What is wrong?
What is wrong? For the past month or so my car has been running like absolute crap and I'm not really sure why. It seems to be missing/backfiring all the time. I checked all my plugs and wires and they seemed fine. My ECT sensor was broken so I replaced it thinking that would fix the problem, negative. So I eventually took it up to my tuner and he said everything looked good when he was data logging. Oh and my O2's were bad so I put some new ones in and he said they were switching like they were supposed, he was actually surprised how well they were switching. Anyway's I'm out in the open on this one....
All the wires are good I've checked them about three times, fuel pressure is good and the only thing in it is 91. I'm taking it back to my tuner tomorrow and he's going for a ride with me to data log some stuff maybe we can figure it out.
Well I went to my tuner tonight and we did some data logging and it showed bad misfires on the #5 cylinder. So we checked the plug and wire looked good but still put a new plug in then went and data logged some more. Still showing misfires on #5 so he said it was either bad coil pack (which he said was rare), bad injector (which I just had cleaned), or broken valvespring (which I just looked at the night before and "looked" ok) so anyway....
Yet another update. Today I put a new coil pack on (didn't solve the problem) so I took the valve covers off to look at the valvesprings and they all looked good, nothing was broken. So then I pulled the injectors and tried cleaning the one on cylinder 5 and again had no luck. Does anyone have a suggestion what could be causing it to misfire so bad on #5?
Take it to someone who has the tools to diagnose the problem. If you want to do it yourself, go buy or rent a noid light and plug it into the injector harness at the #5 injector to see if you are getting a signal from the PCM, a fuse supplies the battery voltage and the PCM sends the ground. You should also check the pins inside the connector, I had one that had a pin partially pulled out so I had intermittant contact with the injector terminal. You can't really clean an injector at home. You can physically clean the outside but that doesn't fix a problem is the injector is clogged.
Try this before you waste more money on throwing parts at it.
Try this before you waste more money on throwing parts at it.
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I had a buddy of mine that is a mechanic at a chevy dealership clean it with some kind of injector cleaner they had there. I haven't thrown anything at it yet, I've just been trying to diagnose the problem. We are going to to a compression test here in a few days, then I will probably start testing the injector itself.
Oh, the plug and wiring all looked good as far as visually looking at it.
Oh, the plug and wiring all looked good as far as visually looking at it.
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always trouble shoot by 'halves'.... to save time & money...
If you thing it's the injector, move it to another cylinder.
If problem goes away & appears in that different cylinder,
than it is the injector. if not, than it's not a bad injector.
Do the same with the coil pack...
Always try to move the easy stuff around, to verify ya or na....
If you thing it's the injector, move it to another cylinder.
If problem goes away & appears in that different cylinder,
than it is the injector. if not, than it's not a bad injector.
Do the same with the coil pack...
Always try to move the easy stuff around, to verify ya or na....
ok, well my buddy had some extra coil packs and injectors lying around so we swapped some new ones onto my number 5 cylinder and I've checked my plug and wire about a thousand times and I'm still getting a lot of misfires on that cylinder. As far as I can tell all the wires look good.
Valvespring? I've looked at them at couple of times and visually they look ok...
Valvespring? I've looked at them at couple of times and visually they look ok...
Just did a compression test on that cylinder and it's holding strong at 180. Checked the wires coming from the crank sensor and the outer aluminum on them was burnt but the actual wires seemed ok, so I rerouted them to get them off the header and added some tape, I think this helped a littel but it's still missing and I've checked everything I can possibly think of right now.
Any ideas?
Any ideas?
Staging Lane
Joined: Mar 2007
Posts: 65
Likes: 0
From: S/W Burbs Illinois
Hi, Just a thought. Have you tryed swapping the spark plug wire itself to another cyl to see it it's the problem? Have a VHOM meter to check it on the ohms read compared to the rest of the wires? Did you replace the coolant temp sensor with a GM part or aftermarket. Some aftermarkets are crap. On the injector, something I do when I think an injector might be bad. Take the electrical plug off, use an ohm meter to measure the resistance on the 2 pins. Do them all to compare the variance. If I don't know the value I'm hunting for. Comparing them will give you a good idea. Just remember, 0.0 ohms is a dead short, a real high value isn't good also. Say your seeing 5.0 ohms on most of them, get a few at 4.0 to 6.0-7.0. Your still somewhat in the range. Get one at 9.0-14.0 or higher. I'd suspect the injectors internal electro-magnets coil is bad. As 69LT1 said. Noid lights are cheap. Dave
Last edited by locodave46; Jul 7, 2008 at 01:27 AM.
Yes I've swapped the plug wires around and the misses still show up on #5. It's not the injectors, my buddy had a brand new set that I put in and it's still doing the same thing. I'm going to put a little more insulation around those wires and see if it helps, it did help some but still misses.
the only thing left you haven't done is the wiring going to the injector and the wiring going to the coil pack. It has to be one or the other. There's nothing left. You need to inspect if very carefully. If nothing is burnt, then one of the wires has come loose in the connector. Lightly tug each one BUT REMEMBER WHERE IT WENT IF IT PULLS OUT. Inspect the pins in each connector. If everything looks good, no wires burnt or loose, shoot the connector pins with wd40 and put it back together. If still nothing, check the ground connections starting with the ones that go to the engine block. (back of head). Take it off and clean... spray and reconnect.
You still haven't checked the wiring from the PCM to the injector. On injector #5 there is a pink wire, 12 volts from inj 1 fuse, this is obviously good becasue it supplies voltage to 1,3,5 and 7 injectors. The terminal itself could still be bad. There should be a blk/wht wire in terminal B, this is the ground signal from the injector driver inside of the PCM. There will be 12 volts at pin A (pink) with the ignition relay energized and the ground at pin B (blk/wht) will be turned on and off by the PCM. Get a test light and make sure this is happening. Like you said, you put new injectors in and nothing changed, if the PCM is not commanding the injector to pulse, new injectors will not do you any good.
Thanks for the advice everyone. I found that there were some wires that run along the passenger side header were actually up against it and the protective covering was burned through but the wires seemed good. I rerouted them and put some electrical tape around them. This seemed to help out quit a bit but it's still missing every once in a while, so I'm going to add some more "insulation" to those wires and see if my problem gets fixed.
Lol, went through all of this to find out it was a wire...
Lol, went through all of this to find out it was a wire...
I lied it wasn't the wire.
And I know what posts they were, sometimes it takes a little bit to find something wrong, especially when you have to put the car up on a lift to actually see the wire...
And I know what posts they were, sometimes it takes a little bit to find something wrong, especially when you have to put the car up on a lift to actually see the wire...
so you still have the problem? Look to see that two wires didn't melt together.
Things like this are a pita. They just take some time in finding them. Good luck, but post what you find so the next guy that searches gets some ideas.
Things like this are a pita. They just take some time in finding them. Good luck, but post what you find so the next guy that searches gets some ideas.
I looked the wires over for about 25 minutes and they all looked ok. I'm getting ready to pull off the rocker arms and pull out the pushrods and see if I can find anything in there...