Hey guys I've been lurking on here for a few months, Not really a poster, but i had a question i can't seem to find an answer to. I have a 2000 Q45 base model 4.1(sadly ). Along with many others i too have pulled the horrible p0400 EGR System Problems code, As i have read many clear it with simple cleaning and some have to do a great deal more. I, sadly, happen to be the latter. Since i cannot do the work myself due to not having the space or tools i take it to a mechanic that i somewhat trust. Before just throwing money at it i had it cleaned, the egr and tube, didn't fix it. I first replaced the EGR unit itself(looked like it was 14 years old so i replaced it, was about 200$) That didn't fix it. Replaced the EGR control solenoid( i read threw the FSM a little, provided by you lovely people , that suggested the EGR-C solenoid about 120$) That hasn't fixed it. I believe when it was cleaned the vacuum lines where checked, i obviously don't know, but someone recently posted that that fixed their problem. Does anyone have any suggestions for me to do? Also does this code give any drive ability issues? Besides the p0400 code i also am getting a p0330 Knock sensor, bank 2 and a p0140 O2S high voltage. Checked the O2 voltages with the OBD2 diagnostics thingy the O2 is completely shot, sitting at one steady number instead of fluctuating like the others. Any place to find a couple of OEM O2 sensors? ones i found online(unsure of the site) are like 140$ a piece for the rear ones and about 125$ for the front ones. Could the KS code give drive ability issues? i assume the O2 code would give some issues, since its jammed at one level. I recently also got exhaust work done, half de-cat with straight 2" to two Magnaflow performance mufflers. sounds good other than the rough running due to the above. Anyway thanks in advanced for any input. Won't be upset if noone cares either.

Welcome, Ortho!

The knock sensor code will definitely affect driveability.

Since the engine computer can no longer "hear" spark knock, it retards the ignition timing enough to minimize knock under the worst possible conditions. Result: Greatly reduced engine power.

IIRC, there was a software upgrade for the ECM that was related to error codes for the EGR valve and knock sensors. Hopefully, someone with a better memory than I will be along shortly to chime in.

Not surprised the O2 sensors are gone, I replaced mine in the 93k range. The knock sensors are also proabably on the list of things to replace. You didn't mention how many miles you have, seems like most people over at least 125 to 150k have replaced knock sensors, 02 sensors, coil packs and in some cases valve covers.

What mileage do you have??? Also for good prices on OEM parts (I would only use OEM if you intend to fix up this car and keep it) Scottsdale Infiniti (www.everythinginfiniti.com) gives good prices and maybe still give a discount for a NICO member (they used to).

Hey guys thanks for the replies. Sorry about not posting mileage, Its got 235k. Still runs pretty good besides the above. Another note on the performance, the car doesn't like the low RPM range seems like when it hits 2500+ it runs alot better. Could that be the o2 or KS? i read that the universal O2 are terrible and would most likely blow out within a couple months, definitely plan on getting OEM. Sorry for the prolonged response.

Just curious, Which one should i fix first the O2 or KS? i Don't have much money so any input on which one to fix first would be appreciated. I've given up on the EGR problem for the moment, It's annoyed me.