# Rough idle after punching the gas **URL:** \ **Category:** Maintenance/Repairs\ **Tags:** van, chevrolet\ **Created:** [August 23, 2018, 7:09pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536 "2018-08-23T19:09:05Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 23, 2018, 7:09pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/1 "2018-08-23T19:09:05Z")
1978 G30 van 5.7 liter 350 small block. The other day I had to punch the gas in order to cross a busy street. Immediately after and ever since it has a rough idle but runs smooth when u̶s̶i̶n̶g̶ ̶t̶h̶e̶ ̶g̶a̶s̶ accelerating. ---
**Author:** ![BillRussell](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/billrussell/32/3179_2.png) [@BillRussell](https://community.cartalk.com/u/BillRussell)\ **Post date:** [August 23, 2018, 7:28pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/2 "2018-08-23T19:28:59Z")
> [@mardimacfly](#): > > runs smooth when using the gas. Don’t understand this, what else would you be using? ---
**Author:** ![shanonia](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@shanonia](https://community.cartalk.com/u/shanonia)\ **Post date:** [August 23, 2018, 7:29pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/3 "2018-08-23T19:29:15Z")
Throttle body injection? ---
**Author:** ![FoDaddy](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/fodaddy/32/717_2.png) [@FoDaddy](https://community.cartalk.com/u/FoDaddy)\ **Post date:** [August 23, 2018, 7:40pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/4 "2018-08-23T19:40:28Z")
Nah, TBI didn’t show up until the mid-late 80’s in the truck/vans, probably has a quadrajet or Rochester 4 barrel ---
**Author:** ![Tester](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/tester/32/15976_2.png) [@Tester](https://community.cartalk.com/u/Tester)\ **Post date:** [August 23, 2018, 7:41pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/5 "2018-08-23T19:41:41Z")
The diaphragm for the accelerator pump may have become inverted allowing gas to leak past it. It’s the component at the upper left. ![](https://global.discourse-cdn.com/cartalk/original/2X/b/becfd5419e96b27f71e447b4ebef8d1b1e0e3dd8.jpeg) Tester ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 23, 2018, 7:42pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/6 "2018-08-23T19:42:06Z")
Not sure. Idk much about carburetors. It has an edelbrock. ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [August 23, 2018, 7:44pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/7 "2018-08-23T19:44:32Z")
Check the secondaries on the carburetor to see if they have closed, the throttle valves may need to be cleaned so that they open and close properly. ---
**Author:** ![sgtrock21](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sgtrock21/32/246_2.png) [@sgtrock21](https://community.cartalk.com/u/sgtrock21)\ **Post date:** [August 23, 2018, 10:21pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/8 "2018-08-23T22:21:27Z")
I know the regulars here have suffered my not being able to resist being a “smartazz”. Perhaps the gasoline was injured from being “punched”. Absolutely no offense to OP as “punching the gas” was a common slang term when I was a teenager 50 years ago. Nevada\_545’s suggestion could result in an improper fuel/air ratio which could result in a rough idle. ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 24, 2018, 2:39am UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/9 "2018-08-24T02:39:16Z")
Haven’t actually assaulted the gas but I have threatened the carburetor. I think tomorrow I’ll try spraying some carb cleaner (specifically seafoam) in it. If that dosn’t work I’ll have to learn how to rebuild it. Is there a way to check if it’s the carb or should I check anything else before I get in over my head and budget? ---
**Author:** ![sgtrock21](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/sgtrock21/32/246_2.png) [@sgtrock21](https://community.cartalk.com/u/sgtrock21)\ **Post date:** [August 24, 2018, 1:14pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/10 "2018-08-24T13:14:01Z")
I would check the throttle linkage including the anti diesel solenoid to insure the throttle plates are opening and closing properly. It could be a weak return spring or a simple adjustment. ---
**Author:** ![shanonia](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@shanonia](https://community.cartalk.com/u/shanonia)\ **Post date:** [August 24, 2018, 1:24pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/11 "2018-08-24T13:24:52Z")
I would check the various externals very closely before committing to an overhaul. Tester’s suggestion about the accelerator pump sounds worthy. If the seal is not sealing, that could be letting excess gas into the carb. On today’s cars that might be compensated for by the electronics and the idle air control motor. But not so on a carb. The accelerator pump on my 1979 Toyota 4X4 had a leather seal that moved up and down in a cylinder - like a bike pump. I had to soak that seal in oil from time to time. It also had an AAP auxiliary accelerator pump which had a diaphragm with gas on one side and engine vacuum on the other. When that diaphragm failed, excess gas poured into the carb and eventually the oil. ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [August 24, 2018, 2:14pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/12 "2018-08-24T14:14:45Z")
> [@mardimacfly](#): > > It has an edelbrock. So it is not the factory carb since Edelbrock bought the tooling to make Carter AFB carbs years ago. Sounds like you need a re-build. ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 24, 2018, 2:41pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/13 "2018-08-24T14:41:45Z")
Looks like my accelerate pump is kinda deep in the carburetor. This is the carb I have. Does the arrow point to the accelerator pump? Is there a way to check it without taking the top of the carb off? ![accelerator%20pump](https://global.discourse-cdn.com/cartalk/original/2X/1/1d68eb908fa01fa4b514048684ade9ee191d0471.jpeg) ---
**Author:** ![shanonia](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@shanonia](https://community.cartalk.com/u/shanonia)\ **Post date:** [August 24, 2018, 2:44pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/14 "2018-08-24T14:44:41Z")
Looks like yes and no. It’s quite possible you can get the top off without wrecking the gasket. ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 24, 2018, 5:26pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/15 "2018-08-24T17:26:28Z")
I don’t think the carb intake cleaner did much. Cleaned all the linkages, none seemed sticky. When I push in the accelerator linkage I noticed some squeaking noise which sounds like it’s coming from the accel pump. One more tid bit that I noticed was that it doesn’t run rough until a few seconds after letting off the gas pedal. I think I’ll buy the gasket but if I can keep the old one intact I’ll take the new one back. You reckon it’s just one and what do I call that particular gasket? ---
**Author:** ![shanonia](https://avatars.discourse-cdn.com/v4/letter/s/9de053/32.png) [@shanonia](https://community.cartalk.com/u/shanonia)\ **Post date:** [August 24, 2018, 5:32pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/16 "2018-08-24T17:32:33Z")
I’d call it the gasket between the main body and the top. Best wishes, keep us informed. ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 24, 2018, 7:25pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/17 "2018-08-24T19:25:29Z")
Will do. Might be a couple days though. ---
**Author:** ![mardimacfly](https://avatars.discourse-cdn.com/v4/letter/m/d26b3c/32.png) [@mardimacfly](https://community.cartalk.com/u/mardimacfly)\ **Post date:** [August 25, 2018, 9:15pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/18 "2018-08-25T21:15:58Z")
Took the top off the carburetor. The accel pump doesn’t look damaged but it is dirty and old looking, may have shrunk. About to ride my bike to the parts store and get a new one. Should I soak the top while it’s off? ![accel%20pump](https://global.discourse-cdn.com/cartalk/original/2X/e/e37bd40e8cd1b4c75f0ab5c8e9f9d2f5bce7af13.jpeg) ---
**Author:** ![Nevada\_545](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/nevada_545/32/41232_2.png) [@Nevada\_545](https://community.cartalk.com/u/Nevada_545)\ **Post date:** [August 25, 2018, 9:36pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/19 "2018-08-25T21:36:24Z")
Did the accelerator pump squirt fuel into the primary bores when you operated the throttle? If it was not working it would cause a hesitation when the throttle is first opened, not a rough idle. ---
**Author:** ![It\_s-Me](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/it_s-me/32/12660_2.png) [@It\_s-Me](https://community.cartalk.com/u/It_s-Me)\ **Post date:** [August 25, 2018, 9:37pm UTC](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536/20 "2018-08-25T21:37:00Z")
Wondering if it could be a sticky vacuum or mechanical advance in the distributor. “Punching the gas” may have take engine RPM’s higher than they’ve been in a long time, causing the advance to go farther than it’s been in a long time and becoming stuck. [Next page](https://community.cartalk.com/t/rough-idle-after-punching-the-gas/123536.md?page=2)