98 Cobra down on power

[98Snakebite]

Ok I have had my Cobra for almost 2 years now and in the last couple of months I have noticed a a marked decrease in performance, notably in the top end. I had the car dynoed recently, and it came up with 252 rwhp and 248 rwtq. Near as I can figure, this means I have like 285bhp. The car has a MAC CAI, and a flowmaster cat-back. It has 90,000 miles, and is well cared for. The ECU isn't throwing any codes. This car is one of the rare ones that really ran good from the factory, as I have has several friends that have had 96-98 Cobras, and mine could outrun all of them when I first got it, despite it being a droptop. If I were guessing by a seat of the pants assesment I would say I am giving up a solid 35 horsies, maybe more. The car also just doesn't sound as "tight" as it used to. Does anyone have some ideas that I can check?

Thanks in advance.
Arin

 

[COBRA90GT]

What do the sparkplugs look like? Dirty air filter? Have you ever cleaned the IMRC's? Just tossing out a few ideas...

 

[98Snakebite]

The spark plugs are new. (well a month old). The filter has a fresh cleaning and oiling. I have never cleaned the IMRCs but I had the controller replaced by my dealer about a year ago. Also, when it was on the dyno I could hear the butterflies open at 3,250. Also, when I got the car, it used a slight bit of oil, now it uses none.

I think a turbo would rectify any power I have lost....

 

[blkstangman88]

the IMRC valves are probly clogged. ive seen a pair of these valves that had 30k miles on them and they looked like the car had over 200k miles....lol they design has its pros and its cons but the worst con is the location of the injector and how badly the IMRC's clog. id say clean them.

 

[tomustang]

^ IMRC plates

 

[mcclellan99]

It could also be the IMRC cable, they have a tendency to frey, then the motor cannot open the valves very efficiently.

 

[SVT32VDOHC]

I've never had an issue with my plates.

And those numbers are normal numbers for a N/A 96-98 Cobra.

 

[NotA5oh]

I found a webpage around a year ago with detailed instructions and pictures about cleaning/replacing the IMRC unit but I cant seem to find it now. Does anyone recall seeing the site or something like it?

 

[BlownFiveLiter]

Originally posted: 04-20-06, 01:41 PM

Let's assume the issue has been resolved, in the past 3 years.