WTF: RPMs hit a wall at 4Krpm, what can this be?

[Gnnr]

Well swapped an early model 95 KA engine into my late model 95 240. I'm automatic. Engine was a junkyard pull. The engine works great, it revs fast as hell, and the transmission shifts quickly (didn't change transmission)...but when I try to redline it when I'm at WOT, it wont go past 4K rpm? It revs real quick then it hits like a brick wall and wont go anymore? As if it had a revlimiter there (which I hear AT transmissions don't have). It struggles and very very very slowly starts to crawl up to 5K.

I took it to the mechanic that did the swap for me, and of course what I call Mechanic's Syndrome kicked in. You know, when you have a problem and it magically dissapears when you take it to them, making you look like a dumbass. Yeah, so he gets in and redlines it twice no problem. I leave get back on the highway, it wont redline. Grrrr.

Whats causing this!? Its really annoying. I can't get past 60mph. *sigh*
Thanks in advance.

[breakindrifts]

Your MAF sensor is probably disconnected or busted, but I dont know about your mechanic taking it back and having it work again

[cotbu]

Is your mechanic doing it under-load? I'm not getting that from the thread. Hmmm you are, right? That maybe the difference. It may not have the power to reach the "redline". What's your speed? why are you trying to redline anyway?

[Gnnr]

Yeah, sorry forgot to mention that. He was in Park when he did it. Altough when I tired it once in Neutral it bogged slightly when I hit 4K rpm. Anways, yeah, when its under load (in drive) is where I'm really getting the problem. So it might be a defective MAF or something? My idle is perfect, so this is wiered...no ruff idle.

[breakindrifts]

I know if you disconnect the MAF sensor on a KA the car doesnt revv above 4k rpms, just seems to hit a revv limiter. This may not affect idle, but do you notice the car running rich at all?

I just say this because it seems like the most common reason your car would seem to hit a revv limter at 4k rpms.

[Gnnr]

Well, If ound out my spark plugs are bad. Do you think this could be the problem, because they wouldn't be getting enough spark (higher revs needs more spark) at those rpms??

I guess I'll have keep the speeds low for now...I'm so broke right now can't even buy spark plugs...have to wait 'till I get paid 2morow and change them over the weekend.

[kazuo]

Its the MAF or the speed sensor.

Try the speed sensor first by disconnecting it from the harness, and see if the problem goes away.

If it doesn't, then test the MAFS using a DMM.

Good luck

[SHIFT_control]

Is it an OBDI engine into an OBDII car?

[Gnnr]

Originally Posted by kazuo

Its the MAF or the speed sensor.

Try the speed sensor first by disconnecting it from the harness, and see if the problem goes away.

If it doesn't, then test the MAFS using a DMM.

Good luck

Where's the speed sensor? Whats a DMM? And how do you use it on the MAF?

Originally Posted by SHIFT_control

Is it an OBDI engine into an OBDII car?

Uhh, not exactly. I asked about this HERE, and they told me it shouldn't be a problem. I'm going to check the ECU for codes because my engine light came on when I tried to redline again. It turned off later in the day though, but hopefully its still stored.

[Blues13]

It's the plugs.. replace them first and make sure they're gapped correctly. Can't afford plugs?! They're cheaper than a half tank of gas.

[Gnnr]

Yep, the situation is that bad lol. I'm running on a tank I filled a few days ago. Not to worry, pay day is today.

[240meowth]

fuel filter or pump ish? =b But my best guess is MAF sensor, clean it w/ a electrical connector cleaner inside and out as well as check the connection.

[kazuo]

Originally Posted by Gnnr

Where's the speed sensor? Whats a DMM? And how do you use it on the MAF?

Speed sensor is on the end of the transmission, ALL THE WAY AT THE END, next to the driveshaft.

Its a big nub thats held into the tranny with a 10mm bolt on the bottom. There is a harness connector right there, disconnect it and see if the problem goes away.

DMM = Digital Multimeter. Search google to learn what it is and how to use it. You can get one for like $20 at RadioShack. Not the best, but gets the job done.

As far as how to check your MAF with it, http://www.zeroyon.com/

Download the FSM, and check the troubleshooting section for the MAF Sensor. It walks you through it.

Good luck

[Gnnr]

Well changed the spark plugs to some NGK Iridium IX plugs, but still the problem persists. The plugs where bad though. I guess this leaves me with the MAF then. I have a new fuel filter and the pump is fine. I have a multimeter that came with my PC toolkit, so I guess its on to the FSM. I also found the water pump belt is quite loose. Its like everytime I get under the hood there's a problem. Hopefully its not raining tommorow morning (stupid hurricanes!) so I can get to fixing/troubleshooting. Thanks for the help again, guys.

[Kinematics]

Check/replace your TPS. I had this issue in my 90 coupe and the TPS was bad.

[Gnnr]

Okay, this might be it. The MAF connector is the brown plug that goes into the Squared box, correct? Well this plug when looking at it from the front of the engine bay has 4 little wires, correct? If so, I'm missing one wire because I only have 3. From left to right I see White/Black/Black/ [nothing] . I can see the little itty bitty remains of a white wire. If there should be a wire there, then I think this is it.

Could I try finding this little white wire and recconnecting it, or could I purchase a new sensor or something? What should I do?

[kazuo]

Gnnr,

Did you even try the speed sensor like I recommended?

I've known several people experiencing a similar issue and the problem has, almost always, been the speed sensor.

Also, unsure about KA24DE, but KA24E/SR20DET have a 3 wire MAF, it could be entirely posible that the DOHC KA has a 4 wire (I've never owned one, nor do I remember offhand. Cross-reference the FSM to verify how many wires its supposed to have)

I'm willing to bet money its a MAF/Speed Sensor issue.

Good luck

[Gnnr]

I was looking at the FSM, but I can't tell from the diagram how many it should be. I see it talks about A, B, C, and D connections so I think there is 4. I can't find "speed sensor" in the index of the FSM. Anyways, I would think its more than likely something in the engine bay, since I just got my engine changed. Because my previous engine had no problem running all the way past 4K, did so like a champ. I know they only touch the transmission for aligning it up again, and the transmission is the same one. Is my reasoning correct?

[edit]
Ok, found it under Vehicle speed sensor, but from reading the description of its purpose, it dosen't seem like that can be it. I failed to mention that I can go over 60mph now...just have to let the tranmission shift at 3K. Just I was trying to go over 60mph shifting at 4K. But it would just hit like a wall at 4K and wouldn't go into next gear. If I let my foot off just a little it shifts over at a lower RPM. Note: By shifting I mean controlling the pedal so it shifts at desired RPM (since I'm automatic) into next gear. Hope that paints a clear picture

[Rennen]

FWIW:

I had a similar problem the first time we got the ITA 240SX out to the track... it felt like it hit a wall at 4k rpm in 3rd, 4th, and 5th gear. About 13 hours of on track trouble shooting later, we discovered that it was related to the speed sensor... but more specifically, that the speed sensor's signal was routed through the gauge cluster before it was sent to the ECU. Since we didn't have a gauge cluster in the car (ITA racecar), it was interrupting the signal.


So what I am saying is, check your connections with the speed sensor and the gauge cluster. Maybe even grab a DVM or DMM and go through the troubleshooting sections in the FSM related to the speed sensor. Of course this is on a 1990 with a KA24E, so it's probably not exactly the same, but a good place to start

-Matt

[kazuo]

I posted this earlier in the thread:

Speed sensor is on the end of the transmission, ALL THE WAY AT THE END, next to the driveshaft.

Its a big nub thats held into the tranny with a 10mm bolt on the bottom. There is a harness connector right there, disconnect it and see if the problem goes away.

I told you where it is, it takes two seconds to do, and wont hurt your car... just unplug it and see if it goes away.

Pretty please?

[90sr]

ur hitting fuel cut i think, my buddy had is 1g dsm and felt like he hit a brick wall at round same rpm, turned out he was hittin fuel cut.

good luck

[captain hammerite]

I'm having this same problem on my ka24de but my engine is manual. Could the problem still be the speed sensor?

[kazuo]

90sr: Yeah, but he's hitting the cut prematurely due to a sensor malfunction, mostl ikely the speed sensor or the MAFS.

captain hammerite: Yes, it probably is. Disconnect it and see if it goes away.

[Gnnr]

Just got my power back, stupid Hurricane Wilma! So, back to my dilema...

Originally Posted by kazuo

I posted this earlier in the thread:

I told you where it is, it takes two seconds to do, and wont hurt your car... just unplug it and see if it goes away.

Pretty please?

Alright, I will. If it turns out to fix the problem, can I just ride around with that plug disconnected or do I need to replace it?

If its worth mentioning, I pulled the code from the ECU, it was giving me a code 37. Closed loop. On the chart that refers me to EC-139 on the FSM for the oxygen sensor. Dunno what to make of it.

[kazuo]

Originally Posted by Gnnr

Alright, I will. If it turns out to fix the problem, can I just ride around with that plug disconnected or do I need to replace it?

If its worth mentioning, I pulled the code from the ECU, it was giving me a code 37. Closed loop. On the chart that refers me to EC-139 on the FSM for the oxygen sensor. Dunno what to make of it.

Yes, you can ride around with it disconnected. Your speedometer will NOT work, though. No other issues beside that.

I seriously doubt the o2 is causing the fuel cutoff, but you can look into it.

The FSM has a troubleshooting guide on how to test the o2 sensor to see if it needs to be replaced.

Good luck

[WhoNeedsTraction?]

i have an 89 and i know it has the sohc but you might check the egr port on the intake(or something like that). mine had the same problem and i tried everything that i could think of but it still crapped out and died at about 3000-3500rpm. it was a butterfly valve on the intake side that got stuck and clogged with crap. cleaned it out. works fine now. just my .02

[KrazyZenki]

If it hit a wall just jump the wall....duh]







cuz you got gas

[Gnnr]

Originally Posted by kazuo

Yes, you can ride around with it disconnected. Your speedometer will NOT work, though. No other issues beside that.

I seriously doubt the o2 is causing the fuel cutoff, but you can look into it.

The FSM has a troubleshooting guide on how to test the o2 sensor to see if it needs to be replaced.

Good luck

Alright, cool. Thanks. It has to be that or the MAF is what I figure.

Originally Posted by WhoNeedsTraction?

i have an 89 and i know it has the sohc but you might check the egr port on the intake(or something like that). mine had the same problem and i tried everything that i could think of but it still crapped out and died at about 3000-3500rpm. it was a butterfly valve on the intake side that got stuck and clogged with crap. cleaned it out. works fine now. just my .02

It dosen't die, more like hit a bottleneck at 4K rpm. I'm going to try and clean the throttle body also when I get some time to work on the car again...probally next weekend.