EGR clogged: side effects and symptoms? (94 Q45t)

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

I'm having lack of power from approx 1500-2000 RPM. Dealer ran a consult and determined it was a clogged EGR. (94 Q45t, 157k miles)

I'm assuming I can trust that diagnosis and I'm getting ready to pull that EGR and clean it. I have 4 questions if you have the time...

1) Can I use regular carb cleaner or the like to clean the EGR?

2) Are there side effects of having run with a clogged EGR that I should remedy or look for while I'm at it? Low MPG, hesitation, fouled EGO sensors?

3) If the EGR can be clogged, I'm assuming the metal pipe can get pretty dirty as well. Is it common practice to remove the pipe and clean as well or better to just replace it?

4) What's the easiest way to get to the bottom end of the EGR pipe?

Many thanks in advance. I'm looking to get this machine running in peak condition and this hesitation at low RPM is killing me. Any info is welcome.

mccluredude

Post by **Q451990** » Mon Jan 06, 2003 11:57 am

In my experience, most of the clogging occurs inside the plenum port, not the valve or tube. You can double check this by removing the sensor that screws in to the plenum in that port. Mine had a very thick (85%+) blockage in there. I've used carb cleaner and brake parts cleaner for this before, but the best stuff I've seen is by BG and it's called throttle body cleaner. If you car has never had the plenum removed and hand cleaned, it's well overdue! Just be sure to have all of the rubber hoses to replace under there if you go that route.

I think one of the main symptoms from a non functioning EGR valve is detonation (spark knock). The cylinders tend to run hotter, so you can have all sorts of side effects. If the knock sensors are detecting knock, the ECU is retarding the timing advance, so that could have something to do with your power loss.

Good luck!

Heath

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

Thanks Heath,I also suspected retarded timing from knock, but this engine is so quiet I can't really hear what's going on. I'll pull the sensor and check it out. Thanks for the heads up. I'm not looking forward to pulling the plenum. Sounds like quite a job.

Post by **Q45tech** » Mon Jan 06, 2003 11:57 am

Won't pass emission with clogged EGR [high Nox reading]!

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

That's strange, I passed SMOG here in California with flying colors just 3 weeks ago. Is it possible that the Consult may be wrong, and that it's not my EGR? Maybe I should call the dealer back and get him to clarify since I did pay for the diagnostic service.

Post by **autotech43** » Mon Jan 06, 2003 11:57 am

While the engine is warm and at idle, you might try and reach under the EGR valve and lift the valve off of the seat and see if you get an engine stumble. One sure way to find out if you have an EGR clog, but also depends on where the clog may be located. One way the ECM knows that the EGR has a malfunction is from the EGR temperature sensor, which as the EGR flows past the temp sensor the voltage will decrease in value. Most cases, the voltage will be around the 1 volt range when you have (no EGR) flow, and the voltage will decrease when you do have (EGR flow). There are no real specifics on that particular sensor due to the hot and cold ratio will somewhat affect the reading. The ECM is looking for the change in voltage!

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

I depressed the diaphragm and did get the stumble expected. Does this mean I should be looking at the sensor instead of the valve itself?

Thanks,Scott

Post by **Q45tech** » Mon Jan 06, 2003 11:57 am

Or the vacuum/electric solenoid which when the rpms are right [non idle, non WOT, only cruise] allows the vacuum to pull the EGR valve open if the coolant is warm above 150F or so.

Post by **Q451990** » Mon Jan 06, 2003 11:57 am

The solenoid will corrode (as with all of the electrical connections). I had to clean it once. You can test it's operation by reving the engine slowly from idle up to about 3000RPM. Feel the bottom of the valve (that you pushed up). It will flutter for a while and then drop out at a higher RPM. I don't remember the exact range, but the EGR only opens at cruise. Make sure the engine is warmed up to operating temperature or the test won't work.

Heath

Post by **SHR XTC** » Mon Jan 06, 2003 11:57 am

So from what I'm reading, is it the Knock Sensor??About how much is it to buy a Knock Sensor??How hard is it to replace??

Thanks~~

Post by **Q451990** » Mon Jan 06, 2003 11:57 am

Knock sensors will show their own code, so unless the tech. that ran the consult test missed something (and that's hard to miss) then it's unlikely that they're causing his problem, unless it's intermittant and the tech didn't notice the stored codes?

To answer your question, there are two sensors plus the harness that should be replaced as a set. Probably about $300-350 for the parts according to where you buy them. The bad news is that they're in the bottom of the "valley" under the plenum, so it's very labor intensive. Allow 8 hours to replace the sensors and every rubber hose you see under there. Count on another couple of hundred for hoses (PCV, Cooling, etc).

Heath

Post by **Q45tech** » Mon Jan 06, 2003 11:57 am

The $600 in KS and all hoses along with 8 hours labor is just a normal part of the 120-150k-/8-10 year rehab process.

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

Is this vacuum/electric solenoid the item very near the EGR connected with vacuum hose? Where is the electrical connection? I see a vacuum hose near the EGR port and one leading to the EGR valve, but no electrical connnection from this thing. Wondering if this is the part you are referring to.

By the way, thanks for the help so far. I'll get this thing fixed soon with all this feedback.

Post by **mccluredude** » Mon Jan 06, 2003 11:57 am

If this is the actuator, am I correct assume that it would be a good idea to remove the connection to the EGR/plenum port and clean it? If this port is clogged, then the actuator will not be getting any vacuum to pull the EGR open right? I think this might show the same as a clogged EGR upon diagnosis.

EGR clogged: side effects and symptoms? (94 Q45t)

EGR clogged: side effects and symptoms? (94 Q45t)

Knock Sensor??

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