Cruisers popping (1 Viewer)

[PAFJ]

Out the exhaust... after firing I guess is what you would call it. It happens both on acceleration (when releasing the throttle while shifting between gears) and deceleration, although is worse on decel. Both cause somewhat of a violent pop, this has never happened untill recently. For these symptoms the FSM says to check timing, valve adjustment and possible plugged air filter. I messed with the timing a bit, put a new air filter in... no joy with either. I wanted to ask for any other ideas before I ripped into the valves, which were also done not to long ago.

TIA-

 

[dslcruzr]

sounds like a lack of back pressure to me. Like when you put on bigger exhaust you'll get popping on decel. Any holes in your exhaust?

 

[FJ40Jim]

For the exhaust to backfire, there are two conditions that need to be present.
1. The presence of hot, unburned fuel.
2. an air leak into the exhaust system.

The coasting decel fuel cut system will close off fuel when coasting, so that must not be working.

And there must be a leak in the exhaust manifold gasket somewhere.

 

[cruiser88]

yep sounds like the start of the leak at the manilold

 

[REKCUT]

Before I put new exhaust system on my truck it used to sound like a machine gun when I would down shift. All's quiet now

 

[cruiser88]

Before I put new exhaust system on my truck it used to sound like a machine gun when I would down shift. All's quiet now

you ever go down a hill turn off the key then turn it back on people that was walking that day still are not right

 

[PAFJ]

For the exhaust to backfire, there are two conditions that need to be present.
1. The presence of hot, unburned fuel.
2. an air leak into the exhaust system.

The coasting decel fuel cut system will close off fuel when coasting, so that must not be working.

And there must be a leak in the exhaust manifold gasket somewhere.

Jim... What else could cause unburned fuel to enter the exhaust? The fuel cut system works as advertised according to the FSM.

I'm pretty sure I have a small exhaust leak, would this alone cause backfiring?

TIA-

 

[TheGr8Doughboy]

...I like that sound....

 

[FJ40Jim]

Verify that the ICS is actually cutting of fuel. Unplug the connector at carb w/ engine idling normally. Engine should shut off.
if not, the ICS is not shutting.

Another possible fuel leak is the secondary barrel. If it does not shut & seal totally, it can suck fuel out of the secondary slow port.

 

[PAFJ]

Verify that the ICS is actually cutting of fuel. Unplug the connector at carb w/ engine idling normally. Engine should shut off.
if not, the ICS is not shutting..

Thanks Jim... yeah I did do this and the engine shut off.

Another possible fuel leak is the secondary barrel. If it does not shut & seal totally, it can suck fuel out of the secondary slow port.

If this is the problem, is a rebuild neccessary or is there a quick fix?

TIA-

 

[PAFJ]

How about this vacuum switch, in the fuel cut system, could this be a culprit? The resistance readings check alright according to the FSM; however, pinching the hose and reving the engine does not cause the engine to misfire. Faulty switch maybe? I dunno I'm really diggin for something here, the backfiring is really starting to annoy me.

TIA-

 

[PAFJ]

Woohoo... found the problem! Something was faulty in the AI system, so I said F-it and removed it. I still need to remove air rail/plug holes, and get an idler pulley. So until then, will it be alright to leave smog pump turning as is with no hoses connected to it?

TIA-

 

[cruiser88]

Woohoo... found the problem! Something was faulty in the AI system, so I said F-it and removed it. I still need to remove air rail/plug holes, and get an idler pulley. So until then, will it be alright to leave smog pump turning as is with no hoses connected to it?

TIA-

take the cruiser to your local parts store maybe at advance.take the belt off and the smog pump,then take off about 4 inches for a start.tell them what your trying to do of course.and shortly you will have the right lenth belt.then procced to throw your smog pump in the trash

 

[cruiser88]

and yes you can leave it on but why

 

[PAFJ]

take the cruiser to your local parts store maybe at advance.take the belt off and the smog pump,then take off about 4 inches for a start.tell them what your trying to do of course.and shortly you will have the right lenth belt.then procced to throw your smog pump in the trash

So... your saying that an idler pulley isn't necessary?

and yes you can leave it on but why

I don't plan on leaving it on... I want it off, but in the mean time (untill I can get an idler pulley) it will stay on.

 

[cruiser88]

So... your saying that an idler pulley isn't necessary?




I don't plan on leaving it on... I want it off, but in the mean time (untill I can get an idler pulley) it will stay on.

im referring to the smog pump i must have missread something

 

[cruiser88]

its a 60 sorry