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SUDDEN ONSET- hard start and mid-throttle pinging

Can Can

Can Can

Pusher Man
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A couple of problems just suddenly appeared a couple of days ago with my 84(305/ 700r4).

First off, when the truck is first started, it just doesn't want to jump to high idle. The motor kind of struggles for a while and after about 10 seconds everything is ok. I've had this same problem for the past few years in the winter, but never when it's been warm out........I might add that if the motor is hot and the truck is left for about an hour, I really have to pour on the juice to get her going, but once she's started, the truck runs fine. I would assume that it is choke related.

The pinging thing started right around the same time. I know that Chevs are notorious for mid-throttle pinging, but I never experienced it until a couple of days ago. Just before it gets to the kickdown point(either while going uphill or passing on the highway) the engine will chatter like CRAZY until I force the tranny to kick down. Could my kickdown cable need to be adjusted?

I've replaced my fuel filter and cleaned all the linkages with carb leaner, but nothing seems to help. Like I said before, both conditions appeared out of the blue on the same day. Is there a chance that something has happened that could cause both problems?

Waiting patiently for King Grim to read this
smile.gif
!!!!!!!!!!!!!!!



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Had you filled the tank just before this started? Sounds like you might have picked up a bad tank of gas. I had this happen once in my '87. It ran like crap until the next time I filled it up (at a different station). Then it started running perfectly within a half-mile or so.
shocked.gif


<font color=black>HarryH3 - '75 K5</font color=black>
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It's a great day to be alive...
 
One more thing to check would be your plugs and wires. When my plugs were in bad shape, I got a lot of pinging and it was hard to start. Mine happened gradually over time so I didn't notice it as much until it was real bad. I just recently replaced the plugs and wires and it has never started easier or run smoother.

Just something to think about.

85 GMC Jimmy <a target="_blank" href=http://tx85gmcguy.alloffroad.com>tx85gmcguy.alloffroad.com</a>
 
Harry- I'm on my third tank of gas since the problems started(I'm on holidays and am putting on LOTS of miles). All three fills were at different stations, too. I changed out my fuel filter hoping that maybe I had picked some crap up somewhere, but nothing has changed.

Tx85- My plugs are next to new, but I haven't put on new wires in at least 25,000 miles. My next step is to do the cap, rotor and wires and see if anything else changes!!!!!!

Is there anything else I should be looking for? The vacuum lines all look good, BTW. Is there a way that the vacuum advance could be screwed up? What about my kickdown cable- anyway to tell if it's working properly? While I'm at it, I'll double check my timing, too.






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OK, night shift guys- Do you have anything to add??? I'm waiting patiently...................



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Have you checked your timing? timing chain? the gap on your plugs? should be .035" if your running a stock ignition , look into the choke.
Shawnboy

If you are having too much fun it's probably illegal.
 
Choke or the mixture solonoide gave it up. I'm leaning towards the mixture solonoid. Not allowing the fuel to richen up would cause it to hard start when cold. Choke could still be part of the problem or both. If the choke doesn't drop it locks out the secondaires so that could explain your ping mid rpm ping. The trottle will force the choke open but you can't get the secondaires to come on so it would lean out and ping. There is a little lever up behind the hoke housing that rides on the high idle cam and gets pushed into the way of a pin on the secondarie shaft.
The Choke and the mix solonoid work on the same electrical circuit. Check that you got power at the choke wire when the engine is running. No power start looking for a blown fuse. Still no power trace the wires back to the oil presure switch that controls them. The switch keeps power from the choke till the engine starts so you don't accidently cycle the choke buy tuning the key to run posisition but not starting the truck. Check and see if you got power on the other side of the oil presure switch. Key in run but doesn't have to be started. Will be located either behind the distibutor or above the oil filter. 3 wires on it one goes to ig, 1 to the choke and 1 to the mix solonoide.

If all that checks out take a meter and probe the temp sensor on the water neck for the mix solonoid. Unplug the mix sensor so you get just a reading on the sensor. Get a cold reading and then start the truck and make sure the resistance changes as it heats. My guess is it would get less resistance as the engine heats. I haven't played with on of these just did some reading on it and don't recall what way it needs to go.

It's not my damn planet monkey boy!
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Grim-Reaper
 
FWIW, if the mix solenoid goes belly up, I believe they are designed to go full rich. They are in the cars with the same general setup.



Dorian
My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>http://www.dorianyeager.com/index2.html</a>
No anti-theft measures on your truck? No pity when its stolen
 
Just so happens that I've had this problem exactly like you described and the timeing was off. Do you have a timeing light? Oh, don't look in it while it's flashing.....it's a very bright light!

I've got a mind like a . . . a . . . what's that thing called?

<a target="_blank" href=http://www.geocities.com/muddin4fun79blazer/>http://www.geocities.com/muddin4fun79blazer/</a>
 
Yeah.......I'm on holidays right now about 400 miles from home and haven't had a chance to check my timing yet. Monday night I'll take a closer look.

I did take a few minutes yesterday to climb inside the engine bay and see if anything other than the timing could be causing the problem. I ended up replacing a whack of dried out/cracked vacuum lines and that seemed to help a bit with the pinging. I also found a pretty decent crack on the vacuum line to the brake booster which probably explained why my brakes have been a little mushy lately...............
crazy.gif


Anyhow, I'll keep you posted as to what I find.



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Just my $.02 but I had a similar problem with my 305 after it had about 180,000 miles. It turned out to be a combination of problems....1st - TIMING - my distributor bearings were shot and I ended up replacing the distributor. This helped a bunch but I still had a problem. 2nd - PLUG WIRES - Two of my plug wires were shot and had worn throught the outer silicone. These plug wires were arcing to the exhaust manifold. I replaced them but the problem still existed when I put the engine under load (climbing a hill). 3rd - FUEL PUMP - The rubber diaphram inside the fuel pump was bad and the engine was not getting enough fuel so the entire engine lacked power and pinged when placed under load. It was not getting the gas it needed. I replaced the fuel pump and it worked like new.

I do not know if any of these fixes will help but that is what happened to me and how I made it all better.
The end.

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1986Blazer- Thanks for the input.

1.Cap, rotor, and wires are on the list.

2. I never really considered a worn out distributor shaft/bearings.........How do you check for wear on a distributor????

3. My fuel pump is electric and gives me as much fuel as I can use.

Thanks again for the helpful suggestions!!!!!
smile.gif




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In my case the wear was obvious. What it was doing was.....I would floor the gas and the distributor would try to adjust the timing based on the sudden surge of power but the adjustment would be negated due to the sloppy bearing and shaft. The difference was night and day once I put in the new distributor. THere are bearing wear tolerance measurements in the manuals but I did not bother with it because mine was so bad. I am sure there are other people on this board that can describe how to tell if it is worn.

Good luck!

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Sounds like the timing to me.

1987 Jimmy Sierra Classic, Palisades Park, NJ 07650
 
Sorry it took so long to respond, ya big lug!!!! It's always a pleasure to hear from you.............You should check in more often- things have changed a lot in the last year. Anyhow, brother, take care. When are you heading up to Edmonton next?

Keep in touch!!!!!!!!!!!!!!!
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