Ok, as some of you know I have a 1994 Mazda MX-3, that has had several problems lately. Thanks to MazdaMech and "Tan" especially for all the help they have given me, the car is "so close" to being perfect and it wouldn't have happened without those two helping me out, also I have learned a lot about my car.

Now saying that I have to add what a rookie I was when I started this project. I did just minor repairs on cars since I was around 15 years old and helping my dad. That was 40-years ago (you can do the math).

Now I'm close to having my car fixed and running great. Only one problem remains now. So I figured we could play "What's my Problem?" We can post a problem and see what replies we get. Then we can apply the "fixes" to the cars and see what was correct (or closest to the correct fix). The winner will receive NOTHING!!, except that nice warm feeling in their heart from knowing they helped someone out. Hopefully others will become knowledgeable and start paying forward the help they received.

Ok, "What's my Problem?"

When I start the car the idle goes to 1500 for a short time until going down to around 750. It runs "rough", not really chugging, not dying, but holds a good idle for a while and the a short soft surge and the idle will jump somewhat. When I drive the car and press on the gas peddle the check engine light goes off, when I let my foot off the gas the check engine light goes on. Also, I'm getting awful gas mileage at the moment. One more thing, sometimes when I push on the gas peddle, the car "holds back", but then when I let off slightly on the peddle, the car picks up.

What is the problem and what is the most logical fix?

Thanks

BB

 

MAP sensor?

 

Fuel pressure regulator?
I think it would be helpful to know if the fuel pressure is correct. When the membrane brakes there is extra fuel going through the vacuum hose into the manifold. If that is the case the fuel air mixture may be so rich that it triggers the CEL. Once you push the gas pedal the air mixture may lean out a bit.
Quick test: pull the vacuum hose off and smell for gas. There should be no gas. Better: loan out a fuel pressure gauge at the parts store and get a reading. Watch a Youtube on how to use it together with a vacuum gauge.

And of course it could have sprung a new vacuum leak.

 

I think I forgot something and it's probably not related to the problem. In all the work I was doing I had to adjust the idle for the car. I adjusted both the screw on top of the throttle body and also the adjusting nut that feeds the cable. Can someone tell me how to adjust these to the point they are perfect? Do I just do it by ear and looking at getting the idle to stay at 750?

BTW I looked into the MAP and watched a video about cleaning it. The MAP did not have a screen in it that needed to be cleaned. What it has is a plunger type thing that is clean and moves back and forth with ease. So this did not fix my problem but it was a new thing to learn so that's a plus.

Don't have the cash to get a loaner fuel pressure gage at the moment. (you have to put the money down on it and then then get the money back when you return it. That may be the problem. So if it is, how do I fix it?

Thx

 

Uhmmmm, I found this on another place:

"How did you adjust the idle?

On an OBD1 car, this is how you are supposed to do it: First get the engine warmed up. Then connect the ten and gnd pins in the diagnostics box with a paper clip. Then adjust the big Phillips screw on top of the throttle body until the idle is around 700rpm. You are not supposed to touch the little tiny throttle stop screw on the accelerator cable."

Therefore: make sure you have a little slack in the cable when the throttle is closed. Then do the procedure as explained above.

I am not sure that you identified the parts correctly: MAP stands for Manifold Absolute Pressure. MAF stands for Mass Air Flow. A MAF sensor may have a screen in front of it. I hope you did not touch the tiny exposed wires with anything. Only use the MAF cleaner spray to rinse those off.
I think the thing with the piston may be the Idle Air Control Valve.



When I borrow tools I have to put it on a credit card. They will take the charge off when I return it.

Could you summarize what you have done to the car? Also put your car's information in your signature. That way we can always see what you have.



I think your engine is misfiring at least from time to time. If it continues have a look at this list by UseYourNoggin:

Missfires Can Be Caused By a Million and One Things,

Vac Leaks
Wiring Issues
Spark Plugs(Even Fresh Spark Plugs That Are Crappy Quality.... E3 And Such)
Ignition Coils
Alternators (Search EMI)
MAFS
Injectors
Injector O-Rings
Intake Gaskets
TB Gaskets
PCV Hoses
PCV’s
Malfunctioning EGR
Malfunctioning CAS
O2 Sensors
Aftermarket Intakes
Intake Hoses
Vac Lines
Timing Chains
Timing Chain Tensioner
Broken Cam Gears
Malfunctioning Cam Sensors
Incorrect Crank Gears(The I4 Has Like 40 Different Configurations For Whatever Reason)
Incorrect PCM Flash
Issues Within The PCM
PCM Wiring
Bad Diaphram Within The FPR
Issues Within The Fuel Pump
Dirty Fuel Filter
Dirty Fuel Lines
Pre-Cats/Poor Exhaust Flow

If the above gaskets/seals have not been changed, change them. Clean your MAF sensor, throttle body.
Change your PCV valve and probably that short hose as well.
Inspect the intake accordian tube for cracks. Inspect for vaccuum leaks.
Put in a good Fuel system cleaner: http://www.redlineoil.com/product.aspx?pid=80&pcid=12
Inspect wires. Re-set ECU after doing above

 

So far?

Original problem was the VRIS #2 solenoid. Took me forever to get manifold off so I could get to the VRIS solenoid. Also, I had oil in one of the spark plug holes and changed the gaskets under both valve covers.

I failed to replace the gasket under the manifold and it was running rough so took the manifold off again to insert new manifold gasket. At first I did the thottle adjustments adjusting the big screw and the cable nut. BTW it was much easier to remove the gasket the second time since I realized now much I didn't need to disconnect the second time around. Realized I didn't connect a hose that was open at the very back end of the manifold. Also this time I separated the throttle body, so I could leave some hoses/wires connected. I did replace the two throttle body gaskets this time around also. So far, have gotten codes 46, 17 and 24. Codes where not at the same time, first code was 46, then after the "fix" no longer had 46, but had 17 and 24.

Now after all this, the car does run better....this time when starting up the idle was HIGH! Car tuned over and rpm's went to 7000. Turned car off QUICKLY! Now adjusted throttle screw and nut again, to get idle to 750. Car ran rough, but didn't die, so played with idle a little more and did the paperclip test again. This time code 16.

I want to the throttle body hose connections and made sure everything was tight as far as hoses and wires. Now I start car and get the code 24 and 41. With all these different things happening, I have a feeling I just didn't connect something or connected something wrong. BTW I used high performance spark plugs, HP spark plug wires, changed the air filter and the PCV Valve. I have not turned the engine yet, but I plan too (got a light off eBay).

FYI:


'NE2' crankshaft position sensor
'G' camshaft position sensor
'NE1' camshaft/crankshaft position sensor
Knock sensor
Volume Air Flow sensor (VAF)
Coolant temperature sensor (CTS)
Intake air temperature sensor (IAT)
Throttle position sensor (TPS)
Barometric pressure sensor
LHO2S inactivation error
Exhaust gas recirculation (EGR) system
LHO2S inversion error
RHO2S inactivation error
RHO2S inversion error
Fuel pressure regulator control solenoid
Canister purge solenoid
EGR vacuum solenoid
EGR vent solenoid
Idle air control (IAC) solenoid
VRIS #1 solenoid
VRIS #2 solenoid
LFAN relay (1993 only)
ECTF sensor (1993 only)

 

So you still have an issue with the VRIS (variable runner intake system). We need to know exactly which engine you have. We need to know the production code. See here what I mean:Mazda MX-3 - Wikipedia, the free encyclopedia

Apparently, there were different open and close points for these engines.

I also would like to know exactly (brand, type and model) which plugs you have. Same for the cables. Did you check the gaps prior to installing them? There are some real POS plugs being marketed as "high performance".

 

Correct about the new problem with the VRIS (this time #1). It just doesn't seem possible I would get a new code after I perform a fix. Remember the 17 and 24 were caused because I didn't hook up a hose to the underside of the manifold. If I would have done that, I would have cleared all my codes.

ok, I filled out some more info in my profile. My MX-3 is 6-cylinders and an automatic (wish it were a 5-speed manual). The engine is a K8, I'm not sure how do find the production code.

The spark plugs and spark plug wires were made by Bosch - premium wires and Iridium plugs. I forgot to mention I changed the oil too, and oil and air filters are Fram. I did not check the gap in the spark plugs. They are billed as "pre gapped:

 

That helps. now go to the CP, Edit Signature and add:'93 MX3,V6, and how many miles on it. That way it will always appear when you post and it will jog our memory about it. It sort of becomes a part or our fleet.
Some guys don't like Bosch, but I grew up with Bosch and I am o.k. with Bosch. There is one thing though: if an engine has been developed using one brand, then the other brands are approximations to the originals. Bosch may be working great in VW, BMW etc but could be problematic in North American Ford, GM etc.
I haven't checked but I believe Mazda worked with NGK and Ford as well. Mastercraft plugs are produced by NGK, I heard. Non the less new Bosch should be no issue here.
Even though they are factory gapped, I check with the feeler gauge. Machines are only so smart...
I will do some more research on VRIS on the V6 and how to test them.

 

Thanks Tan, maybe someone else has similar problems and my quest for more info and to get "nugs" running perfect will help someone else.

Even before you replied I had checking the spark plugs on my to do list today. Also I did replace the distributor cap, so I'm going to remove it and make sure the wires are on tight. When I hooked up the wires originally it was hard to connect the wires to the underside of the cap. On the distributor cap there is a small hole on the outside that is covered with a plug. Is this right to leave that alone, or is there a hose somewhere that I should connect to it. I didn't notice any hoses that were hanging loose in that area.

As far as the fix goes, and let me know if you agree, I'm going to start small and easy and then go on to more difficult fixes. So I'm going to start at VRIS #1 and make sure all hoses and plug-ins are connected. Then follow the hoses towards the throttle body and check all those out. Still need to disconnect the vacuum hoses and check for a gas smell, so that is on my do to list also.

Added 6-cylinder to car description also.