Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > Porsche Forums > Porsche 911 Technical Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Lucky Luca
 
Join Date: Aug 2010
Location: Rome, Italy
Posts: 41
Low idle speed after spark plugs change

Hello,

I finally (after 11 year of poor usage BTW, 1500 miles only) I changed the spark plugs and the spark plugs wires (BERU, not shielded) on my 911 1974 2700 Erupoean version.
Immediately I noticed low rpm idle speed (400/500 against the usual 900).
I took the car for a spin; the car runs much smoother and reactive than before so apparently the change was made right.
How can it be? Should I just change the idle or it worth to investigate further?

Luca
__________________
______________________________________
Porsche 911 2700 1974 Gelbgrun
Honda CB 400 F SuperSport 1976 Candy red
Yamaha FZ750 1985 Grey/Red

Last edited by luca_hoston; 02-10-2019 at 02:19 AM..
Old 02-10-2019, 02:08 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #1 (permalink)
Registered User
 
Join Date: May 2014
Location: Italy
Posts: 221
Garage
Ciao Luca,
An Italian Pelican is here!!! (from south Italy).
You didn't tell us what spark plugs you used and how they are gapped.

I had similar problems and i discovered that the gap was was out of spec.

Also,
how does the car starts up (cold and warm)... if you feel it difficult to start up it could be a distributor timing problem that has emerged with the spark plugs/cables replacement.
__________________
911 2.4T from 1973 Gemini Metallic Blue
Old 02-10-2019, 03:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #2 (permalink)
Registered User
 
Join Date: Sep 2010
Posts: 2,315
Garage
In the words of a very well
known Porsche mechanic in San Diego, “ These cars are old “. Also when you mess with them they often just do weird things.
Old 02-10-2019, 09:28 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)
Lucky Luca
 
Join Date: Aug 2010
Location: Rome, Italy
Posts: 41
Ciao Fizeus (if I'm not mistaken we met before on this pages, I should still have your phone number, we are in the same area!)

Thank you for your reply, if you don't mind let's keep talking in English so this post can be hopefully useful for someone else.
You are right, I didn't mention spark plugs kind and type. I replaced the old ones with the same brand and model (Bosch WR5+).
I have checked just by naked eye comparing the old with new ones's gap with the only purpouse to see the 11 years wearing; then yes I'm going to check it using the proper tool (feeler).
The car starts immediately both cold and warm with no issues at all; distributor cap, points, rotor have been replaced recently and at that time I ckecked the timing but good point to investigate further.

See you @ Bar Raphael one of these days!

Luca
__________________
______________________________________
Porsche 911 2700 1974 Gelbgrun
Honda CB 400 F SuperSport 1976 Candy red
Yamaha FZ750 1985 Grey/Red
Old 02-10-2019, 09:48 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #4 (permalink)
Registered User
 
proporsche's Avatar
 
Join Date: Sep 2011
Posts: 1,983
Garage
luca..you should not use wr plugs restictors,these plugs should be for Carrera engines. Use wdc plugs..and yes the gap will change your timing as Fiz said..

Ivan
__________________
1985 911 with original 491 115 miles..790 372km.

Last edited by proporsche; 02-10-2019 at 10:47 AM..
Old 02-10-2019, 10:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #5 (permalink)
Registered User
 
Join Date: May 2014
Location: Italy
Posts: 221
Garage
Hi Luca,
Nice to read you again ... and yes I also have your phone number ... i'll try calling you tomorrow
Hope pelicans here will excuse my offtopic :-D

Getting back to the discussion Proporsche has pointed the suspected problem ... wrong sparks and a fast check to the PET confirm that there are two different part numbers for 1974 spark
plugs.

If I were you i'll try to switch back to old sparks to check and if the problem disappear you know you need 6 new spark plugs!

Keep us posted please !
__________________
911 2.4T from 1973 Gemini Metallic Blue
Old 02-10-2019, 11:50 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #6 (permalink)
 
Lucky Luca
 
Join Date: Aug 2010
Location: Rome, Italy
Posts: 41
I installed Bosch WR5DC+ , same as before..I'll double check if they are the right ones and at the same time I'll check the timing
__________________
______________________________________
Porsche 911 2700 1974 Gelbgrun
Honda CB 400 F SuperSport 1976 Candy red
Yamaha FZ750 1985 Grey/Red
Old 02-10-2019, 01:08 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #7 (permalink)
Registered User
 
proporsche's Avatar
 
Join Date: Sep 2011
Posts: 1,983
Garage
luca ,as i said wrong plugs..................

this is the plugs if not W%DC you should use...
__________________
1985 911 with original 491 115 miles..790 372km.

Last edited by proporsche; 02-10-2019 at 01:57 PM..
Old 02-10-2019, 01:45 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #8 (permalink)
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 11,321
R is just for resistor in the plug. you want copper plugs. the WR5+ is fine.

take a look at how clean the plugs are when you pull them.

did you drive it before you changed the plugs. if you did not then it may not be related to the plugs. if it has been sitting you likely have other issues.
make sure you did not create any air leaks when working on the car.

check your timing but make sure your advance is working like it should. you should see the timing advance as you rev the engine.
if you have any vacuum pots on the dist make sure they are working.

did you change the cap and rotor.

with it idling, push up or pull down on the sensor plate and see if it idles up. you have to remove the air filter.

have you messed with the mixture in the past
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 02-11-2019, 05:59 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #9 (permalink)
Registered User
 
proporsche's Avatar
 
Join Date: Sep 2011
Posts: 1,983
Garage
the OP said he only changed spark plugs..unless we are missing something..?

Ivan
__________________
1985 911 with original 491 115 miles..790 372km.
Old 02-11-2019, 08:19 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #10 (permalink)
Registered User
 
Ronbo's Avatar
 
Join Date: May 2001
Location: Tarzana, CA / Oxnard, CA
Posts: 872
Quote:
Originally Posted by proporsche View Post
the OP said he only changed spark plugs..unless we are missing something..?

Ivan


He changed the plug wires also, not that this should cause his issue.


Sent from my iPad using Tapatalk
__________________
Ron
'88 Coupe (formerly)
Old 02-11-2019, 11:20 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #11 (permalink)
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 11,321
Quote:
Originally Posted by proporsche View Post
the OP said he only changed spark plugs..unless we are missing something..?

Ivan

and wires

asked to make sure.
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 02-11-2019, 11:53 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #12 (permalink)
Registered User
 
proporsche's Avatar
 
Join Date: Sep 2011
Posts: 1,983
Garage
ops i am getting blind...
still, the only difference will be if the spark plug gap is to big on the old spark plugs and the timing was set then.So if the plugs have the correct gap the timing will change...

Ivan
__________________
1985 911 with original 491 115 miles..790 372km.
Old 02-11-2019, 12:39 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #13 (permalink)
Registered User
 
Join Date: Jun 2014
Location: Rimouski/Québec
Posts: 68
Do you double check your ignition timing? You change your spark plug and your wires. It takes nothing to make a big change to ignition. Double check your gap also it change a lot about timing ignition. Do you also check you CO%, maybe with new plug you're out of spec. Maybe your previous plug was just too old and by the time the car adapt himself to run with it. An old porsche is like an old man, it takes time to adapt to new stuff.

Last edited by elt0m; 02-11-2019 at 12:54 PM..
Old 02-11-2019, 12:51 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #14 (permalink)
Registered User
 
proporsche's Avatar
 
Join Date: Sep 2011
Posts: 1,983
Garage
most of the mysteries on 911 repairs is to try to solve it for a clients if they will not tell you the whole story .Unless you dig it out of them ,it will take more time to repair or diagnose the problem..that is what i learned in 35 years working on our beasts;-).............
__________________
1985 911 with original 491 115 miles..790 372km.
Old 02-11-2019, 01:04 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #15 (permalink)
Registered User
 
scarceller's Avatar
 
Join Date: Oct 2006
Location: Southern MA
Posts: 3,472
Garage
Double check the firing order, you could possibly have 2 wires swapped? It happens, double check.
__________________
Sal
1984 911 Carrera Cab M491 (Factory Wide Body)
1975 911S Targa (SOLD)
1964 356SC (SOLD)
1987 Ford Mustang LX 5.0 Convertible
Old 02-11-2019, 01:30 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #16 (permalink)
Registered User
 
T77911S's Avatar
 
Join Date: Oct 2006
Location: MYR S.C.
Posts: 11,321
sorry, I just cant buy off on spark plug gap changing timing, especially on a points dist.
I have never seen an early 911 with points be stable enough that you could ever tell.

I have searched and cant find anything that supports that
__________________
86 930 42kmiles [__] RUNNING:[__] NOT RUNNING: ____77 911S widebody: SOLD
88 BMW 325is 200K+ SOLD
05 BMW 330CI 130K:: [__] RUNNING: [__] NOT RUNNING:
08 VOLVO V70 190K:: [__] RUNNING: [__] NOT RUNNING:
90 B2200[__] RUNNING:[] NOT RUNNING:__2000 MER E320 WAGON [] WRECKED:[]RUNNING:
Old 02-12-2019, 04:49 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #17 (permalink)
Registered User
 
scarceller's Avatar
 
Join Date: Oct 2006
Location: Southern MA
Posts: 3,472
Garage
It's also possible a plug broke/cracked while installing? Are you certain it's idling on 6 cyls? Double check with an IR temp gun on each exhaust port.
__________________
Sal
1984 911 Carrera Cab M491 (Factory Wide Body)
1975 911S Targa (SOLD)
1964 356SC (SOLD)
1987 Ford Mustang LX 5.0 Convertible
Old 02-12-2019, 05:40 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #18 (permalink)
 
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 07:54 PM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.