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#1 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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My truck has a slight miss! BUt NOT ALL THE TIME?? Help me out here!
I have a 305 in the truck, I did a complete tune up on it about 3 months ago, rotor, cap, wires, plugs. All new, it has been running great. Smooth, but before I did this it had a slight miss, but not all the time, and just at idle, not under a load. Well, now that slight miss is back, but it is not all the time. What I mean by this, is some days it runs very very smooth, then one day I might get in it and it pull up to a light, and there it is, it is not a constant miss either, just every now and then you can feel it. Hell, I might go a whole week with out feeling it, then all of a sudden, there it is again, I have also upgraded my chargeing system, I thought it might have been that at one time, but it's still doing it! I have a 140 amp alt, internal regulated. One wire .Sowhat doyou think it could be? I wish I could some how, exssplain better of what it is doing, but it's hard too.
Sam
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72 LWB chevy truck. Pasadena, Texas |
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#2 |
Registered User
Join Date: Mar 2003
Location: Stillwater MN
Posts: 1,166
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sam, I hear ya buudy... I have the same thing in my 95 K1500 with 350. Replaced the coil, wires, cap, rotor, and plugs. Thought the intermittent miss was gone, and a week later it came back!! Sorry I'm no help, but I know what you mean, and will be closely monitering this post for advice also. Drives ya nuckin futs doesn't it!!!
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69 GMC K10 ..some restoration required....still.. ![]() |
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#3 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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class of 69,
Yeah it will drive you nuts! I don't understand this one, hell there is times when it goes away for like a month, then it's back, then it might do it everyday, for like 5 days, then it goes away, it isn't a big miss, just real slight, enough to feel it. Sam
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72 LWB chevy truck. Pasadena, Texas |
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#4 |
Registered User
Join Date: Jan 2001
Location: Killingworth, CT. USA
Posts: 3,378
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The carb (assuming it's carberated) may be running a little off. How do the plugs look? What color? Are they uniform? What color does the inside of the tail pipe(s) look like?
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1971 C10 swb stepside 350/700R4/3.73posi (retired as of 4/22/03) 1998 S10 short bed 2002 S10 Blazer 1942 Oldsmobile 1958 Massey Harris Pony 1951 Wife Killingworth, Connecticut May those who love us, love us, any of those who do not love us, may God turn their hearts. And if God is unable to turn their hearts, may he turn their ankles so we may know them by their limping. A man who works with his hands is a laborer; a man who works with his hands and his brain is a craftsman; but a man who works with his hands and his brain and his heart is an artist. |
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#5 |
Gotta Startem Early
Join Date: Oct 2001
Location: Amarillo, TX, USA
Posts: 364
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Had the same problem on my 99, I changed the plugs and it went away. The original plugs only had 25K miles on them. I installed the new Bosch Platinum 4, hadnt had a problem in 12K miles.
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67 SWB In Progress, one piece at a time, maybe 3 years I will be finished |
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#6 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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It is carerated, I have not pulled the plugs out since I put them in about three months ago, they don't have 5000 miles on them yet, they are Auto lite platinum. I have adjusted the carb, to where I recieve max vacuum on a gauge. Way does'nt it do it all the time? It acts like a egnition problem, but hell it does not do it constant enough to try and pin it down.
Sam
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72 LWB chevy truck. Pasadena, Texas |
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#7 |
Registered User
Join Date: Mar 2002
Location: Fairdale, Kentucky
Posts: 46
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They stick autolites in fords don`t they? That could be your problem.
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#8 |
Roadtrip!
![]() Join Date: Feb 2003
Location: Grand Rapids MN
Posts: 13,724
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miss
Running headers? Might want to check plug wires just to make sure they are not arcing on metal somewhere. Even if wires are new doesn't mean they are good.
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#9 |
My other Love
Join Date: Aug 2001
Location: Castlegar B.C. Canada
Posts: 4,085
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Speaking of Fords no matter what I do to my 300 straight 6 it still misses at idle, so as far as I am concerned it can miss till the cows come home.
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![]() Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life |
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#10 |
Senior Member
![]() Join Date: Feb 2003
Location: WIS
Posts: 1,752
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miss
If your ignition is up to snuff, check for a vacuum leak, especially around the intake/head areas. Possibly to power brake booster.
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#11 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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I don't have headers, I looked at this the other night, didn't see any arcing at all. Now as far as a vacuum leak, that is what I was thinking also, going to check it out this weekend, probabley change out all the hoses and see how that goes.
Sam
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72 LWB chevy truck. Pasadena, Texas |
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#12 |
Registered User
Join Date: Jan 2003
Location: Washington State
Posts: 8,834
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sam's 72, I have to agree the Autolites belong in the F**ds (don't like to swear on the board)
adamls I like the Bosch plugs, I put them in my 89 Harley.
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1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo |
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#13 |
I miss this truck.
Join Date: Dec 2001
Location: Lexington, KY U.S.A.
Posts: 2,863
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Sam, electric or mechanical fuel pump? On my '91 w/350 I had EXACTLY the problem you are describing until the electric pump quit completely one day. After replacing pump, miss went away.
Class of '69, on your '95, you should be able to hear the pump. It'll be a real high pitched buzz coming from the behind the cab. If it sounds kinda sick or intermittent when the truck is missing, then I'd go to NAPA and get a pump for $30. Make sure you drive most of the gas out before you drop that tank, though. HEAVY.
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'07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT. |
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#14 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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The fuel pump is mechanical, I have removed the fuel filter from the carb, and installed a inline filter.
Sam
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72 LWB chevy truck. Pasadena, Texas |
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#15 |
Registered User
Join Date: Feb 2000
Location: Edmonton, Alberta, Canada
Posts: 599
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What are your plugs gapped at? My truck was idleing poorly, pulled the plugs, one was at .06?!? regaped them all to .45, smoothed it out alot. maybe too much vac advance at idle? Good luck
Jesse
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Edmonton, Alberta, 67 c-10, Long fleet, front disks, 5 lug rear end, 327 with Vortechs, edlbrock manifold, comp cams XE 256, 600cfm carb. Backed by a getrag 5 speed and 1 piece driveshaft. 1993 Dihatsu Hijet Jumbo cab 4x4, currently converting to battery electric power. |
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#16 |
Spank 'em if you got 'em!
Join Date: Nov 2002
Location: Kansas City
Posts: 628
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Mine does the same thing. Someone told me once that it could be the RV cam that I put in it, makes it harder to even out at idle. But I don't know anything about that. I think I might try that idea for checking the gap on the plugs.
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Long Knight '71 C-20, 350ci, TH350, Edl. 1406 Carb w/elec.choke, Ignitor ignition, Viper Tires, Orange Dipstick |
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#17 |
Registered User
Join Date: Mar 2003
Location: Stillwater MN
Posts: 1,166
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Tynee, I didn't feel it was fuel caused, but i may have to rethink that. The miss appears so suddenly, it's like the ignition switch is being turned off and on quickly. There have 3 times now when at a stop light , it just starts running really rough, and allmost feels like it will die. but when the light changes, and i give it throttle, it comes around again and runs smooth like nothing ever happened. Are these TBI's dependant on constant fuel pressure, unlike a float system?? The truck just turned 103 rounds, so any thing is possible. I put in the MSD Blaster coil, and Accel super stock wires, cap, and rotor. Stock AC plugs. It starts much quicker now, and runs very nice... until it starts missing!!
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69 GMC K10 ..some restoration required....still.. ![]() |
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#18 |
I miss this truck.
Join Date: Dec 2001
Location: Lexington, KY U.S.A.
Posts: 2,863
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Class, that sounds EXACTLY like my '91's symptoms. Had electronic diagnostics run, and they said the fuel pressure was low, probably due to a bad pump. I think the TBI's must be dependent on that constant pressure. If you've got a buddy with one of those Sun-pro scanners from Snap-On, it'll tell you what kind of pressure you're getting.
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'07 GMC Acadia SLT. Sweet ride. '08 Crew Cab Z-71 short bed. Really like this truck A LOT. |
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#19 |
Registered User
Join Date: Mar 2003
Location: Stillwater MN
Posts: 1,166
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Tynee, I'd have to take it to a shop for diagnosis.... may as well use the money for a new pump!! With the mileage on the truck, it won't hurt to just change it out. I'm planning on a 1600 mile parts run next week, And I don't need it dieing some where on the freeway! thanks for the help.. I hope Sams72 got some help from HIS thread!!??
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69 GMC K10 ..some restoration required....still.. ![]() |
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#20 |
Account Suspended
Join Date: Jan 2003
Location: Shadow of Lambeau Field
Posts: 5,597
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CO69, I replace a lot of GM fuel pumps, some even at 80,000 ticks. I would also look at the TPS. Also clean the fuel injectors and the valves.
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#21 |
Registered User
Join Date: Apr 2000
Location: Frisco, Tx, USA
Posts: 606
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Are you still running points? The dwell has a tendency to not stay set very long.
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http://home.comcast.net/~r.landrum/w...tos.html-.html '68 C-10 LWB, '98 Z-71 350 w/accessories (Serpentine), Edelbrock Performer, Edelbrock 1405 (600cfm) carb, GM HEI, CompCam Extreme 4x4 roller cam, Thorley Headers, Carter Electric Fuel Pump, Vintage Air, 700r4, 3.73, disc brakes and power steering upgrades. |
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#22 |
Seasonal Poster
Join Date: Apr 2002
Location: Kelowna BC Canada
Posts: 896
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Could be the Idle circuit in your carb is dirty, try cleaning the carb really well, this happened to me before, same sort of thing.
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67 GMC Short Step 350/4-Speed/3.08 Posi Front/Rear Sway Bars Kelowna BC, Canada Member of DTPW |
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#23 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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I posted this last week, I have not done anything to the truck, and now this week, it is running smooth as silk! I don't understand why it does this, makes me think that I might be getting bad gas, maybe a little water in it.
Hell, I don't know! Sam
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72 LWB chevy truck. Pasadena, Texas |
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#24 |
Account Suspended
Join Date: Jan 2003
Location: Shadow of Lambeau Field
Posts: 5,597
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Sam,
It just warmed up by you didn't it? Your choke might be off, and when it's cold, you could be rich, causing the plugs to foul out. When it warms up, the plugs clean up, and runs well. Sure sounds like that, or a secondary ignition problem of sorts. |
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#25 |
Senior Member
Join Date: Nov 2001
Location: Pasadena, Texas, USA
Posts: 1,005
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No, it does it after it has been warmed up, I can drive it 30 miles and sometimes this miss is there. But this week, it is running smooth. This has been going on for a while now, every since i bought the truck, and the miss is not constant, it is very slight.
dtlilly, what do you mean by secondary ignition problem of sorts. What can I look for? Sam
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72 LWB chevy truck. Pasadena, Texas |
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