Renix Help Please

89 Ltd, 4.0, AW4, 242

Idle speed has been running 1100-1250 when warm, in park or neutral. After reading several posts here I understand this is symptomatic of a vacuum leak. Start looking around and sure enough, the vacuum line from the EGR relay to the transducer is just hanging unattached.

I reconnect and go for a test drive. Idle is great, back down to where it used to be. Very smooth.

Problem - stall or near stall with light throttle at take off. Feathering pedal will coax it into acceleration and then it smooths out. Cruise feels like its missing at low (1k) rpm.

What do I look at first? EGR & Transducer? Something else?

Do I cap the transducer input a leave it as it has been (not wanting to stall at an inopportune time)?

Sounds like a vacum leak. Check the lines, also have the EGR vacum tested. The rubber diaphram might be bad. There might be other problems.
Tom

It sounds like the EGR is having trouble. If you aren't the first owner, maybe the previous one had EGR trouble and disco'd it and lived with higher idle. See if the exposed part of the shaft will move in and out manually, then put a vacuum pump on the hose to it and see if you can open and close it that way too. You'll see if it binds, or if the diaphragm leaks.

If it ran OK otherwise before, the quick fix would be to insert a golf tee in the hose you reconnected to plug it. No vac leak, no EGR problem. That's if all was OK with it other than idle before.

However, based on symptoms, it is probably the electrical valve that operates vacuum to the EGR - sounds leaky. Plugging would still be the quick workaround. I believe it should be shut off at idle though, so if it was sucking at idle (plugging fixed it), it's leaking and staying on at light accel when it shouldn't and messing it up.

Make sense?

Makes perfect sense; thanks for the reply. I'll give it a try and post the results.

Checked vacuum before EGR solenoid. 17"
Zero at idle (warm) after solenoid.
Unplugged solenoid - 17"
Pulled vacuum on EGR during idle, engine died immediately.
I assume with above that solenoid is operating properly and EGR is functioning OK. Is this correct?

Strange thing is, I still have high idle, even with golf tee in EGR line. Idle is normal only when plugged into transducer (before EGR) - but then I have stall or near stall when starting from stop @ warm idle.

I just don't understand the idle speed difference when plugged into the EGR vs a golf tee - leaky golf tee? And why it hesitates/stalls when plugged into EGR when the EGR wouldn't be operating

Running-Snail said:

I just don't understand the idle speed difference when plugged into the EGR vs a golf tee - leaky golf tee? And why it hesitates/stalls when plugged into EGR when the EGR wouldn't be operating

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The valve could be clogged with exhaust gas residue or damaged. Take the EGR Valve off; give it a good cleaning. When it is clean, attach a vacuum tube to vacuum port, suck air out with your mouth and verify the operation of the EGR valve closing/opening.

Let's see:

Running-Snail said:

Checked vacuum before EGR solenoid. 17"
Zero at idle (warm) after solenoid.
Unplugged solenoid - 17"

Click to expand...

This sounds right.

Pulled vacuum on EGR during idle, engine died immediately.
I assume with above that solenoid is operating properly and EGR is functioning OK. Is this correct?

Click to expand...

This doesn't make sense. You said vac was 0 at EGR at idle, so it shouldn't be a problem to disconnect it at idle. In the first note you said the hose was just hanging. Did you make it just hang the same way again, but with a plug tee instead? How did it stall right away this time, yet ran with it off before?

Strange thing is, I still have high idle, even with golf tee in EGR line. Idle is normal only when plugged into transducer (before EGR) - but then I have stall or near stall when starting from stop @ warm idle.

Click to expand...

Can you hard accel and it work OK from a stop?

I just don't understand the idle speed difference when plugged into the EGR vs a golf tee - leaky golf tee? And why it hesitates/stalls when plugged into EGR when the EGR wouldn't be operating

Click to expand...

I don't either - especially if you say the vacuum is 0 at idle, even letting it hang shouldn't bother it. Could it be a loose connection at that vacuum junction bracket? Maybe something moved in moving things around?

If the EGR slams shut if you pull on it's shaft and let go, do it a few times in case it's got some crud. It's not sounding stuck open, IMHO.

Need more info on the differences noted above.

Skipc - I wasn't very clear with that second grouping (as you have it):

I left the connection off the EGR solenoid which allowed vacuum through at idle (while line was still disconnected at transducer). When I touched the line to the end of the transducer, the engine immediately stalled. Thus, the engine died when vacuum was applied to the EGR. This is a normal condition I think????

All good following suggestions. I'll check and get back.

Also pull EGR and see what condition it's in/clean it up.

skipc said:

This doesn't make sense. You said vac was 0 at EGR at idle, so it shouldn't be a problem to disconnect it at idle. In the first note you said the hose was just hanging. Did you make it just hang the same way again, but with a plug tee instead? How did it stall right away this time, yet ran with it off before?

Click to expand...

See previous post. Plugged in vacuum line after by-passing solenoid.

skipc said:

Can you hard accel and it work OK from a stop?

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Yes! Hadn't tried this but works OK with anything other than a light throttle. Light throttle stalls nearly every time - if it doesn't stall then it nearly does.

skipc said:

I don't either - especially if you say the vacuum is 0 at idle, even letting it hang shouldn't bother it. Could it be a loose connection at that vacuum junction bracket? Maybe something moved in moving things around?

Click to expand...

Maybe another (several) posts have provided the high idle answer - while checking vacuum lines, I also checked the torque on manifold bolts I could easily get to. The top, front most intake bolt (under fuel regulator) was so loose I could turn in with my fingers. I'll check torque on all Sunday pm - but it now runs with golf tee result with low (normal) idle and normal throttle response. Plugging in vacuum line to EGR transducer results in low (normal) idle and stall with light throttle.

skipc said:

If the EGR slams shut if you pull on it's shaft and let go, do it a few times in case it's got some crud. It's not sounding stuck open, IMHO.

Click to expand...

It sounds like it is closing tightly and quickly when I pull the shaft out and release. I'm questioning the transducer - I didn't really test it - not sure what impact it would have on EGR with light throttle; would the ECU think I'm in "cruise mode" and energize the solenoid?

By the way - thanks for the response to these posts. I rarely post questions and usually have found great info simply by searching. This site has been great in helping to resolve numerous problems in the past. If I wrote them down, I would end up with a long list of items my son & I have fixed, upgraded or changed as a result of instructions posted here!

What problems do you still have? High idle on a Renix is caused either by a vacuum leak or electrical problem (TPS, wiring from it to the ECM, or the ECM itself)


Mike R

Mike R -

My problem is a stall when EGR vacuum line is connected and light throttle is applied. No stall if throttle is anything other than "light"

Currently I have a golf tee (my last one!) in the EGR line before the transducer - good idle, no stall.

Running-Snail said:

Mike R -

My problem is a stall when EGR vacuum line is connected and light throttle is applied. No stall if throttle is anything other than "light"

Currently I have a golf tee (my last one!) in the EGR line before the transducer - good idle, no stall.

Click to expand...

I assume it's hooked up like the underhood diagram shows with the EGR solenoid, EGR transducer, and EGR valve?

Mike R

EGR line before the transducer

Click to expand...

There is no transducer do you mean the EGR solenoid on the fender?
The vacuum line comes from the manifold tee to the EGR solenoid valve then from the solenoid valve to the EGR under the manifold.

langer1 said:

There is no transducer do you mean the EGR solenoid on the fender?
The vacuum line comes from the manifold tee to the EGR solenoid valve then from the solenoid valve to the EGR under the manifold.

Click to expand...

Vacuum goes to the solenoid on one line (and is switched as needed), out from the solenoid to the transducer (plastic housed diaphram) on one line, then there are two hoses that go to the EGR valve. The transducer is not shown in the diagram (in most cases it comes with a new EGR valve) you posted but should be on the vehicle. If it's missing you will have to get one. Here's a photo showing the EGR and transducer connected to it (top hose only shown)




Mike R

Yes, I have a transducer and it is hooked up between the solenoid and the EGR valve.

Could my idle problems be caused by a faulty transducer? Is there something else I should look at?

Running-Snail said:

Yes, I have a transducer and it is hooked up between the solenoid and the EGR valve.

Could my idle problems be caused by a faulty transducer? Is there something else I should look at?

Click to expand...

Could be a weak spring in the EGR, bad transducer (should come with a new EGR valve), bad solenoid, or some reason the wiring or ECM is activating it.


Mike R

OK, everything is OK with the golf tee in the line BEFORE the solenoid and everything else, right?

The high idle says vacuum leak (you can fix it by changing vacuum lines around as you've done, so it isn't electrical as in a TPS or bad Renix).

With the hose plugged, all is fine, which says the problem is after the plug point.

The stalling on light accel and not hard accel, says EGR is open to some degree when it shouldn't be.

Working fine with it all disconnected says the valve itself is closed and fine.

Bypassing the solenoid and putting vacuum to the egr should stall it - the egr is working.

If I understand it, connecting the solenoid to engine, but leaving the solenoid to egr line off, made the idle stall. If the solenoid leaked, and caused the egr to come on at idle, it would stall it. Not sure if you had any accel tests that way though with it stalling at idle - might be tough to do. If it did leak, then there may be enough of a leak to raise idle with nothing on the egr side of the solenoid, yet not be enough to pull the egr on. However, the leak may cause too much vacuum at light accel and cause that symptom. It should be full on at hard accel, so that's why that is fine.

Did you try a vacuum pump, with engine off, on the engine side of the solenoid? Do it with the egr side disconnected. Then test the egr. Both should hold vacuum. Replace what leaks, starting with the egr valve. The solenoid should allow air to enter the egr side when off through a vent, and close off the vacuum side. When on, it should connect vacuum side to egr side and close off the vent.

Now, I may be totally confused about the test results (and not everything is consistent, but I think it's just in the descriptions or in my following it), but my bet is the solenoid sounds bad. Of course, it's big job is to keep spark knock down, so if it runs fine with the tee in the right place, and you've been running without an egr so far, the tee will last as long as you want it to...


-Skip

Heres a better drawing. I guess they do call it a transducer, I call it a EGR pilot valve.

Idle Air Control clogged up. Get a can of throttle body cleaner (NOT uncertified carb cleaner! They have chemicals that can damage O2 sensors and the like) and a can of electronic contact spray (from NAPA {where I work but don't get paid for this shameless plug} or Radio Shack) Clean the EGR and throttle body along with the CCV engine ventillation system. (Take the line off to clean it and look for cracks and make sure the breather in the valve cover isn't clogged by blowing through the cleaned line into the cover to see if you can do it) Also check and blow out the MAP sensor tube. (off the motor till it's clear, then a little bit towards the intake through the line and crank it up to clear it out)
Then take apart EVERY electrical connector under the hood and clean it with the contact spray (including the TPS) and that should return your idle to normal as well as pump up fuel economy (because all the proper signals are getting through. A partially clogged MAP sensor line took 3 mpg off my '93 XJ and '87 Comanche!)

ok guys - you're giving me plenty to do - I'm trying to replace the drive chain in my transfer case tomorrow but perhaps when (if) I'm done I can get busy cleaning/checking lines.

Skipc - I did vacuum test the other night, not completely in the manner you're suggesting but did try to pull vacuum on the engine/manifold side of the solenoid with engine off - connecting at the solenoid and pulling back to the manifold. vacuum did not hold.

Tried pulling vacuum from the manifold back to the solenoid - vacuum didn't hold in that direction either - dropped about 1" every 2-3 seconds.

I checked vacuum on the manifold side of the line at the solenoid with the engine running and was getting 17" so I figured this was OK.

Should I be able to hold vacuum, engine off, pulling back to the manifold?