Diagnostic Results

[junkstang95]

My 95 Cobra has been surging while at low rpm's and as I start to accelerate. I can watch the rpm needle bounce up and down (+/-) 500-1000 rpm's at idle or while I'm accelerating or driving at a consistent speed.


I had a diag done at a local Ford shop and they said that my right side upstream O2 sensor was bad and my purge canister needed replaced.

Of course I'm not going to pay the $600 they quoted to have them fix anything I just needed a starting point to fix things myself.

Now, I replaced the right side pre-cat O2 sensor and I still have the surge.

Should I have replaced both upstream sensors while I was under there?

What is the purge canister and could it be related to the surging?

Any other suggestions?

Thanks in advance.

 

[gcomfx.com]

http://forums.stangnet.com/showthread.php?t=687869

Unplug it... see how the car runs.

 

[junkstang95]

I'll give it a shot.

 

[tjh566]

dont tell me even the ford comps think we have 4 O2's

 

[junkstang95]

dont tell me even the ford comps think we have 4 O2's

Not sure, all I know is that the diag results stated pre-cat O2 sensor which is where they're located. I didn't assume anything else.

 

[HISSIN50]

I don't see either of those creating a surge. The tach jumping suggests an ignition issue.

The purge cannister isnt even needed and it should not affect or create a surge.

Good luck.

 

[junkstang95]

The tach jumping suggests an ignition issue.

Thanks. Any suggestions?

 

[tjh566]

coil, wires, could be a few things.

 

[HISSIN50]

The PIP can also cause a tach studder - you'd likely feel a slight chug or shudder if the PIP is the cause.

 

[junkstang95]

PIP?

 

[mo_dingo]

pip=profile ignition pickup, a.k.a. halls effect sensor or ignition module. The sensor on the bottom of the distributor.
Scott

 

[HISSIN50]

Don't ask for an ignition module if you need to replace a PIP - they will give you a TFI module.

Stator is pretty conventional nomenclature for a PIP - only if you find that you need one.

When a PIP totally craps its pants, you can use a DMM and check the wave coming from it - but with a slight burp there's no way a DMM can help. And anything short of an oscilliscope probably won't help.

 

[HGFireHazard]

dont tell me even the ford comps think we have 4 O2's

They do, or at least my local one does. I went there last Summer to get O2s before getting my S/C tuned and they asked me which ones I needed...

Come on now.