o2 problems continue...

[m3456y]

I posted a week ago about installing headers, replacing my o2 sensors with new ones and suffering from a "loaded up" feeling engine until about 4,000 rpm. I thought maybe the ECU had to re-learn the new sensors, and the problem would correct itself. I still have the problem, and now sometimes it dies upon letting up on the gas, it sometimes catches itself and idles fine. The check engine light came on today and the codes were P1204,P1205,P1206,P1300 all indicating a misfire. I checked plugs and they looked fine, they were replaced less than 1000 miles ago and, at the same time the valves were adjusted. I'm not sure what to try next. Any suggestions before I give in and take it to the dealership? Thanks.

 

[Briank]

Those codes are all for misfire on the front bank cylinders 4,5,6 so your o2 sensors shoud be ok. Check the connections to the coils, injectors, igniter and you may want to redo the valve adjustment on the front bank. Also check that the vacuum hose is on the fuel presure regulator and is not pinched.

 

[m3456y]

I checked the coils, connections, plugs have 1,000 miles on them, valves were just adjusted by the dealership so hopefully they should be right. No kinks or leaks that I can find in any hoses. Just finished cleaning out the throttle body. It almost seems like a vacuum leak, but I can't find one.

 

[Briank]

So it ran ok after the valve adjustment and just started having a problem after the header install, right?

 

[m3456y]

That's correct...ran perfectly before headers, o2 replacement. Just got back from test drive number 10 today. Cleaning the throttle body solved the idle problem - but it still loads up under 4 grand...not horrible and very driveable but not like it ran before. BTW plugs look like new....not like they've been fouled. Next step is to reverse o2 sensors. I know they are the same but...I can't think of anything else to try at this point. Check engine light has not come on.

 

[Briank]

Make sure to reset the ecu and recheck the codes each time you get a MIL (CEL). What you are reading may be old news. Normally o2 problems cause o2 codes 1,2 and 41, 42 and people see the engine running rich. Because you are not seeing fouling on the plugs the problem sounds more like a fuel filter or fuel pump problem.

 

[m3456y]

I have been reading/resetting the ECU with a OTC Genysis diagnostic tool - so the codes I believe were current. Should I reset the ECU via the clock fuse also? Again the car ran perfect before o2 replacement and headers. Thanks for the help - Mark

 

[Jett]

Just throwing this suggestion out there...have your coil packs been replaced? It's an easy DIY (even I can do it) and failing coil packs can "emulate" 02 sensor error codes.

 

[m3456y]

I'm not sure if the coil packs have been replaced. I know it's any easy process as I had them all out when I checked the plugs. It seems odd that the car ran great before o2 replacement. Someone mentioned that the coil packs were part of a recall - is that the case? I'm willing to try anything at this point.

 

[drew]

Did you save your old O2 sensors? Did you replace the O2 sensors with OEM? Apply any lubricant?

I would try replacing them with the used old ones and see what that does....

Also check the voltage of the O2 sensors when warmed up.

Drew

 

[m3456y]

Did you save your old O2 sensors? Did you replace the O2 sensors with OEM? Apply any lubricant?

I would try replacing them with the used old ones and see what that does....

Also check the voltage of the O2 sensors when warmed up.

Drew

I replaced the old ones with new ones because I could not remove them, and one was a "generic" sensor with a butchered wiring job. Ordered new coils and a fuel filter today...based on the other threads I've read. Hopefully that will cure it.
Mark

 

[m3456y]

Ok, got the new coils and installed them. Replaced the fuel filter. Went out and test drove the car. Still loads up and stumbles up to 4,000 rpm then clears up and runs great. Took off the Ingen intake and re-installed the factory (new) filter. test drove and had the same problem. No check engine light to look at fault codes. I have 2 questions. Is it possible that a new o2 sensor could be bad? It definatley feels like a mixture problem. Does the dealership have diagnostic equipment that can tell the problem if on my hand-held unit, I am getting no codes? Any other suggestions...I'm still suspecting an o2 sensor as everything was fine until I replaced those as I installed headers. If nobody has any ideas, I'm going to buy another o2 sensor, and swap it between the two I replaced to see if one is bad. Any input is appreciated. Thank you.
Mark

 

[DanO]

Put it in 2nd and accelerate from 5mph to 35mph and back all the way to idle. Do this several times. What you're looking for is a CEL to help with the diagnosis.

Good luck,
DanO

 

[m3456y]

Put it in 2nd and accelerate from 5mph to 35mph and back all the way to idle. Do this several times. What you're looking for is a CEL to help with the diagnosis.

Good luck,
DanO

I drove the car for almost a half hour accelerating and letting off - no CEL. I'll try your routine tommorrow. Thanks.

 

[Briank]

I still vote for a bad fuel pump. Very rare problem but it does happen, check the fuel pressure. The problem goes away at 4000 rpm because that’s when the pump is switched to full power.