TOPIC: Isuzu 2001 dualcab 2wd 3.2l V6 Petrol hungry. Need some hope!

So far so good, Neil, and thanks for the pics too!
BTW- so did you completely block off the IAC port w/ that socket? I'm confused on that point. I'll ask a question here, risking ignorance, since I didn't re-read this whole thread--so if this is a cable-driven TB, is there an idle stop screw that holds the plate slightly open at idle? 'cause by blocking off the IAC port completely as it looks, how does it get air for idle RPM?

I have many times RESTRICTED an IAC port/system to maintain good manifold vacuum, but never blocked it entirely. IF there is an idle stop screw, it could be adjusted to open the plate a bit to allow for idle RPM's Then again, there are disadvantages to doing that- the plate is now further open and "downstream" from original position. If the idle stop screw is adjusted to open the plate at idle from original stock position, AFTER the Groove was cut in the original position- that goes right against normal Groove practice.

IF you had or can take more comprehensive pics of this TB, showing the inlet side, and all round, well, at least MY curiosity will be slated, Neil!

I agree with Greg and others' posts here. 50 thou isn't an especially big plug gap, and should cause no issues, as long as rest of Ignition system is in good shape.

Keep goin', Neil!

Thankyou Tracy,
I don't have any other photos than the two already posted, I don't really want to remove it again just to take photos, cos of the gasket, I have a spare one if you just want to see how the idle screw is located. When I cut the groove i used a business card just like I've seen Ron do to correctly locate where the groove belongs. Yes the IAC is completely blocked, it has an idle adjusting screw, I guess the throttle sits open about 1 degree for Idle air to come through, the idle does vary about 350rpm depending on whether its cold, hot or aircon on, I am happy with that and I don't understand how it could cause any negative effect. And it also seems obvious to me that the groove is working and has made a significant difference, although not much to mileage.
I am quite lost where to go next apart from Greg's suggestion of retarding the advance, and I'm a little unsure of whether I am up to that yet. I have done a lot of work so far, noticed significant changes following the groove, but with such a small improvement in mileage it seems I must have missed something basic. I would call the mileage gain so far at barely 10 percent, which would not be unreasonable to expect following all the other things I have done; without the groove.
I have tried to find some before and after mileage improvements others have gotten from the groove (plus associated work)....and I didn't find much that I thought I could compare to or expect from mine.
Basically I'm asking if I am going ok and what should I be expecting?
I'll give anything a go, I just don't really know what to do next.
Thanks again, Neil

Like I said, you’re the expert on this engine, so it’s up to you to do the experimentation to find what works best.
That said, for spark plug gap, increases of 10% of the original gap each time is probably a conservative way to proceed. That’s 4thousandths of an inch, and nano or pico (or atto or femto...REALLY small) seconds at the speed of light, but when the crank is spinning, how many degrees of retard does that translate to, that you then have to compensate for somehow with advance? Nobody's Quite figured out he math around here yet...so hunt and peck until you hit the bullseye.
The MAP circuit has helped me...and my gap is something like 200% but it’s not the only modification/upgrade I’ve made. So you must look at things holistically, and have a bit of patience until you hit on the formula for your vehicle.

Thanks Greg!
So I've been busy working for a few days and now about to do what you suggest and open the plug gaps some more. I had time to connect a scan tool and watch the MAF output, it showed an occasional fault where it registers NO airflow for a split second! ...sort of good to find a fault.... I will get another one and assume those little hesitations on acceleration were because of that.
Can I have some advice on what sort of plug gap I might get up to?
This car uses coil over spark plug so I think this is the best setup for the biggest gaps?
Factory is .044 thou and is currently .050 thou. I was thinking if .100 thou is possible it might make it worth taking a bigger jump. But am reliant on someone to help me out here. Otherwise I will have to just follow Ron's instruction.
I did have a read of a lot of posts and I didn't find any final plug gaps that anyone is running with but sort of sounds like 100 thou might be what some are running with.
Kind regards, Neil

There’s really no way of telling how wide is too wide other than to open them up until it gets hard to start, misfires/runs roughly and/or your fuel consumption goes up instead of down. You’ve probably taken things too far when you notice a marked decrease in throttle response, indicating timing that is too retarded.

Sort out that MAF issue first though! Trace the wires in the harness/loom from one end to the other is where I would start, paying attention to the connectors/pins on each end. Cleaning the contacts may resolve things, but it could also be a computer issue. Also, possibly, look into how the engine is timed- cam and crank sensors.
When was the last time you swapped the fuel filter and checked the pressure regulator/fuel pump?

Neil- reset the plugs to 60 thou, and go from there. The method Greg recommended is ultimately the right one re: plug gaps, but I'd go to .060 then increase from there if ya like. 100 thou sounds a bit big to me, but only you can try!

Tracy G

So I am now running plug gaps at 62 thou. Seems to run great. If there is any advice to keep going wider I'm all for it!!!... but pretty happy to leave the plugs gaps there when I look at the tip of the spark plugs...and hasn't made any difference I have noticed yet going out to 62 thou.
Anyway I am still using about 12 L per 100kms.
I have seen other post on this website in similar scenarios where they have done a groove, then noticed significant differences, yet without mileage improvement.
So I have been scanning the posts for what to do next before troubling you guys, I saw a few possibilities but couldn't really find a scenario that fitted mine and someone still got over the line and moved into some great mileage.
A few posts have been reminding me that I have to do this engine myself. Well, I'm all ready to go and never was looking for any magic answer so if you hit me with a suggestion you can be confident that I'll see it through.
I hear talk about baffles in the intake manifold
I realise adjusting timing is preset but I need to know am I trying to retard or advance the timing? I presume less advance is required if fuel is being vaporised/prepared better.
I'm just thinking aloud and looking for help.
I think if Gadgetgroove guys are reading this you will know where I am at and know what to suggest if you've been here before. Please let me know if you are taking an educated guess tho, cos I'm hoping to hear some advice that is referenced to how it much mileage difference it made.
As part of this I am also interested to hear of the motors or type of motors that respond well to the groove. It is not an impossible thought that I might change vehicles and continue experimenting with the groove on something else. Types or design of engine advice is best because we don't have the same vehicles in Australia as you do in America.
From what I gather reading.... carby and distributor is a great benefit.
Kind regards to all, Neil

In a car with an engine that has sensors relaying realtime data to a computer controlling it, you have to verify how the sensor data relates to what you're trying to achieve, and then determine how altering that datastream may move you closer to achieving your goals, and how to go about doing that.
MAF sensors, MAP sensors, o2 sensors, IAT and ECT sensors, Cam and crank position sensors, vehicle speed sensors...
I speak often of modifying MAP and o2 sensor data to complement what the groove is doing when the engine is running, and have results from doing so on my daily driver, but as you point out, every vehicle is different. You have to do your own research and experimentation and be willing to have expectations just as dashed as you hope they will be exceeded; losing a battle doesn't mean you've lost a war.

Neil, I scanned thru most of this thread to see if I can give anything useful.
Spark plugs: 62 thou gap seems Ok, could go bigger I'd say try 75 thou, see if it likes that. To save time, just change one plug, if it still runs OK, do the rest.

Did you change the tire size yet?

I didnt see any mention in my quick look-thru of this thread of checking all round for vacuum leaks. Ron always has said that vac. leaks are a common thief of mileage gains. Check every hose/line connected to manifold vac. spray carb. cleaner, etc. around intake manifold gaskets, TB base gasket, etc. or use propane torch unlit. RPM change in response shows a vac. leak needing remedy. Small vac. leaks are SNEAKY, often won't give rough idle or poor throtle response or anything you can feel, O2 sensor will detect 'em and ECU will cover them w/ more fuel.

I think all your work so far has been up to scratch. If you have the TB off again, check that your re-cut Groove is full depth, put large bit into it, see that bit flat base touches Groove flat wall AND that the taper on the bit shaft just behind the cutter is touching TB bore.

Again, if TB is removed, give us more pics of this TB- from different angles including outside, the inlet side, and enough so we (I) can get a complete sense of this TB.

In any case, it sounds as if this Groove is working, based on changes you've already mentioned. If power and off idle throttle response has improved, and if the hot engine exhaust has cleaned up, that generally means the Groove is a sucess. Though, there are often further improvements available. Get someone to check the tailpipe smell...!

Without looking 'round further...have you used any Snake Oil in this truck yet?

Tracy G

Tracy Gallaway wrote: I didnt see any mention <snip> of checking all round for vacuum leaks. Ron always has said that vac. leaks are a common thief of mileage gains. Check every hose/line connected to manifold vac. spray carb. cleaner, etc. around intake manifold gaskets, TB base gasket, etc. or use propane torch unlit. RPM change in response shows a vac. leak needing remedy. Small vac. leaks are SNEAKY, often won't give rough idle or poor throtle response or anything you can feel, O2 sensor will detect 'em and ECU will cover them w/ more fuel.[/i]

Felt this needed emphasizing, the havoc little parasitic vac leaks can wreak on a car's mileage.

Hi Tracy!
Thanks for the info. I'll try to reply without missing anything.
1. I will will do the plug gaps very soon.
2. Yes, tires are back to standard 205 wide tires as suggested on this site.
3.I have blanked and checked many vacuum lines etc and will use my unlit propane torch soon to.
4. I will definitely take a heap of photos next time TB is off but I am confident I did correctly do the things you mentioned (its about my 4th groove)
5. Its a real shame my sense of smell has basically gone, I can hardly smell propane! Too much industry toxins i think....I do believe I have noticed a nicer smell couple of times tho.
6. Its also a shame I barely used a tank of fuel in this vehicle before I grooved it but I definitely can tell it sounds different with the groove.
7.I am keen to try the snake oil despite already having another additive in use, but I will concentrate on getting a groove/mileage response first. With freight and exchange rates I think the snake oil will cost a lot to get it to me...
I am getting busy with work atm but hopefully report back soon.
I have been learning playing with both the O2 sensor and MAF sensor. Any advice on which one to modfiy first or will give the best results?
Many thanks, Neil

Now I can control my fuel.
Just giving some feedback, I have been trying to lean out the fuel following no mileage improvement after grooving.
I fitted an AFR gauge on my dash and it seemed the oxygen sensor was maintaining correct air-fuel ratio, I could watch the short and long term trims through the scan tool - this proved the fuel was constantly adjusting from the o2 sensor.To rule out the possibility of the O2 sensor and AFR gauge being out of calibration I then disconnected (cut a wire) from the o2 sensor so the the computer was forced into "open loop" or preset values. My AFR gauge on the dash was still connected to the o2 sensor and I saw basically no change (the preset computer values ran same AFR's)....also after another fuel economy check there was no change in fuel consumed.
I then had a known value that I could expect from the o2 sensor, so I made a o2 spacer about 16mm long. The o2 sensor has 4 rows of holes that sit in the exhaust stream, my spacer retracted 2 rows out of the exhaust pipe...hence only the forward 2 rows were still in the exhaust stream. This seemed to make NO DIFFERENCE. I hoped that it would read richer so i could reconnect it and expect the computer to lean out the fuel. I decided to give up on this idea because of the NO DIFFERENCE that I witnessed by spacing the o2 sensor outward.
I then went to "adjust" the AFM (air flow meter), it has three wires that are easy to probe with a standard multimeter. One has 12 volts, one has zero volts(earth) and one has 1.55v at idle which increase as I rev the motor (the highest I saw was 3.3v). I have fitted a 50,000 ohm variable resistor in this wire.
At 5000 ohms the voltage dropped to 1.51v. at 10,000ohms voltage dropped to 1.46v, at 20,000 ohms the voltage drops to 1.36v and this seems to be the point where I loose power drivability etc. The resistor I used is mounted on my dash next to light dimmer.with 1.5 meters of 2 core wire run to the AFM. It is called a Potentiometer Linear single gang 50K. I am looking forward to next fuel economy check.
The potentiometre knob has a white dot on it. In the 4 oclock position it is zero ohms and makes no effect on anything, as I wind it up to the 12 oclock position it comes to the point where driveability is effected, so I like it at about the 1 oclock position. It can also wind around to an 8 oclock position where the engine has no power and barely runs.
I liked that I can wind the fuel back, whilst idling, to the point that the motor revs drop off for checking for vacuum leaks with an unlit propane torch, I think any response to engine revs would be so much more obvious when the motor is forced to run this lean.
I regret that I am now driving with the computer being unable to Adjust fuel or timing, but one thing I liked is that all presets are safer ranges, such that I believe less ignition advance is used. I believe that vaporised fuel must burn quicker and want less advance anyway, I hope that the knock sensor still will retard timing if my motor experiences any detonation.
Any comments would be greatly appreciated.