2nd Gen Engine won't rev

[jbbatten21]

I have searched the boards without much success. My 97 Mark Viii has 52k original miles, but sat without care for around 5 years. I have already cleaned the tank and replaced the fuel pump as well as cleaned the fuel lines and replaced spark plugs. The car runs good, but will not rev past 3k rpms when it has a load on it. When in park or neutral it will rev freely with no problems. I already did the seafoam treatment and made sure the IMRC are moving freely. Right after the fuel pump replacement the car ran great, it would pull hard to redline through 1st and 2nd gear, but every now and then it would lose power to the point of not being able to hold highway speed, but after a 10 sec pause it would be back to normal. I checked fuel pressure and get around 34psi with the vacuum line connected and 40psi with it removed. I am at a loss on this one. Any direction on where to start next would be great.

Thanks.

 

[Dave 88 LSC]

I had a similar problem before I changed my fuel pump. Car would cut out when hot in warm weather.

Attach a fuel pressure gauge and tape it to the windwhield. See how the pressure is when you drive the car and what happens when the problem kicks in.

TPS could also be bad.

 

[driller]

X2 - you need to check the fuel pressure under load.

 

[chris2523]

X2 - you need to check the fuel pressure under load.

x3

 

[LowLincoln]

clogged cat(s)? Hear any rattling under the car?

 

[Buckeye68]

Mine is doing it atm and I have a 255 to put in it this weeks

 

[zmt325]

mine did almost the same thing i cleaned the map sensor and voula fixed

 

[Chris_Murder]

mine did almost the same thing i cleaned the map sensor and voula fixed

Do you mean maf sensor? I've seen dirty msg sensors do wacky things to mn12's and fn10's alike, but I don't recall fn10's utilizing a map sensor.

 

[zmt325]

Do you mean maf sensor? I've seen dirty msg sensors do wacky things to mn12's and fn10's alike, but I don't recall fn10's utilizing a map sensor.

yes i pulled it out of the air box, sprayed the shat out of it, and it was all good. you can test it by unplugging it. it wont idle right but it should rev once unplugged if it is the problem

 

[Dave 88 LSC]

Cleaning a Mass air sensor is never a bad thing. Just use a Mass air sensor cleaner spray and spray it well.

 

[slowmkviii]

Also check all cop. Boots for cracks and did you have any oil in
The spark plug area.

 

[jbbatten21]

Thanks for the replys. I picked up a fuel pressure guage, but it is junk so I am waiting on another one so I can test fuel pressure under load. I have already cleaned the MAF and I have a code reader that gives me live data so I know the TPS sensor is working as it should. The readings on the MAF also seem to be good. I will check the COP boots and make sure there is no oil around the plugs.

Thanks guys.