Help! Long Tube Header Surge

[Marv02]

I put a set of SPL long tube headers on my 86 Vett.

the headers came with a 3 wire heated O2 sender I put the stock 1 wire O2 sender in I was not sure at the time which wire did what.
But now I know.

I just checking is the NON heated O2 sender causing my motor to surge at Idel it ok at first at a stop light or in stop and go trafic but after a minute or two it starts surging.

After you able to give it some gas the surge go's a way.

I been thinking the 1 wire O2 is getting cold that cause the surge due the sender now in the Header collector instead of next to the old stock Exhaust manifold.

Or what else would cause this it a new motor not stock it's a mild build I still working the bugs out the new build this is one of them.

But I getting there.​

 

[vetteoz]

been thinking the 1 wire O2 is getting cold that cause the surge due the sender now in the Header collector instead of next to the old stock Exhaust manifold.

One way to find out ;
hook the 3 wire O2 up to keep engine in closed loop
Well documented that O2 sensor by the collector in LT's goes cold at idle so engine goes open loop

 

[boomdriver]

I put a set of SPL long tube headers on my 86 Vett.​

the headers came with a 3 wire heated O2 sender I put the stock 1 wire O2 sender in I was not sure at the time which wire did what.
But now I know.​

I just checking is the NON heated O2 sender causing my motor to surge at Idel it ok at first at a stop light or in stop and go trafic but after a minute or two it starts surging.​

After you able to give it some gas the surge go's a way.​

I been thinking the 1 wire O2 is getting cold that cause the surge due the sender now in the Header collector instead of next to the old stock Exhaust manifold.​

Or what else would cause this it a new motor not stock it's a mild build I still working the bugs out the new build this is one of them.​

But I getting there.​

Look at the IAC motor, the temp sensor and all the vac fittings for a leak that the IAC is trying to adjust against.If your T-body has the coolant bypass the bottom plate is a great place to get air leaks.

The O2 sensor heated or non is still doing a specific task under specific conditions. If its not working right due to being cold, the ECM just stays open loop. The cat has to be near 600 degrees to lite off, and by that time the o2 sensor would be hot as well, even way back from the heads. The heated sensor just allows the system to upshift to closed loop a little sooner.

 

[vetteoz]

If its not working right due to being cold, the ECM just stays open loop. The cat has to be near 600 degrees to lite off, and by that time the o2 sensor would be hot as well, even way back from the heads.

Nah ; with LT's O2 will drop out at idle as he describes it above.
Mine does it all the time ; pull up at lights ; can see the O2 Volts go static then come alive again as I drive off

The heated sensor just allows the system to upshift to closed loop a little sooner.

The ECM shift to CL timeout is programmed in the tune ( 3 min cold engine with L98 ) so a heated O2 has no effect on it's activation ( so long as O2 is hot enough )
Most run a heated O2 for the cooling off reasons as described

 

[boomdriver]

Nah ; with LT's O2 will drop out at idle as he describes it above.
Mine does it all the time ; pull up at lights ; can see the O2 Volts go static then come alive again as I drive off


The ECM shift to CL timeout is programmed in the tune ( 3 min cold engine with L98 ) so a heated O2 has no effect on it's activation ( so long as O2 is hot enough )
Most run a heated O2 for the cooling off reasons as described

So, drop out at idle is common?
Interesting...I would have thought that the heated sensor would have been intergrated in such a way to prevent that since idle conditions are one of great concern with emissions.

 

[Hib Halverson]

Your headers came with a heated O2S for a reason...with the O2S location in the headers, at idle and low speed/light load the single-wire sensor is cooling to a point that the data it sends is erroneous. That maybe why your engine's lacks idle stability after a minute or so at idle.

Install the three wire sensor. Typically, they have two wires of one color and one with of another. Connect one of the two same-colored wires to ground. Connect to other to a B+ source that is hot with the ign. on. Connect the different-colored wire to the existing sensor wire.

 

[Marv02]

I just installed the 3 wire O2 about a hour ago I take the car to work tomarrow and see how things work out.

Your headers came with a heated O2S for a reason...with the O2S location in the headers, at idle and low speed/light load the single-wire sensor is cooling to a point that the data it sends is erroneous. That maybe why your engine's lacks idle stability after a minute or so at idle.

Install the three wire sensor. Typically, they have two wires of one color and one with of another. Connect one of the two same-colored wires to ground. Connect to other to a B+ source that is hot with the ign. on. Connect the different-colored wire to the existing sensor wire.

 

[boomdriver]

I just installed the 3 wire O2 about a hour ago I take the car to work tomarrow and see how things work out.

Ya know, the more that I think about it,.:duh the more I can see how the o2 sensor could be the reason for an idle surge. I know that I have experienced a slight surge of 200-300 rpm for about 1-2 seconds during a shift in ECM status....even in the L-98. Actually, mine is very noticable as the temp rises past 150. Its only 200 rpm, maybe, but its noticable. Never gets past 900 while warming.

Knowing that the long tube headers have to place the bung so far from the cyl heads so its past the collector, it also is so far away that its able to get cold with low rpm or load. Initially I would have thought that a hot Cat might help keep that area up to normal temps.
Shorty headers with a collector about where the stock collector is would'nt suffer from this. The bung cannot be moved closer in the long tube because it would then be subject to the effects of a single cylinder that would then dictate how they all performed...

 

[Marv02]

As normal my luck sucks.
The 3 wire O2 is bad.

 

[Hib Halverson]

As normal my luck sucks.
The 3 wire O2 is bad.

How did you determine that?

 

[Marv02]

How did you determine that?

Code 13

 

[Hib Halverson]

DTC 13 doesn't necessarily mean the sensor is bad it means the O2S circuit is open.

Make sure you've got the right wire on the sensor connected to the O2S signal circuit. If you've got the the heater wires misconnected, code 13 will set.

 

[Marv02]

2 Blue wires 1 Power other Gnd.
1 Black is the O2 .

DTC 13 doesn't necessarily mean the sensor is bad it means the O2S circuit is open.

Make sure you've got the right wire on the sensor connected to the O2S signal circuit. If you've got the the heater wires misconnected, code 13 will set.

 

[Hib Halverson]

Before I'd buy another sensor, I'd make sure the signal wire is not broken somewhere in the harness.

The FSM will have a wiring diagram. You want to check that wire from the ECM down to the sensor.

 

[Marv02]

I put the 1 wire back in no code.

Before I'd buy another sensor, I'd make sure the signal wire is not broken somewhere in the harness.

The FSM will have a wiring diagram. You want to check that wire from the ECM down to the sensor.

 

[Hib Halverson]

You've done your homework then. Either the three-wire sensor is bad or there's some incompatibility.

I recall that the header maker supplied the sensor. Have you been back to them with your concerns?

 

[Marv02]

I was given the Free SPL Long Tube headers so I cant complain at all.

I go to the Local Napa Store the ownner gave me the headers He will know what O2 to buy.

They came off his old 1985 C4 it had a fuel leak and burn to the ground.

You've done your homework then. Either the three-wire sensor is bad or there's some incompatibility.

I recall that the header maker supplied the sensor. Have you been back to them with your concerns?

 

[Marv02]

Installed a new Bosch O2 3 wire sender Part # 13077.
The surge is gone now.

 

[vetteoz]

Installed a new Bosch O2 3 wire sender Part # 13077.The surge is gone now.

Like I said in post #2 ;a well known problem with LT's