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4.3 vortec sputter random
07-27-2013, 11:20 PM
Post: #1
Shy 4.3 vortec sputter random
Need serious help chasing a ghost! 97 chevy express 4.3 a one wagon service truck been down 3 weeks not running I am not working, it has been to 3 shops and the dealer , still same problem (symptoms) cold engine patt the gas and a slight choke idles smooth, engine temp at about 120 it begins to stutter even on lite acceleration ok here we go items that have been replaced in this order, fuel pump a good one @55/58 psi,plugs ,wires,distributor,icm went out,cooling sensor,injection spider,and upstream 02 sensor, dealer said timing advanced 14dg.claim to adjusted (BS)no clue how starts very easy does not stall, just stutters like Mell Tillis, some low popping not really a backfire some valve rattle on bank 2 where codes have said random misfire.[/b] alternator, 6 mo. old plenty of juice.no Cat Thanks
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07-28-2013, 08:40 PM
Post: #2
RE: 4.3 vortec sputter random
I have a small fleet of 4.3 vehicles and I have seen this before, but always a different solution.

What you have not replaced is the ignition coil, and that's about the right age.

Secondly, every aftermarket distributor I have use has had a bad cap / rotor within 10,000 miles or less. Nobody outside of Delco / Delphi has figured out how to make a good cap for that engine.

Both of these items can give you a random misfire code.
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07-29-2013, 12:36 AM (This post was last modified: 07-29-2013 01:04 AM by maxx.)
Post: #3
RE: 4.3 vortec sputter random
(07-28-2013 08:40 PM)Rupe Wrote:  I have a small fleet of 4.3 vehicles and I have seen this before, but always a different solution.

What you have not replaced is the ignition coil, and that's about the right age.

Secondly, every aftermarket distributor I have use has had a bad cap / rotor within 10,000 miles or less. Nobody outside of Delco / Delphi has figured out how to make a good cap for that engine.

Both of these items can give you a random misfire code.

Hey Thanks for the reply, However I have a twist check this out, I noticed oil on front of the engine this morning below harmonic balancer. Pulled front of engine down and noticed plastic timing chain cover, removed the camshaft sensor and it was chewed up. appears that the timing chain cover has warped from heat or just age, so it has caused damaged to the sensor,by contact to the component target wheel it reads, also News to me this cover is a must to be replaced when timing work is performed (its plastic and the autoparts store does stock them $36.00) I hope this will help a lot of people save some $ I have thrown away not to ever forget the frustration. this case resolved

I would like to add some info there is a Bulletin on this and you would think the Chey dealer would check for it.however there is a youtube video I would like to share on a quick roadside fix for this problem called to shim or not to shim http://www.youtube.com/watch?v=KLC0E7N47Lw for informational purpose only I am not promoting. it kinda explains this problem. Thanks Again
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07-29-2013, 10:10 AM
Post: #4
RE: 4.3 vortec sputter random
Just for clarification this is the crankshaft position sensor and usually sets it's own code (P0335) when there's a problem. The 4.3 cam position sensor is part of the distributor, which is why most of these do not have a traditional timing adjustment. Typical timing found with a scan tool runs between 12 and 19 degrees at idle and is set by the PCM. I knew about those single use timing covers. Have only changed one in 20 years. They are pretty tough and don't usually leak. Now, the question in my mind is why don't we have a code in storage for the crank signal?

What I would do after you get it runnng again is get those codes cleared and drive it for a week to make sure there are no intermittent issues. That way if the light comes on again at least you know it's something new and not old information.
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07-29-2013, 10:45 PM
Post: #5
RE: 4.3 vortec sputter random
(07-29-2013 10:10 AM)Rupe Wrote:  Just for clarification this is the crankshaft position sensor and usually sets it's own code (P0335) when there's a problem. The 4.3 cam position sensor is part of the distributor, which is why most of these do not have a traditional timing adjustment. Typical timing found with a scan tool runs between 12 and 19 degrees at idle and is set by the PCM. I knew about those single use timing covers. Have only changed one in 20 years. They are pretty tough and don't usually leak. Now, the question in my mind is why don't we have a code in storage for the crank signal?

What I would do after you get it runnng again is get those codes cleared and drive it for a week to make sure there are no intermittent issues. That way if the light comes on again at least you know it's something new and not old information.

Yes, It is a CPS and during one of the visits to the shop there was a code, however it had been replaced, I am leary just too see if this is only one or several things, i have suspected a coil also a few weeks ago while driving at 60-70 mph it just died and a no start, come to find out no fire something knocked out the ICM any direction on this.and the coil has never been replaced with 187K on it.
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07-29-2013, 11:03 PM (This post was last modified: 07-29-2013 11:06 PM by Rupe.)
Post: #6
RE: 4.3 vortec sputter random
Ignition control modules do go bad but the most common reason is old age. (and I suspect the extra heat because this is a van) Seeing as the vehicle is 15 years old I don't find this unusual. A bad ICM does not usually set a code.

I suspect you will continue to chase this ghost unless you get down to business and do a proper diagnosis, like using a scanner and seeing exactly what the codes are. If you post the codes we can more easily guide you through the process.
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10-01-2013, 12:03 PM
Post: #7
RE: 4.3 vortec sputter random
(07-29-2013 11:03 PM)Rupe Wrote:  Ignition control modules do go bad but the most common reason is old age. (and I suspect the extra heat because this is a van) Seeing as the vehicle is 15 years old I don't find this unusual. A bad ICM does not usually set a code.

I suspect you will continue to chase this ghost unless you get down to business and do a proper diagnosis, like using a scanner and seeing exactly what the codes are. If you post the codes we can more easily guide you through the process.

Rupe, I took your advice after the reply to 'get down to business' and found someone who could do a proper diagnosis, and after a history review he determined that (new cheap wires I installed) where the problem the wires were cross firing to the heat shield at the boot(2) wires to be exact, what makes it so bad is when you think new parts are good parts the cheap wires were $42.00 and the good ones were double the $$ its been several weeks now and no problems.turns out to been a headache.
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10-01-2013, 09:41 PM (This post was last modified: 10-01-2013 09:46 PM by Rupe.)
Post: #8
RE: 4.3 vortec sputter random
BINGO! (and thanks for the follow up)

Now, something we can all learn from...

You said they found at least two (obvious) bad wires, which if the skip had gone on long enough would have set individual codes. (cyl 2 and cyl 4 for example) It takes 3-5 seconds of the problem persisting before the ECM will set a code. 2 seconds off a traffic light will not do it. OTOH, because they just happened to be bad / leaking juice for the same reason then that's why you got a random misfire code. IOW, the same condition (heat, moisture, etc) was the cause of leaking high voltage on a chinsey set of wires. BTW, that may also be the cause of the ICM and / or the coil going out. They were weak with age and the voltage spikes finally got to them. I have been changing them at 200,000 miles "just because" I don't want down time on the fleet. (half on my fleet is over 200,000 miles)

Short side track here: A few years ago I sent one of our 4.3 V-6 Astro vans out to have the engine changed and all was fine for about a year, then a random skip set in. Further investigation showed the guy had installed off brand plugs gapped at .080" and that application calls for platinum plugs gapped at .060" so I figured I had found the issue. (nope, not yet) The guy had also put the exhaust manifolds on with an air gun so those small heat shields for the plug wires were twisted. There was no clearance and they had chaffed through a couple of the spark plug boots on the wires! Fixing the lack of clearance and a new set of OEM wires with OEM plugs solved the problem.

Now the obvious... OEM parts (Delco in this case) are over $200 for a tune up at wholesale price. (cap, rotor, wires, plugs) OTOH, they will last 100,000 miles. Which is cheaper, the discount parts or the down time and head scratching to do it right down the road? As I stated earlier, I have a small fleet and down time is an issue when it comes to the bottom line in business. If the van needs to be towed only once it was probably cheaper to spend the extra $100 for the OEM parts. The time spent in the shop is probably another $600 / day of lost income for a man not being on the road. (not counting my time for repairs)

Oh, and thanks for listening to my short rant!
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