Symptoms of EGR trouble

[wolfox]

This applies to a '95 4.3 CPI engine:

Well, I guess my Marvel Mystery Oil treatment was working better than planned. It knocked a big 'ol chunk of carbon suspiciously shaped like either the back of the pintle, or the pintle seat itself loose and wedged it in sideways between the pintle and seat. This of course left it nearly more than 75% open and resulted in:

1) Cold start up issues: The engine would lope and sound like it was going to stall. It would jump up into a high idle, then drop back down again to an almost stall condition, over and over again.

2) Warm idle/light throttle problems:
SES light would turn on... The engine would surge randomly and strongly at light throttle when at cruise speed, and would not settle down until having to brake. Braking pressure was more than normal to overcome surging engine output, and then would settle to a near stall at idle/stop, jump up in RPM and then nearly stall while at a standstill.

To remove it and clean it, first drop 5 bucks for the high temperature seal that goes around it at your local parts shop. Using a 3" extension, 12inch extension, U-joint knuckle and a 10mm socket, one can make quick work of disassembly and re-assembly. A corner of duct or scotch tape put inside the mouth of your 10mm socket will make retreival of the bolts easy.

Disconnect the negative terminal of your battery. This will reset the learned behavior and reset the code this problem will light the SES light over. I disconnected the cruise control and throttle cables to allow a little more clearance without hinderance around the side of the throttle body after removing the intake, and the IAC valve electrical connector. Using the 12" extension and your taped 10mm, one can sneak the socket to the lower, right hand bolt on the EGR to one side of the tensioner pully and belt. Swap for the 3" extension and knucle to remove the upper bolt on the left side of the EGR assembly sneaking the socket and knuckle along the side of the EGR from the top between the manifold butterfly and the left side of the EGR. Tollerances are tight here and your knuckle may take a few false starts when it hangs on the side of the valve. Patience and slowly backing the bolts out a 1/2 turn at a time at the start will be needed, but she will come loose.

Remove the EGR carefully, sneaking a finger under it to make sure you do not drop the gasket into the unseen parts of your engine interior. Mine slid right out between the inkate manifold butterfly and the side of the tensioner and the radiator hose without having to remove either. I turned it over and sure enough, a semi-circle of 1/4" thick carbon was wedged in beside the pintle and seat. Using the handle of a pair of needle-nose pliers (The plastic coating on the handle) I pushed the pintle in just slightly and turned the valve over. The chunk fell out! Releasing the pressure let the valve close all by itself, and rather smoothly at that. I then dipped the unit for 30 minutes in a bucket of Chemtool Carburetor and Parts cleaner. Swish the basket every 10 minutes and re-dunk a few times to make sure the fluid touches everything and breaks up more carbon. Seriously, hard deposits literally just fly off on contact.

Remove from the dip and clean with carburetor parts cleaner from a spray can to remove the thin oil left all over the entire surface of the unit. Flush out the valve body too, but do not do it over a garage floor. The black crud that comes out will be substantial, but I had a completely clean part when done.

Replace the unit with your fresh $5 high-temp gasket and torque your 10mm bolts back in, again using the duct tape to hold the bolt until you are ready to turn loose of it. Reconnect your battery and start her up. Let her idle in gear for two minutes with your foot on the brake to re-learn your fuel curves/trim and idle RPM. Instant fix that only cost me solvents, gaskets and a 1/2" strip of duct tape. She's back in fighting shape!

[BlazerLT]

Be prepared for even more carbon coming out in the future.

[wolfox]

Though nothing is for certain, the passages were very clear and open. No visible build-up or deposits other than a light tan color with a few of the rough surfaces shining through. The MMO seems to be working. With the EGR cleared of the chunk that was *exactly* the same curvature of the pintle face's seat I am hoping that was the last I will see of that for a while. If it blows another chunk free, it does and now with the mystery of plucking my own valve out solved after a day of rough running - easy as pie.

Is there reason to think that more chunks may blow out of the heads and into the passages/pintle again?

[BlazerLT]

Originally Posted by wolfox

Though nothing is for certain, the passages were very clear and open. No visible build-up or deposits other than a light tan color with a few of the rough surfaces shining through. The MMO seems to be working. With the EGR cleared of the chunk that was *exactly* the same curvature of the pintle face's seat I am hoping that was the last I will see of that for a while. If it blows another chunk free, it does and now with the mystery of plucking my own valve out solved after a day of rough running - easy as pie.

Is there reason to think that more chunks may blow out of the heads and into the passages/pintle again?

Are you using the MMO in the gas or in the oil?

[wolfox]

Gas only. In the oil scares me for more than 1000 miles and if that, only at half strength for a maybe once a year/two year flush. Egads, could never rest well with myself if I put a full quart in the crankcase. Solvents in my experience and opinion are the polar opposite of lubricants. Besides, MMO in the oil has no chance of cleaning out the recirc. plumbing if it's in the crankcase. Unless of course, you are burning as much oil as gas...

[BlazerLT]

I'm thinking about doing a treat of MMO sometime in the near future myself.

Heard good things about it.

[wolfox]

On an older '84 Oldsmobile Delta 88 I had, (Carbureted Holly Quadrajet on 307 V-8) it would keep it idling smooth and the interior of the carb jets, bowls and top end clear. Not a spot could be seen on the piston heads either when it was torn down after suffering from a cracked block. (Old age caught up with it) It also helped to keep the EGR system from rotting out every 2 years as it was prone to do on a car used primarily as a grocery fetcher and railroard station machine for most of it's life. (Short trips - never fully warming up) Mix 4 oz./10 Gallons of gas and over time, it will clean even the most fouled up and carbon gunked machine. Once it's clean, I keep the tank filled with a quality gas and cut the MMO back to 4 Oz./20 gallons of gas as a maintenance dose. Hey it's cheap - it's sub $3 at Wallyworld, and as far as I know, though more than 50 years old the stuff works well in fuel injected vehicles.

I use a pint of MMO in the oil once a year for 1000 miles as a flushing agent. It can usually silence sticky/rapping lifters in under 500 miles at such strength. It de-gunked an 86 CJ-7's Ford slant 4.2 litre I-6 within 9 miles. (Horrible, multiple lifter clatter that got *so much* louder when raised above idle. Sounded like a thrown rod) I used it for 1000 miles as described above to silence a lifter tick when I first brought my Blazer home. It was gone in about 500 miles, barely noticable after 250 at first.

When run in the gas, the engine eventually just seems to "settle down". Idles like silk, makes RPMs under load much more swift and powerfully with no pinging and rattling going on under the hood. It seems to also smooth out the burning of not so quality fuels. Like when road tripping an you cannot find your station/brand of choice. Bringing the dose back up to a ratio of 4 Oz./10 gallons makes even the cheapest 87 feel like premium and it helps combat the crud that will build up after a brand-x fill up, in my experience.

How does it work? That's the Mystery I guess.

[murfthesurf4]

Originally Posted by BlazerLT

Be prepared for even more carbon coming out in the future.

I just pulled my egr and took out 3 chunks of carbon. since my egr was replaced only 3 months ago and has been pulled out 3 times since I didnt replace it. As I have read on other posts I added 4oz/10 gallons of gas of MMO to my fuel tank.This was my first time for myself with the egr and I'll be ready for the next.thanks to all the posts MURF

[wolfox]

You should have bet me, BlazerLT - you would have won. This time I got a SES lit again for a generic EGR malfunction. (There is only one EGR code in the OBD 1.5 Blazers, it's not granular at all like 2.0 version computers) When I pulled the EGR off, it was closed; not wedged open as I expected. Truck idled fine, and power brakes were there, etc. What had happened is another good sized chunk got BEHIND the pintle and stuck it shut. Easily remedied however:

Soaked the EGR "head" that attaches to the block in more carburettor solvent for an hour. Turned it over and shook it out, loads of little dusty black particles poured out with the fluid. It was still frozen shut - but under advisement, I found myself a Torx bit large enough to fit the head of the pintle. Standing it upright with the Torx bit in place, I gave it just the *merest* tap with the handle of a screwdriver to the butt of the torx bit. It cruched the carbon chunk behind it enough to restore free operation. Stuck her back in with a fresh gasket (This time with a $1.25 NAPA special overnighted to me) and took her for a ride without resetting the computer. The light went out after a minute at idle and never came back on...yet. Hopefully the MMO's done it's job and got the big ol' chunky bits out of the recirc. system. I will be taking her 3000+ miles round trip, cross country on vacation next week.

Now, now - before anyone tries to eat my lunch on "tapping" or "Striking" a "sensitive piece of electronic equipment" like this, I have it on good authority from 5 different opinions, three of which came from dealerships no less that if done as I described, no harm will come to the unit. It's not like it's made out of marshmallows or anything. However, "rapping" on it when still mounted to the engine is a big No-no. You can force a big chunk of carbon to be released and sucked through the intake and hanging a valve or worse. Second, the back cap of the unit though stocky, is plastic. You can fracture it to pieces if it's struck dead on with a screwdraver + hammer, etc. You must remove the unit before you attampt to clean it safely or to free a sticking pintle. Doing it on the block is just foolish. I tried to start the engine with the EGR removed, but she simply wouldn't catch. After 4 failed attempts I skipped the "let her run a few seconds to blow anything else out of the EGR tube" trick for fear of running down my battery even further. I will just pop the EGR off again when she clogs and do my best to clean what I can reach. It's not hard to do afterall.

[blazee]

If you have the old style ECM, you may want to read this:
http://www.automotiveforums.com/vbul....php?p=3223914

[wolfox]

Spot on brotha - that's good info for us to know. Unless you have the right scan tool or remove your DCM to look at the sticker on your PROM, you will not know if you have the right Memcal or not. I left a comment on your thread on how I got the Memcal revision/PROM revision using a very swank scan tool. (Borrowed of course) My friend threatened to just take my truck if the tool was returned damaged in any way. They're *that* expensive!

Originally Posted by blazee

If you have the old style ECM, you may want to read this:
http://www.automotiveforums.com/vbul....php?p=3223914

[blazee]

Thanks.
I bet borrowing that scan tool was fun....I like playing with expensive tools. I'm thinking about getting an Autotap, sounds pretty similar to the one you described.

[wolfox]

Autotap is software you load on a PC or laptop and then interface with a serial port to your OBD-II connector. This was some dedicated expert system embedded on a tablet PC. It was orange and grey on it's plastic covers and came with a multiple "Octopus" of cable/connector headers with a ring of "keys" on the cable end near each plug. To get it to work with my truck that has OBD-II style connector, but an OBD-1.5 computer under the glovebox; One would use a standard OBD-II connector with the pre-'96 GM truck key inserted into the slot just behind the connector. Then you punch in the manufacture date and VIN number of the truck and it manages to communicate through that port. A standard OBD-II "Scantool" did not work, I tried and borrowed three of them. Autotap in my same truck would not work...otherwise I would have that! Autotap works with fully compliant OBD-II equipped vehicles only.

[blazee]

I meant that the user interface and capabilities sounded similar to the autotap. Based on your description, I can just about picture what it looks like. I imagine that it looks fairly close to the electrical test equipment that I use at work.