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Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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jcalan
Novice
Oct 31, 2012, 10:14 AM
Post #1 of 21
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Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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96 Chevy C1500 4.3 V6 auto 150k.
Sudden onset while driving a couple days ago. Running perfect for the past year, then wile sitting at a stop lite after 30 minutes driving, changed abruptly to rough idle, misfire, backfire and stayed that way.
This doesn't feel like something wore out over time, but failed abruptly.
Runs like it's severely out of time.
This should be a simple one but it has me stumped.
I don't have access to diagnostic equipment or code reader, but a sudden failure like this may point to the issue.
Here's what I've checked so far.
serpentine, idler pully, tensioner, all good
MAF sensor unpluged, no change
Cap and rotor (replaced a year ago) no signs of scorching or wear.
I suspect the distributor gear may have skipped, but if that's highly unlikely, you can save me pulling it needlesly.
I know there are lots of possibles, but I'm hoping someone can help me narrow it down with what I've given you above.
Thanks,
John
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Hammer Time
Ultimate Carjunky
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Oct 31, 2012, 10:29 AM
Post #2 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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You have to read codes first for a starting point. There is no wild guessing these days.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Oct 31, 2012, 10:48 AM
Post #3 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Thank you Hammertime, Being an early 96, throttle boddy injection with a single coil, I can bridge and get the codes from the check engine light. I suspect it will only confirm the ECM is working, and I have multiple misfires but it won't tell you what's causing them. That still leaves a host of possibilities.
I'm just trying to shorten the list to the most common causes, and from that list, the things that tend to fail suddenly, vs wear out over time.
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Hammer Time
Ultimate Carjunky
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Oct 31, 2012, 11:51 AM
Post #4 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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No, you can't get flash codes from that truck. You need a code reader.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Oct 31, 2012, 12:07 PM
Post #5 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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yes I discovered that after I found and printed the schematics and trouble codes. Looks like it could be a dozen different things from TPS to cam position sensor to a bad coil etc. Fuel delivery seems fine, Spark is strong and steady, just off time. I'm guessing a crank or cam position sensor. I guess I'm off to buy a code scanner, or find a shop that will do one for free. I can swap out parts, that's not tough, just need to know which ones to replace. Thanks for your help.
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Hammer Time
Ultimate Carjunky
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Oct 31, 2012, 1:33 PM
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Any Autozone or Discount Auto will do it for free.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Oct 31, 2012, 5:44 PM
Post #7 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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I did find another problem, though possibly unrelated. Connector for upper heater hose is cracked, losing pressure and coolant. I have a new connector I'll install tomorrow but I doubt the loss of pressure would have made it run this bad. Once it will hold coolant pressure again, I'll take it in and get it scanned for codes if the symptoms persist. And before you ask, no, I did not run it hot. When the misfire started, I was less than 5 minutes from home at the end of a 45 minute commute, limped it in and went under the hood to inspect. The temp guage never rose and the engine did not feel overheated in the least. Left it parked until today for a closer check and still plenty of coolant.
Possible the coolant leaked onto a sensor and compromised it. I'll need to wait to see what the scan shows.
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Tom Greenleaf
Ultimate Carjunky
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Nov 1, 2012, 5:57 AM
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Staying out of it but found a complete kit to make this TBI which also stated for non emission controlled vehicles only. TMK all real model year '96 did not have TBI. Hmmm.....kit and wiring cheaper than replacing this.......
So now what?
T
(edit out typo)
(This post was edited by Tom Greenleaf on Nov 1, 2012, 6:06 AM)
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Hammer Time
Ultimate Carjunky
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Nov 1, 2012, 8:26 AM
Post #11 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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No, that does not make it TBI. It never was and never will be a TBI injection. It's a "W" motor.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Nov 4, 2012, 10:35 AM
Post #12 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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I have real info now
Code scan results P0302
#2 cylinder misfire
flashing O2, EGR, and Cat
Compression test 160 psi for #2, rules out blown head gasket?
PCV valve sems good (old school rattle test)
Starting with new plugs and wires even though the plug looks fine. Lots of possible suspects, but if anyone can tell me what's most likely, I'd appreciate it.
I apologize for my earlier errors. I sold new/used chevys from 1989-2006 and got my facts mixed up.
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Hammer Time
Ultimate Carjunky
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Nov 4, 2012, 10:39 AM
Post #13 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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The first thing I would do is pull the plug and see what it looks like. If it's snow white and clean, you can pretty much eliminate spark as the issue and go right to the injector. If the old plug is dirty and fouled, the plugs and wires sound like a good idea.
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jcalan
Novice
Nov 4, 2012, 11:54 AM
Post #14 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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further research, I've found the following:
"The “W” engine code on 1996 and newer uses Central Sequential Fuel Injection, (CSFI) controlled by OBDII engine controls. There are 6 injectors that are centrally located inside the plenum. There is a fuel line connected to each injector; at the other end of each line is a plastic nozzle with a spring loaded poppet valve."
Do you think it's more likely to be the injector itself, of the nozzle? Or should they both be replaced together?
At $63 each, I don't have the coin to replace all 6 injectors or throw money at it putting in parts that don't resolve the problem. I don't have a way of checking fuel pressure either.
Thanks
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Hammer Time
Ultimate Carjunky
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Nov 4, 2012, 11:56 AM
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Nobody suggested replacing any injectors. Are you readings these posts?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Nov 4, 2012, 12:02 PM
Post #16 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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you wrote
" If it's snow white and clean, you can pretty much eliminate spark as the issue and go right to the injector."
The plug is snow white and clean, so I'm goning right to the injector.
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Discretesignals
Ultimate Carjunky
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Nov 4, 2012, 12:06 PM
Post #17 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Sticking poppet valves was common on CSFI. Something to consider.
You still need to verify good spark, injector control, and do a running compression test to check engine breathing. You could have a stuck closed exhaust valve and still have good compression. Another possibility is a stuck rich O2 sensor on that bank causing the engine controller to lean out that bank. You really need to have it diagnosed by a qualified technician if you don't have the right equipment.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Nov 4, 2012, 12:22 PM)
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Hammer Time
Ultimate Carjunky
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Nov 4, 2012, 12:08 PM
Post #18 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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"going to the injectors" would mean testing injector operation, not throwing parts at it.
That would involve doing an injector balance test using a fuel pressure gauge with a timed injector opening and verifying injector pulse to that injector
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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jcalan
Novice
Nov 4, 2012, 2:47 PM
Post #19 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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thank you. Heading to the shop next. I just replaced the plugs and wires and it made a moderate improvement but the problem remains. Cap and rotor are less than a year old and show no signs of wear. I've gone as far as I can on my own. So my next move is to follow your suggestion and take it in for diagostics. It's a rough enough vehicle it's not worth spending hudreds on, so I may try a new nozzle first, they're cheap, but probably not. I've about had it on this one.
side note:
the coolant leak mentioned above was a cracked heater return hose fitting. It was unrelated and I found it when I was digging around for an ignition problem. A tiny bit of sideways pressure on the hose and it started to squirt from the fitting. Less than a gallon of coolant was lost. The thing is that when I just went to unclip the hose from the connector, the exposed part of the connector came off in my hands (metal fatigue?) leaving anout 3 threads sticking out of the manifold, nothing left to get a grip on to remove the rest. Easy out didn't work, I was able to get enough torque on it that the wrench actually snapped and the threaded pipe didn't even budge. So I had to drill it out and re-tap. it's not easy finding a 3/4" pipe thread tap. But I found one after a few phone calls, tapped it, installed the new connector, ran it up to temp and re-filled the coolant. So at least I was able to get that little problem fixed with a $10 part and $30 in tools I'll never use again. I know I saved a couple hundred in labor costs :)
"there are many things I don't know how to do, until I do them. A new and unfamiliar task is the best educator"
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Sidom
Veteran
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Nov 4, 2012, 3:34 PM
Post #21 of 21
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Re: Sudden onset while driving, misfire, rough idle 96 C1500 4.3
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Just a quick footnote.......These caps had/have a big problem with crossfiring in the cap and because of the design, a lot of the times you can't see it......
If you have access to a ign scope you could comfirm it with that.....
I would only use an a/c cap, I've had bad caps right out the box with am brands...
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