Car bogs down when in gear at WOT
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
Car bogs down when in gear at WOT
77 with a q jet, Car will rev fine (5500 rpm's) in neutral but bogs down when in gear If I go WOT. I think its the Carb. Timing is fine , runs fine. shifts good. what could cause the bog?
Tech Contributor
Joined: Aug 1999
Posts: 14,382
Likes: 6,402
From: At my Bar drinking and wrenching in Lafayette Colorado
There are 3 likely causes:
1. Secondary airvalve spring windup is too loose. Make sure the spring windup is set at 3/4 turn and no looser.
2. Plugged filter. Replace the in-carb filter and make sure there are no other filters installed in-line anywhere.
3. Kinked rubber fuel line section. There are rubber fuel line sections back at the fuel tank and between the frame and the pump. Make sure none of the rubber lines are konked (common problem).
Lars
1. Secondary airvalve spring windup is too loose. Make sure the spring windup is set at 3/4 turn and no looser.
2. Plugged filter. Replace the in-carb filter and make sure there are no other filters installed in-line anywhere.
3. Kinked rubber fuel line section. There are rubber fuel line sections back at the fuel tank and between the frame and the pump. Make sure none of the rubber lines are konked (common problem).
Lars
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
There are 3 likely causes:
1. Secondary airvalve spring windup is too loose. Make sure the spring windup is set at 3/4 turn and no looser.
2. Plugged filter. Replace the in-carb filter and make sure there are no other filters installed in-line anywhere.
3. Kinked rubber fuel line section. There are rubber fuel line sections back at the fuel tank and between the frame and the pump. Make sure none of the rubber lines are konked (common problem).
Lars
1. Secondary airvalve spring windup is too loose. Make sure the spring windup is set at 3/4 turn and no looser.
2. Plugged filter. Replace the in-carb filter and make sure there are no other filters installed in-line anywhere.
3. Kinked rubber fuel line section. There are rubber fuel line sections back at the fuel tank and between the frame and the pump. Make sure none of the rubber lines are konked (common problem).
Lars
Thanks
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
Okay did the secondary windup and it was loose so I tightened it up as told. Car still bogs when driving with a WOT burst. Funny thing is it will have no problem in neutral as it will shoot right up to 5K. I'm confused here.
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
Points or electronic ignition?
edit:
Either way, ohm the spark plug wires, and the coil wire. Be sure to do the math for the different lengths.
edit:
Either way, ohm the spark plug wires, and the coil wire. Be sure to do the math for the different lengths.
Last edited by BigBlockTank; Dec 23, 2008 at 08:45 PM.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
Race Director
Joined: Jun 2000
Posts: 10,049
Likes: 676
From: FL
Air door = secondary air valve. Remember, the Q-Jet is a mechanical secondary carb but the air valve only opens on demand and there is no demand at idle even when revving the engine.
For timing, look for 36 degrees mechanical advance all in by 2500 rpm and an additional 14 degrees of vacuum for light cruise. I don't set advance at idle since I rarely drive with the engine at idle.
For timing, look for 36 degrees mechanical advance all in by 2500 rpm and an additional 14 degrees of vacuum for light cruise. I don't set advance at idle since I rarely drive with the engine at idle.
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
another problem?
Racer
Joined: Nov 2004
Posts: 485
Likes: 1
From: Oakville ON
There are brass tubes from secondary fuel wells that feeed the air door as it just begins to open. I havve seen these fall out onto the wells - no fuel as the air door starts to open = lean stubble. They are just a pressed fit into the air horn. If you have never taken the air horn off a Qjet before, I suggest you get some knowledgeable bud to help.
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
There are brass tubes from secondary fuel wells that feeed the air door as it just begins to open. I havve seen these fall out onto the wells - no fuel as the air door starts to open = lean stubble. They are just a pressed fit into the air horn. If you have never taken the air horn off a Qjet before, I suggest you get some knowledgeable bud to help.
Drifting
Joined: Aug 2007
Posts: 1,838
Likes: 13
From: Kingman AZ
If you let off the throttle a bit while its occurring do you regain some power and or bucking? If so I had the same problem. I thought it was the carb. So the smart thing was to get everything else right first. Tune-up, plugs wires,set up timing (32* all in.) Air filter fuel filter etc. It still bogged. So I rebuilt the carb. It still bogged. As a lot have explained in regards to a kinked fuel line, this was also my problem. It appeared to be OK looking at it but The fuel line from the frame transitioning to the pump was half collapsed and would not flow enough fuel to run over 4000 rpm while under load. Hope you can find the problem. It drove me nuts
Last edited by rayluka; Dec 24, 2008 at 02:24 PM.
Thread Starter
Melting Slicks
Joined: May 2000
Posts: 2,305
Likes: 5
From: Orlando,Fl,USA
If you let off the throttle a bit while its occurring do you regain some power and or bucking? If so I had the same problem. I thought it was the carb. So the smart thing was to get everything else right first. Tune-up, plugs wires,set up timing (32* all in.) Air filter fuel filter etc. It still bogged. So I rebuilt the carb. It still bogged. As a lot have explained in regards to a kinked fuel line, this was also my problem. It appeared to be OK looking at it but The fuel line from the frame transitioning to the pump was half collapsed and would not flow enough fuel to run over 4000 rpm while under load. Hope you can find the problem. It drove me nuts
I just can't understand the load vs no load difference.
Burning Brakes
Joined: Jul 2008
Posts: 876
Likes: 0
From: Canastota Ny
yeah this really sounds like an ignition problem to me. how is the module? has it been replaced or did you put a new one in with no heatsink compound? it sounds like something cant quite catch up to the rpms. its accelerates fine up to 5500rpm? almost like the coil heat up and drops off. have you changed anything latetly?