97 Pickup EGR problem

viper2 · Aug 25th, 2003, 10:30 PM

I have had a hesitation problem for a while now with many attempted fixes from a slew of mechanics. I recently went on About.com and stated my problem, the moderator suggested I disconnect the EGR valve. I did this and the problem disappeared.

I did a test on the BPT valve (checked out okay) and just replaced the EGR valve. The problem returned when I hooked up the hoses back to the new EGR. Now I'm a bit lost.

The computer is not reading this problem, it does not even read my EGR is disconnected (don't know if it's supposed to). I see something called an EGRC selenoid in the emission schematics. ???

Anyone have any suggestions of where I should look next for this problem? It runs great without the EGR hooked up and I live in a no inspection state. But I like my truck to work the way the designers intended. I hate leaving it at the dealer.

1997XETruck · Aug 25th, 2003, 10:53 PM

Not having your EGR connected can cause higher combustion temperatures and detonation (spark knock). The EGR puts exhaust fumes back into the combustion mixture at cruise to slow combustion slightly by starving the mixture of some oxygen. Does the control solenoid work correctly? I've had a situation on my Q45 where the electrical connections on the EGR solenoid were corroded so the valve didn't work correctly.

We also had a mid 90s Chevy S-10 for a short while that had a surge that was related to the EGR valve. We replaced the control solenoid first (cheaper and easier to reach) and then the EGR valve, and that fixed it.

Your inclination not to run the truck without the EGR valve is correct - you can damage your engine!

I'd replace the control solenoid, and also remove the valve and make sure the plenum isn't clogged with carbon build up in the EGR passage...

Is your truck a 4cyl or 6cyl? How many miles on your truck?

Heath

viper2 · Aug 25th, 2003, 11:00 PM

It's a 4 cylinder 2.4L. 2 wheel drive. 123,000 miles. I cleaned the passages pretty well when I replaced the EGR. Also the list of replacements for the very issue are (keep in mind when I brought the truck to a mechanic the first time he stated my EGR was working fine): rebuilt transmission, new O2 sensor (pre converter), fuel filter, cap, rotor, wires, plugs, egr valve, new front brakes/calipers. Light came on when I got the truck (had another truly unconscious owner previously) for EVAP emissions and I took 6 hours to clean all electrical connections to the purge tank and fuel tank. This killed the light but problem remains.

Now is the control selenoid the small black tubular gizmo connected to the BPT valve?

How much around are we talking?

If it is that round black module, how do you get it off? I guess I could figure it out but why invent the wheel again when I could just ask? =)

Thanks for your help.

1997XETruck · Aug 26th, 2003, 09:33 AM

Wow!!! A rebuit transmission! I've heard of throwing parts at a problem, but this is amazing!

I'm looking at the service manual now... does the valve open between 2000 and 4000 RPMs? Check out this picture from the service manual...

1997XETruck · Aug 26th, 2003, 09:35 AM

I'm not sure why that's so big, but at least it's easy to read...

BORNGEARHEAD · Aug 26th, 2003, 09:32 PM

I've seen BPTs go bad also. 1 cheap fix is to replace all the vacuum hoses that you can see that have to do with it.

1997XETruck · Aug 26th, 2003, 09:44 PM

I thought of that later today... it apparently also helps control the EGR. I flushed the BPT valve on my Q with a can of brake parts cleaner and got a decent amount of carbon out... might be worth a try. By the way Viper, did you use OEM parts or aftermarket on that EGR valve, spark plugs, wires, etc?

Heath

viper2 · Aug 27th, 2003, 05:47 AM

I used OEM parts. I tested the BPT valve and it checked fine. Here is what I got as an answer from an online mechanic:
-------------
Hi Keith,

With the engine running, ground the white/blue wire at the EGR Control Solenoid. You should hear it click and the EGR should activate. If it does, ground the white/blue wire at terminal 103 of the PCM. if everything works, the PCM is bad. If not, there is a break in the wire between the EGR-CV and the PCM.

There should be battery voltage, with the key on, at the black/white wire. If not, check fuse #9 and the wiring between the fuse and the EGR-CV.

If all that checks out, replace the EGR-CV.
------------------

Now, what's the "PCM" and the EGR-CV? Is that the same as the control selenoid? This test he gives seems pretty specific and what I may need. if I can't figure out where all these emission controls are it's off to the dealer. I wish I had a detailed emission schematic of my emission controls. The Haynes manual is absolutely horrible and vague and does not get into the 1997 truck much at ALL. Let alone where terminal #103 and fuse #9 are!

1997XETruck · Aug 27th, 2003, 08:57 AM

Does the valve lift when you rev the engine between 2000 and 4000 RPM? That's the first step to see if the valve is working, and that it's getting a signal! If it's not, then I'd run this test the online mechanic recommends - if the valve lifts, then don't worry about this test. Also, does your engine choke down or at least idle very slowly if you manually push the valve upward at idle? If not there's an obstruction somewhere (perhaps at the other end of the EGR tube where it bolts in to the exhaust).

Keep in mind that you can get the factory service manual at www.nissan-techinfo.com for $19.99. How you ask? Sign up for the one day "viewing" subscription and then I've been told you can download the entire document as a .pdf file to your computer. It's best to have a high-speed connection for that as I've heard it's slow even with a cable modem, so I wouldn't try it with dial-up.

The online mechanic is calling the ECM (computer under the passenger seat) a PCM for whatever reason. That's one thing about cars - nobody knows what to call all of this new fangled emissions stuff. I've seen the junk yards just call it the "brain box" - real sophisticated

- the EGR-CV is the solenoid. He's right on with the pin numbers and wire colors as compared to my factory service manual.

Heath

viper2 · Aug 29th, 2003, 02:06 AM

I want to thank you for your help XE. I eventually took the truck to the dealer (I really had no time to do all the tests). The problem turned out to be a clogged system and the timing was advanced slightly. I now have a truck that feels absolutely new.

So, only a few thousand dollars later, and a $112 problem was the culprit the whole time. The truth is, that now I really do have an almost new truck quite littorally.

1997XETruck · Aug 29th, 2003, 04:28 PM

Wow... a sad story with a happy ending! Just for the record, did they mention where the EGR clog was (plenum or tube)? I'd love to know for future reference.

Glad to hear that's all behind you!

Heath

viper2 · Aug 30th, 2003, 06:27 AM

Not really sure but I'll put the exact quote they put on the invoice:

"Emissions Gas and recirculation passages were clogged. Cleaned passages and Advanced Timing." $112

Hope that helps. If not, I can always call and ask them specifically.