egr system problem

[driftdizzle]

i have a 1993 infiniti g20 high port and i failed emissions today. well i am searching for the solution my hc's and nox are higher than they should be. i went to check the egr valve and when i pulled the vaccum line at idle there was no vaccum to the egr and i have a feeling that that is the reason the nox is so high. what can i do to fix this problem. any info on this subject will be greatly apreciated.

[Q451990]

Vacuum should only be present when the valve would be opened... say at 2500 RPM?

If the G is anything like the Q it probably a clogged valve or port where it bolts to the plenum. The easiest test is to put your hand on the bottom of the valve and push it open at idle. The engine should stumble and almost choke down. If it doesn't you have a major clog. Then at idle, put your hand on the bottom of the valve while reving the engine... you should feel it lift (sort of flutter) at about 1500-2000 RPM and then drop out at higher RPMs. If it never lifts, you probably have a control problem.

Good luck!

Heath

[driftdizzle]

thanx i hope i can figure this out.

[driftdizzle]

ok would it help if i list how it failed. the hydrocarbons wur 1.78 and the standard was 1.0. the carbon monoxide is 7.78 and the standard is 12.00. the oxides of nitrogen wur 5.89 and the standard was 2.5. can anybody stear e in the right direction.

[driftdizzle]

bump

[Q45tech]

Dirty partially plugged up egr metal hose from exhaust to valve, valve itself, or entrance to plenum.

[driftdizzle]

how would you go about cleaning that

[Q45tech]

The same way its been done for the past 40 years since EGR became common.

Disassemble parts and use solvents and wire brushes in appropriate sizes.

Probably the most common proceedure after changing spark plugs, clean the years of crud build up in various air/exhaust systems.

Do it yourself assumes the person has some formal automotive education [2 year trade school] or apprentice on the job training or prison...........where they spend a few year on work release repairing state or municipal crown vics and other vehicles.

[goody90q45]

I'm going to describe the process for EGR valve cleaning on a Q45 (not the G20) but from what I've seen other Nissan/Infiniti engines use the same EGR valve so it should be the same process or very similar.

You should have a new EGR gasket on hand before starting. Removal of the EGR valve is straightforward. Disconnect all vac hoses, remove the solenoid above the EGR valve, and remove the pair of 12mm bolts securing it to the intake manifold. Clean the valve internals with brake parts cleaner and an assortment of brushes. I use a toothbrush and a lab size bottle brush. Use the entire can to remove the carbon buildup.

The intake to the EGR valve is the 3/4" diameter metal tube and it can also be plugged. Push a coat hanger (or equivalent) through the tube and to the exhaust manifold to make sure it's clear.

There's a temperature sensor attached to the intake at the plenum. Remove it and clean the tip of carbon deposits so it sends an accurate reading to the ECU.

Lastly, you'll need to clean the intake path on the plenum (intake manifold) body. Pick away at any deposits (careful it's aluminum) blocking the flow until you have a clear path to the inside of the intake.

Were you able to manually push up the EGR diaphram from the underside? Did the engine stall or was there no change (plugged EGR)?

[driftdizzle]

i tested the egr when the car was off with a vaccum pump and the pintle actuated.the problem is that the egr isnt getting vaccum at 2000 rpm like it should im thinking it could be the vaccum solenoid or the bpt valve.

[maxnix]

You are on the right track, but never the less if you have 50K of heighway driving, plan on cleaning the EGR valve and its passages.