00 SVT poor high speed performance

[Ryan Casey Silas 0]

So to start out, my SVT is bone stock. off the line, it pulls pretty good for a 215k mile car, but one im up to interstate speeds it gets a bit sluggish and about 115mph is all it has, My girlfriends LX outruns me on top end lol. i know i have a stuck downstream O2 sensor that i plan on replacing soon along with some colder plugs, new wires, and a new coil. just wondering if theres anything i need to check along with that. I should also mention that i have an intermittent idle hang issue that i have already replaced in IAC for. My next move if the basic maintinence doesnt fix it is to monitor my fuel pressure at high speeds and see if i may have a weak pump but i would think that would affect bottom end performance as well, and i have already replaced the filter. I love the car and plan on building an engine for it hopefully within the next year but its currently my daily so im trying to get the small bugs worked out. Thanks

Edited November 11, 2019 by Ryan Casey Silas

[BuckeyeSVT 79]

Normally well before that age the IMRC usually dies and the secondaries fail to open which means no power on the highway. I was once passed by a stock Honda Civic when my secondaries were dead. I fixed that fast...lol. IMRC is the box on the front valve cover that connects by a cable to the lower intake manifold. It's not too hard to change, and easy to diagnose. They normally quit when the engine heats up and you can test by revving the engine up to 4,000 RPM. It should move the lever on the lower intake manifold if working correctly. If not, it's failed.

 

That's the easiest thing that kills power - Then we move onto exhaust restrictions like converters failed and such.

 

-Dominic

[Ryan Casey Silas 0]

ill check it. i always assumed it was working as i can feel the engine pick up a bit in the higher RPM range. If all else fails, ive been looking at headers and a cross pipe anyway lol. One quick question tho, are the 2.0 and 2.5 downstream sensors the same? i have a 2.0 parts car that i may steal one from if so for testing, but when i go through the trouble of getting headers then ill replace them all.

Edited November 12, 2019 by Ryan Casey Silas

[BuckeyeSVT 79]

The length of the sensor lead may be an issue, but electrically they are the same.

 

-Dominic

[Ryan Casey Silas 0]

sorry for the late reply. I do have a code for my SRV but its currently working. im gonna swap sensors tomorrow and do a compression test for giggles and see what i come up with. I daily the car currently 120 miles a day and im starting to notice that its feeling a bit sluggish through the powerband and im finding myself stalling out a lot more coming to a quick stop in the city. ill post my findings as soon as i can.

[Ryan Casey Silas 0]

well, looks like i found the culprit. Compression readings are as follows

 

#1 - 145psi

#2 - 145psi

#3 - 115psi

#4 - 140psi

#5 - 145psi

#6 - 125psi

 

To my understanding, minimum spec is 170ish psi, so looks like ill be hunting a 3L sooner than i planned.