Drop in RPM GQ petrol

Engines and Engine Systems
User avatar
Jules
Patrolman 1000+
Patrolman 1000+
Posts: 1901
Joined: 08 Apr 2009 09:13
Full Name: Julius
Nickname: Jules
Home Town: Rietjiesvlei, Zoeloeland
Current 4x4: GQ Patrol
Home Language: AFR
Has thanked: 87 times
Been thanked: 47 times

Drop in RPM GQ petrol

Post by Jules » 30 Jan 2019 07:09

Morning, last night driving home my lorrie had a suuden loss of RPM at robots, from 750 to about 300 and idling rather erratic
I have replaced the bogey cords about 2weeks ago
Walk by FAITH not by sight
Patrol 1995 SGL
aka "Nomakanjani"
ProComp Extreme A/T 31x10.5R15
ARB Bullbar
OME, Frontrunner Roofrack
60L Snomaster Freezer/Fridge

User avatar
ricster
Patrolman 1000+
Patrolman 1000+
Posts: 6153
Joined: 13 Jan 2010 11:16
Full Name: Cedric Warner
Nickname: Cedric
Home Town: Alberton Gauteng
Current 4x4: '99 Nissan Patrol 4.2 Turbo Diesel
Home Language: English
Location: LA..... No not Los Angles ..... Lower Alberton, Gauteng
Has thanked: 299 times
Been thanked: 298 times

Re: Drop in RPM GQ petrol

Post by ricster » 30 Jan 2019 08:28

I know very little about petrol motors, but could that not be a carb problem, possibly dirty jet or sticking butterfly.

PETER CONNAN !!!!...... look here.....hahaha
Regards
Cedric
Nissan Patrol GL 4.2 Diesel Turbo (Iron Maiden)
Nissan SANI 3.0 V6 4x4 (SOLD)
Isuzu KB 280 DT 2x4 ('ol Smokey) - SOLD
Suzuki TL 1000R "V twin" (Growler) - SOLD

User avatar
Alex Roux
Patrolman 1000+
Patrolman 1000+
Posts: 2673
Joined: 11 Jul 2011 10:54
Full Name: Alexander Roux
Nickname: Witblits
Home Town: Johannesburg
Current 4x4: 2004 GU 3TDi (Lexus) - aka "Witblits" (sold)
1996: GQ TB48 conversion - aka "Skilpad"
1993: GQ SWB TB42 - aka "Shortie"
Home Language: Afrikaans
Has thanked: 43 times
Been thanked: 151 times

Re: Drop in RPM GQ petrol

Post by Alex Roux » 30 Jan 2019 09:00

Jules wrote:
30 Jan 2019 07:09
Morning, last night driving home my lorrie had a suuden loss of RPM at robots, from 750 to about 300 and idling rather erratic
I have replaced the bogey cords about 2weeks ago
Sounds like the carburetor is dirty. I had exactly that on Shorty.

All traffic and no open roads makes Carburetor a dull boy.

Mr Connan taught me a bush trick that sorted it out.
Open up die air filter and try to suffocate the engine with a towel or similar, while someone else is revving the car up to about 2500.
As the engine suffocates, your partner on the pedal need to push down further to try and keep the revs up.
The engine should still suffocate if you seal it off well enough.
Do this two or three times.

Carburetor should revert to idling smoothly thereafter.
Skilpad & Shortie

User avatar
Jules
Patrolman 1000+
Patrolman 1000+
Posts: 1901
Joined: 08 Apr 2009 09:13
Full Name: Julius
Nickname: Jules
Home Town: Rietjiesvlei, Zoeloeland
Current 4x4: GQ Patrol
Home Language: AFR
Has thanked: 87 times
Been thanked: 47 times

Re: Drop in RPM GQ petrol

Post by Jules » 30 Jan 2019 10:54

ricster wrote:
30 Jan 2019 08:28
I know very little about petrol motors, but could that not be a carb problem, possibly dirty jet or sticking butterfly.

PETER CONNAN !!!!...... look here.....hahaha
Ek sal bietjie Doom spuit vir daai bottervlieg 😁
Walk by FAITH not by sight
Patrol 1995 SGL
aka "Nomakanjani"
ProComp Extreme A/T 31x10.5R15
ARB Bullbar
OME, Frontrunner Roofrack
60L Snomaster Freezer/Fridge

User avatar
Jules
Patrolman 1000+
Patrolman 1000+
Posts: 1901
Joined: 08 Apr 2009 09:13
Full Name: Julius
Nickname: Jules
Home Town: Rietjiesvlei, Zoeloeland
Current 4x4: GQ Patrol
Home Language: AFR
Has thanked: 87 times
Been thanked: 47 times

Re: Drop in RPM GQ petrol

Post by Jules » 30 Jan 2019 10:57

my carburator is so paar maande terug ge refurbish, Peter het nog vir my die kit gestuur , so surely it should be rather clean ???
Walk by FAITH not by sight
Patrol 1995 SGL
aka "Nomakanjani"
ProComp Extreme A/T 31x10.5R15
ARB Bullbar
OME, Frontrunner Roofrack
60L Snomaster Freezer/Fridge

User avatar
ricster
Patrolman 1000+
Patrolman 1000+
Posts: 6153
Joined: 13 Jan 2010 11:16
Full Name: Cedric Warner
Nickname: Cedric
Home Town: Alberton Gauteng
Current 4x4: '99 Nissan Patrol 4.2 Turbo Diesel
Home Language: English
Location: LA..... No not Los Angles ..... Lower Alberton, Gauteng
Has thanked: 299 times
Been thanked: 298 times

Re: Drop in RPM GQ petrol

Post by ricster » 30 Jan 2019 11:51

Not sure.... but if it's got wheels and wears a bra, there is a possibility it will give you hassles.....hahahahahaha..... just kidding
Regards
Cedric
Nissan Patrol GL 4.2 Diesel Turbo (Iron Maiden)
Nissan SANI 3.0 V6 4x4 (SOLD)
Isuzu KB 280 DT 2x4 ('ol Smokey) - SOLD
Suzuki TL 1000R "V twin" (Growler) - SOLD

User avatar
Peter Connan
Moderator
Posts: 5617
Joined: 10 Sep 2010 07:21
Full Name: Peter Connan
Nickname: Piet
Home Town: Kempton Park
Current 4x4: 1996 Patrol 4.5SGL
Home Language: Afrikaans
Location: Kempton Park
Has thanked: 369 times
Been thanked: 446 times

Re: Drop in RPM GQ petrol

Post by Peter Connan » 30 Jan 2019 15:29

Mine sometimes does this when the tank is close to empty.

I would say:
1) Check that all those new plug leads are well and firmly plugged in.
2) Check all the vacuum hoses are plugged in and don't have holes.
3) Check the petrol filter.
4) Strangle it as Alex described.
Mag ons ons kenniskry met lekkerkry aanhoukry.

User avatar
Alex Roux
Patrolman 1000+
Patrolman 1000+
Posts: 2673
Joined: 11 Jul 2011 10:54
Full Name: Alexander Roux
Nickname: Witblits
Home Town: Johannesburg
Current 4x4: 2004 GU 3TDi (Lexus) - aka "Witblits" (sold)
1996: GQ TB48 conversion - aka "Skilpad"
1993: GQ SWB TB42 - aka "Shortie"
Home Language: Afrikaans
Has thanked: 43 times
Been thanked: 151 times

Re: Drop in RPM GQ petrol

Post by Alex Roux » 30 Jan 2019 19:03

... what about the distributor?
Skilpad & Shortie

User avatar
Peter Connan
Moderator
Posts: 5617
Joined: 10 Sep 2010 07:21
Full Name: Peter Connan
Nickname: Piet
Home Town: Kempton Park
Current 4x4: 1996 Patrol 4.5SGL
Home Language: Afrikaans
Location: Kempton Park
Has thanked: 369 times
Been thanked: 446 times

Re: Drop in RPM GQ petrol

Post by Peter Connan » 30 Jan 2019 20:00

Alex, my list was not intended to be a fully comprehensive and exhaustive list of everything that could cause such a problem, merely the most likely causes.

I guess the distributor could cause something like this, either if the locking screw has come loose and the timing has drifted off, or if something has gone wrong with the vacuum advance?

But I suspect that, based on my limited experience:
1) If one or two cylinders are "losing spark", the engine might struggle to idle smoothly, and since the plug leads were recently replaced, this could be the likeliest option.
2) Failing that, I think the most likely following cause would be a fuel supply issue. This could be from a number of causes.
3) Pretty much everything else I can think off (including the two distributor issues above) would most likely cause symptoms throughout the rev range?
Mag ons ons kenniskry met lekkerkry aanhoukry.

User avatar
Alex Roux
Patrolman 1000+
Patrolman 1000+
Posts: 2673
Joined: 11 Jul 2011 10:54
Full Name: Alexander Roux
Nickname: Witblits
Home Town: Johannesburg
Current 4x4: 2004 GU 3TDi (Lexus) - aka "Witblits" (sold)
1996: GQ TB48 conversion - aka "Skilpad"
1993: GQ SWB TB42 - aka "Shortie"
Home Language: Afrikaans
Has thanked: 43 times
Been thanked: 151 times

Re: Drop in RPM GQ petrol

Post by Alex Roux » 31 Jan 2019 08:42

Got it.

In my case the idling was only erratic at low revs, which is what Jules's case also sounds like.
And then it seems most likely either fuel supply or spark, as you say.
Skilpad & Shortie

Post Reply

Return to “09. Engines”

Who is online

Users browsing this forum: No registered users and 2 guests