[Toby96]

Title says it all. Over the past few days I've noticed that my Sierra tends to switch itself off at anywhere I stop, or in 1st gear travelling through carparks the acceleration seems delayed. In the carpark situation when I say delayed, I mean that I put my foot down on the accelerator and nothing happens for about 2-3 seconds. Out of no where it gives me a sudden jolt of movement as if I'm bunny hopping it.

In the auto cut off situation it seems that every now and then the car decides it no longer wants to stay on when I come to a complete stop. I can prevent this though by having my foot lightly on the pedal to keep the revs around 1/1.5kpm but if I don't do that - the car's revs slowly drop to a point where it just cuts out.

I'm not all that mechanically sharp (Hence why I bought a Sierra as my 1st car as there's nothing to them and provides a great place to start) but have a few idea's in mind that maybe it has something to do with my fuel pump, potentially my alternator as the car has issues starting up every 2nd-3rd day (Just purchased a new car battery about 1 week ago) or something to do with the idler.

I recently replaced my Carby with a refurbed one if that makes any difference. Any and All feedback/info/suggestions will be greatly appreciated!

Regards,
Toby.

[Reubs]

The problem lies with your carby. The symptoms sound like you have a blocked idle jet.

[tanshi]

yep idle jet or perhaps choke.

[Heideisadog]

I was just about to make this exact same post, so I have the same problem as you.
Could it be that the idle revs isn't set correctly? I think it's just a small screw on the carby.,,

[tanshi]

if it worked fine and then stopped working its not the idle speed

[Marko_SJ]

Toby96 wrote:

Title says it all. Over the past few days I've noticed that my Sierra tends to switch itself off at anywhere I stop, or in 1st gear travelling through carparks the acceleration seems delayed. In the carpark situation when I say delayed, I mean that I put my foot down on the accelerator and nothing happens for about 2-3 seconds. Out of no where it gives me a sudden jolt of movement as if I'm bunny hopping it.

In the auto cut off situation it seems that every now and then the car decides it no longer wants to stay on when I come to a complete stop. I can prevent this though by having my foot lightly on the pedal to keep the revs around 1/1.5kpm but if I don't do that - the car's revs slowly drop to a point where it just cuts out.

I'm not all that mechanically sharp (Hence why I bought a Sierra as my 1st car as there's nothing to them and provides a great place to start) but have a few idea's in mind that maybe it has something to do with my fuel pump, potentially my alternator as the car has issues starting up every 2nd-3rd day (Just purchased a new car battery about 1 week ago) or something to do with the idler.

I recently replaced my Carby with a refurbed one if that makes any difference. Any and All feedback/info/suggestions will be greatly appreciated!
Regards,
Toby.

The refurbed carby, did it do this before AND after the new carby?

Or only after?


If it happened before, I'd be thinking its a factor other than the carb:

I'd be checking fuel lines, filter, fuel pump, apparently the pickup in the tank can gunk up too.

Also make sure you dont have any air leaks in the vaccum lines.

[Toby96]

Reubs wrote:

The problem lies with your carby. The symptoms sound like you have a blocked idle jet.

Say it is a blockage, is it a matter of just pulling it apart and clearing the blockage? Or is there more than meets the eye?

Marko_SJ wrote:

The refurbed carby, did it do this before AND after the new carby?

Or only after?


If it happened before, I'd be thinking its a factor other than the carb:

I'd be checking fuel lines, filter, fuel pump, apparently the pickup in the tank can gunk up too.

Also make sure you dont have any air leaks in the vaccum lines.

It doesn't help my case but I never noticed it beforehand. Whether it's because it wasn't there to start with or because I didn't drive it very often (only got my p plates last week). However when I would drive it towards my logbook I never noticed this, only issue was the battery not holding charge but that has since sorted it out.

The car has trouble starting some days (usually every 2nd-3rd day) - could it be a result of a blocked idle jet?

[alien]

I had similar happen in a mates vitara (carby model) where the immobiliser was faulty, and would occasionally cut the engine... for some reason it would only do it at idle, and sometimes you could keep it running after you heard the immobiliser click if you gave it a rev (which was also delayed, no idea why).

One time it cut out on me half way through an intersection with oncoming traffic right as i was about to accelerate - at that point i got a sparky to disable the immobiliser cos it was a safety issue.

[Toby96]

alien wrote:

I had similar happen in a mates vitara (carby model) where the immobiliser was faulty, and would occasionally cut the engine... for some reason it would only do it at idle, and sometimes you could keep it running after you heard the immobiliser click if you gave it a rev (which was also delayed, no idea why).

One time it cut out on me half way through an intersection with oncoming traffic right as i was about to accelerate - at that point i got a sparky to disable the immobiliser cos it was a safety issue.

Definitely not an immobilizer causing it, the previous owner never bothered about wiring up the aftermarket one. That and the rust proofing system he had no idea about

[steve125]

A 95 Sierra should have an idle solenoid on the front of the carby, see pic, its the one with the green wire going into it, when you take your foot off the throttle the solenoid stops the butterfly suddenly closing all the way, if it's faulty, the butterfly closes too quickly and the car dies. A new solenoid is close to $200 just for the part. Mine still dies but not as badly after I put new vacuum lines in, cleaned the carb, new fuel pump, new rubber fuel lines and an extra filter between the pump and carb.

The above is just for stalling when coming to a stop, not sure what your acceleration problem could be. Why was the carb replaced, what else between the tank and carb was changed?

[johnmath]

Sounds to me like you have a manifold air leak or a vacuum hose off somewhere letting air into the manifold. One the engine is revving and the throttle is open, a small leak like a missing hose doesn't make much difference. But at idle when the throttle is nearly closed a small leak is a big leak - If the mixture gets too lean the engine will stall. When lean, it is also sluggish from slow revs like taking off in first gear.

[Toby96]

Cheers everyone, they're definitely things I'll have a look at during the week. Sorry about the lateness on my replies; as it stands I'm on the moderated list because I'm still a noobie

[droverdave]

The above suggestions are all good, the only other thing i would do is go and buy a can of carby cleaner, and go to town with it. spray it around in the carby with the engine off, then fire it up (it will be harder to start), once its started rev the guts out of it and keep spraying it in until it all looks spotless.

you can also put your hand over the carby with the engine running, this creates more vacuum and will tend to pull any crap through and clean it all out.

This should get you in a good place for further diagnosis.

[Toby96]

Don't know what happened over the weekend but it seems to have fixed itself. Perhaps it was just a blockage that cleared itself. Nonetheless thanks all for the diagnosis - I now have some starting point god forbid it happens again.