This will be the second time in 4 years that this has happened. The first time I "knew" it was the timing chain (but wasn't) and installed a direct drive gear set. Re-timed and has been running fine since.
Just the other day, I was driving through a neighborhood, almost idling. I turned onto a street, gave a bit of gas. and the engine stuttered - And just like that, it is now running like poo.
I can testify that everything is operating smoothly (bearings, push rods, etc) by using an automotive stethoscope all over the top and bottom of the engine. I just cant reason "how" the timing jumped, nor can I find where it jumped to. All I can achieve at this point is a very rough idle and a QJ that backfires under heavy pedal with no load.
A bit of info for the engine: 350 with stock internals, SMI QJ, Edelbrock 3701 intake, Accel Correction 8141R dizzy cap, new AC Delco plain jane spark plugs, Proform noisey direct drive, vacuum lines less than a year old.
I can only come with 2 ideas, both ignition related. Either my timing mysteriously jumped somehow, or my stock dizzy went south.
So before I tear down my engine, I thought I'd come through and present this case to the Pirate crew. Hopefully, someone can point out something I haven't thought of or considered looking at.
I hate asking for help, but here I am. Ask any questions and I'll respond quickly. Comments and suggestions are appreciated also.
Okay, thanks - I will take the carb to initial turns tomorrow and see what happens.
The QJ isnt even a month old from SMI and was running well. The cap is also just as new with no signs or odors. The rotor looks to be in good shape too, but I will remove it for better inspection tomorrow as well.
Isn't carb backfire a tell tale sign for timing being off ? I thought I read that somewhere a long time ago (Memory may be distorted at this point).
Thanks for the quick response, I'll provide feedback tomorrow.
Could be a vacuum leak from one of the intake gaskets. With the engine trying to idle, spray something flammable above each intake port and hope the idle improves.
If TH350, could be a bad vacuum regulator diaphragm, but then you should get some smoke out the exhaust.
Same deal but no smoke if it's a bad diaphragm for the vacuum advance.
Have an EGR valve on there?
The intake was installed not a month ago, for a second time within a weeks time. I didn't get a good seal on the rear right corner the first time. I am not suggesting the intake isn't a possibility, though - I'm just providing further information. I'll find something to shoot the ports with and give feedback.
"Just the other day" is actually 2 weeks ago - I haven't been able to get back to the issue until now. So, in a time frame perspective, this all happened approximately two weeks after I (1) replaced the dizzy cap with the corrective cap (to dress my cables), and (2) installed the new SMI carb and new intake. I had just finished tuning the carb (over a week of 30-40mph driving) when this occurred. The thing that blows is I was happy with it and ready to walk away. I guess the engine had other plans.
There is no vacuum on the dizzy.
There is an EGR - How would I check it ?
Let's talk about smoke out of the exhaust for a minute. It amuses me for some strange reason that you brought it up. I have very minimal smoke from my tips. BUT, I have a blow-by issue on both sides, right side being the worse of the two.
I'll shoot a picture of it and link it to my Bucket acct - I doubt I can post it here with under 20 posts. But, I have wondered if some rings gave up. I really need to run to Harbor Freight for a compression kit to check my cylinders but haven't yet. Maybe once I check all the previous suggestions I'll go pick one up.
The reason it amuses me though..... I've been looking at 383s all night.
I would take that accel corrected cap off and get a good replacement. I have heard nothing but problems with those things. Try that and see if that clears the problem up.
Troubleshoot the damn thing. Nobody gives a damn what you swapped 4 years ago.
Look at what is happening now, and figure it out with a fucking brain, instead of a goddamn internet thread.
What do your plugs look like?
Replace them, along with your cap and rotor. It's just basic maintenance.
What is your fuel pressure?
What is the condition of the filter. Nevermind, it doesn't matter. Swap it for fucks sake. It costs all of 3 dollars.
Quit fucking wondering if your timing jumped. It's a simple matter of hooking up a timing light and checking.
Hook a fucking vacuum gauge to it.
There are absolutely no secrets to troubleshooting a carbureted 350.
Go thru the basics and find the problem. It isn't hiding, and it isn't going to be mysterious, when you quit fucking around and start troubleshooting.
Troubleshooting is the act of making informed assumptions of what the problem might be, and then systematically either ruling them out or confirming them, thru the use of diagnostics. It isn't hocus pocus, and it isn't guessing on the internet.
It isn't running rough for no reason? There is a very real reason, and it is most likely a simple one
Oh, and why the hell do you not have vacuum to the distributor. If it isn't a comp only rig, it should be there:shaking:
Checking the EGR is easy enough, but if it idles but doesn't power up above that, it probably isn't the problem. Same goes for vacuum leaks. Typically the symptoms of both of those is worse at idle, and clears up to a degree when you feed it more fuel.
This is a 1986 350 with regular oil changes using Castrol GTX High Mileage 10W40 with no additives.
I pulled the cap this morning and basically stopped there. The cap and rotor are in good shape, but the ignition coil has a bare positive and a broken ground wire being held together with the insulation.
I am going to get a new coil and module. I will provide feedback once installed.
I'm going to go with a "no" on the roller cam. I have nothing special on the rocker arms, rods appear to be stock.
The module and coil are installed - It seems to be pretty smooth and responsive atm - Lost the carb backfire. I'm going to re-install my exhaust now so that I can hear better - Straight headers atm.
It was running smoothly until it got to operating temp. Backfire is back and a noticeable thump can be felt if I touch the AC comp. It doesn't have any particular rhythm to it but seems like a bearing on the way out perhaps.
I believe this is resolved - A week of driving will tell all.
So, this morning I ran out and bought an inline spark plug tester before beginning anything. I came back and checked my odd side. It was so inconsistent that I decided to go another route.
I pulled my cap, broke all my plug wires loose of clamps and such, and swapped from the correction cap to my old regular.
Problem is now gone. I drove around the neighborhood and a few main streets checking for response and all the symptoms that had disappeared - I found none.
So, I timed it back to 4+ approx 750-800 rpm, turned my QJ back down to 2 turns each side, and shut down. I'll DD it this week and see what happens.
I appreciate everyone's input in helping lead to a solution. I'm glad I chose to post as a last effort before tearing down - It turned out much better than if I hadn't that's for sure.
I'm still going to run a compression test later - Just not today. I'm curious of bleed down and the condition of my cylinders.
Nothing to see here - All points look fine.
But if you look at the top, all but 2 points (1&4) are scarred in some way. I didn't realize the impact this would have. I do now !
The ground is hanging by insulation right below the burn in the positive wire.
Just eye candy of July's paint job.
I'll report back next weekend with feedback and hopefully put this behind me for good.
This weekend I'll fine tune the QJ and check my cylinder compression numbers.
Thanks, once again, to everyone that responded with suggestions.
Troy B
Ft Hood, TX
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