EGR Modulator Question (1 Viewer)

[Theecomer]

So, I've been having some hesitation and stumbling in my FJ60 and read a thread here about a year ago where someone suggested disconnecting the vacuum hose on the EGR vacuum modulator that points towards the engine and plugging it (not either of the two hoses that point towards the drivers side of the vehicle). Annoyed by this hesitation, I did this and it worked.

The truck accelerated wonderfully and seemed like an entirely new vehicle. Shot right off the line (as much as a 60 can!) and made me smile at the results. Obviously something is wrong in this general area and I have no idea what is causing this. I've thumbed through the emmissions manual, but since I have no tools, I cannot deduce what to fix.

Does anyone have any insight on how to rectify this? I cleaned the little filter things in the modulator but the issue persists. I've put a screw in the removed hose and it drives like a charm. Still, I want to fix this problem and don't know where to start.

All help is appreciated!

 

[Spike Strip]

Do you have the Emissions FSM ?

 

[Lugal]

I had the same problem, and it turned out to be a bad modulator. Cleaning it didn't help, and while bypassing the EGR worked, it also gave me some nasty pinging at highway speeds.

You really need the emissions control FSM to troubleshoot this. There are a couple switches, the modulator, and the EGR valve that all need to be tested independently of the others--but without some basic tools (including a vacuum gauge), you're SOL. The one thing that you can do w/o any tools is check that your vacuum lines are plumbed correctly. That way, at least, you'll be sure that the problem isn't caused by some mis-routed hoses.

 

[RedfishBluegrass]

I had the same problem, and it turned out to be a bad modulator. Cleaning it didn't help, and while bypassing the EGR worked, it also gave me some nasty pinging at highway speeds.

You really need the emissions control FSM to troubleshoot this. There are a couple switches, the modulator, and the EGR valve that all need to be tested independently of the others--but without some basic tools (including a vacuum gauge), you're SOL. The one thing that you can do w/o any tools is check that your vacuum lines are plumbed correctly. That way, at least, you'll be sure that the problem isn't caused by some mis-routed hoses.

I totally agree. Chances are your modulator is sticking and you can try to clean it. Do a search to get some ideas on the best way to clean.

 

[2mbb]

OK. In your first post it says you have the emissions manual, but no tools. So here is an opportunity to get some tools. What you need to test the modulator is a vacuum gauge. These are inexpensive and easily found at any autoparts store. If you don't want to buy one then see if you can find a store that will rent one to you--although they are pretty cheap. To test the modulator, I don't thing you even need to remove anything from the engine so you won't need wrenches, etc., yet...

 

[Gurr]

This is how one guy explained it in another thread.

vipergrhd, I talked to a mechanic friend of mine that told me my EGR diaphragm was "soft". This made the EGR activate before it should. The solution, and I don't have it right yet, was to restrict the vacuum between the EGR modulator and the EGR valve. This allows the EGR to stay inactive longer and may help you out.
The way I did it:
take a piece of tube (mine was the casing of a length of wire with copper pulled out) that the OD is roughly the same as the ID of the vacuum tube. Insert said tube into the length of vacuum tube between the modulator and the EGR. This restricts the vacuum and slows the opening of the EGR.
The bucking between 1200 and 1500 RPMs decreased dramatically, but it hasn't gone away completely. I will have to keep messing with it until it works properly.
The other solution I have been thinking about is inserting a VTV in that line. This would cause the EGR to open slower and may also mask the issue.
I am new to the vacuum world, but a little OJT is helping that out...

 

[Theecomer]

Thanks guys. I'll go ahead and get a vacuum gauge (almost a necessity with vehicles anyway) and see where the emissions manual takes me. Like I said, I attempted cleaning the modulator already with no difference in performance, so I thought there might be a clear concensus on what the cause would be at that point.

Appreciate all the feedback, so again, thanks a lot!

 

[Spike Strip]

2mbb, you gotta stop reading the threads that closely ! You may actually figure out what somebody is asking - what fun is that ?!?

 

[FJ40Jim]

The OP's symptom is usually caused by a dying EGR modulator. There are tricks to get around the symptom (a BB in vac hose, restrictor in vac hose), but the correct fix is a new modulator.

 

[Theecomer]

Thank you, Jim. I'll get one and go from there.

Appreciate everyone's help.