TOPIC: 2000 Mazda B2500 - First Groove

[/colHere is one problem I am having with the IAC and engine idling at 1600-2000rpms with restrictor plate
Suggested - increase input hole to full size and output to 1/8" ---no change
Suggested - increase output hole bigger-did 3 times to now 3/8"----no change
Suggested - change IAC for a new one since it was not working ----no change
So I finally got tired of not solving the problem of very high idle so I took the restrictor plate off and now its back to normal 700-800 rpms.

Im getting confused. Should I soak the new IAC in gas? Thought the gas soak would be for removing
gunk buildup but there is none on a new IAC. The high RPM's were from the restrictor plate since it was on the old IAC so it was suggested I buy a new one and install and that would solve the problem.
Since the restrictor was on both and both had the same results with high RPM's, the only thing that brought the rpms down was removing the plate. The plate hole was enlarged to eventually 3/8" before removing restrictor. Unless I put the smaller hole on the wrong side. The small hole which began at 1/8" was on the groove side(out flow hole coming out of IAC) leading in to after the throttle plate. Maybe Im missing something here.
Should I call you instead?

Hi Karl, instinct tells me there is something still wrong here.

Has the exhaust smell ever changed/cleaned up.

Can ya put a vacuum guage on manifold vac and just watch it at idle?

What is idle Quality like? Is it smooth and even?

Anything else that seems odd, have there been other issues that were there before the Groove?

Forget if you said, but how many miles on this one?

Restricting the IAC and idle speed went UP, changing to new one, all stuff w/ IAC sounds weird.

Disconnect brake booster hose from manifold vac, and cap that port (only for test). See if anything changes, do w/ vacuum guage connected to manifold a vac. port. Get a Mityvac vacuum pump connect to brake booster hose pull 20 inches of vac. to booster see if it holds vac. and how long.

Pull IAC make a block off piece of flashing w/ no holes, to completely block the IAC air and re-install IAC. If still idles, cap off every vac. port you can find, one at a time, all w/ vac. guage connected to manifold vac.

Process of elimination...

Check torque on manifold bolts...

Let us know...

Tracy G

does not suprise me ,sometimes the idle will increase as the groove is drawing the air in at idle sometimes if the groove is to close to butterfly this happens, some will learn but some dont.
Chev 5.3 and 6.0 dont have iac the ecu teaches it to idle so I reccomend leave it open or if you still want to cut the air down make a much larger hole the groove wont have the lift which will idle normal.

"Some cars are just frustrating and stubborn w/ the Groove."

I have a 4 cylinder(8 plugs)with the same throttle body as Ron said that someone he did a groove for now gets 54mpg. I only get 27 mpg so somethings wrong here.
Had a vacuum test done to see if there was a vacuum leak by the local mechanic and it read in the green zone which supposedly means no leak the mechanic stated. Wanted to have it tested by someone in the know before I went out and purchased my own gauge and got the same results.
Frustrating to get no results from the groove when supposedly others with the same engine got stellar results. 'Also getting a knocking in the engine when I accelerate or go up a hill which only goes away by going to high test. Asked the mechanic if I could re-time the engine to eliminate the knock since this happens within 6 months or so after getting a new timing belt. Guessing the belt is stretching and knocking the timing off but the mechanic stated I cant re-time/advance the timing on my engine. If the wheel has the marks for TDC and the increments before and after I would guess this is for timing it. Am I wrong??? Want to eliminate that knock by re-timing instead of going to more expensive high test. Any suggestions?


I put tape on the port to the MAF to cut off the flow of air in half to lean out the gas mixture.Have had it on for over 3 weeks but notice no change in MPG. When I go to cut off more air(from 50% to 60%) the engine runs rough and sometimes stalls so had to go back to 50% reduction.

Will gapping the plugs up 20% help with HP loss issue by my cutting off the air on the MAF?

Should I regap the plugs up 20%,
Buy Extreme Spark plugs which give out much more spark,
Or side gap the plugs which seems to add more spark as regapping?

I also heard on the boards about a device that tricks the O2 sensor into reading a hotter temp thus making the computer lean out the fuel mixture. I would like to give this a try instead of replacing the sensors which are very old and will cost over $100 to replace not counting buying the tool for it.
Doing everything suggested to find the problem of why no HP and no MPG improvement with the groove but coming up empty.

May be time to do a leak down test on the motor

Hi again Karl. I just re-read most of this thread, this one is still not responding.

Overall, I think it sounds like this is a tired high mileage engine, and it's a Ford twin plug. How many miles on this one, Karl? IF the engine is getting pretty worn, well, I would say that's the real story. I agree w/ 4 wheel Bill, a leak-down test is likely in order, it will give indication of ring seal and condition of valves, I'd do a compression test too.

Can't re-time ignition on this one, it has coil pack not dist. The knock--is it a higher or lower pitch sound? Higher pitch is likely pinging or spark knock, lower, could be main bearings I think (sure hope not!)

If it's pinging, either the plug heat range is too high (have you changed them) OR it's wayy too lean under load, OR there is a lot of carbon/crud in the chambers that has driven compression ratio up. I don't know if this one has a knock sensor. IF this is a high mile engine, and you are running full synthetic oil, then oil might be getting in the cylinders, oil has awful Octane properties! Of course I'd expect to see smoke and oil usage w/ poor oil sealing.

We've been discussing details about the Groove job & associated stuff, but gut tells me it's time for just basic mechanic analysis w/ your Mazda. I dont remember if ya told how many miles on this Ford 4 cyl, and it's overall condition. If this one is tired then it's time to find out what you are really working with. Trick parts and mods can't fix major wear IF that's the reality. XADO might help out some with friction surfaces (bearings, cam lobes, anywhere oil goes that is worn and metallic), only fix w/ valves is valve job.

Anyhow Karl, that's my 2 cents worth, I would want to establish the engine's state of health. We work with what we have--my Subaru has become a Lab Rat on wheels. but it has a rebuilt engine.

Maybe someone else has input to share here?

Karl, I still say you did one of the cleanest lookin' Grooves ever!

Tracy G

Hi Karl

It sounds to me that your mechanic and you measured the vacuum with the engine running.
Did you try putting your tester on each hose coming of the manifold (with your engine off), pumping the vacuum up to 23-25 bar and leaving it there for at least 10 seconds without the needle dropping?
If you pulled one of these small hoses of while running, you will still get a half decent vacuum showing up on your gauge. That's not telling you the full story. You need to check them individually.

The device you mention (I think) is an EFIE. Check this page out and read up on how they work on that website.
It changes the oxygen content reading to the computer which will then lean out the fuel delivery.
It has nothing to do with the temperature though.

The same site also sells the mapster for the MAP or MAF sensors (Ron has a few in stock so buying one from him will help him in his time of need). They even have an article on how to make your own with only 2 parts (less then $5)..
As others here have mentioned though, if your engine is too tired that may well be the cause.

The increments on your engine are for when you use a timing light to adjust your ignition timing. The cam belt is either positioned right or wrong and if it's wrong it will run like a pig or not at all.

Edison failed over 1000 times with his light bulb, don't give up!

Here are my answers to Terry.



<em>Overall, I think it sounds like this is a tired high mileage engine, and it's a Ford twin plug. How many miles on this one, Karl? </em>

Have 260k and mostly highway miles.

<em>Can't re-time ignition on this one, it has coil pack not dist. The knock--is it a higher or lower pitch sound? Higher pitch is likely pinging or spark knock, lower, could be main bearings</em>

<strong>Im guessing its a higher pitch. The first time I heard it was about 20k miles or one year after purchase. Only heard it when I needed more power like when going up hills or fast acceleration. Went to higher octane and that seemed to do the trick. When I had the timing belt changed the knock/ping left but now it seems to have returned 6 months after the belt change. Thought it was the belt stretch since when it was new when I first bought it and now a new belt, both times I didnt have the knock/ping and both times is when the belt was new. Maybe just a coincidence but my deduction does play into that it may be the belt since when both belts were new, I had no problem using regular gas with no ping. Maybe its something else and just a coincidence that I had no ping with a new belt.</strong>

<em>If it's pinging, either the plug heat range is too high (have you changed them) OR it's way too lean under load, OR there is a lot of carbon/crud in the chambers that has driven compression ratio up.
</em>

]The plugs and wires were changed with the timing belt 6 months ago.
As far as the too lean, I do have a P0701 code which supposedly means too rich or too lean which occured before I put the tape over the MAF hole to restrict flow.Looked for possible causes and found it could be the MAF(I changed it last year)or a vacuum leak in numerous places, low fuel pressure from fuel pump starting to go or a clogged fuel filter(just changed fuel filter)or the PVC which I rerouted to passive side like in the pics. As far as the carbon/crud buildup, I had a clean out twice. Once 4 years ago and another 6 months ago along with the timing belt and plugs.Did all these things 6 months ago to try to find the reason for the pinging which did stop and has now reappeared.

IF this is a high mile engine, and you are running full synthetic oil, then oil might be getting in the cylinders, oil has awful Octane properties! Of course I'd expect to see smoke and oil usage w/ poor oil sealing.

Do use full synthetic but just started to two years ago. The ping started 12 years ago about a year after I bought it.


Karl, I still say you did one of the cleanest lookin' Grooves ever!

Thanks, but did a wiggle test after with the bit and its not tight like it should be. If I thought a cleaner/tighter groove was the issue, I would fill and re-groove first thing and right away.
I also was wondering if filling the groove with solder would be better than JB since the solder may hold better to the metal and can be re-grooved in 5 minutes. Also the solder may hold better with the oil asperations from the PVC re-route. I'm sure others here have thought of that and have not seen it on the boards so am assuming its not a good idea or else it would be used.
Also, what is your assessment on the re-gapping of the plugs in my last post. You have the Extreme spark plugs but would a 20% increase or side gapping be just as effective? Would that also give me more HP and better mileage? Thanks again for your insight and knowledge.

Here are my answers to Rino


It sounds to me that your mechanic and you measured the vacuum with the engine running.
Did you try putting your tester on each hose coming of the manifold (with your engine off), pumping the vacuum up to 23-25 bar and leaving it there for at least 10 seconds without the needle dropping?
If you pulled one of these small hoses of while running, you will still get a half decent vacuum showing up on your gauge. That's not telling you the full story. You need to check them individually.

Will buy a gauge right away at Harbor Freight and test the best I can and see if that turns up anything.


The device you mention (I think) is an EFIE. Check this page out and read up on how they work on that website.
It changes the oxygen content reading to the computer which will then lean out the fuel delivery.
It has nothing to do with the temperature though.

Have seen it in videos on Youtube. Went to the link to read and it seems like the hook-up process is a little complex so I just might go and change the O2 sensors first. Dont like wasting money and time on something that doesnt work or fix a problem.
Read about a device on the boards that costs $5 that can fool the sensors and thought this was a more viable alternative than replacing them even though they are original and 13 years old.
If I do replace them, should I replace both or just the one before the CAT?

The same site also sells the mapster for the MAP or MAF sensors (Ron has a few in stock so buying one from him will help him in his time of need). They even have an article on how to make your own with only 2 parts (less then $5)


Didnt see the article on how to make my own but if I end up purchasing one, I will buy it from Ron.

The increments on your engine are for when you use a timing light to adjust your ignition timing. The cam belt is either positioned right or wrong and if it's wrong it will run like a pig or not at all.

So I am guessing those marks do me no good in adjusting the firing on a computerized engine but I remember doing it on my 70 Nova with the distributor till I got it to run smooth.
Is there any way to adjust anything to advance/retard the firing if this is the cause for the knock/ping?
Boy do I wish I had my 70 Nova again. I am getting to hate the computer run cars but as Ron has pointed out, its all by design from those who control us.
This I know very well from my hours of study every week on the coming NWO.

Thanks for your response to my problem.

Hi Karl

Oops, forgot to paste the link to the $5 thingy, sorry..

The first O2 detector is the most important. You really should replace it as the computer will ignore it if it does not work properly. Once it does that it will use previously mapped values and that will never give you any improvement. 80000 to 10000 km is really the max life you can expect so I would not be surprised if that is what's happening. You can find them for around $40 on line if you look around a bit.
The tool will come in handy for your customer's cars later, it's not that expensive anyway.

To do the job properly the second one should be renewed as well but it's not as crucial.

The MAF enhancer comes after the CO2 so I would do that first..

Some of the earlier electronic ignitions could be adjusted. If you have a distributor then you may be able to. The newer types don't have a distributor cap at all.

Good luck

I completely covered the Intake Air port on my 98 Honda CR-V (glued the side out of a soda can over it with RTV). Idle was a little weak so poke a teeny hole in it - idle got a little better.

The Intake Air opening leaks a lot of air into the intake manifold, going around the throttle plate (and your Groove). However - it always goes thru a valve or two first. One is heated by your radiator water - kind of works like the old fashioned automatic choke - riches up the mix until you get warm. The other is controlled by the ECU. Ron's advice to me was to plug both valve ports, and I did.

In the temperate climate where I live (SF Bay Area) there is not a lot of change in temp - we do not have to deal with freezing mornings, ever. So these mods worked pretty good. Do what you think you need to do where you live. It is late summer now - so not a alot of weird temps, you can probably get pretty bold with your experiments.

The Intake Air opening leaks a lot of air into the intake manifold, going around the throttle plate (and your Groove). However - it always goes thru a valve or two first. One is heated by your radiator water - kind of works like the old fashioned automatic choke - riches up the mix until you get warm. The other is controlled by the ECU. Ron's advice to me was to plug both valve ports, and I did.

Hey Mark,

The only valve I know that the Intake Air comes from is the IAC. I am guessing that when no gas pedal is applied and the throttle plate is closed, that the engine gets its air from the IAC which opens to let air in so the engine runs. I plugged the IAC with a restrictor plate as suggested and poked 1/8" holes in it to let some air in or the engine I guess would choke itself off. The engine ran fast at over 1500rpms at idle instead of 7-800 rpms. So I kept enlarging the restrictor plate hole with no success so I finally took it off.
In my throttle there is no radiator hose water running through it like I see in some videos Ron posted. The only other hole in my throttle is one after the groove on the opposite side. It is a hole that has a short pipe that connects to some hose that goes who knows where. I was not instructed to mess with this hose so I left it alone.
You can see my throttle in all the pics provided.
I do appreciate your intake on my problem here but it sounds like the mod you did to yours would not apply to mine since it is constructed differently. If you have any other ideas, let me know.
I desperately want to get more HP and definately higher MPG and am having no success.
Thanks again.