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I have a 1973 Omega with a 1969 Rocket 350 in it, over the last few years, and mainly this year ive been putting work into gradually to get it running and driving perfect while using it as my daily driver at the same time. This is the first year ive had it on the road all year basically though.
Over the last few weeks I got the car running pretty much damn near perfect, but a few days ago it started sort of having a very slight miss at idle that would seem to come and go. The car however runs flawless when driving. gradually it got worse until the car was idling crappy all the time. A few months ago I changed all the ignition parts, plugs, coil, points condenser, etc everything except for the cap as the one on their looked ok and money was tight, well I decided the cap might be the culprit and when I replaced it noticed a few of the terminals looked a it burnt. Replaced it and the car ran pretty much perfect for a day or so and then it started coming back. It could have just been coincidence.
I've tried screwing with the idle mixture and set it a few times with a vacuum gauge and tinkered with it back and forth from there. Ive noticed when I bottom out the idle scews one is 90 degrees opposite the other, ive been turning them out the same amount of turns each but shold I be adjusting them slightly differet? tried re arranging plug wires and making sure theyre all spaced and not touching as much as possible.
One of my wires off the negatve side of the ignition coil had sort of got hooked on the positive terminal, I fixed this and the car seemed to run really good when I Went up to the store to buy spark plug wire seperators, but once I got home and put the wire seperators in it seemed to have come back and was pretty bad when I shut the car off.
My air cleaner sits really close to the ignition coil and infact sort of rubs up against it and sits close to the negative terminal. This hasnt been a problem before but I covered the bottom side of the air cleaner closer to the coil with electrical tape to see if it made a difference.
I noticed that it seemed to be the worst after coming to stop sometimes, that I could get it to go away screwing with the car but then once id take it around the block itd come back.
The carb is rebuilt by me a few months ago and the float and everything was ok then and I Dont think its gone bad but I guess it could be a possibility.
Ive noticed that when the problem is there my aftermarket tach can be quite jumpy but when it isnt there the tach is nice and smooth which makes me think it is some kind of misfire issue but I guess it could also be an idle mixtue issue? Im thinking it might be a fuel issue too because sometimes the idle speed seems to fluctuate a bit with the problem.
This is starting to drive me nuts and gtting frustrating because I had the car running flawlessly for a bit and now a new issue.
Am I setting the idle mixture wrong? I'll turn the idle screws out to about 2 turns and fire the car up and then turn each screw a quarter turn at a time unti I get the most vacuum and the car runs smooth. Ive tried running it on the rich side of this and the lean side of this with no improvement, could it be a problem with the mixture from side to side?
Also I feel I should add that it doesnt seem to do it in park when the idle is higher as much as it does it when it is in gear, dont know if that helps at all
What is your dwell and timing set to? When you adjusted your a/f mixture screws did you adjust for the highest vacuum making them even and the turn the screws in 1/8 of a turn? Are all your spark plug wires seated correctly? Have you tried driving it with the tach disconnected?
I don't think you can do much more than what you have. Except even more carefully scrutinize the same things once again.
I'm not surprised this gremlin occurs when you idle in gear. The weakest link rears its head here, you just have to find it. It might be electrical OR carb related..It could even be a mechanical problem, like a valve not quite sealing every few revs or maybe even a little oil fouling on plugs now and then.
One might suggest a electronic ignition upgrade but I wouldn't rush out and do that.
An older engine with some miles might just behave like this, its a compromise to get it to run best you can. Sometimes its just not perfect.
I would be curious to know what a vacum guage reading looks like on your engine, have you got a reading on that? Is it steady?
Cant rememeber what we set the dwell to but it was the suggested setting for the engine from the books I have. Timing was set to the same specs but I think the timing chain is a bit stretched as I advanced it from there a little bit and got the engine making more power but I dont know the exact setting.
Yes I adjusted the air fuel for highest reading but I did not turn them 1/8th in after and I did set them evenly, I did screw with them after that so maybe I got them mixed up, I'll re set them tomorrow.
Vaccum reading was a steady 21-22 or so in park, and id say just over 15 when in gear. It would sometimes jump if the car missed but other than that was steady. At least im prety sure its steady, there would be a tiny bit of movement sometimes but I mean not enough movement that the reading was changing. This is plugged into main manifold vacuum.
I would think maybe the engine was just like this if it wasnt running so strong just a few days ago.
Im pretty sure all the plug wires are good as they are a few months old but I just bought basic cheapo ones.
I havent tried taking the tach out, I just put it in a few weeks ago and had no issues, I dont think the connection on the ignition coil are a problem as I double checked them today.
Any chance this could be connected to the fast idle adjustment screw somehow? Maybe something on that side of the carb acting strange?
The fast idle cam works hand in hand with the proper choke setting, are suggesting this to be a problem?
OR...Are you saying...If you trying to adjust the curb idle screws and they do nothing at all, its possible the throttle plates are past the idle ports.
Just so were clear here, any time you adjust your dwell or your timing, you will most likely have to adjust your idle screw on the driver side of the carb.
No the idle screws work fine I was just tooling around with the fast idle a couple days ago and thought maybe I could have screwed something up but I just checked it now and its set ok.
The dwell and everything was set a couple months ago at school with my teachers assistance when I changed the points, condenser etc. 30 sounds about right.
Choke is set right or at least good enough, Ive been through making sure all of that is working right a few months ago when I had to fabricate a custom bracket to mount a thermostatic coil that was missing as my car has a late 70s GMC truck carb on it and they have a different coil than an Olds quadrajet.
The idle screw on the side of the carb, that is new to me, could you go into more detail please?
Yeah those are what I have been adjusting to set the fuel mixture. Gonna reset them again tomorrow when its light out again and I wont be keeping the neighbors up revving it haha
Your vacuum is good and steady, so I would rule out any valve issues. I would also suggest to look down into the throat of the carb and see if its dribbling or spitting fuel while its idling.
I was thinking this maybe, I always run 91 in my car though as its a high compression engine. But the car again doesnt have any problems off idle so would think bad gas would be bad all the time?
I'll start messing with the carb again in a little bit here.
Last edited by CyberCholo; October 30th, 2016 at 11:30 AM.
Pulled the new distributor cap off and noticed some of the terminals had black soot on them. cleaned them off and notice a big improvement but the mis was still there. At this point I realized the end of the rotor had some black build up on it too, cleaned that up put it back together and the car ran and idled perfect. Tach needle was dead steady.
Took it around the block once floored it a few times and ran great noticed the idle mixture seemd a bit rich so took it back home and changed it noticed when I got home tach needle seemed jumpy when I shut the car off but the wire also runs fairly close to some spark plug wires but at the same time it was perfect just before that.
Started it back up car idled good and tach wire didnt seem jumpy anymore, took it around the block one more time and noticed when I got home tach needle was a jumping a bit again and seemed to have a very slight miss here and there when idling.
Havent opened it back up yet but any ideas to what this could be?
Distributor had a problem with water penetration, when you open the hood up and its wet water will drip down right into the area of the dizzy. It has a lot of surface rust inside except for the new points etc.
I noticed on the bottom of the rotor there was a fair bit of rust coloured dust.
Could the problem be rust powder in the cap floating around in there somehow and causing arcing?
Also is there supposed to be some sort of rubber o-ring on the bottom of the cap to prevent moisture getting in? It is the rainy season now here but today is dry and sunny.
No, there is no oring at the cap. Does your engine have blowby, smoke coming from the valve covers and oil fill tube? You may be getting some up through the distributor. Double check your pcv and you may need to add a way to vent the opposite valve cover to the carb air cleaner for some additional relief.
The engine does not have any smoke coming out of the valve covers, I have a brand new PCV valve on one valve cover and a brand new crankcase breather on the other valve cover. If I pull the PCV valve out when its running there is some smoke but im guessing thats to be expected as thats the crankcase ventiation of gasses?
I have not ran the engine with the oil cap off to see if smoke comes out but none comes out when I run it with the cap on.
The engine does burn a little bit of oil though so I wouldnt be surprised if thee is some blowby.
Maybe I will replace the PCV valve anyways, they are cheap enough.
Ok well I cleaned it a second time and blew everything out with compressed air and took it for a drive and it seems to be good but there was a moment it missed 3 times slightly at a light just before I got home that kind of scared me.
Im wondering if its possible the ignition coil has had some sort of problem or failure early? Its just a cheapo one I got off rockauto when I was in school as I didnt have a whole lot of money, it was the cheapest one in the direct replacement section WPS was the brand, now im wondering if maybe I should have sprung for a few more bucks and got a Standard Motor Products one.
I'll replace the PCV tomorrow and see what happens after some more driving.
If the pcv was replaced and correct I see no reason to buy another new one. If your getting a good spark out of your current coil its probably fine. Generally they work or they don't. If the inside of your cap and rotor are getting coated with an oily film then my theory is correct and your engine is going to need some additional help by running a breather tube from the valve cover opposite from the pcv to the air cleaner. It may provide enough negative vacuum to suck it back through the carb and relieve the pressure going to the distributor. I can't remember if under rotor in the distributor shaft there is a felt plug stuffed in there.
It looks like it was there, I could see a little back wire running into what appeared to be a felt/rubber plug of some sort, felt soft.
I ran it by my teacher and he was of the opinion its getting moisture in it somehow, I mean it has started getting really rainy here now but I dunno water doesnt drip right onto the cap.
I drove the car to school and back today and it seemed good but now im super paranoid of every slight bump from the engine and tach needle shake. I gave everything a very thorough clean and blew the distributor out with compressed air, noticed some rust dust piled up by where that felt cap was. Well see how it holds for a few days, if not perhaps I'll have to get a cover for the distributor.
Have you finally fix the problem? I have a 72 CS with all original Rocket 350, and it has identical problem like yours, even the rust dust in the distributor, and I also use it as daily and suddenly car idle bad and my tach also jumpy, I try to fix it and replaced everything related to ignition, but problem still there
October 29th, 2016, 06:55 PM
