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Discussion Starter #1
Hey people,

found myself a new project car, a 1995 J2. Yes its a late 95 j2 Australian Delivered.

It's a 1.8L Auto. It was having an issue where it wasn't starting, after some trouble shooting, the crank pos sensor had died. So i replaced it. Before it died, the car would struggle to start but would run fine.

The car now starts first time every time however, it will not rev more that 1500rpm and when you try to rev it up, it falls on its face and drops down to idle(800rpm).

(Side note, there is no check engine light... and wasn't when the crank pos sensor was bad either)

Any ideas?
Thanks in advance!
 

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Sounds like a possible timing issue
Do you have use of an oscilloscope, two amp clamps?
One clamp goes on the battery cable
The second goes on the number one cylinder
With engine running, watch and check timing
Try to accelerate engine rpm a little and watch timing
It should show you whether there is a timing issue

No to oscilloscope??
When was the last time the timing belt was changed?
Thinking

Try using the old sensor again??
See if the engine runs the same (hard start and runs fine?)
Could it be another bad sensor??
 

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The car now starts first time every time however, it will not rev more that 1500rpm and when you try to rev it up, it falls on its face and drops down to idle(800rpm).
Here is something quick and simple that doesn't involve an oscilloscope....try removing the upstream O2 sensor and see if the engine is able to rev up with it removed from the exhaust. You might have a blocked CAT causing excessive exhaust back pressure. Removing the O2 sensor will give the exhaust gasses an escape route which will allow the engine to breath.

Do you have use of an oscilloscope, two amp clamps?
:rolleyes:
 

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Discussion Starter #4
Hey guys,

thanks for the quick reply.

Sadly i do not have an oscilloscope.

As for the CAT being clogged, I will try what is suggested, but the car ran fine fairly recently. It would rev out and run great. I really don't think that is the problem.

As for timing, the same response, It runs great while idling. (no jitters or shaking, rpm is stable) (which does point fingers at the CAT. I'll give it a look)

Motor has NOT been out and I haven't re-timed it since it last ran.

I'll pull the plugs and see if its fuel related too. I preemptively bought a fuel filter, so i might just slap that on as well.

One clarification, the old sensor does not work at all anymore. The car will not start at all with it back on. :(

If the ecu wasn't seeing something, what would it be? Something might be unpluged, i will have a better look today.
 

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If the ecu wasn't seeing something, what would it be? Something might be unpluged, i will have a better look today.
Just a thought....some of these older Hyundai engines had a MAP sensor that was mounted on the bulkhead and linked to the inlet manifold by a small vacuum hose. If your engine has one of those sensors it might be worth checking that the vacuum hose isn't split/pinched. I'd imagine that would illuminate the CEL though, but worth a look.
 

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That was a good idea about clogged exhaust
It would let engine idle but not rev high
Taking out upstream O2 sensor would let engine breathe

No check engine light might be due to not having enough drive time or drive cycles
Would check map sensor and associated hoses as Autospark suggests
Would also see of blocking purge hose might help
Thinking is the purge valve may be stuck open which allows too much air for the engine to rev up

Please remember that these are all guesses here
We can't see the car nor can we test it
 

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Discussion Starter #7
Thanks for your help guys, I do appreciated it!

This is a MAP sensor type engine. I unplugged it while it was running and it idled like a turd, replaced the vacuum line on it and no change.

Exhaust smells very rich with petrol.

I unplugged the idle control valve and as expected, the engine died. So check that off as working.

I haven't been able to test the CAT for blockages, however it ran like gold before the CPS died. So I still could be wrong on that but that kinda tells me the CAT is ok. (car ran mint a few weeks ago)

I unplugged the TPS while it was running, rev'd up the engine a bit and there was no change, could the TPS be dead? Seems odd that it would die for no reason.

Not game enough to disconnect the Cam position sensor while it's running, but i would guess that the engine would die instantly as the ecu doesn't know where piston #1 is.

Purge valve seems to be working, I disconnected it from the intake and plugged up the hole, to no effect.

Still willing to try pull the O2 before the CAT off just to test. (waiting for someone else to be here, just in case the car falls onto me and kills me)

I am thinking about that TPS. If the computer doesn't know where that butterfly is, then it could be on a base map to keep it idling but surely it would go lean if it didn't adjust fuel mixture.


For the record, it has a full take of fuel at the moment, so its not a lack of fuel.

cheers
 

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I unplugged the TPS while it was running, rev'd up the engine a bit and there was no change, could the TPS be dead? Seems odd that it would die for no reason.
The TPS is similar to a rheostat or variable resistor.
Can be checked with a DVOM (digital volt ohm meter)

Not game enough to disconnect the Cam position sensor while it's running, but i would guess that the engine would die instantly as the ecu doesn't know where piston #1 is.
Would not do that.

Still willing to try pull the O2 before the CAT off just to test. (waiting for someone else to be here, just in case the car falls onto me and kills me)
The upstream O2 sensor should be near the front part of the engine
Always use jack stands when jacking up vehicle
Remember safety first

I am thinking about that TPS. If the computer doesn't know where that butterfly is, then it could be on a base map to keep it idling but surely it would go lean if it didn't adjust fuel mixture.
DVOM to check TPS
Put meter on disconnected TPS and move the TPS cable
Reading should follow the TPS position

Good luck
 

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Discussion Starter #9
So just checked the TPS, its fine, matches what the haynes book says.

Just for the record
On Youtube bqX1Q-YZeBo

thats the weird stumbling thats going on.
 

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What are you doing with the throttle to make it do that?

Is the fuel gauge broken? If not you might want to add some petrol to the tank....just in case.
 

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Discussion Starter #11
Simply pushing on the peddle does that, i'm not moving my foot all crazy, it does that by itself. That is the problem i'm having, it does that even if i bypass the cable.

Fuel gauge is fine, it has a full tank.

The saddest part is, it now has some kind of ticking sound.... hoping the timing belt hasn't jumped. Didn't make that sound before changing the spark plugs :(
I hope i haven't damaged the engine. It's only done 95k :(
 

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Discussion Starter #12
I'm not doing anything to the throttle to make that happen. The car is doing that itself, i am revving it up and holding it, the car does that jump.

The fuel gauge is fine, the car has a full tank of fuel.

I changed the spark plug wires just because i had some lying around and, it does the same thing but now there is a ticking noise :( the ticking changes with rpm but when ignition is cut, it stops. (spark leak?)

Still wont rev. I think i'm going to have to buy a fuel pressure gauge.
 

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I think i'm going to have to buy a fuel pressure gauge.
There are 2 things you could try before doing that.

1) You could try removing the O2 as I suggested earlier and see if that helps. If you can't get under the car to get at the O2 you could maybe loosen the exhaust manifold and move it back off the cylinder head a little. It doesn't need to be much. You just need a wee gap to let the exhaust gasses escape.

2) You could use the O2 output voltage to see if that suggests you have a fuel delivery issue. I don't think you can monitor it on the scan tool on your car though so you'd need to either back probe your voltmeter into the sensor connector or the PCM connector.
 

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Discussion Starter #14
Hey again people.

So after a little bit of time, i pulled the CAT off and ran the car, same issues.

I bought a new MAP, same issue.

I changed the Fuel pressure reg, same issues,

I have done the ear test for the injectors and they all sound like they are working.

Why would my AFR's be off after a CPS change?

Which scan tool do i need to get for my car? Is it OBD2?

It seems to be in some kind of limp mode, the rev limiter is at 1500rpm.

I think i should add that the CPS i put in is the newer plastic body one, the original sensor was a metal bodied one. (shouldn't make a difference?)

If i can't fix it, i'm towing it to a mechanic. Realllly don't want to drop $$$$ on this.
 

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Which scan tool do i need to get for my car? Is it OBD2?
It's not OBD2 so you'll need something with Hyundai specific software. I've no personal experience with it but the Foxwell NT510 (loaded with the Hyundai software) looks like decent tool for the money : Foxwell NT510 PRO - For KIA & HYUNDAI

Brayden9707 said:
I think i should add that the CPS i put in is the newer plastic body one, the original sensor was a metal bodied one. (shouldn't make a difference?)
It shouldn't make a difference as long as it's the same dimensions as the original. Was it a genuine Hyundai sensor? Personally, I wouldn't buy an aftermarket crank sensor.

Another thing that sometimes causes issues when replacing the crank sensor is the rubber 'O' ring. Sometimes the 'O' ring comes off the original sensor and stays in the cavity on the engine block. If you fit the new sensor with it's 'O' ring on top of the old 'O' ring the air gap between the sensor and the tone wheel on the crank will be too large. That usually causes a complete non start though but thought it was mentioning just in case.
 

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Bogs down ... could be O2 sensors ...
Hmm, wish there was a way to monitor the O2 sensors
If O2 sensor shorted and out put is stuck high then ECU could cause it to run lean
Which would cause the bog down when touching the gas pedal.
Wait, does the 1996 to 2000 Elantra's have O2 sensors?? Should but not sure.

Limp home mode could be caused by faulty O2 sensors or faulty speed sensors??
 

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Bogs down ... could be O2 sensors ...
Hmm, wish there was a way to monitor the O2 sensors
If O2 sensor shorted and out put is stuck high then ECU could cause it to run lean
Which would cause the bog down when touching the gas pedal.
Wait, does the 1996 to 2000 Elantra's have O2 sensors?? Should but not sure.

Limp home mode could be caused by faulty O2 sensors or faulty speed sensors??
Wouldn't a '95 have just one O2 sensor? (sorry to butt-in)
 

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Discussion Starter #19
Hey all,
yeah only 1 O2 on this car. Should i get one from the wreckers just to check it?

I did the fuel filter and the high pressure fuel line today, no change.... Hope the ECU isn't tombstoned. Surely if it was bad, the thing wouldn't run at all...


Lifter tick common with the beta? Only just started doing it really.
 

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Hey all,
yeah only 1 O2 on this car. Should i get one from the wreckers just to check it?
No, if it had two then the ECU would use the O2 values to determine how much fuel to use per firing cycle

I did the fuel filter and the high pressure fuel line today, no change.... Hope the ECU isn't tombstoned. Surely if it was bad, the thing wouldn't run at all...
I believe you're right. The engine wouldn't run at all if the ECU was bad.
There isn't a distributor. So it uses a crank sensor.

Lifter tick common with the beta? Only just started doing it really.
Yes, have had a tick with my 2001 Elantra forever.
And I change the oil regular ... every 3000 miles.


I am stuck. Don't know what else it could be.
I would try something like injector cleaner in the gas tank
Not too expensive to try??
 
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