Phil: Changed the coolant temp sensor today and it was not as big a deal as I thought it was. I didn't remove the tire or wheel-well but instead just reached up in there, put the socket on first, then the wrachet. The new one went in as easily as the old one came out. But the bummer of the whole thing is....IT DIDN'T MAKE ANY DIFFERENCE... <img src="/forums/images/graemlins/frown.gif" alt="" />

Bigpoppa: Thanx for the input. I hadn't even thought of thread tape but thanx for the heads-up. It's good info to store away in my already befuddled mind.

A.T.: I was looking for the Fast Idle Solenoid today as well as the VSV (Vacuum Switching Valve, though I'm sure you already knew that). My idle was really slow...it was alternating between 600 - 800....bouncing up and down like a yo-yo. When in gear it would drop even lower and I would have to put it into neutral at the lights. In park or neutral it idles at 900 - 1000 and a little steadier. So I got to thinking that maybe I should adjust the idle but Haynes says to disconnect the VSV right? And I think the FIS too. But damn it, the pic in the book looks nothing like mine. Chapter 1, page 25, illustration 37.5 I believe. It's at the top-left of page 25. The bracket they show where the VSV is supposed to be...my bracket is empty...just a bunch of holes. There is no little white plug to disconnect, and no VSV. I didn't have access to All-Data today to see what the hell is going on. So against better judgement, I adjusted the idle screw anyways....it went 5 FULL turns counterclockwise just to get it to idle at 900-1000. But it still drops to 600-700 in drive or reverse. I would like to adjust those things properly but I need a pic of something that looks like my truck. I do have multiport fuel injection, and a pressure regulator (brand new one since I thought that might have been the problem). The sniffer test (Exhaust Gas Analyzer) said I am running rich..very rich..once at op temp. I haven't reached the end of my rope yet but I'm only hanging on by a thread. With my teeth, I think. Hard to drink a beer with a rope in your mouth. And I think I need one 'bout now. Anyways, to end this short story. The next thing I am gonna do is the first thing I wanted to check. I will drop the tank one more time and double check the return line on the fuel pump assembly. I've had some trouble with it before and it's possible that not enough fuel is being sent back to the tank which would leave too much at the engine thereby making it run rich right? Don't think about it, just say "Right!".

Thanks for your input...If you have any helpful pics for me....please send them my way.

Hi Folks,

I do have a similiar issue on a 92 3.2SOHC manual gearshift. Running rich and a big idling problem, especially with the engine warm. So far, I identified and repaired problems with

* Vacuum leak (that sucked, required 2 workshops to find them all)
* Fuel return line was badly fixed on the fuel tank.
* PCV-Valve full of oil
* Dirt in the fuel filter
* Spark Plug Cables bad, spark plugs got changed anyway

Now it is not running rich any more, but idling is not really good.

The special point about my problem is that it does not repeat itself under similar conditions, sometimes it happens when the engine is cold, sometimes when it is hot, the only circumstance I was able to identify clearly is that it gets worse the higher I drive in the mountains. Last thing missing to check is the EGR-Valve, maybe someone can help me out there. Unfortunately, there are no Isuzu workshops in Venezuela (thanks GM) and access to literatur is rather limited, too. I know this belongs in the dumb and dumber section, but could anybody tell me where the EGR-Valve is (or should be) on the V6 3,2 SOHC (maybe with picture), as I was not able to find it <img src="/forums/images/graemlins/confused.gif" alt="" /> ?

Week of 11-01-04 to 11-07-04
replaced O2 sensor
replaced coolant temp sensor
examined return line on fuel pump assembly and replaced fuel
pump strainer
new fuel filter

Something worth noting: at the beginning of the week, if I put the truck in O/D off mode it seemed to help give it a bit of a boost due to the higher RPM I guess Then we adjusted the idle and now O/D off mode makes it considerably worse.

She is still very <img src="/forums/images/graemlins/barf.gif" alt="" /> and it's making me feel like a <img src="/forums/images/graemlins/baby.gif" alt="" /> cuz I still can't figure it out.

I've gotten some really good advice about the TPS and Throttle Body Assembly, so that will be my next step.

Something bizzarr worth mentioning is that though I had gotten the "Check Engine" light a few times....but when I went to retrieve the trouble codes the ECM just kept flashing code 12 over and over again in a loop.

I'd take another look at what RT1 had to say. Sounds like the Air Regulator Valve may be stuck open:



I've been having the opposite problem - rough cold start & idle, everything normal at regular temp. I think the air reg valve is stuck shut. PITA to get to, totally buried under the intake manifold...

Just want to add this...

Though it runs considerably better on cold start and until it's warm when the ***** really hits the fan....it does do a little skip (almost unnoticable) when taking off but seems smooth while driving and accelerating...it actually feels like it's got balls (pardon).

Sometimes, intermittantly, even when the truck is warm and really screwy, I can find that "happy spot" in the pedal and it will drive "almost" as if nothing is wrong with it...stumbling badly one minute and "boom"-takes off the next: let off the pedal, try again, and shazaam. But there are also times when it seems as if it is o.k. and then suddenly will begin to stumble again and no matter how many times I play with the peddle....it's just not happy...big time sad-face...:(

RT has a good suggestion and I am gonna check out what he said...I got a bit side tracked with other crap but his advice is sound and worth checking out.

Just gonna throw this out there for the shits and giggles... could this be a fuel pump or return line issue? I can't see how it could run so much better on cold start if it was but...I'm am truly baffled and I know that I do have problems with the pump assembly. The return pipe on top of the cap broke in half a short while back (someone on this forum said it best..."it's a rase against rust and the trooper is loosing)and my pressure dropped considerably. I removed the broken piece (about half) and just put the hose down further on the line. There are burrs but they are outward bound, not inward (know what I mean?). I am trying to locate a used/good assembly but they are proving harder to come by than I thought.

I don't think it has anything to do with the current problem but every now and then I do get a little puddle of fuel under the truck (maybe the size of a sand dollar). And last weekend when I dropped the fuel tank to check everything out and replace the strainer, I did notice that the top of the tank seemed saturated with fuel. Am I barking up the wrong tree here or could all my current problems be a result of a bad assembly/return line blah-blah, yadda-yadda???

Ya know, I just have to mention that though I've had many problems lately with this truck...though it's old, it's by no means, a rust bucket. It's in really good shape for its age and well worth the time, money, and effor to fix.....If I just knew what the frig I am supposed to be fixing. And I thought math made me feel like a dumb-ass. After all I've done to this thing, I should know what to do from here but I don't....for shame, for shame....

dawn...

Friend of mine had chronic roughness with his 91 pickup 2.6. Finally checked the fuel pressure at the jets (nozzles...whatever the things are at the cylinders...I don't know the word cause I have a carb). And it was low. Turns out the previous owner had put in a smaller-than-required fuel pump. New fuel pump in tank...happiness followed. <img src="/forums/images/graemlins/wink.gif" alt="" />

hfoobe: thanx for the advice but "been there-done that" with regards to the fuel pressure...I could tell you stories. It's not related in that way but I appreciate your advice.

dawn...

I feel your pain. <img src="/forums/images/graemlins/wink.gif" alt="" /> that's pretty much been my story between my Troop & car for the last year or so. comes with the territory of self-teaching I suppose - such is the price for gain of knowledge & wisdom, right?

anyway, you mentioned looking into the TPS - did you follow through on that?

how about spark? checked cap & rotor? coil?

MAF sensor?

have you had any problems with the battery or possible charging issues? there is that voodoo relationship between the alt & fuel pump...

just trying to throw some other ideas out there for you.

regardless if your fuel line issue is related to the stumble, I'd make that a top priority to rectify. I suppose if the high pressure line from the pump was leaking enough then the injectors could be starved, but that would be a lot of gas spewing all over and I'd think would be pretty obvious.



are you talking about the fuel pump housing? I recently destroyed mine on my car while attempting to replace the fuel pump & associated lines/hoses. I found one on car-part.com for $30 under the 'fuel pump' listings - it said 'housing only'. you may try looking there. if none are listed that way, call a bunch of the yards that list the pumps and ask about it, you may find one for cheap.

Pucci...Got a throttle body assembly and TPS on its way. But I think I may ohm out my switch today just for the fun of it.

I checked the cap, changed the rotor, and wires. Did notice last week that I was getting arc at the number four plug and discovered that in my haste of reassemble after the valve adjustment I had forgotten to put the wires in their little clippy things. The wire had been resting against the engine and got too hot. I ohmed out the old one, put it back on, and no more arc. Haven't thought about the coil too much cuz it doesn't make sense that it would be almost fine on cold start and then go extremely funky once warm. It had been suggested to me though.

The MAF sensor...Yeah, gonna check that out today. I'm guessing maybe I can ohm it out, or at least check contacts? I may even price one out just to see. It's easy enough to change right?

Changed the battery a couple of months ago when the alternator went. Changed the alternator too (duh right?)

Yep, you're right about the fuel system. I had put it off initially cuz I thought I needed to buy a new assembly and had considered a new tank as well. Have had to repair the tank for pinhole leaks in one little cluster just above the seem. But I did drop the tank last week and the feed line is good, the return line seemed o.k.....hoses, and metal line (what's left of it) but the top of the tank seemed saturated. The cap is looking worn and the gasket is not happy at all. But when I pressure test, I am getting higher than specs, not lower. Exhaust Gas Analyser shows I am too rich, not lean. It's as if once the engine is warm, the air/fuel mix is not adjusted and the engine is drowning, not starving. There is no backfire, maybe just a little "pfftt" out the exhaust once in a while. Though it stumbles, and sputters, there are no other signs of engine failure or something really bad happening like black smoke, or head gasket issues. I'm not even getting the "Check Engine" light anymore so FRED isn't even aware that soemthing is messed up. But hey, "Garbage in-garbage out" right. FRED can only use the information he receives and what he's beging fed is not supposed to be on the menu.

I did do a "google" search for salvage yards and Isuzu salvage last night. I made some inquiries and got some good deals sent my way but none as good as the one you got. I'm gonna have to go check that out. The only salvage yard in town (within a 150 mile radious)didn't believe I knew what I wanted yesterday. The guy kept saying "So you need the sending unit" and "o.k., you need the pump". And I kept saying "No, I need the fuel pump assembly" and then I had to describe the darn thing to him. I think sometimes they just don't want to believe that a girl just might really know what she's talking about. It's all good though. I don't deal with them very often and I get lots of respect from Sanels, Napa, and just about everyone else I do deal with.

in my brief mechaniking career, I've found that getting the correct parts you want & dealing with the boobs selling the parts is a greater challenge then the actual wrenching. the yards & stores in my area are a joke and I get most of my recycled parts from all over the country. I find the south often has the cheapest prices on used import stuff. even with shipping, I get my parts for well under asking price of 'local' based recyclers.

I took a quick look for fuel pumps on www.car-part.com and found a listing that may be what you need.

it's from an 89 Trooper, the descrition is "LINES ONLY,PUMP NFG" - $42. it is at P&G Auto, you can search inventory from the link in lower right of page.