EGR question... is this right??

Hello all,

So in an attempt to fix my poor idle situation I have questions about the EGR. On my 89 Cherokee the vacuum lines look to do the following...

1 goes from the egr to the lil electric control on the fenderwell

2 goes to the airbox lid

Is that correct?

It is to hard to tell in the vacuum diagrams I have found in the forum search.

Thanks...

AboveNBeyond said:

Hello all,

So in an attempt to fix my poor idle situation I have questions about the EGR. On my 89 Cherokee the vacuum lines look to do the following...

1 goes from the egr to the lil electric control on the fenderwell

2 goes to the airbox lid

Is that correct?

It is to hard to tell in the vacuum diagrams I have found in the forum search.

Thanks...

Click to expand...

There should be a vacuum diagram underhood on a label that may be easier for you to read - have you checked that?

IIRC, there's one line from the solenoid (electonic control thingy) to the EGR valve, and one from the solenoid to the throttle body. The two on the airbox are for the "thermal vacuum valve" to turn the intake heater on and off (aluminum flexible line to the sheetmetal dingus over the exhaust manifold.) The third "line" is just a filter over a vent port for when the EGR is not being activated (or is it a cap? I haven't checked.)

OK wait up...

Maybe I am looking at the wrong thing? I am talking about the deal that is connected to the intake manifold, it has a steel tube that goes to the exhaust down tube. and the vacuum lines I mentioned above...

I will search for a pic of the EGR location in the mean time. Also there is no diagram, it looks to have been scraped off.

is the egr on an 89 easily removed, or will it screw with the computer too much. I was considering just taking mine off.

wolfpackjeeper said:

is the egr on an 89 easily removed, or will it screw with the computer too much. I was considering just taking mine off.

Click to expand...

Bump, I want to get rid of mine too, but not sure the procedure, and no straight answer on whether it would fail emissions without it...

Anyone know for sure, and what the proper procedure is for removal?

Remove and cap off the vacuum line.

The engine will run fine without the wretched thing - and cleaner besides (this isn't me - I have "before and after" tests with a failed/replaced EGR floating around here somewhere. Replacing the EGR sent my emissions through the roof from damned near zero, with the thing AFU.) The ECU won't care.

The only problem with trying to remove it and use a block-off is the way the EGR ports are set up in the intake.

And, if you're subject to regular Air Police inspections, this will allow you to simply plug the thing in when the time comes. A quick check to make sure it's still functioning is to let the engine idle, apply vacuum to the valve with a hand pump, and see if the engine stalls (if it does, the EGR is working. If it does not, secure and install a replacement.)

I don't normally advocate removing or bypassing an emissions device, but this is one I can honestly consider "unnecessary" and have the test results to show it.

I'm with 5-90 on this. The effect of the EGR is minimal at best, and the engine will likely never know the difference, especially on a Renix setup with a knock sensor. I would not remove or block the device itself unless it is leaking when it's closed. And don't remove the solenoid and vacuum lines either, because it does double duty for evaporative canister purging. What you can do is simply to plug the line to the EGR. If you expect the underhood area to be scrutinized, plug it internally and reconnect it. Presumably without the EGR your NOX levels might go up, but the operation of the EGR is so intermittent and dependent on various factors such as back pressure, that I doubt very much if any emissions test would detect whether it's opening when it should.

On the original question, I was under the impression (haven't had a Renix in years) that there was a direct line from some vacuum source to the solenoid. I'll look and see if I have a diagram, but I think there may have been a mixup if you're getting a line from airbox lid to solenoid.

edit to add: I just checked my temporary copy of the 87-88 FSM (thanks to 5-90 for moving and having no address to send it to), and it appears that the solenoid should be getting straight engine vacuum. I think someone has switched lines there.

If you have the 88-up style EGR with the separate transducer, it should receive vacuum only when the solenoid is not energized, and open when that vacuum is combined with the correct back pressure to operate the transducer. The diaphragm should be vacuum tight. If you have the early type which has no separate transducer, the back pressure valve is built into the diaphragm. It's important to note this, because an 87 EGR valve will ALWAYS fail a vacuum test even if it is good.

Matthew Currie said:

I'm with 5-90 on this. The effect of the EGR is minimal at best, and the engine will likely never know the difference, especially on a Renix setup with a knock sensor. I would not remove or block the device itself unless it is leaking when it's closed. And don't remove the solenoid and vacuum lines either, because it does double duty for evaporative canister purging. What you can do is simply to plug the line to the EGR. If you expect the underhood area to be scrutinized, plug it internally and reconnect it. Presumably without the EGR your NOX levels might go up, but the operation of the EGR is so intermittent and dependent on various factors such as back pressure, that I doubt very much if any emissions test would detect whether it's opening when it should.

Click to expand...

Theoretically, the EGR is there to keep NOx emissions down. Practically, it don't do nothing - the CR on our engines is too low, and the quench is too good for it to make a difference (there is enough turbulence to keep temperatures down enough to matter, and it's not going to get that high due to compression in the first place.)

On a high-compression engine, the EGR can serve a practical function - but that function is better served with other systems that don't crap up the intake hardware and fuel injection.

And, there is a tradeoff to lowering NOx via EGR - HC and CO emissions spike horribly.

Here's a thought - did you know that an engine can be tuned to run cleanly and efficiently without any emissions devices at all, save a PCV valve? If they'd get out of the way of those of us who are truly interested, we'd have air a lot cleaner. Take it one step farther - if you can come in with lower emissions than when your vehicle was built, how about a discount on your renewal?

Yeah, right. As long as I'm dreaming, I'd like a pony...

To "Cap" mine off I cut EGR tube, pinched end flat, hammered, and rolled.
Did that to both ends, now NO EGR. (Wouldn't fit easily with Pacesetter Header)

NOx= high pressure, high heat, and slow burn.
Allowing enough time for Nitrogen and Oxygen to bond

sweet, looks like the 4 angry squirrles will lose the egr when I get around to it.

I was looking at the egr, and trying to figure this out. it has a vac line from the drivers fender to a black disc at the egr, then from the bottom of the disc it goes into a metal L shaped tube into the manifold, and another vac line on the other side of the disc going to the egr. so what gets disconected and plugged?

Harlee&Tahoe said:

To "Cap" mine off I cut EGR tube, pinched end flat, hammered, and rolled.
Did that to both ends, now NO EGR. (Wouldn't fit easily with Pacesetter Header)

NOx= high pressure, high heat, and slow burn.
Allowing enough time for Nitrogen and Oxygen to bond

Click to expand...

I had to do that on the 87 when the valve end of the tube rusted off. Fortunately no visual inspection of emission controls here in VT.

xj88superjeep said:

I was looking at the egr, and trying to figure this out. it has a vac line from the drivers fender to a black disc at the egr, then from the bottom of the disc it goes into a metal L shaped tube into the manifold, and another vac line on the other side of the disc going to the egr. so what gets disconected and plugged?

Click to expand...

If you disconnect and plug the line from the solenoid on the fender well, that should do it.

Matthew Currie said:

I had to do that on the 87 when the valve end of the tube rusted off. Fortunately no visual inspection of emission controls here in VT.

Click to expand...

Our certification is required upon transfer of ownership.

OK, ok... I am a little lost still, and it aint the beer.

I don't know what the hell... I do not think I have the EGR valve, but I think I do have the transducer if thats possible??

I looked closely and here is what I have...
Tube from exhaust manifold to egr/tranducer that is bolted to the intake manifold
It has 2 vaccum lines one going to the deal on the drivers side fenderwell
One going to the airbox lid (this line happens to have a crack in it too... nice huh)
The deal bolted to the intake does have a vacuum diaphram and if I move the plunger with a screwdriver, it will stall the engine.

I have an 89 body with the 96 block, retaining all the renix system.

Does anyone know where a pic is of the egr and transducer that are seperate and together so I can figure this out?

Thanks.

AboveNBeyond said:

OK, ok... I am a little lost still, and it aint the beer.

I don't know what the hell... I do not think I have the EGR valve, but I think I do have the transducer if thats possible??

I looked closely and here is what I have...
Tube from exhaust manifold to egr/tranducer that is bolted to the intake manifold
It has 2 vaccum lines one going to the deal on the drivers side fenderwell
One going to the airbox lid (this line happens to have a crack in it too... nice huh)
The deal bolted to the intake does have a vacuum diaphram and if I move the plunger with a screwdriver, it will stall the engine.

I have an 89 body with the 96 block, retaining all the renix system.

Does anyone know where a pic is of the egr and transducer that are seperate and together so I can figure this out?

Thanks.

Click to expand...

The RENIX top end will fit on the later short block without trouble, so it's possible that you did retain the EGR.

The EGR valve is mounted on the intake manifold, near the brake booster - and sounds like it's still working for you.

"Capping" it off is simple - pull the vacuum line off of the thing (the one coming from the solenoid to the backpressure transducer, if you have that as well) and put a plug in it. Problem solved - it won't work anymore, and can be reconnected if and when.

There are two styles of EGR valve - the "simple" valve, that looks like a flying saucer on a pedestal; and the "backpressure transducer" valve, which has an additional flying saucer made of black plastic next to the Cd-plated steel one (the gold colour - to keep the mild steel from rusting. Or maybe it's zinc chromate? I'm not sure...) Sorry I haven't any pictures, but that should help you get sorted. Both styles of valve are mounted in the same place.

The EGR was deleted for the 1991 model year as part of ChryCo production.

5-90 said:

The EGR was deleted for the 1991 model year as part of ChryCo production.

Click to expand...

So what do the HO's use as EGR, how do they get around this requirement?

Harlee&Tahoe said:

So what do the HO's use as EGR, how do they get around this requirement?

Click to expand...

I've been told it's exhaust gas reversion due to cam timing, but the cam specs (as far as I've been able to tell) are the same. I honestly think the EGR isn't necessary on the 242ci AMC six - and test results have borne this out. I've really got to find those old test reports...

Exhaust gas reversion would accomplish much the same effect, without the hardware, and without crapping up the intake. However, our CR is low enough (even the later engines were sub-9.0:1) that I honestly thing that EGR/reversion simply isn't necessary - proper tuning and an effective three-way catalyst will suffice.

As long as they can show that the engine, properly maintained, will show acceptable emissions levels (or lower) for the EPA-prescribed period (or longer) with factory parts, they can do it however they like. My only argument is when EPA/CalEPA won't let us do the same thing - and further lower emissions and increase reliability as a result (simply be eliminating "potential points of failure" - excuse me, "unnecessary parts" - drat - "stuff we just don't need." Damn - I can't think of an acceptable way to say that...)

5-90 said:

The RENIX top end will fit on the later short block without trouble, so it's possible that you did retain the EGR.

Click to expand...

I should have use the word "Long" sorry,
I have the entire long block from a 96, with all the 89 renix stuff on it, or atleast I think all the stuff. lol

5-90 said:

There are two styles of EGR valve - the "simple" valve, that looks like a flying saucer on a pedestal

Click to expand...

I have this one...

5-90 said:

and the "backpressure transducer" valve, which has an additional flying saucer made of black plastic next to the Cd-plated steel one (the gold colour - to keep the mild steel from rusting. Or maybe it's zinc chromate?

Click to expand...

Not this one...

And eitherway, when I plunge the diaphram it studders or stalls the engine so I guess it works, but I don't think the vacuum lines have a good seal.

So if I have the one above, one line should go to the deal on the drivers fenderwell, where should the other go? Manifold vacuum or Airbox lid?