Gs300 Annoying Missfire

[IanCornwall]

Hi all its me again

My GS300 mk1 that I bought stood in a garage for a few years before I got it as the owner was overseas, it now starts a dream, and after replacing the water pump and a few persished hoses (yes they did blow) and a few other rubber bits that looked perished, i have a problem

The problem is that i have what i percieve to be a missfire / hunting of the engine,

On tickover, it is as if a plug is missing, a slight feeling of a shudder sometimes and when on cruise speed again i can just feel its not quite right

Plugs seem fine, dizzy seems fine, leads seem fine, no sign of tracking the spark

I wonder if there is a dirty sensor anywhere or another that needs cleaning

Any clues anyone ??

[legendswraith]

Hi all its me again

My GS300 mk1 that I bought stood in a garage for a few years before I got it as the owner was overseas, it now starts a dream, and after replacing the water pump and a few persished hoses (yes they did blow) and a few other rubber bits that looked perished, i have a problem

The problem is that i have what i percieve to be a missfire / hunting of the engine,

On tickover, it is as if a plug is missing, a slight feeling of a shudder sometimes and when on cruise speed again i can just feel its not quite right

Plugs seem fine, dizzy seems fine, leads seem fine, no sign of tracking the spark

I wonder if there is a dirty sensor anywhere or another that needs cleaning

Any clues anyone ??

bet the leads have broken down change them and it will be ok mine was exactly how you describe when i changed my leads and didn't connect a lead properly

[IanCornwall]

hey all just thought i would share the result of the missfire with you

I removed the throttle body as per instructions I found on the web board here and it was like someone had a BBQ running in it, took it off, full can of carb cleaner and wow it shines, cleaned out the hoses and jeesh the wifes tea towels will never be the same again (please don't tell her she thinks the tea towel fairies have been)

Although the plugs all seemed to be firing (checked by disconnecting the HT lead) as the throttle body was off, I pulled all the plugs out, 5 absolutely brill plugs and 1 oddball one marked NGK R BKR6EK R1

This has 2 electrodes all corroded and looked rubbish compared to the others

So I changed the plug to match the other iridiums (which are correct) and doused everything with the WD40 and bolted it all back up with the wonderfully shiny throttle body

It started first time and ran like a tank on steroids, lumpy, noisy, horrible, :tsktsk: I was about to throw a complete wobbly then I remembered the hint of resetting the ECU I read on here

out with the fuse, sang a song for a few minutes, and replaced it

Started it again, immediately sprang into life, tickover very high, but left it alone for a minute then I thought it had stalled, I couldnt hear a damn thing from the engine, but the tacho was on 800 RPM, a quick blip on the throttle and wow what a difference, it runs so smooth, so quiet, and up the 1 in 4 hill from where i live it was amazing compared to what it was like before

Hope it stays like it is now, a few days should tell

Thanks to everyone on the boards that has given me some tips and hints, it was worth it

[IanCornwall]

Okay here we go again

Car starts brilliant cold or hot, pulls like a train, ticks over ace (you know something is coming don't you), even seems economical 31 mpg last weekend over 250 miles

Now the symptons, I am driving along all lovely and tickling the throttle at any speed, i floor the throttle and it really hesitates as if its thinking about making its mind up, the engine gives a slight missfire, then the engine thinks yeah why not, and goes for it big time and whoosh away it goes, drives brill again

If i am up and down the accelerator it never happens but then after cruising again same thing happens i go to accelerate and its really hesitant until it decides its time to go

any clues anyone ?

[legendswraith]

Okay here we go again

Car starts brilliant cold or hot, pulls like a train, ticks over ace (you know something is coming don't you), even seems economical 31 mpg last weekend over 250 miles

Now the symptons, I am driving along all lovely and tickling the throttle at any speed, i floor the throttle and it really hesitates as if its thinking about making its mind up, the engine gives a slight missfire, then the engine thinks yeah why not, and goes for it big time and whoosh away it goes, drives brill again

If i am up and down the accelerator it never happens but then after cruising again same thing happens i go to accelerate and its really hesitant until it decides its time to go

any clues anyone ?

well if its going ok normally then i'd discount the fuel side of it which leaves air and spark.

have you checked all your vacuum hoses are ok? specifically those around the throttle body if they get crushed or damaged they give you all kinds of weird and wonderful intermittent faults the main culprit is the one right on top of the throttle body on its own especially if you have a strut brace.

I have a good contact for silicone vacuum hosing too ;)

I'm still not convinced those leads are 100% either

[ColinBarber]

Try the same test but leave the gear selector in 2 so the gearbox doesn't try and change down.

[IanCornwall]

Hi all and thanks for the clues

In response to Colin and legends, hi mates,,,, as i was driving along,,,,, i was playing with the gears as well seeing if it made a difference

in overdrive, going about 70 it was a definite sluggishness and even jerky on accelerating, and without the overdrive on the same speed it seems a bit better but still not right

it is only when your in tickling the throttle mode cruising, driven a bit harder you dont notice it as the load and revs are that bit higher

I am going to check all the vacuums and sensors tomorrow as this has happened after I removed and cleaned the throttle body and done the plugs etc, thinking about it, it went like a rocket after i did that, but that didnt involve cruising at motorway speeds

I wonder if a vacuum hose isnt quite sealing and i am not advancing or retarding the spark properly

will let you know

[star a]

this is also symptoms of a failing TPS (throttle position sensor) is just a rheostat or potentiometer, and can get dirty if unused for a long period of time reducing it's conductivity and then giving an incorrect signal to the ECU...

[IanCornwall]

this is also symptoms of a failing TPS (throttle position sensor) is just a rheostat or potentiometer, and can get dirty if unused for a long period of time reducing it's conductivity and then giving an incorrect signal to the ECU...

Hi Star,,, the car hadnt been used for about a year or so as the owner was overseas, hence the rubber perishing as my earlier listing,,, so this could be a good idea

but can you please let me know which bit i have to clean ?

[star a]

it's fixed to the side of the throttle body, you can't really open it and clean it up, heres a link with a pic courtesy of another forum member.

link

[IanCornwall]

Hi again

The saga continues

In the effort to solve my missfire, I got out the trusty screwdriver, removed the 2 bits (technical words here)on the throttle body front, removed the bit (yet more techy language) on the air intake front left hand side just after the air filter, and then marked all the vacuum hoses and in turn checked all of the vacuum hoses I could reach

Made sure they were all clean and sparkly and no vacuum hoses were perished and re assembled them

Damn car wouldnt start, so I checked I had all the electric plugs back in and they were tight and kept cranking, then reset the ECU by removing the fuse in case I had to

eventually it started and it was rubbish, black smoke from exhaust, lumpy and more like a cement mixer

I thought lets see if it moves and wow, little brakes, they had almost stopped working with a very hard pedal and running even worse

Under bonnet again and removed all of the bits and made sure I hadn't damaged any of them

Now my luck changes

This time I only rested the front sensor by the air filter in the hole not having screwed the 3 philips headed screws in and it ran like a dream, and the brakes came back,,, wonderful

So in went the screws and it all changed to rubbish again

slackened off the 3 screws and wonderful, runs a dream, and my brakes came back as well

The original missfire is still there, but only only just, and almost negligible so I think I will leave it

So if you do up the sensor screws it obviously puts pressure on the item inside, just thought I would share it with anyone who has the same problem

:)

[winnie]

And the moral of this story:

Once you've got it running right,

Leave it alone :D

[IanCornwall]

And where is the fun in that ?