Rev Limits at 2 grand.

[Trite]

Okay I made a thread about this a few days ago, but have since gathered more information.

So here it goes.

____

Car: 1992 Plymouth Laser, 1.8 Liter.

Symptoms:

The car rev limits at 2000 rpm. If you try to cross 2k, it will cut the spark and the car will stall for a moment and restart after the revs drop below again. The idle remains the same when the problem is occuring. There is no surge or anything out of the ordinary below 2k rpm.

The CEL comes on. Error codes trace back to the MAF sensor, but problem persists even if MAF is unplugged temporarily. I know for a fact that the car will run without the MAF, so if the MAF were causing this, then it the problem should not persist if the MAF is unplugged.


When:

The problem occurs after the car runs for a few minutes. It doesn't matter if I am above 2k or not at the time.


What I have checked:

I have tested and recalibrated the TPS sensor.
Tested the ISC Motor.
Cleaned all connectors.
Cleaned the TB.


Any help is greatly appreciated. My car has been down for about 2 months. I just dropped in a new transmission, and am getting ready to replace a BHG. I was hoping to have this problem solved by the time the BHG gets fixed.

Thanks in advance.

 

[GTM]

Okay I made a thread about this a few days ago, but have since gathered more information.
...
The car rev limits at 2000 rpm. If you try to cross 2k, it will cut the spark and the car will stall for a moment and restart after the revs drop below again. The idle remains the same when the problem is occuring. There is no surge or anything out of the ordinary below 2k rpm.
...

When was the last time you changed the fuel filter?

You can always remove it and blow backwards into a clean coffee can to inspect for water or other foreign material.

Cheers,
GTM

 

[Trite]

The fuel filter has not been changed. It can be though if you believe that it may be the cause of this problem.

I went ahead and took a video of the Tach when this happens.

It seems to precise on the limit to be caused by the fuel filter, plus the car runs normally before the CEL light comes on.

The first thing I thought was that maybe even though the car isn't at idle, it may be thinking that it is, so it won't let it cross a certain point.


http://streetracinglounge.com/media/videos/100_0905.MOV
3.85 megs

 

[Trite]

Okay here is an update.

I went out there and hooked a voltmeter up to the tp sensor to test the resistance thru the throttle range when the problem occured.

Everything came back normal.

I then pulled the plug for the isc sensor, and the car started running normally.

So does this mean that I have a bad isc sensor.

Here is an image of the plug just in case I got the name wrong. This is an old image, the car is currently completly put together.



Thanks again.

 

[GTM]

Okay here is an update.
...
I then pulled the plug for the isc sensor, and the car started running normally.
So does this mean that I have a bad isc sensor.

This makes sense and caused you to get involved with your repair knowing we can only offer an educated guess. The neat thing about coming here is that others are willing to pay attention and help you through a problem even if their ideas are wrong. At least you have established a discussion with back and forth info.

Cheers,
GTM

 

[Trite]

Thank you for that help.

Like I said, it is very much appreciated.

And don't go thinking I didn't take your advice. A new fuel filter is in the works once I cash my paycheck tomorrow.

About the ISC sensor, I was considering going to a JY and picking up a new ISC sensor and the motor and the bracket they are on.

So far the car has ran fine, but it has an awful idle surge. It idles at 1500 when I am rolling in neutral, and drops to 500 once the car stops.

Thanks again for your help.

 

[GTM]

Thank you for that help.

Like I said, it is very much appreciated.

And don't go thinking I didn't take your advice. A new fuel filter is in the works once I cash my paycheck tomorrow.
...
So far the car has ran fine, but it has an awful idle surge. It idles at 1500 when I am rolling in neutral, and drops to 500 once the car stops.
Thanks again for your help.

Your welcome, I've seen plenty of plugged fuel filters cause engines to act like some governor had imposed it's self at a precise rpm under load. With gas prices what they are people's driving habits have changed so they run their tank down to "E" and start sucking up the debris and water, this also goes to the gas stations not changing their filters and pumping garbage into your tank.

Idle surge can be caused by vacuum leaks, biss screw adjustment, ISC, ign. and valve timing to mention a few that come to mind.

Cheers,
GTM

 

[Trite]

Right now I am hoping that the idle surge, and high idle (1500-2000) are caused by that connector being taken off currently.

I'll let you know how it goes once I get that faulty sensor replaced. I also went and bought a fuel filter, I will be installing it once I get the sensor.