Throttle hesitation during light acceleration
Thread Starter
Instructor
Joined: Sep 2022
Posts: 119
Likes: 19
From: Aberdeen Washington
Throttle hesitation during light acceleration
Throttle hesitation during light acceleration.
87 convert anytime light acceleration is applied from a steady speed light hesitation is experienced, every time. Any ideas?
87 convert anytime light acceleration is applied from a steady speed light hesitation is experienced, every time. Any ideas?
Drifting
Joined: Jul 2022
Posts: 1,805
Likes: 365
From: Central Florida
A bit more info might help these great people help you.
1. How old is the tune-up?
2. test fuel pressure?
3. Air and fuel filter ages ?
4. Does it idle and start well, hard accelerate well ?
5. Any codes ?
6. Have you / how did you test for vacuum leaks?
7. How old are the O2, IAC, TPS ?
8. Any mods to engine ?
8. How old are fuel injectors, ohmed out with meter ?
9. The hesitation, is it a dead spot, a stumble = shakes/stutters a little, misfire, does nothing for a second etc ?
10. Soot in exhaust, smells rich, fuel mileage down ?
1. How old is the tune-up?
2. test fuel pressure?
3. Air and fuel filter ages ?
4. Does it idle and start well, hard accelerate well ?
5. Any codes ?
6. Have you / how did you test for vacuum leaks?
7. How old are the O2, IAC, TPS ?
8. Any mods to engine ?
8. How old are fuel injectors, ohmed out with meter ?
9. The hesitation, is it a dead spot, a stumble = shakes/stutters a little, misfire, does nothing for a second etc ?
10. Soot in exhaust, smells rich, fuel mileage down ?
Last edited by Vets-Vet; Jan 9, 2023 at 08:05 AM.
Melting Slicks
Joined: Aug 2003
Posts: 3,401
Likes: 397
From: Lakeville MI
Any time that there is any throttle movement, there should be a nearly instantaneous engine/vehicle response.
Here's an example log with some small throttle inputs and the resulting response shown (both step and ramp inputs): https://datazap.me/u/tequilaboy/roll...3656-3513-3552
Note how quickly the MAF, injector pw and IAC signals follow the throttle position, you can also see how the rpm and vehicle speed signals respond as well but to a lesser extent. There is no apparent delay other than maybe 100 ms, or so.
Without data, I would suspect an intake flow restriction like a clogged air filter or a fuel flow restriction, but I wouldn't expect a fuel related issue to recover quickly (assuming it does recover). Check the fuel pressure.
Other ideas: If auto trans could be converter slop and or unlocking that you feel. Ignition issue possible. Simply guess-work on my part.
Logging data with the appropriate tools can be useful to help diagnose issues like this.
Here's an example log with some small throttle inputs and the resulting response shown (both step and ramp inputs): https://datazap.me/u/tequilaboy/roll...3656-3513-3552
Note how quickly the MAF, injector pw and IAC signals follow the throttle position, you can also see how the rpm and vehicle speed signals respond as well but to a lesser extent. There is no apparent delay other than maybe 100 ms, or so.
Without data, I would suspect an intake flow restriction like a clogged air filter or a fuel flow restriction, but I wouldn't expect a fuel related issue to recover quickly (assuming it does recover). Check the fuel pressure.
Other ideas: If auto trans could be converter slop and or unlocking that you feel. Ignition issue possible. Simply guess-work on my part.
Logging data with the appropriate tools can be useful to help diagnose issues like this.
Last edited by tequilaboy; Jan 9, 2023 at 12:27 PM.
Thread Starter
Instructor
Joined: Sep 2022
Posts: 119
Likes: 19
From: Aberdeen Washington
Hesitation
Thank you for your replies. This car starts quickly takes throttle well stationary and during acceleration. Has recent injectors, clean air filter, clean exhaust.
No hesitation after initial one, like a late response to throttle. This car is my collector car and is rarely driven. Maybe 50 miles a year over the last 15 years. Sad I know. It’s a great car except for that. I’m considering selling it as I have too many cars but don’t want to pass on this issue.
No hesitation after initial one, like a late response to throttle. This car is my collector car and is rarely driven. Maybe 50 miles a year over the last 15 years. Sad I know. It’s a great car except for that. I’m considering selling it as I have too many cars but don’t want to pass on this issue.
