Rough Idle SES-Lite on- OBD1, No Codes Found

[Benesesso]

1995 3.8. Engine suddenly started to idle rough, SES lite came on, stays on now. Had AutoZone scan it (OBD1, 12 pin), no codes found. Scanner is supposed to read both OBD1 and 2, and was brand new. Scanner could not make SES light go off.

Engine has fairly new NGK Iridium plugs, runs very well except at idle and at very light throttle. Checked TPS with digital VM, was fine.

What problems affect idle and make SES come on, but don't set codes?

[nicke66]

Nothing but codes make the SES come on! If the SES comes on, there is at least one error code!

The guy at autozone did not know how to hande the scanner, the scanner was defective, or it was not able to read GMs ALDL 8192 baud!

Common problems causing rogh idling is vaccum leaks or a bad EGR or IAC-valve.

You can erase the codes by disconnecting the battery for some hours.

[Benesesso]

At this point I'd buy a freakin' scanner if I knew of a cheap one that could read the thing. My laptop just died so I can't even use that with the software to see what's going on. Guess I'll have to get another laptop.

[nicke66]

Yes, get another laptop and pull the codes yourself. I guess you already have an interface and software. You can get software for the 3.8 here:
http://www.pontiac-transsport.de/ind...ile&fileid=809

This software works in pure DOS.

[Benesesso]

No, I don't have the interface OR the software. Don't even have a laptop at present. Sounds like the scanner that Checker Auto (not AutoZone) used wasn't reading right. Whatever has set the code must be causing my terrible idle, so it must be an electrical failure, not mechanical, right?

Guess I'll go buy a new EGR cylinder; it's so easy to change-I hope.

[Benesesso]

Hmmm, my Haynes book says that the 3.8 uses a stepper motor and is closed at idle and when the engine is cold. I think that rules out an electrical failure, unless the stepper motor has stuck and is keeping the valve open.

Time to look up the IAC thing.

[Benesesso]

From a previous message.

"EGR valve:
94-95 3.8 has a linear EGR valve with a solenoid and a position sensor. There is a 5-pin connector. Pin 1 and 5 goes to the solenoid, and pin 2 to 4 goes to the sensor. You can check the valve with an Ohm-meter.
For the solenoid, you should read about 9 Ohm between pin 1 and 5.
For the sensor, you shoud read about 4 kOhm between pin 2 and 4. The reading between pin 3 and 2 (or 4) should vary with the position for the valve, and be between 0 and 4 kOhm. The reading between 2 and 3, plus the reading between 3 and 4 should for any position for the valve be equal to the reading between 2 and 4.

Bad connection inside the sensor is common falure, and means the sensor has to be replaced. The valve can have start going bad even if the check engine light is not on. If there is just a little bad connection inside the sensor, the CEL does not turn on."

I just ran an ohmmeter check. Solenoid and sensor check out fine, but the total of pins 2-3 AND 3-4 do not total 4 k-ohms. I measure 0 ohms for one pair and 1100 ohms for the other. Not sure which pins are 2 and 4, but it may not matter. Pin 3 must be the center pin.

I think I'll remove and blank off the EGR valve and see what happens.

Where is the IAC goodie?

[LMP]

this (from nicke66 shop manual) might help in identifying the EGR valve connectors.
www.avigex.ca/xport/dtc1406.jpg

IAC is part of the throttle body
www.avigex.ca/xport/maf.jpg

[Benesesso]

Removed the EGR valve and cut a small rectangle of fairly thick "glass reinforced" sheet gasket material to use as a block-off under the valve. END of problem! Van runs almost good as new. Called AutoZone for new EGR price. $165!!!!! It will be quite a while before I buy one. SES remains on, of course.

Thanks for the help.

[nicke66]

Yes, the engine vill run fine without the egr-valve, but how about yearly inspection with the SES on?

Have a look at ebay for a new (or used) valve. I did have a quick look and found one used:
http://cgi.ebay.com/ebaymotors/94-95...spagenameZWD1V

[Benesesso]

Thanks, hadn't thought of eBay. I think I'll wait until I find one that's garaunteed to work. This seller has a great reputation, so I suppose I should ask him about returns.

I live out in the desert where there is no inspection required. That will probably change some day, as we get more California garbage every day.

BTW, I see you're in Sweden. I worked with Sandvik near Gavle a few years ago--made 3 trips up there from Italy. Great country you have, except for the cold.

[nicke66]

If no inspection is required, and you can live with the SES light on, I don´t think you really need a new valve. Perhaps your car will emit some more NOx, but as a matter of fact, the first model year with 3.8 engine, 1992, didn´t even have an EGR-valve!

I did bought a new valve on Ebay fros US a few years ago. From a private seller, but unused. I think I did pay about 90$. Retail price in Sweden was more than 300$!

I live about 200 north of Gävle. I am familiar with Sandvik, even though I am working at a paper mill. Yes, Sweden is a great country. This time of year a little bit cold, but I have only 5 km to go to the hills for skiing!

[rockwood84]

clean the egr with a can of carb cleaner two or three days or so before you are going to take it off spray some wd40 or liquid wrench on the metal pipe that goes to the egr and spray it good and let it get hot as you drive and it will come loose pretty easy when you go to take it loose.

[shoman44]

Its Your Crank Sensor, I Had The Same Problem , Ses Light With No Code!!!!! Misfire Under Light Load,and Sitting And Was Fine On The Eway.....i Have A 94

[Benesesso]

There are only 2 nuts that hold the EGR valve on, and they and the valve came off easily. There is no metal pipe on a 1995 3.8.

Looks like my crank sensor is OK, because the van is running fine so far with a piece of high-temp. sheet gasket covering the ports. I'll have to see how long it lasts before the heat destroys it.