Where'd my horses go?

[bittertech]

1990 SHO, 3.0l 249k miles, 160k on the engine, 60k service (minus valve shims) done ~20k ago.

In the last 3 months by buttdyno tells me I've lost 20 horses. It doesn't pull as hard as it once did, especially before the secondaries open up -- and when the secondaries open up, it doesn't slam you back into your seat like it used to, just pushes you. The engine used to be freakishly strong, crisp on the acceleration -- its still pulls strong, but just not what I remember.

I ran seafoam thru the intake, new fuel filter. O2 filter was replaced when we did the 60k (we did an engine swap at the time) -- Plugs, wires, Crankshaft position sensor, 02 sensor. Apparently I've got a leak coming from the camshaft covers but I'm waiting to do a valve adjustment before I tackle that.

Think I might've broken the front motor mount recently too (also replaced during the engine swap), shifting has gotten sticky (especially in 1st and 2nd) and I noticed the engine had some play on an emissions dyno today.

So.. short of a compression test, any ideas what I could check out?

 

[SHOtime2511]

any oil in the plug wells?? any top end noise?? valve grinding ext.

 

[bittertech]

I'll check the plug wells, no top end noise that I've heard, rhythmic tapping at idle that coincides with RPM when cold.

 

[stevetatro]

Old fuel pump? According to those that have replaced an old pump, a new one feels like a performance mod. You may not notice the pump getting weak as its performance slowly declines, but put in a new one and zoom-zoom.

This is all word of mouth. Mine is still original.

 

[bittertech]

I'd read about the fuel pump, which is why I went the cheap way and tried a new fuel filter. It might have helped, but I think it was just placebo effect. I would think a fuel pump would help on the high end, but mid-range lag before the secondaries open up (3,000-3,900rpm) is the most noticeable degredation.

Without ODBC-II(?), is there a good way to see if its running lean?

 

[Huntervf]

Throttle cable may be stretching out some. This has happened to a lot of people...the result is that simply your car isn't going WOT even when you floor the gas. Have someone press the gas down while you watch the TB. If the butterfly doesn't open all the way then your throttle cable has stretched out.

 

[jelloslug]

The gas pedel arm bent in my '90. It would hardly go past 1/2 open...

 

[bittertech]

Throttle cable stuff.

Good suggestion, but it looks like its going right up to the stop.

 

[DHMag]

check your plugs for indications of overheating. i experienced a loss of horsepower over a year ago. inspected the Motorcraft 32PPs, after less than 8K miles, and they were clearly overheated. installed Bosch plugs, 2 ranges hotter, and havent had a problem since.

also, what plug wires did you install ? check them for resistance and insulation cracking.

 

[SonicRiot]

You must know your car pretty well... you've got a ton of miles on the clock. Why don't you check your motor mounts first and follow your own suggestion? Everyone else is just throwing out ideas... you obviously have SOME idea where to look.

Also, who rebuilt the engine? If the mounts are all ok, start with a leakdown and a compression test and save yourself the trouble of searching for odd things right off the bat.

 

[bittertech]

We were a 3 SHO family at one point, a Maroon 90 with 120k when purchased, a white 90 with ~10k purchased, and a green 91+ with ~100k and sold cuz it was a northern car. When I decided to sell my SHO (the red one) it had 140k on it, and my dad, with his now 222k miles on his engine, decided to do an engine swap.

2 years later (yeah.. lots of life-stuff happened in between there) we get my engine into his chassis, and I total the car I had sold my SHO for, and thus I'm handed down the white with my engine that has 140k on it. Now its 3 years and 20k later, and I've known this engine for 40k.

I had moved across the country while the majority of the engine swap took place, with my father doing most of the work. I'm not much of a gear head, but I'm a helluva computer tech and alot of troubleshooting instinct crosses over to cars -- but I'm afraid I don't have enough knowledge to test what I'm guessing at or know if what I'm thinking is correct (plus my dad is a private pilot and we've relocated most of our tools from the house to the hangar which is now 60 miles away).

What does a burned sparkplug look like? I guess I really should pull some (I do know what a fouled plug looks like, I learned alot of small engine repair from my grandfather) plugs and take a gander.

As far as what went into my SHO -- dad did (almost) all of the work, and bought most of the parts from Doug Lewis (cps, o2 sensor, plugs and wires, mounts). And if I ever get another car, he gets the SHO. And my brother just got a Volvo 850 Turbo (222hp) so now I *must* get this car back into shape (seeing as I'm the oldest sibling.. its a pride thing..) I probably won't have access to a compression test till I get down to the hangar which'll be in 2 weeks or so.

 

[SWM]

Just a thought, my horses started to go as the "crank cancer" began to show itself. 94ATX many problems...

 

[Camarok]

Old fuel pump? According to those that have replaced an old pump, a new one feels like a performance mod. You may not notice the pump getting weak as its performance slowly declines, but put in a new one and zoom-zoom.

This is all word of mouth. Mine is still original.

well... a cheaper test would be to replace the fuel filter, if that thing is cloged, gas aint getting through! See... it's one of the forgotten filters!