12-15-2013, 03:15 PM | #1 |
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Qjet issue
I have a 305 with qjet that's giving me fits and I'm fresh out of ideas. So when the engine is cold it fires right up. The fast idle,choke and choke pull off work fine. Engine will kick off fast idle after couple min(it's -30c) here right now so it needs a few min warmup. Issue is it will die the second you try to drive away in gear if it's not warmed up longer than I feel it should need. If the engine is cold if you try to rev it up it will have a flat spot off idle circut and die out. And if you rev it up to around 1200 or so and hit throttle briskly it sounds like it just sucking air.
Carb has a fairly fresh rebuild but this is the first winter with it on,accelerator pump was changed and I have no idea why cold it would drive like this but warmed up it's ok.. It does have a delay when floored from a slow speed even warmed up but pulls hard once it kicks in. Engine is stock only egr is blocked off idk if that would make it act like that though. Thx for any insight . |
12-15-2013, 03:23 PM | #2 |
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Re: Qjet issue
Engine is stock!
Do you mean everything right down to factory exhaust, heat riser valve working, hot air to air cleaner from exhaust manifold kinda stock or have you modified any of that? |
12-15-2013, 03:26 PM | #3 |
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Re: Qjet issue
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12-15-2013, 03:36 PM | #4 |
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Re: Qjet issue
Try richening up your choke!
Turn the black cap ccw. |
12-15-2013, 03:40 PM | #5 |
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Re: Qjet issue
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12-15-2013, 04:19 PM | #6 |
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Re: Qjet issue
What's your timing set at?
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12-15-2013, 05:11 PM | #7 | |
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Re: Qjet issue
Quote:
Minus 22º c sounds cold. Is that pretty normal up there?
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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12-15-2013, 05:22 PM | #8 | |
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Re: Qjet issue
Quote:
Once engine is warm it's awesome so it's not the chokes fault. Car starts excellent in very cold temps it's the long warmup time to be able to drive away that's the issue. |
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12-15-2013, 05:31 PM | #9 |
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Re: Qjet issue
It's simple then! Your heat riser's not closing or the passage under the intake is plugged causing the fuel to puddle in the intake until the intake gets warm enough to keep the incoming fuel vapourized.
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12-15-2013, 05:37 PM | #10 | |
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Re: Qjet issue
Quote:
If it were mine, I would take the carb apart and double check everything including running wires through all the little openings (I use a cut guitar string), spray cleaning and air blowing all the small passages. Maybe another kit to insure the one in it is not defective.
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68 GMC 250/3 speed Saginaw p/b p/s 69 Chevy 350/350 currently in pieces still lookin for a cab 06 Trailblazer I just want a vehicle that I can work on, that won't talk to me, leave error msgs or keep track of how I drive... |
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12-15-2013, 05:40 PM | #11 |
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Re: Qjet issue
I thought of that too and it's seems to be closing via vacuum when cold and opens with the air cleaner door when warmed up. I would guess it's possible the flap in the riser is rusted away? I would guess I would need to take it apart to see for sure. I suppose I could disconnect it to see if the problem is no worse and it would give me an idea. Thx
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12-15-2013, 06:01 PM | #12 |
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Re: Qjet issue
I'd be more inclined to suspect a plugged intake passage. When you start it up cold and just before you'd normally kick it down, put your finger on the intake where the crossover is closest to the plenum and test for heat. If all is working right with the heat riser you should feel heat right away. No heat tells you it's plugged or the heat riser valve is not working.
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12-15-2013, 06:14 PM | #13 | |
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Re: Qjet issue
Quote:
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12-16-2013, 08:53 AM | #14 |
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Re: Qjet issue
Well I checked there and it was warm but not as warm as I'd think so it's a possibility that's the issue.
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12-16-2013, 10:30 AM | #15 |
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Re: Qjet issue
If everything is working like new you should at least feel some heat right away. At least in the first minute.
Does the flapper close completely on the air cleaner snout? |
12-16-2013, 02:18 PM | #16 |
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Re: Qjet issue
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12-16-2013, 02:31 PM | #17 |
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Re: Qjet issue
If you suspect the intake passage is plugged or the heat riser is gone you could set the flapper on the snout to stay closed all the time. Warm air fulltime won't hurt.
If the flapper is opening at 30 below the sensor on the air cleaner might be hooped. |
12-16-2013, 05:13 PM | #18 |
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Re: Qjet issue
Make sure the accel pump is working OK. Try raiseing the float level a little. If it has adjustable metering rod, raise the rods a little from the low position.
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12-16-2013, 05:36 PM | #19 |
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Re: Qjet issue
WOW at -30C you should have problems hehehhe
at single digits temps in F mine gets to be a picky girl that wants more heat up time a good 5mins+ and lots of rev's to clear her up to go. [ was 9F today, thermo stuck, coolant all over, fun] |
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