car bogging when accelerating
Thread Starter
Heel & Toe
Joined: Apr 2015
Posts: 15
Likes: 0
car bogging when accelerating
Hello, I need your help please. I have an 85 corvette. About a week ago the car was completely bogging when you hit the gas. I brought it somewhere and after diagnosing it for over 3 hrs they said the fuel pump was bad. They were not able to do the work that day so I brought it somewhere else and told them it needed a fuel pump. This place (Sears) did not diagnose it. They put a new pump in, they said the screen was 90% clogged and changed the fuel filter. The car ran awesome after leaving. The next day I noticed it was bogging down again if I punched it or pushed the peddle more than half way. I brought it back today and they checked the pressure and all is good. One of the techs test drove it all ND said this is happening because the transmission isn't downshifting. The car ran great b4 I had this fuel pump issue. If anyone has any ideas it would be greatly appreciated. Thank you in advance!
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Is this a 4+3 or a auto? Either way if its not downshifting yes it would be sluggish. The automatic has a kickdown cable and they do need adjusted from time to time. Does the car downshift when you punch it from say 40mph?
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
What happens if you punch it and manually down shift (when speed is appropriate for a down shift, of course)?
Safety Car
Joined: Sep 2010
Posts: 3,752
Likes: 190
From: Indiana PA
Ok, lets narrow this down real fast. Take the car for a spin. Manually change the gears. Using 3 2 and 1. So get up to speed in D, then manually select 2nd and see if it then accelerates like it should. If it does, the transmission is NOT kicking down on its own. If it does not then you have other issues. RPM's should jump when you select 2nd. I would do this at about 40mph or so.
Thread Starter
Heel & Toe
Joined: Apr 2015
Posts: 15
Likes: 0
I have tried manually shifting. If I manually shift, it's fine til about half throttle. Then boggs down. If I'm in drive and drop down to 2nd it seems to accelerate better, but still boggs when you punch it. This jus started after new pump was put in. I never had this issue b4. If you punched it, it wouldn't hesitate at all??
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Sounds like you have two problems;
1. It should down shift when you "punch it", provided you're going a speed that is appropriate for a down shift
2. You're still starving for fuel, for what ever reason. Put a fuel pressure gauge on it, go out and recreate the symptom (bogging) observe your fuel pressure. Should be some where around 40 or so.
1. It should down shift when you "punch it", provided you're going a speed that is appropriate for a down shift
2. You're still starving for fuel, for what ever reason. Put a fuel pressure gauge on it, go out and recreate the symptom (bogging) observe your fuel pressure. Should be some where around 40 or so.
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Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
Are you able to accelerate long enough to get an o2 sensor voltage reading on a scanner? Needs to show the voltage during a full throttle pull. Driving at full throttle for about 5 seconds should be enough time to see o2 sensor voltage at full throttle.
Thread Starter
Heel & Toe
Joined: Apr 2015
Posts: 15
Likes: 0
I haven't checked O2 sensor yet. The car is just getting worse as I drive it. If I'm in park, I can't rev the engine more than 2400 rpm's. Driving is worse! It is completely bogging down which leads me to believe something is clogged. After getting the fuel pump replaced on Friday, the car ran the best since I've owned it.. so maybe a bad pump, although it was reading 40 psi? A few times I've noticed when I let the car go down to 1/4 tank it started to run sluggish. Maybe there is crap in the tank and the filter and or screen got clogged again? ?
Melting Slicks
Joined: Jun 2013
Posts: 3,065
Likes: 39
I haven't checked O2 sensor yet. The car is just getting worse as I drive it. If I'm in park, I can't rev the engine more than 2400 rpm's. Driving is worse! It is completely bogging down which leads me to believe something is clogged. After getting the fuel pump replaced on Friday, the car ran the best since I've owned it.. so maybe a bad pump, although it was reading 40 psi? A few times I've noticed when I let the car go down to 1/4 tank it started to run sluggish. Maybe there is crap in the tank and the filter and or screen got clogged again? ?
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,216
From: Park City Utah
Thread Starter
Heel & Toe
Joined: Apr 2015
Posts: 15
Likes: 0
Car still bogging
Hello, I'm still having some kind of restriction on my 85 corvette. It's ridiculous. It's has great fuel pressure, I had the cat hollowed out today cause they said it was clogged. Still same issue. Check engine light is finally on but probably because of the hollowing of the cat? Please help
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
Hello, I'm still having some kind of restriction on my 85 corvette. It's ridiculous. It's has great fuel pressure, I had the cat hollowed out today cause they said it was clogged. Still same issue. Check engine light is finally on but probably because of the hollowing of the cat? Please help
Race Director
Joined: Mar 2015
Posts: 15,926
Likes: 579
