Raptor661 Posted April 24, 2008 Share Posted April 24, 2008 Ive got a 96 chevy that keeps throwing out cyl. 5 misfire codes. Ive got 130-140 compression on all cylinders. New bosh plugs and wires along with new lifetime warrenty cap and rotor. Anyone have any suggestions on what would cause it to idle rough and keep throwing out the same code? Also ive got 62psi on my fuel rail...it doesnt bleed down at all so I dont think its a fuel problem though the plugs do look a little lean. Quote Link to comment Share on other sites More sharing options...
dunefreak Posted April 25, 2008 Share Posted April 25, 2008 There's a number of things it could be, but the most probable cause is a faulty fuel injector on that cylinder. Even though it is holding fuel pressure, it still may be bad. When is it misfiring? Idle, accelerating under load, cruise, all the time, ??? Without special test equipment, there is no way I can tell you how to test it. You will have to have an injector balance test done on it to see if it is working properly. You still could have other problems such as: -no pulse (signal) to that injector from the PCM. -vacuum leak somewhere near #5 -cracked spark plug -possible worn distributor gear -possibly worn camshaft lobe(s) -or....there is a bulletin for the valve guides causing the valves to bind and stick. Typically, cylinders 3,4,5 or 6 will be the ones to experience this. Usually this happens when towing or on hard acceleration. Make sure you don't have any wire damage at the injector harness/ connector. Unplug it and make sure there are no sign of fuel in there. You can also take the plastic cover off the top of connector and inspect the wiring for breaks. Sometimes the wires in the harness fatigue at the bend and pull inside the insulation. Oh...and get rid of those Bosch plugs. Put some AC Delcos back in there. Hope that helps somewhat. Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted May 1, 2008 Author Share Posted May 1, 2008 It only runs rough on an idle and at a steady driving speed if its not under a load, say im going on a slight down hill or I drive in drive and not OD. The injectors are about the onlything left it can be that I havnt checked closely. Ive went over all the wiring and vaccum lines with a fine tooth comb. Im going to try a lucas fuel injection treatment on it and see if that helps. Is the injector balance test something only a dealer can do, or is there another way to do it? Im about 97% sure its not enternal motor...The heads only have 10k on them along with the rest of the motor. Quote Link to comment Share on other sites More sharing options...
dunefreak Posted May 2, 2008 Share Posted May 2, 2008 You need special equipment to do an injector balance test. What it is is an instrument that commands each injector to fire for a certain number of pulses (with the engine off). You do it for each cylinder with full fuel rail pressure and watch the amount of fuel pressure drop per injector. Usually only dealerships or decent independant shops will have the tools necessary to do the test. Usually injectors don't fail at just idle and cruise speeds, but anything is possible I suppose. Have you checked for vacuum leaks around that cylinder? If you lived in vegas I'd check it out for ya, but damn you aren't anywhere near me. Quote Link to comment Share on other sites More sharing options...
Richard Cheese Posted May 2, 2008 Share Posted May 2, 2008 bring that sh*t over here!!! i've got a mean crecent wrench!!! Quote Link to comment Share on other sites More sharing options...
indasand Posted May 2, 2008 Share Posted May 2, 2008 bring that sh*t over here!!! i've got a mean crecent wrench!!! :6pak: Left handed? LOL Quote Link to comment Share on other sites More sharing options...
Richard Cheese Posted May 2, 2008 Share Posted May 2, 2008 Left handed? LOL no, im abidextrious :shocked2: :6pak: Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted May 9, 2008 Author Share Posted May 9, 2008 You need special equipment to do an injector balance test. What it is is an instrument that commands each injector to fire for a certain number of pulses (with the engine off). You do it for each cylinder with full fuel rail pressure and watch the amount of fuel pressure drop per injector. Usually only dealerships or decent independant shops will have the tools necessary to do the test. Usually injectors don't fail at just idle and cruise speeds, but anything is possible I suppose. Have you checked for vacuum leaks around that cylinder? If you lived in vegas I'd check it out for ya, but damn you aren't anywhere near me. Im pretty sure its not vacuum leak ive checked all of those closely. I did a lucas fuel treatment and thats actually helped alot. Now, sometimes it runs perfect, ill shut the truck off to go in the store and come out and it starts to idle bad again....let it sit for a few min again later and it starts to run fine again. Quote Link to comment Share on other sites More sharing options...
dunefreak Posted May 9, 2008 Share Posted May 9, 2008 Sounds like an injector to me. Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted May 9, 2008 Author Share Posted May 9, 2008 Now can I replace just one injector or do i have to replace that whole spyder assmbely thast under the intake? The whole assembely runs around 300-400 bucks. I called the dealer about the test and they said it was 105 to do it and i still had to pay even if they didnt find anything wrong, which really sucks..being that I just got divorced moneys pretty tight Quote Link to comment Share on other sites More sharing options...
dunefreak Posted May 10, 2008 Share Posted May 10, 2008 Now can I replace just one injector or do i have to replace that whole spyder assmbely thast under the intake? The whole assembely runs around 300-400 bucks. I called the dealer about the test and they said it was 105 to do it and i still had to pay even if they didnt find anything wrong, which really sucks..being that I just got divorced moneys pretty tight The "spider" assemblies are only on the older 4.3 Vortecs ( like 94-95) and have to be replaced as one whole unit. You can just replace only one injector on yours. Although, there is an updated design for the fuel meter block and new stlye injectors that go with it as one assembly. If that is 300-400 bucks then that is a pretty good price if you ask me. If it only does it like sometimes, I'd try running some good injector cleaner through a couple tanks of gas before replacing it if you aren't certain that it is bad. I hear ya man. :breakdance: I wish you were in Vegas. I'd take a look at it for you for nothin. :breakdance: Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted May 10, 2008 Author Share Posted May 10, 2008 The "spider" assemblies are only on the older 4.3 Vortecs ( like 94-95) and have to be replaced as one whole unit. You can just replace only one injector on yours. Although, there is an updated design for the fuel meter block and new stlye injectors that go with it as one assembly. If that is 300-400 bucks then that is a pretty good price if you ask me. If it only does it like sometimes, I'd try running some good injector cleaner through a couple tanks of gas before replacing it if you aren't certain that it is bad. I hear ya man. I wish you were in Vegas. I'd take a look at it for you for nothin. Ive ran about a tank of lucas through it, its helped but not cured. sometimes it runs great and other times kicks the engine light on and acts funny. I found the whole spider kit for it, ive got a friend who owns a shop and at least I can get it a little cheaper that way. If its a needed upgrade then ill go ahead and do it to prevent problems in the future. Ive always had fords so im just learning about this one as I go. Would you replace the injectors or the whole assembly if it was your truck? If I go through the trouble of doing it I dont want to do it again anytime soon. and thanks for the info! Quote Link to comment Share on other sites More sharing options...
dunefreak Posted May 11, 2008 Share Posted May 11, 2008 I would replace the whole unit with the updated injectors. It will prevent any problems in the future. They have a different design that prevents them from having the issues that they've had in the past. It's not needed, but recommended. Good luck, man. Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted May 11, 2008 Author Share Posted May 11, 2008 Alright, ill look into that, thanks! Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted November 21, 2008 Author Share Posted November 21, 2008 Well its been months and my truck still doesnt run right. Heres what ive done. AC delco plugs, cap, rotor, injectors and fuel filter. Im running MSD 8.5 wires. I keep getting a misfire code. It runs fine when its cold outside but when it warms up it idles bad. It has a miss when the engine isnt under a load at all. Ive done a vaccum check (19psi) and a smoke test on the intake. what am I missing that will make this thing run better. Its about ready to be part of the campfire on the thanksgiving trip.... Quote Link to comment Share on other sites More sharing options...
EY3BA11 Posted November 21, 2008 Share Posted November 21, 2008 coil? Quote Link to comment Share on other sites More sharing options...
britincali Posted November 21, 2008 Share Posted November 21, 2008 (edited) coil? Edit : I just saw you did the injectors...... Burn it If it were a COP motor I would agree but seeing as it had a distibutor I cant see it only afftecting one cylinder. About the only thing I can think of now is a clogged or faulty injector on that cylinder Edited November 21, 2008 by britincali Quote Link to comment Share on other sites More sharing options...
EY3BA11 Posted November 21, 2008 Share Posted November 21, 2008 i know on my old f250 when the coil went out it did some weird CHIT! alot of headaches for a $30 part lol.. Quote Link to comment Share on other sites More sharing options...
Raptor661 Posted November 21, 2008 Author Share Posted November 21, 2008 I was reading up a little and found a few articles about the distributor gear. Its not any certian cylinder anymore its just misfire code. I would seriously trade this thing for a ford that was older at this point. Quote Link to comment Share on other sites More sharing options...
dunefreak Posted November 21, 2008 Share Posted November 21, 2008 I was reading up a little and found a few articles about the distributor gear. Its not any certian cylinder anymore its just misfire code. I would seriously trade this thing for a ford that was older at this point. You should have just read my post earlier in this thread! There's a number of things it could be, but the most probable cause is a faulty fuel injector on that cylinder. Even though it is holding fuel pressure, it still may be bad. When is it misfiring? Idle, accelerating under load, cruise, all the time, ??? Without special test equipment, there is no way I can tell you how to test it. You will have to have an injector balance test done on it to see if it is working properly. You still could have other problems such as: -no pulse (signal) to that injector from the PCM. -vacuum leak somewhere near #5 -cracked spark plug -possible worn distributor gear -possibly worn camshaft lobe(s) -or....there is a bulletin for the valve guides causing the valves to bind and stick. Typically, cylinders 3,4,5 or 6 will be the ones to experience this. Usually this happens when towing or on hard acceleration. Make sure you don't have any wire damage at the injector harness/ connector. Unplug it and make sure there are no sign of fuel in there. You can also take the plastic cover off the top of connector and inspect the wiring for breaks. Sometimes the wires in the harness fatigue at the bend and pull inside the insulation. Oh...and get rid of those Bosch plugs. Put some AC Delcos back in there. :angry2: Hope that helps somewhat. If the gear is worn it can misfire at random times. One or multiple cylinders (usually close to each other in firing order) will misfire and set p0300 codes. Pull out the distributor and check it. You could also have worn bushings. I bet that gear is worn though. Look at the teeth closely. Usually 1/2 the teeth will be paper thin and the other half will be thick and fine. A bad coil is pretty rare with these especially since it's only one affected cylinder. Quote Link to comment Share on other sites More sharing options...
EY3BA11 Posted November 23, 2008 Share Posted November 23, 2008 i would lay odds on the distributor gear especially after seeing the one you pulled outta the tahoe.. Quote Link to comment Share on other sites More sharing options...
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