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1996 Isuzu Bighorn 4JG2T UBS69
Hey all, took my airbox out on the weekend to clean a whole lot of crap around from under it etc, and in the process had to remove the bits and pieces from the side of it that were connected with vacuum lines I'm assuming, to the EGR valves. These pretty much all came undone when moving things around and now the truck is noticeably laggy. I am going to remove the EGR's completely sometime in the coming weeks but until then I need to know what vacuum line goes to what because I'm guessing that's what's causing the problem?
Or I've read maybe it's possible to just block those lines for now coming from the EGR's?
EGR Vacuum lines
Re: EGR Vacuum lines
Leaving the leads off the EGRs should cause no engine issues but you should blank off the vac line feeding them as this can affect brakes etc. You may of also dislodged the boost line to the top of the injector pump. The other end of this is on the inlet side of the intercooler. Having this disconnected will reduce fuel under boost making the engine quite flat
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96IsuzuBighornNZ
- Posts: 9
- Joined: Sun Oct 05, 2014 9:31 am
Re: EGR Vacuum lines
Excellent thanks so much Geeves, sounds exactly right
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96IsuzuBighornNZ
- Posts: 9
- Joined: Sun Oct 05, 2014 9:31 am
Re: EGR Vacuum lines
Geeves, the only thing I can see that isn't attached to anything is this little T-section, does it go to either of these?
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Re: EGR Vacuum lines
Thats not a good picture. I dont know what that pipe is. The one we are interested in goes to the rear of the pump just below the top cover. With the pipe shown I would get rid of the T piece
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96IsuzuBighornNZ
- Posts: 9
- Joined: Sun Oct 05, 2014 9:31 am
Re: EGR Vacuum lines
Okay sorry about that, can we start with the two pieces I am holding in the pic, solenoids I think? They were both mounted to the factory air box, what exactly are they for and do they need to be connected to anything seeing I have blanked off the vaccum lines to the EGR's?
Re: EGR Vacuum lines
There are 3 solinoids. 1 is the fast idle for the air con the other 2 are egr. None should effect the running of the engine
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96IsuzuBighornNZ
- Posts: 9
- Joined: Sun Oct 05, 2014 9:31 am
Re: EGR Vacuum lines
I have the engine running fine now, I don't think I had blanked the egr vacuum lines properly. Since doing it properly the truck is running great, better than before even, but the brakes are doing what everyone else describes. From what I can see on all these forums people are replacing brake boosters etc but I'm sure it must be that I've missed something. I can't see any hoses that I've missed but it may help knowing exactly where to look, or if I need to bypass something etc?
Re: EGR Vacuum lines
I am basing my answer on a 96 Mu so I don't know if this is the same as a Bighorn. Just a couple of other things to consider/look at.
As Geeves has mentioned earlier there are vacuum lines that activate the Fast Idle and the EGR.
He has also mentioned the boost line to the Boost Compensator on the top of the Injector Pump.
You may also have vacuum lines on the passenger side going to:
- your engagement mechanism on the front diff
- a small vaccum accumulator mounted to the chassis under the passenger seat
- the QWS valve on your exhaust (also on the passenger side)
The only things that really matter are the boost line to your injector pump, vacuum to your brake booster and vacuum to your front diff engagement solenoid and mechanism.
Fast idle is desirable but not essential and only triggered by the use of air conditioning.
You can live without the EGR and QWS valve in your exhaust not working.
Also check that the QWS valve in your exhaust is in the 100% open position. I have had one partially close and it adversely affected power.
Block off all vacuum hoses that are not being used as these are just a source of vacuum leak and may affect your brakes.
Nb. The boost line(s) usually have small spring clips on their joints and the vacuum lines just push on.
As Geeves has mentioned earlier there are vacuum lines that activate the Fast Idle and the EGR.
He has also mentioned the boost line to the Boost Compensator on the top of the Injector Pump.
You may also have vacuum lines on the passenger side going to:
- your engagement mechanism on the front diff
- a small vaccum accumulator mounted to the chassis under the passenger seat
- the QWS valve on your exhaust (also on the passenger side)
The only things that really matter are the boost line to your injector pump, vacuum to your brake booster and vacuum to your front diff engagement solenoid and mechanism.
Fast idle is desirable but not essential and only triggered by the use of air conditioning.
You can live without the EGR and QWS valve in your exhaust not working.
Also check that the QWS valve in your exhaust is in the 100% open position. I have had one partially close and it adversely affected power.
Block off all vacuum hoses that are not being used as these are just a source of vacuum leak and may affect your brakes.
Nb. The boost line(s) usually have small spring clips on their joints and the vacuum lines just push on.
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96IsuzuBighornNZ
- Posts: 9
- Joined: Sun Oct 05, 2014 9:31 am
Re: EGR Vacuum lines
Thanks for your reply, I did find that the vacuum hose to the brake booster had also split/come loose and have overcome the brake problem. Driving fine apart from a slight lack in power which seemed to appear from nowhere, as when I first blanked the egr's there was an increase, and now i seem to have to floor it and change down just to speed up a little on the motorway, im interesed in this qws valve and thought maybe that's it, I've also changed the airbox over to an aftermarket one coming from snorkel but I don't think that's caused the drop in power