In a predicament, please help

[DarkMesa8]

My car is throwing two codes and is detonating like a Mofo with regular gas. I put premium in, and the detonation stopped, so I know its detonation.

I got codes

327 - EGR valve position cirvuit below minimum voltage.
328 - EGR closed valve voltage lower than expected.

So its the EGR valve. I took it off and cleaned it out really well, its only 2 years old since it was replaced.

I can get a new valve for $70, but it does not come with the position sensor. The position sensor is $25.

Money is tight, I can afford both but I'll be flat broke. If I buy the sensor and need the valve, I've wasted 25.

Do those codes sound more like the position sensor? Like I said, the valve works fine, I used a screw driver to open and close it.

But the car still detonates. Can a faulty sensor cause detonation, or is it definitely the valve?

 

[Red_LX]

What year car is this?

On my '90 the EGR valve wasn't even hooked to any sensors aside from a vacuum line, I blocked it off when I put on my header and never had any problems. I don't really see why a faulty EGR valve would cause detonation either.

Have you checked your timing?

 

[Bearded Forever]

Timing would make it ping more than an egr.

 

[DarkMesa8]

Do you check it the exact same way you check it on a 5.0L?

Its a 1991. Which wire is number one? The plug on the intake side, or the plug on the exhaust side?

The car is DIS, so I guess all I could do is see if the belt jumped a tooth.

 

[Red_LX]

Ahhh....I have no idea how you check the timing on a DIS car. Hopefully someone here can chime in.

However it might be worthwhile to check the timing belt. Any idea how long it's been since it was changed?

 

[DarkMesa8]

July 29, 2002 5:24PM at 196,157 miles. Dayco Dynaflex belt. I am currently at 220,000 miles.

 

[Touring23]

I hope this helps. I don't know the '91 that well; my maintenance book doesn't mention any difference in the EGR circuit over 89-93.
* The purpose of Exhaust Gas Recirculation is to lower combustion temperatures. Thus, less tendency to ping.
* Ignition timing on a DIS is just like most EEC-IV's: pull the SPOUT plug and look for 10* advance +/-2 on the #1 (front) cylinder. Please note there's no (simple) way to change it.
* Cam timing: Rotate the crank to TDC with a 7/8" socket (clockwise only!!!) and confirm the mark on the cam pulley lines up with the mark on the (belt shield, I believe. It's obvious). You may find the cam mark is 180* off, that's OK, rotate the crank one more revolution.
* You haven't mentioned what may be the key. The EGR Vacuum Regulator (EVR) controls vacuum to the EGR. Either a plugged vacuum line or a malfunctioning EVR will cause the EGR not to function. Again, my book doesn't say whether the '91 has an EVR. You'll need to trace the vacuum line from the EGR and confirm for yourself. The EVR is a small, black cylinder with two vacuum connections (in & out) and the electrical connector and is probably on the firewall.
You made a very good point when you asked Can a faulty sensor cause detonation. Not in this case, I don't reckon.
Hope this helps, good luck!

 

[DarkMesa8]

* You haven't mentioned what may be the key. The EGR Vacuum Regulator (EVR) controls vacuum to the EGR. Either a plugged vacuum line or a malfunctioning EVR will cause the EGR not to function. Again, my book doesn't say whether the '91 has an EVR. You'll need to trace the vacuum line from the EGR and confirm for yourself. The EVR is a small, black cylinder with two vacuum connections (in & out) and the electrical connector and is probably on the firewall.

OK, here's the deal. I found the EVR.

I pulled the vacuum lines off the EVR, and applied vacuum to the EGR line. The valve opened.

I than reattached the lines to the EVR, and pulled the line off of the vacuum tree. I pulled a vacuum, and it did not hold. The EGR valve did not open. Thing is, the car was off and there was no power to the EVR. Should it hold vacuum anyways?

 

[Touring23]

I pulled the vacuum lines off the EVR, and applied vacuum to the EGR line. The valve opened.

Check. EGR valve functions OK.

I than reattached the lines to the EVR, and pulled the line off of the vacuum tree. I pulled a vacuum, and it did not hold. The EGR valve did not open. Thing is, the car was off and there was no power to the EVR. Should it hold vacuum anyways?

Da Book says the EVR has a constant internal leak by design.
The reason why the EGR didn't open in this test is the EVR needs power to open. From the first note we know the vacuum line is OK.
Next test would be to check for voltage to the EVR, should be battery voltage KOEO on one of the two pins (the other pin goes to the PCM, switch-to-ground). The voltage should be 0 DCV during hot idle.
It doesn't mention imposing a voltage on the EVR to test it. Probably a good way to burn out the solenoid. Try this at your own discretion, and only for brief moments.

 

[DarkMesa8]

OK, pulled vacuum on the line when the car was running, and it held it, so I'm thinking the EVR is fine.

I pulled a plug, and its white like its extremely lean. I drove it around really easily so there was no detonation, pulled it again, and it was still white.

My new theory, is that the 220,000 fuel pump is not keeping up. The fuel filter is new.

And, since a lot of people are running with no EGR at all and its fine, I'm starting to believe EGR has nothing to do with it.