1988 Isuzu Trooper, 2.6 freshly rebuilt. It's Running extreamly Rich, Very Very Black build up on tail pipe. Now I know something Is missing in the engine bay that I think should be there. Ok, its on the passenger side up almost on the fender and it looks like another fuel regulator but Im really not sure. Looks as though 3 hoses go to it. almost strait accross from the fuse box under the hood. I have no idea what goes there and what the part is called, will the little piece affect the richness at all?? if you dont know what im talking about ill try and get a Pic to show you guys, maybe I wont have to. The smell is so bad It makes your eyes burn and I know it will never pass Emissions If I ever took it to do so. LOL <img src="/forums/images/graemlins/lol.gif" alt="" />

In general, I'd say yes, you need it...

Yer probly talkin about one of the vacuum switching solenoids in that area. I'm guessing that you probably have got some vacuum hose issues, maybe missing hoses, causing vacuum leak. Yeah, that could screw up running I guess, but I'd think it would run lean.

One of those solenoids switches vacuum to the fuel pressure regulator, increasing the pressure under certain conditions. Maybe you've got high pressure all the time causing a rich condition ...

I'll wait for pics!

Well, Its running rich for some reason, I thought the same you did about it running lean.. But guess not. Ill have to get a pic of where its at and what we did to fix it then, cause I was strapped for cash and couldnt go to try and find one. I think a Junk Yard has a couple Ill see what they want for it.

There's a temperature sensor threaded into the underside of the intake manifold that signals the engine control unit to run rich on a cold start. It works in conjunction with the air regulator (big black tube off the side of the throttle body) mounted on the side of the engine block under the intake manifold. MAKE SURE your block and head are filled with coolant. It's possible the sensor isn't in contact with coolant so isn't sending the signal. For me the best way is to unthread the air bypass valve from the top of the thermostat housing, pop the cap on the radiator and fill the radiator 'til coolant flows out of the thermostat housing. Some like to park on a hill with the engine up and run the engine with the radiator cap off to burp any air out. The important thing on any engine rebuild or head rebuild is to make sure no air is trapped in the galleries of the head. I didn't on one head rebuild and was rewarded a year later with melted exhaust valve seats.

TAKE A LOOK UNDER THE INTAKE MANIFOLD AND MAKE CERTAIN THAT THE AIR REGULATOR CONNECTOR IS NOT MIXED UP WITH THE CONNECTOR FOR THE ENG TEMP SENSOR, IT WILL CAUSE IT DO DO EXACTLY AS YOU DESCRIBE THE E CONNECTOR S ARE THE SAME DESIGN, AND ARE EASY TO GET SWITCHED , THE ONE FOR THE TEMP SENSOR HAS A GRN/YL WIRE AND A BLK WIRE THE AIR REGULATOR HAS , A YEL/GRN AND A SOLID GREEN , JERRY

I betcha Jerry is the winnah!

Gettin' to them is gonna be a royal pita though.

Unless you have a lift available, the best way
is through the pass side fenderwell. Remove tire,
remove rubber flap (them "push pins" pull right out
pretty easy, and go back in easier). Now you can at
least see a bit of what you need to see.

Good luck!

How old are your vacuum hoses?

The Engine was just rebuilt in April and im using all New Silicone Hose. I check them often to make sure they dont split. I have had a couple do so already. Ill have to look for what your talking about Jerry, You Seem to know all when It comes to the Zu's. Other than that I runs Awsome and dont have any complaints, Other than I need MORE. I really can understand why that would Affect Fuel Mix. Rather Obvious at that still dont know why i over looked that HAHA. Is there any way to get the connections crossed by accident, Like maybe the connectors are the same?? But Im still curious as to what that little box looking thing is where I was describing. I want to get that fixed and taken care of.... and I really DONT want to take the intake plenum off again.. I had to take it off several weeks ago to fix the Injector seals and that was a VERY FUN JOB*. Ill take a look at it and see what I can come up with. Thanks for the Input guys. Very much appreciated.. another question: Is Isuzu shutting down due to poor sales or are they just producing what GM wants them too? I dont know but again Im curious...

That's exactly what Jerry said, re-read his note! Note that he gave you wire colors too, that's what you need to look at. You should be able to SEE at least the wires on the air regulator when you look through the fender well opening, and know at a glance if that's the problem. If it IS the problem, then the fun starts trying to get them connectors off and back on again.



Where's them pics ?

I believe that it's the solenoid that switches the vacuum to the fuel regulator... tell me this:

Where does the vacuum hose on top of the fuel regulator go to on your truck ?



They're cutting ties with GM, probably completely by this time next year... but I don't have any insider info... ha!

Sorry I work 12 hrs a day... I need to read more detailed... but as tiredness comes along.. duh I get Retarded. Now I get those wires and they are right. SO I bet that Vacuum Solinoid is what is giving me the running rich smell. so I have one now since I managed to get one from a scrap yard. Ill try it and find out if that was the problem. It seems to run very rich once its warmed up, Funny part is it that @ high RPM it leans out and get a better smell, still unpleasant but better @ idle it goes back to rich again.... so Ill bet its that vacuum problem. Thanks guys and Jerry I can be a poor reader LOL thanks.