half throttle woes

[eacyde]

No matter what gear I am in or what speed I am going, if I push the throttle more than half way it feels like im pulling a 10,000lb trailer.

The car accelerates great until you get to half throttle. It almost seems like the rev limiter is kicking in.

What could be causing this issue?

The car is a 1995 MTX ~106K Miles

 

[jimtash]

Codes?

 

[eacyde]

I'm going to try to get out and get them later. Tonite the family dinner

 

[SHOspazz92]

If your just cruising and then put your foot down (in the same gear) and it does this I would think its a spark Issue. My Track car will do this if there is water in the plug wells. It also did this when my coil-pack started going bad. I have no "proof" to back it up, but I would bet its a spark issue. Run the codes, see what it says, it should be able to tell you that one of the cylinders is not firing correctly (From a bad wire, coilpack..etc).

-Sam

 

[eacyde]

Here are my codes
189 - Adaptive fuel rich limit is reached (LH).
211 - PIP circuit fault.
214 - CID circuit failure.
452 - Insufficient input from vehicle speed sensor (VSS).
542 - Fuel pump secondary circuit failure.

Not sure what PIP & CID are?

How do I fix this stuff?

 

[eacyde]

Forgot the KOER codes
116 - ??
225 - Knock sensor (KS) not sensed during dynamic response test.
538 - Operator error (dynamic response / cylinder balance tests).

I followed the directions and the balance test didnt work.

 

[rubydist]

you didn't follow the instructions properly, that is why you got the 538 operator error code.

pip is the crank sensor - I have never seen that code except for a failing crank sensor. a bad crank sensor will leave you stranded, so you need to replace that.

cid is the cam sensor - you may have a bad sensor or connector/wiring issue there - nearly always you have issues with the tach not reading properly as well.

vss is the vehicle speed sensor - that is on top of trans and the speedo cable plugs into that. on the mtx, the only significance to a bad vss is that 1) cruise will not work and 2) engine will drop to idle speed before you come to a complete stop rather than staying up at ~1200 rpm until you stop.

your issue at half throttle + is unlikely to be any of those. that is the typical symptom of a tps that is going bad. your 189 rich limit code could be related to that because the tps may be telling the pcm that the throttle is closed when it is not, therefore more air than expected so the pcm is richening the mixture.

I would change crank sensor and tps, and see how it runs after that.

 

[rooster]

How old is your fuel filter?

 

[jimtash]

Check all the vacuum lines and connections as well. Anything that operates with a vacuum solenoid or switch at certain throttle positions or RPMs is suspect. Nor will any issues be apparent until those vacuum operated parts are turned on. And you'll notice it at part throttle more than any other throttle position.

 

[eacyde]

Thanks for the tips. I'll harvest the parts from my parts car and report back.

The VSS symptom described above is exactly what is happening now, sometimes the car stalls out, but usually drops the RPM to the point that the oil light comes on briefly.

Fuel filter needs to be change as its age is unknown.

 

[sdpatt]

Another possibility of poor performance at high exhaust flows is a blocked exhaust system. In the SHO's case, this would likely be due to one or more failed catalytic converters. Tap on the cats with a wooden broomstick to check for the death rattle of broken ceramic internals.

 

[eacyde]

Another possibility of poor performance at high exhaust flows is a blocked exhaust system. In the SHO's case, this would likely be due to one or more failed catalytic converters. Tap on the cats with a wooden broomstick to check for the death rattle of broken ceramic internals.

That is definitely not an issue since the previous owner removed the cats.

 

[quake]

Same thing happen to me,Ifound out it was the fuel sock in the tank.The car ran fine at a idle give it gas,but soon as you steped on it nothing a little jerking and no power.

 

[eacyde]

After driving the car a bit more, it seems that the secondaries are not opening. Is there any way of knowing for sure if they are working or not?

 

[rubydist]

the secondaries are open when the engine is off. vacuum is applied when you start the car to hold them closed. you can visually confirm that the actuators are working properly by noting their position before and after you start the engine.

 

[eacyde]

So I ran the codes again and I only got 452 & 542 for KOEO

and 538 for KOER

The car seemed to to the balance test but I still got the 538.

I pushed the throttle to get 2000 RPM them snapped it to the floor for WOT. What am I doing wrong?

Thanks

 

[rubydist]

iirc, you have to mash it to the floor until the rpms get over 2500 at the appropriate time in the test cycle.

 

[eacyde]

iirc, you have to mash it to the floor until the rpms get over 2500 at the appropriate time in the test cycle.

That is what I did. I'll have to try again.

 

[lincster2]

Similar codes

I'm having similar problems plus the engine just dies sometimes.
Key On Engine Off
Codes
211.... PIP ie. crank sensor
452.... VSS vehicle speed sensor
542.... basically tells me that at one point in time the engine stalled

Key On Engine Running
538....not enough RPM change during "goose test"

I've performed these tests 8 times over 2 days.... engine warmed up...using a OBD 1/2 tester from O'Reillys Auto Parts.
Now let's go through each of the codes.....

211 .... this code came up only once during the 8 tests. If the crank sensor is going bad that would explain the engine dying.

452 .... this code came up all 8 times. A bad vehicle speed sensor can cause a non operation of the cruise control & the "moving" idle rpms to drop below the correct 1,200 rpms. My car has both problems. Possibly bad connectors or wiring.

542 .... fuel related, or just reporting that the engine stalled. Many other codes would pin point a fuel problem. Replaced the fuel pump, engine still dies randomly.

538 .... the tester prompts when to raise the rpms, all 8 times it reported that not enough rpm change had occurred. Floored the accelerator, once 5 full seconds, other tests snap, 1~2 seconds etc.
My thoughts are that the faulty crank sensor is not giving information to the tester/car's computer.

In addtion to the engine stalling, when applying extra fuel to a smooth running engine it would stumble slightly then accelerate. Checked the fuel pressure.... it was running way too high... 70 PSI, about 35 PSI is normal when running. Change the fuel pressure regulator.. stumbles no more.

Many mechanics told me that the only way to positively test for the true cause of the engine dying is to test when it happens, engine dies then test it right then & there. It's like trying to charge your battery by running around hoping that LIGHTING strikes it.
Anyway I'll report back when I change out the crank sensor. Hope this post helps you.

 

[eacyde]

Something interesting happened yesterday, The car stalled and I bumped in first gear. It was a bit violent, but the car started as usual. However, the battery light came on and it idled at 1200RPM.

It is still idling at 1200RPM and the battery light is out. Would this symptom be related to the failing VSS?