Engine set code for EGR valve and 02 sensor simultaneously. Idles very rough.

[KZOO3800]

97 SE 3800 SII. 188K miles.

I let her warm up for 20 minutes today. It was about 10F here in Michigan. Has been running a little rough at idle through the outrageous winter we've had but no 'service engine light' in 3 years til today. I drove about 1-2 miles and pulled up to a stoplight. My tachometer started suddenly fluctuating wildly between 500-1500 RPMs and the service engine light came on. I thought she was going to stall. Never stalled but that might be because I kept throwing her in neutral and revving up to 1000 rpm at idle until green light. Plenty of power so long as I had my foot on the gas but going back to idle caused massive fluctuations in RPMs. Nailed the throttle a couple times up to 80 mph on the freeway, tiny bit of hesitation when applying throttle from dead stop but no chugging/sputtering so long as my foot was on the gas. Fluids all look good, nothing dripping underneath.

Got codes scanned by my mechanic. EGR related code and also an 02 sensor related code. Having them inspect the engine for any signs of a larger problem that might have erroneously set a code for both components. They're not always very up front about what's going on.

Wondering what this means for both the EGR and 02 sensor to set a code at the same time. Anyone else able to draw a correlation between the two?

I appreciate your advice tremendously. After I resolve this issue I can help less experienced forum members like myself with the same issue.

[Explicit_Spade]

As we discussed in chat, the best diagnosis would require knowledge of the Check Engine Light Code.

Based on the information provided, the Exhaust Gas Recirculation Valve most likely either needs to be cleaned or replaced. A stuck EGR valve will allow unmetered air into the intake manifold, which would throw off o2 readings.

DELPHI Part # EG10169 is $87.99 on Rockauto

While you are fixing potential issues, and do not know the last time it was done, it would not hurt to replace the o2 sensor as well. The o2 sensor upstream of the catalytic converter controls the engines Air/Fuel ratio.

Upstream: BOSCH Part # 13474 is $26.79 on Rockauto
Downstream: BOSCH Part # 13444 is $24.79 on Rockauto

Both the EGR and o2 sensors are fairly easy to replace and can be done with a simple tool set as well as the use of an oxygen sensor socket.

Oxygen Sensor Sockets are $8-12 at any local auto parts store.

[KZOO3800]

Thanks Spade.

[KZOO3800]

Issue resolved. New EGR valve installed. Hate to have paid a shop for this but they fixed all issues I had noted in this thread. Markup on this part was absolutely incredibly effing high FYI. Then there's diagnostics/labor on a $87 part and you can pretty much deduce the dollar amount of rape I subjected myself to by letting a shop do this. Recent promotion at work prevented me from doing this myself because sadly I've been too busy to even look at a wrench lately. All OBDII codes clear now. 02 sensor code was for heater circuit only. Try as I might to understand why the 02 sensor heater code was set I just haven't had time to worry about it again until it returns.

*EDIT*
I could really use a code-scanner for situations like this one. I just need something basic. Any suggestions? Thanks.

[Explicit_Spade]

Actron makes a few code readers for under $50. I would spend the extra $75 and get an aeroforce scan gauge so you can monitor everything else your gauge cluster isn't telling you.

[Russosaur]

Issue resolved. New EGR valve installed. Hate to have paid a shop for this but they fixed all issues I had noted in this thread. Markup on this part was absolutely incredibly effing high FYI. Then there's diagnostics/labor on a $87 part and you can pretty much deduce the dollar amount of rape I subjected myself to by letting a shop do this. Recent promotion at work prevented me from doing this myself because sadly I've been too busy to even look at a wrench lately. All OBDII codes clear now. 02 sensor code was for heater circuit only. Try as I might to understand why the 02 sensor heater code was set I just haven't had time to worry about it again until it returns.

*EDIT*
I could really use a code-scanner for situations like this one. I just need something basic. Any suggestions? Thanks.

If you have a smartphone you could buy an OBDII Bluetooth adapter($12-$14) and buy the Torque App (3 for 4 bucks) You can clear and read codes also check for KR, and a bunch of other stuff in real time.

[Explicit_Spade]

There are a lot of variables that can slow down that real time estimate. I'd like to see a side by side comparison of torque and aeroforce but nobody ever wants to do one...

[Russosaur]

Send me one an I'll do it, its cheap and worth the money still until you can get an areoforce.

[KZOO3800]

My roommate has an OBDII bluetooth setup like Russosaur mentioned on an '07 Eclipse GT. Not sure which one I'll have to ask him. Guy owns zero tools so that kinda defeats the purpose. His motor has a lot of custom work and I was impressed when he showed me how he monitors everything on the app. I've never messed around with a nice scanner like an Aeroforce.

[nik12937]

I personally just use my phone and the torque app as well. The refresh rate really depends on the adapter, mine seems to refresh every .1-.2 seconds if I'm not scanning more than 3 or 4 things at a time. I'd consider it pretty damn good for the money, but the Aeroforce WILL give you a slightly quicker refresh rate. Not to mention it's consistent. If you're phone is like mine and occasionally hiccups, that WILL hinder the refresh rate on the app when it happens.

I'd say it's good until you're running a cam or something to that extreme, then I'd want that instant KR reading.