# EGR Not Functioning but no MIL



## punchodex (Feb 21, 2011)

I have an overdue CA smog check and it barely passed 2 years ago so I doubt it will pass. I hit the max on HC and pretty high on NOX too. I have already done a tuneup: cap, rotor, plugs (stock), PCV and grommet, air and fuel filter, all new vacuum hoses except brake booster. No MIL at all. Runs fine. I fixed the slight stumble after the vacuum hoses were replaced and a good cleaning of the IAC valve. 

The EGR does not move unless you bypass the EGR/Canister solenoid valve and apply vacuum directly to EGR valve or BPT valve. I removed EGR valve and cleaned it and the tube to BPT, they were already clean and unobstructed. The passages to intake are clear b/c it stalls if you apply enough handheld vacuum to EGR. 

No vacuum comes out of the solenoid valve when it should (proper warmup and RPM). I pulled out the solenoid valve and did the FSM checks for air continuity with voltage applied and it didn't pass one test so I ordered a new one. To no avail-I wasted $80 b/c the problem seems to lie elsewhere. I replaced the BPT also. 
It isn't the supply hose to this solenoid valve either b/c I hooked up a strong vacuum hose (the fuel pressure regulator hose) and it still didn't let vacuum through. 

I tried to see if the EGR was somehow working while driving since their was no MIL to show no or low-flow EGR. I disconnected the vacuum hose to EGR and ran it for two days, no MIL. 

My mind is boggled. The MIL should come on when no EGR is flowing but it doesn't??? And why won't the EGR/Canister Solenoid supply any vacuum? Is there was way to reset the ECM so it will relearn everything? Maybe then the solenoid would work. 
Any input is appreciated.


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## punchodex (Feb 21, 2011)

I have a few updates and I think I've figured it out, in case this helps anyone who has strict smog checks. I will post a final update after I get the appropriate parts and do the smog check. 

I removed the coolant temp sensor and EGR temp sensor and tested them in the appropriate temp water on my stove. The EGR temp sensor was not fun to reinstall b/c I had to remove the EGR to Intake tube which has a PITA bolt to install on the bottom of it. Unless you have a smaller open ended wrench than I have, or if you are willing to grind down part of it to fit it between tube and manifold/throttlebody or I'm an idiot. I think the prior owner (my sister) had this sensor replaced and the clown of a mechanic didn't put it on tight enough b/c it was super loose on removal. 

The test was difficult getting leads on and keeping it in water which was hot as hell while avoiding dropping the sensors in. Coolant temp sensor was probably at the top end of the range or out of the range so this tells computer the water is colder than it actually is. Therefore, the ECM thinks EGR shouldn't be required b/c it's too cold of an engine and thus no low-flow indicator necessary. So that's why it didn't matter when I disconnected EGR completely b/c maybe ECM thought car never warmed up enough to have EGR. Also, I checked MAF sensor resistance values and it only hit low 2 volts at 4k RPMs, where it should be close to 4 volts. The EGR and canister solenoid won't work with a defective MAF or too cold or hot of an engine. The MAF sensor seems to be a popular part to replace around here, so after 180k miles I think mine is due. 

The odd thing was that after reinstalling the 2 temp sensors and warming it up and checking for lack of EGR valve movement, there were 3 codes and a MIL which have never come up before. The coolant temp code, EGR low-flow, and intake air temp code. Also, the scanner said the O2 and catalyst system were "incomplete." I didn't read my neighbor's scanner manual enough to know what that meant. Probably a new CAT but we shall see. 

I hope after a new coolant temp sensor the EGR solenoid will work. I barely meet the income requirements for the CAP where state pays $500 of repairs for smog if you fail. So maybe I won't have to buy that MAF sensor after all. Perhaps one of the many reasons CA is broke.


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## azkicker0027 (May 31, 2002)

so far, my EGR issues were limited to old, cracked, and leaking vacuum lines. i do remember though having an issue with a client's EGR on an SR20DE. there was a small restrictor installed within the vacuum line going to the valve from the solenoid. it wasn't visibly obvious, but i felt it when checking the lines for leaks and tears. it didn't open the EGR valve enough and kept the combustion chamber temps on the high side.


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## punchodex (Feb 21, 2011)

The new coolant temp sensor didn't do anything.

I replaced all of the vacuum lines with generic from Kragen so the restriction in line wasn't an issue, unless it's part of the Y connector b/c I left stock one on there. 

I disconnected the EGR and canister solenoid valve, which allows the vacuum supply straight through to the EGR and EVAP canister and drove around for a week. The MIL comes on of course. I could always feel the EGR valve movement and the pipes to and from EGR valve were hot. It only had a rough off idle stumble when it was cold but after warm-up it drove pretty normal. I reconnected and no movement from EGR valve even after clearing code and completing the drive cycle for the system readiness test for the Catalyst and O2, which was an ordeal. 

I skipped the MAF sensor b/c I figured it was expensive and CA can pay for it. Luckily the car ended up squeaking by on the smog check. The 15mph test it was 1 ppm from the max. I know EGR wasn't working but it still passed luckily. Curiously, the 25mph test must have been in a different gear than last check b/c it was only 1800 rpms (vs 2500 rpms last time) and the EGR shouldn't work until 2k rpms according to FSM. 

I never really solved the problem but when/if I do I will update.


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## EvilPotato (Sep 6, 2005)

your EGR must have worked then, i went for pre-smog with a non functional EGR and the NOx (NO ppm) was more than twice the allowed value at 15mph


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