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Discussion Starter #1
Hey guys,

Thanks for looking. I just have a question as to what the fvck is going on with my fiance's car. None of the people I know really have done much with carby engines.

The car is a MAZDA 121. 1992 1.3ltr Carby engine.

It has an automatic choke which I think is where the problem lies.

The problem she is having is a very jerky first, second gear. It is thinking the revs are all over the place when they are constant (Looking at the tacho it jumps all over the show but revs are increasing constantly). It only happens every now and then. There is sufficient air and fuel entering the engine. Its not a fuel problem as she has filled and emptied 3 times since it started doing it.

The automatic choke is a computer operated one with a sensor on the carb. I think this is the problem as it seems to be an electrical fault due to the way the tach is reacting. I think the sensor might need replacing but dont want to do that without knowing anything about the problem.

Anyone got any ideas or backup at all. I can get pics and stuff if need be.

--Aaron--

[Edited by Crusty_04 on Feb 13, 2006 7:51 PM]

[Edited by Crusty_04 on Feb 14, 2006 5:50 PM]
 

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Jumpy tach can be a disturbance in the coil. Does the same stuff when i floor it in my 74 Courier...

Check your ignition- timming, spark plugs wires, cap & rotor... stuff like that.

For the choke... i dont know what to tell you... take it off, and get a manual one. :puzzled:

[Edited by wilburisthecoolest on Feb 4, 2006 11:37 PM]
 

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Is it a bimetallic passive type carburator or a fully electronic solenoid feedback type?

Does the problem go away after teh car is warmed up? Try disconnecting the solenoid/sensor to the carb when the car is warm, see if it idles down. If it does, it's your prewarm/autochoke solenoid acting up.

Jerking is caused by poor valve/float adjustments, gunked up circuits. Usually the time between Idle and power circuits, internal passages are blocked and resricted from varnish buildup. Try running some carb cleaner on a near empty tank. You could also try readjusting your float level. There should be a sight glass on the side of the bowl(s): Adjust the plunger until the fuel aligns itself with the dot or line. Setting it too high forces fuel out of the bowl and into... well, I don't know how your carb is built but usually back into the return line or through some passages where it's not supposed to go, such as in the barrel.

Is it a one or two barrel carburator mechanical secondary or vacuum actuated? Sidedraft?

I would need to know more details. Can you provide a picture?

If a Pony carburator happens to bolt up, I strongly suggest it. Suzuki Samurai (1.3, 1.5) tuners LOVE pony carburators. 55 degrees worth of pitch and a large float bowls to keep it going up a hill for a long period of time.

Carbs are tricky. Each one is different yet the same. They are about as temperamental as girls sometimes.

Show me a pic of this one if you can.
 

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Discussion Starter #4
Pictures below.

[EDIT] PICTURE REMOVED AS IM PRETTY SURE THIS ISNT THE PROBLEM [/EDIT]







Hopefully they help answer some of your questions Jed cause I dont know sh!t about carbies. The jolting only happens while the tacho is going spastic and almost always after the car has been run for a while then let to cool then run again. It did it once while driving, just out of the blue last week. When it is going stupid, it runs ok when off the gas but when accellerator is pushed, jump jump jump...

Let me know what you think.

Sorry I cant be more descriptive. When it first happened we fiddled with the connectors in the first pic and it ran fine after that for a while. Thats another reason we think they're the problem. Any idea what they are? Im pretty sure one of them has something to do with the auto choke. Would it be possible to replace it with a manual choke and do you think this would help.

--Aaron--

[Edited by Crusty_04 on Feb 13, 2006 7:52 PM]
 

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That is not a carburator.

That is a Throttle Point(or body) Injection. They suck balls. Here's what it is most likely, from my experience with TPI/TBI on '87 escort and '93 swift. Take the 2 top screws holding the "injector" in place. Remove the injector and verify it's mist spray pattern by applying condensed air into the inlet port. A simple foot pump will suffice. It should spray a fine mist. Any obstructions or droplets indicate a clogged meshing. Check the rubber seal around the injector body housing for leaks (the escort was particularily prone to this) any leaks will add unwanted fuel into the mixture, flooding it temporarily. If the injector checks out, replace it back into the assembly and check the fuel filter. Actually, check that first.

If the problem continues, my guess would be a bad ground or a faulty wire. Obtain a wiring diagram and verify all resistance values. The process is similar for a feedback carb (my chilton's tells you how to do it to a 87 stellar carb) so maybe check that out. Let me know how that goes.

Some TBI systems (like in my current '88 sentra) emply a MAF sensor within the housing just below the throat under the butterfly. Check that one too. They routinely fail (such is common on the B12 GA16DE SOHC) and sometimes they just need a good cleaning.

Keep me posted.

It could also be the camshaft pos sensor, I had a Pontiac 6000 V6 2.8 do the same... you couldn't restart the car after it heated up because the heat would move the sensor mount plate sufficiently away from the notches in the cam to take a proper reading.

[Edited by Jed118 on Feb 5, 2006 10:18 PM]
 

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Discussion Starter #6
Well I told you i dont know sh!t about carbs... :dead:

Well I will replace the fuel filter first and see how she goes then start fiddling with it in more depth.

Much thanks Jed. Great help. Sorry for the confusion.

--Aaron--
 

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Hehe I just feel sorry for you... TBI sucks!!

;):

Good luck. 8D
 

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Discussion Starter #8
OK still having trouble.

Replaced the fuel filter so far but still having lots of trouble.

I have played with it a bit now and think I know kinda whats going on.

The problem is only happening around the > 3000 RPM range. We (Myself and housemate) think it might be putting WAY too much fuel into the mixture and trying to flood the engine while its running, hence causing it to involuntarily jump start the car with every few hundred rpm cycles, therefore causing it to feel jerky. In theory in my head that is a very possible scenario, but feel free to tell me im wrong. Take a look at what i think is what.



Note 1: This is where the fuel "injector" is. I think this is still a possible cause. It seems to be spraying properly but has a funny locking mechanism on it so I cant figure out how to get it out to have a closer look at it.
Note 2: I am pretty sure this is the fuel pressure regulator, although I thought the fuel was flowing the other way as the fuel filter is on the other line... :ermm:
Note 3: Is it possible that as the fuel filter is on this line that the fuel is flowing in the opposite direction to the arrows in the pic and the fuel pressure regulator is regulating from that side of the injector by stopping the fuel flowing and building up the pressure? (As im typing im thinking this is a more reasonable explaination and would cause a lot of problems if reg is blocked or not functioning properly, therefore causing a build up in pressure and more fuel flowing through injector).

What do you think?

Replace the fuel reg next?

--Aaron--
 

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Discussion Starter #9
I found a wreckers with the same engine just around the corner so am going and buying the reg today. If it works Ill be a happy man but if it doesnt I think my fiance is going to take my manhood away from me and take it to a shop to get it fixed...:dead::dead::dead:

Hopefully I have a brain and its funtioning properly cause it seems like a good idea I have going here.

I just keep thinking that if its blocked or not functioning correctly then its going to be building a lot more pressure in the lines and at high rpm its going to be pushing a lot more fuel in.

Will let you know how I go.
 

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Discussion Starter #10
Well that didnt work...

Its still as bad as it was.

Heres some of my observations...

  • Only happens when its warm. It ran for about 10 mins before buggering up today.
  • Has a lot of trouble starting once it has stalled. Could it be battery? Its going room room room clunk... Could a dodgy battery be doing this?
  • Im thinking it still could have something to do with the choke as it is starting to seem electrical again maybe aswell.
I dont think it is flooding the engine anymore... It has to be something else. I had a look at a haynes manual that suggested either Fuel Pump, Regulator, Injector System, Engine Electrical Systems.

Is there any way to measure battery voltage while the car is driving?

Let me know what you think guys.
 

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Discussion Starter #11
Originally posted by Jed118
[body]
Take the 2 top screws holding the "injector" in place. Remove the injector and verify it's mist spray pattern by applying condensed air into the inlet port. A simple foot pump will suffice. It should spray a fine mist. Any obstructions or droplets indicate a clogged meshing. Check the rubber seal around the injector body housing for leaks (the escort was particularily prone to this) any leaks will add unwanted fuel into the mixture, flooding it temporarily. If the injector checks out, replace it back into the assembly and check the fuel filter. Actually, check that first.
[/body]
Just highlighted the important bits of a previous post of yours that i was looking at. I had a look at the injector but couldnt work out how to get it out. Any help with that would be great.

You mention the rubber seal. Thats the one above the injector isnt it... Whats the deal with those? They apply pressure on injector or something? I thought it was just a dust cover type thing.

Please help me. Im struggling.
 

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Discussion Starter #12
hi again,
Jed would you mind having another look? Still not having any luck. Thanks
 

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Hmm, the rubber seal I mean is the round one that goes around the injector in the housing assembly. Im not familiar with mazda's CFI, but it should have one. You're gonna have to figure out a way to get that injector out mang, practice on some junkyard cars first. And then of course, pocket the injector itself. Also try to unbolt all the connectors and actuators from a junkyard carb. Pocket those too!

Also, if it runs well when it's cold, and then starts to bog, it could be a clogged catalyst. How many miles on the mazda?

Measure battery voltage at the terminals, it should read 13.8v. over 1000 RPM (mine measures like, 9v at idle, the alternator is going) A dead battery doesn't make a difference, because once the car is running, the alternator takes care of the rest.
 

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Well, I will add my two cents as well.

My first suggestion is to look high and low for a vacuum leak. All of your symptoms could be caused by a vacuum leak. Post back if you don't know how to do that.

Any leak in the injector assembly could be causing your problem by the way of flooding while it's leaking. To investigate further you really need to pull the injector for further inspection. (as Jed said, just clarifying that it's not necessarily a specific gasket, but rather any seal)

If you can't figure out which way the fuel is flowing pull the hose connectors off at both sides of the TBI and point both into a bucket. have a friend turn the key to the "on" position briefly and see what hose the fuel comes out of. Also this may tell you if the fuel pump is pumping erratically (visible sputtering), or has low flow (should come spraying out like crazy). If nothing happens you have a mechanical fuel pump (doubtful) and you will have to have your assistant turn the engine over to get fuel flow. A mechanical pump generally has much lower pressures.

To verify if the engine is flooding when the car dies and will not restart pull a spark plug and if it's wet and smells like gasoline the engine is flooded.

If it's a problem that is actually associated with the tach reading erratically it could be because the ECU does not know how fast your engine is spinning and the load on the engine, making it impossible to inject the right amount of fuel, and depending on the ignition type causing problems with your timing advance/retard.

I could do you a little better but I am not familiar with your particular vehicle. Hopefully I was at least a little helpful though...
 

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Yeah but these are real simple motors, my tach does that too. Vaccum leaks, yes that is something I missed entirely, and especially CFI has some bypasses which open at a temperature that could be leading air into the throttle assembly, or causing vacuum to leak into it. Either way it will compromise the mist from the injector and cause the car to run poorly.

Even on my pony (mechanical pump that's driven off teh cam) it's 3-4 PSI but let me tell you, teh volume and pressure coming out of there is great.
 

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The closest thing I really have to compare it to is my old 85 S-10 Blazer TBI 2.8l. We're basically into the type of car I don't want to touch with a 10 foot pole if I can help it. I hate the partially computer controlled cars. I don't mind non computerized, and I'm cool with computerized motors, but I hate the mix and match systems used on many cars from the early 80's to 1995.

In 1992 I would be concerned (if simpler methods fail) that the ECU is controlling either the fuel or timing off of the tach reading that is all funky. If the car has a CPS running the tach it could be faulty and Mazda could be using that signal. Please fully realize that I am speculating, and have no first hand knowledge of the car at all, or really anything comparable.

[Edited by 187sks on Feb 21, 2006 4:24 PM]
 

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Also run a new wire from the coil to the ECM. Try putting in a new coil!
 

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Discussion Starter #18
Thanks again for the help guys.

187sks - I really have no idea how to test for a vac leak. Some help would be great.

We will take it for another drive to see if it is flooding by testing the spark plugs as 187sks said.

It feels like the tach doesnt know what its doing and the engine tries to follow it so it could be the CPS too. How would you suggest fixing this?

Whats CPS??? Cam Position Sensor???

Whats CFI??? Central Fuel Injector???

Am I right in saying that no-one seems to think its a sensor on the TBI?

I dont think I can see a coil Jed. Not a good old conventional one anyhow. Not like the one in my dad's old commodore which is the last one I remember seeing. Where would it be? Could it be part of the distributor cause there are a few wires running in there.

---Aaron---
 

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I know this may be a stupid question, but the problems your experiencing seem verrrry familiar to me...is it an automatic or manual tranny? I ask this because my mom's previous car, a 2000 Honday Odyssey, had almost exactly the same problems. We took it to my buddy's dad's shop, and he figured out that it was a worn-out solenoid clutch pack. Basically, Honda was too lazy to completely build an automatic tranny from scratch, so for a while they just used their existing manual tranny and converted it to an automatic using a variety of solenoid packs. Like I said, I don't even know if cars like your fiance's even had any solenoids period in them...lol...just a thought.
 

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Originally posted by Crusty_04
[body]
187sks - I really have no idea how to test for a vac leak. Some help would be great.
[/body]
In order to see if you have a vacuum leak you will want a vacuum gauge. Then you can test a vacuum hose to see if you have good vacuum. If you do have a leak you can listen for a hissing noise and look for cracked or disconnected vacuum lines visually, fixing any problems you find. If you can't find any problems that way you can start the car and take a propane torch and turn the gas on (do not ignite the propane!) and follow vacuum lines around with the torch to find a leak. If there's a leak the engine will suck propane in through the leak and rev up higher, so all you have to do is listen for your idle to rise. Obviously it will rise if you spray it right into the intake also though, so if you're looking around that area you need to verify the engine's not just sucking propane into the intake.

Originally posted by Crusty_04
[body]
We will take it for another drive to see if it is flooding by testing the spark plugs as 187sks said.
[/body]
To clarify you only need to test one plug, and directly after the car dies and won't restart. Preferably don't try to restart the car at all, just let it die from this problem and then test one spark plug.

Originally posted by Crusty_04
[body]
It feels like the tach doesnt know what its doing and the engine tries to follow it so it could be the CPS too. How would you suggest fixing this?

Whats CPS??? Cam Position Sensor???
[/body]
The CPS I'm referring to is the Crankshaft Position Sensor. CPS is also an acronym for Camshaft Position Sensor, but not what I was referring to...I should have clarified. There are multiple ways for a tachometer to be driven, and the crank position sensor is one of them. The traditional way is simply a signal from the distributor which reads each time the coil fires. That's why most tachs are 4, 6, or 8 cylinder specific, but other than that universal. If this type malfunctions it will almost always only read as a lower rpm than actual because about the only way it can fail is to not transmit a pulse every time. It would be helpful if you can figure out what type of ignition system the car has and if possible how the tach is driven.

Originally posted by Crusty_04
[body]
Whats CFI??? Central Fuel Injector???
[/body]
CFI is Central Fuel Injection. Another name for Throttle Body Injection. Has all the downsides of a carburator, and all the downsides of early fuel injection electronics.

Originally posted by Crusty_04
[body]
Am I right in saying that no-one seems to think its a sensor on the TBI?
[/body]
I don't believe it's your electronic choke or your TPS. The TPS can cause some of the problems you're describing but I personally would be surprised if it was that.

Originally posted by Crusty_04
[body]
I dont think I can see a coil Jed. Not a good old conventional one anyhow. Not like the one in my dad's old commodore which is the last one I remember seeing. Where would it be? Could it be part of the distributor cause there are a few wires running in there.
[/body]
There should be 5 wires on your distributor cap. 4 of those are to your plugs and the other one is to your coil. Trace the wire back to your coil. The wire in question is probably right square in the middle of the top of the cap. If that doesn't match what you see take a picture please.
 
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