a built in light, when it sees a signal it lights up. You could switch the injectors around and then look at your plugs again. You could also take the passenger valve cover off to see if everything looks ok like the rocker arm shaft. Good luck
 

ThikStik

My sleep apnea is winning
J,
Using a vom set to ac volts , at idle get a number froma good cylinder's inj harness. Then test #4's. See then if you get comparable value on vom. The signal may be too low of a hertz for the vom on ac, if so set it to dc volts. Otherwise , you could switch injector to another cylinder and see if plug changes. Thatll eliminate inj and harness or an induvidual bad driver in ecm. I wish my miss was all the time, then I could find it.
Good Luck
 

Jerryl

Tall Unvaccinated Chinese Guy
....... i replaced the spark plugs. My old ones looked like crap and the #6 was gunked up with crud. ...... missing erratically at all RPMs. I replaced the spark plugs with autolite 23s and took it back out for a test run, and the miss was completely gone, so i figured it was the spark plugs. I just drove it 15 miles to a gas station, and the miss is back worse than ever. Its missing constantly, a dead miss and i dont know which cylinder it is.

Compression test revealed that all cylinders are in good working order with 160-170 psi.
[/B]

Did you get this figured out?
I have the same issue. Carbon fauled plugs and #4 is bone dry (white) New plus wires, plugs, coil pack, ECM, MAF. Car sounds like she is running on 4 cylinders. Stated out missing on one cylinder but now it sounds like ......... well, you know ....
Only ,misses when hot and under load. Idle is "So so" but she "gurgles" when you get on it.



Installing injectors this weekend.
Thsi is a hot air and injectors have about 74K on them.

Thanks!
 

slim6

New Member
i ran into a simular problem i had all my injectors cleaned and flowed but that did not help and my harness looked good but when i finaly got the hole harness of just one of the prons was pushed throw so when i would shake it it would work some times but never under load did it seem to work just my experience

slim6
 

Jerryl

Tall Unvaccinated Chinese Guy
Originally posted by slim6
i ran into a simular problem i had all my injectors cleaned and flowed but that did not help and my harness looked good but when i finaly got the hole harness of just one of the prons was pushed throw so when i would shake it it would work some times but never under load did it seem to work just my experience

slim6


Do not want to hyjack this thread but a quick Question ........Did you just replace the harness and did that resolve it?
 

slim6

New Member
yes it did but i would look over the hole harness before you go and buy a new one and i got mine from casper it is nice

slim6
 
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