V6 Discussion and questions about the base carbureted or MPFI V6's and the rare SFI Turbo V6.

Random erratic rpms at highway speeds.

Thread Tools
 
Search this Thread
 
Old 04-05-2012, 04:16 PM
  #1  
Junior Member
Thread Starter
 
BigLoubowski's Avatar
 
Join Date: Oct 2011
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Random erratic rpms at highway speeds.

I'll be driving along going 60-70 in OD and all the sudden the tach will start twitching a few RPMS up. It continues slowly until it's jumping a thousand RPMs up and down (3000-4000-3200-3800, ect in a back and forth fashion) very randomly.

I just replaced all the major electrical parts, coil, rotor, ICM, dizzy, plugs, wires, yadda yadda yadda. It had been burning the middle plug wire on the passenger side so I had replaced it but now it's doing it again and the plug wire is fine.

It's random, sometimes it will do it and then not for several days and then it's back. If you let it go it becomes so erratic that it will die. It does it 90% of the time at speeds above 60 but it has happened a couple of times going 30-40. I had been able to drop it into 3rd and after a short while shift back to OD and it would disappear but it's not like that anymore.

Stopping the motor and letting it sit for a few seconds seems to reset the issue but it will continue to reoccur on the same drive.

Is this a flaky injector or something? I've always had carburated cars so this is new for me.

Thanks in advance!!!
Old 04-05-2012, 05:59 PM
  #2  
Member
 
19camaro83's Avatar
 
Join Date: Jun 2010
Location: Beatrice, Nebraska
Posts: 301
Likes: 0
Received 0 Likes on 0 Posts
Car: 1983 camaro sport coupe
Engine: 2.8l v6 - stock motor
Transmission: NWC t-5
Axle/Gears: whatever came stock (?)
Re: Random erratic rpms at highway speeds.

Well depending on which transmission you have, I would put my money on a torque converter going bad. If you have a manual transmission, I would suspect a bad clutch/clutch component.
Old 04-05-2012, 07:06 PM
  #3  
Junior Member
Thread Starter
 
BigLoubowski's Avatar
 
Join Date: Oct 2011
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Re: Random erratic rpms at highway speeds.

Originally Posted by 19camaro83
Well depending on which transmission you have, I would put my money on a torque converter going bad. If you have a manual transmission, I would suspect a bad clutch/clutch component.
When I pull over and put it in park it will continue to do the erratic RPM although not as severly. I should've said that about two months back it slips out of OD when I start from park to about 30-40. Once it's over 40 or around 1500rpm it'll shift into OD just fine with a slight hesitation. It's an automatic.

Would the torque converter do this chaotic RPM thing in park?
Old 04-05-2012, 07:32 PM
  #4  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Random erratic rpms at highway speeds.

its not ur converter u would know if it was it would feel like the trans mission slipping as the tach went crazy.

check all ur plug wires carefully, a arching plug wire will cause the tach to bounce like that. if the ignition system all checks out more then likley u have a bad wire to the tach and or the tach is just going bad
Old 04-05-2012, 07:45 PM
  #5  
Supreme Member

 
Gumby's Avatar
 
Join Date: Oct 2001
Location: NWOhioToledoArea
Posts: 8,113
Likes: 0
Received 5 Likes on 5 Posts
Car: 86-FireBird
Engine: -MPFI
Transmission: T5
Axle/Gears: 3:42
Re: Random erratic rpms at highway speeds.

^ does your butt agree with the tach on the RPM changes, or is it just visual???
Old 04-06-2012, 02:01 PM
  #6  
Junior Member
Thread Starter
 
BigLoubowski's Avatar
 
Join Date: Oct 2011
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Re: Random erratic rpms at highway speeds.

I can feel the car jerking so it's not just the tach misreporting. It will do it in park after a severe episode on the highway. Once it's starting doing it I can shift to neutral as I pull over and it's still jumping around and often stalls. After a few seconds turned off its fine for a few miles pr even the rest of a drive. I'm really confused by it.
Old 04-10-2012, 01:31 PM
  #7  
Junior Member
Thread Starter
 
BigLoubowski's Avatar
 
Join Date: Oct 2011
Posts: 4
Likes: 0
Received 0 Likes on 0 Posts
Re: Random erratic rpms at highway speeds.

Butt agrees
Old 04-10-2012, 10:54 PM
  #8  
Supreme Member
iTrader: (1)
 
project89's Avatar
 
Join Date: Apr 2008
Location: Utah
Posts: 10,401
Likes: 0
Received 2 Likes on 2 Posts
Car: 89 RS 89 iroc 87 firebird
Engine: 3.1 Turbo/ 355 twin turbo
Transmission: a4 w/ 4500 stall/ a4 / t5
Axle/Gears: strange s60 /w 3:42's
Re: Random erratic rpms at highway speeds.

then its nothing in the transmission, my bet is on bad plug wires or something fualty in the ignition system, and oir a bad connection somewere
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
tommy z-28
Cooling
5
10-06-2015 10:58 PM
MSRed91Camaro
Cooling
22
10-06-2015 01:56 PM
Bubbajones_ya
Cooling
23
09-14-2015 08:38 PM
Jk_Under
Tech / General Engine
1
09-08-2015 08:13 AM
SG91camaro
Camaros for Sale
2
09-05-2015 10:27 PM



Quick Reply: Random erratic rpms at highway speeds.



All times are GMT -5. The time now is 11:49 PM.