bigs

For quite some time now, my '93 GTS seems just a wee bit anemic in the power department.

Sure enough, Ketchmi put 'er on the dyno this past week, and RWHP only came out to 265.

The car is an AT, so I expect maybe a 15% drivetrain loss. And we're at roughly 4500' in altitude, so I know I'll lose another few HP. But with a claimed 345 crank HP, I'd expect stock RWHP in a GTS to still be around 280-285ish, no?

The car runs perfectly smoothly in every way. Starts right up, idles smoothly, drives great... But it just seems to lack maybe 20 horses. I'd greatly appreciate any ideas. We're kinda scratchin' our heads here...

Here's a list of applicable work I've already had done on the car in the last 1.5 years:

1. Timing belt, WP, etc. (And timing still checks out correctly)
2. New 30lb fuel injectors and RRFPR - dyno tuned to the correct A/F mixture. (I put these on just in case we SC the car in the future.)
3. New MAF
4. New plugs, distributor caps, rotors, and Magnacor plug wires
5. New ignition coils
6. Transmission rebuild by a Mercedes tranny specialist in SLC
7. All fuses replaced and relays checked
8. TT rebuild
9. New high flow cats
10. New WOT switch

Plus a lot of other stuff not really performance/power related. Like I said, in every way, the car starts, idles, and runs smooth as silk. It just seems a little weak.

Any help in finding my lost ponies would be greatly appreciated!

Tom. M

First thing....check the flappy..make sure it's flapping.....otherwise...cam timing???

good luck finding the culprit.

Later,
Tom

Ketchmi

Flappy is working fine, shows up well on the dyno chart. One of the strange things is that this GTS only puts down 305'# of torque. I haven't checked cam alignment, only cam gear timing.

It also didn't like the SMT6, wasn't stable at all. It would tune/run fine one time, wouldn't idle and would run fat the next time you started it. Then maybe a different symptom the next time you started it like a high idle. Seeing the numbers made me think that maybe some one lost the 5.4L and replaced it with a 5.0L but it is a 28/50. If it were an S4, it would be right in the ballpark if not a touch strong but as a GTS?

Nicole

maybe it needs an Italian tune-up...

Ketchmi

But I'm Irish.....

Steve Cattaneo

Start with the basics, compression and leak down test, proper cam indexing and timing. You install new injectors and a FPR; confirm fuel pressure with a gauge. Ignition timing, does the controller advance the timing under a load. I would do the fuel and timing test on the dyno. Restricted exhaust, loosing the Y pipe from the manifold and drive the car. What is the air/ fuel mixture ratio under a load.

macreel

Bigs... git a rope !! We got rustlers. You're short 20,
Mark is missing 40, I was shy some at the last track
day ... what's going on ??

We gonna have us a necktie party.

Tom. M

Isn't 305 rw torque...just about right for an AT..?....that equates to 385 ftlbs using 20% loss? Stock is 369 ft-lbs..so..only the HP is at issue...could the oil ingestion of the 93' GTS's possibly causing probs?..how much oil does it use.?..

Just some random thoughts..

Later,
Tom

worf928

Hall Sensor. (see Powerless GT, Hall Sensor? or not? What else? )

The symptoms described are very similar to my GT - very smooth, but no power.

Or knock sensor fault.

Put a Hammer or Spanner on it and see if it can read a fault in either.

Bill Ball

Dave C is onto it. Hall and/or knock sensor. The rear knock sensor and the Hall sensor both clip to the harness under the passenger side fuel rail cover via a single connector. The connector came apart on my 89. The Spanner informed me "broken rear knock sensor" and "Hall sensor missing". This happened to me after I had the fuel rails off. I hadn't fully seated the connector. Thank JDS or I might never have found it.

bigs

Doesn't use all that much oil. I presume one would check simply by inspecting the plugs?

bigs

BTW, thanks to all for the ideas and links! If anyone else has additional ideas, keep 'em coming.

ErnestSw

Don't assume the MAF is in spec. Try another one to rule out a problem with yours. What's your mixture look like across the dyno chart?

worf928

There are four of these 3-pin connectors. One each for the two knock sensors. One for the Hall sensor and one for the speed/reference mark sensor. The rear knock sensor connects to the main LH harness toward the rear of the passenger side fuel rail (as Bill describes) and usually this connection is fastened via a bracket on the fuel rail. However. on my GTS the rail has no bracket and thus the connection is 'floppy' and I would suspect subseptable to damage from vibration.

The hall sensor connector is fastened to a bracket on the outside of the sensor cover which is mounted (deeply) behind the passenger side sprocket backing plate. The sensor connector connects to the main LH harness at this cover/bracket. This last bit of the LH harness should then run under the sprocket plate toward the front of the engine then up and around to rest of the branch of the LH harness that feeds the passenger side injectors. It is very possible to dislodge or damage the connector or harness for the Hall sensor when doing a t-belt R&R.

Recently, on a '87 that had lived it's life in a hot climate, I discovered that all of these connectors had a consistency very much like crumb cake. When I disconnected them for an intake/cam-cover R&R they crumbled to dust. The interpretation by the LH/EZK of the signals from these sensors is highly sensitive to noise. So, crumb-cake connectors, or damaged shielding in the harness or connector bodies can result in the signals being useless to the ECUs.

bigs

Actually, I had the problem with my original MAF, then I swapped one out with Dave Lomas with no difference. Now I have a new (rebuilt) one installed. Still no difference. So we tried three of them with no improvement.

I'd have to have Dave chime in on the dyno chart results, but since he didn't mention any problem, I'd have to assume the mixture looked fine.