Down about 20 HP. Ideas?

[93rev2sev]

What are the symptoms of a SHO with a faulty secondary fuel pump circuit?

The reason I ask is that I think(I know) my silver 93MTX is down a significant amount of HP...at least 20WHP according to some quick math (ask my brother). Other than the low power, it runs and sounds great so I don't think it's missing, just way down on power.

The secondaries ARE opening at @ 4k and they do increase power, but still... not where it should be.

I will be swapping MAFs and O2s between the cars this week to try to find the cause but I will NOT be swapping fuel pumps for obvious reasons.

I can pull codes but I'm terrible at reading the blinks. I know I got 114 and 116, but I think I got o2, MAF and fuel pump codes too.

The MAF and O2s are easy enough...I just hope that helps...

 

[dantheman68]

plugs (gaps too)? wires?...

catalytic converters?


O2s sound good though

 

[AREA 91]

Pull codes
Check fuel pressure
Check plugs/wires
plugged cats
bad thermostat
MAF
O2's

 

[SASHO91]

Id start with cleaning the MAF as its the easiest.... regaurdless of codes.
But if that dosent help, then check fuel pressure and change the fuel filter(10 bucks)... then possibly the plugs....
After those, it would probably be an O2 sensor problem.

I notice that when my MAF gets dirty, the car starts running very lean.

 

[93rev2sev]

OK I'm going to swap MAFs tonight.

 

[projectSHO89]

The "secondary fuel pump circuit" is simply the circuit that supplies the pump from the output of the CCRM. Fault codes related to it are seldom useful unless the car is completely dead.

While some of the othe items suggested are possible, most will not cause your symptom.

I'd suggest checking your timing belt tension. A stretched belt allows the cam timing to get very sloppy and will dramatically cut top end performance.

Steve

 

[93rev2sev]

The belt is tight. I bought the car last month and it needed a CPS. I re-used the belt because I could still read the lettering and see the lines and it looked like it was in pretty good shape. I snugged it up good and started the car. I could hear the belt and thought I better not squeeze it that hard...so I loosened it slightly. I can still hear it, but barely.

The black car (the FAST one) had a new timing belt about 40k ago. I'm sure it's sloppy as **** by now since I havent touched it since.

If you are saying a loose belt will slow the car down, I certainly agree.

What about an old belt that's been retensioned? I guess not so much...this is a very noticable amount of power.

1.3 seconds longer going from 60-80 in 3rd gear. It is also very repeatable.

 

[dantheman68]

wait... does it feel less powerful or are you timing it and determining that its less powerful?

sometimes if youre timing it it can be off, since the speedo and the stopwatch arent nessicarily prescision instruments.... but usually if you can FEEL that teh car is slower, it is

 

[warmonger]

are you sure a rear calipar isnt sticking?happened to me

 

[93rev2sev]

I was feeling that it was slower...I told my brother that it was slower....he said "let run em"...so we did. We ran side by side and the black car blew away the silver one.

Then we checked the speedos...they were the same at the same RPM. Then we timed them, repeatedly. The silver car is 1.3 seconds slower from 60 to 80.
Here are the times:
Silver 05 Stang GT 5sp: 3.9-4.3 seconds
Black 90 MTX SHO: 5.3-5.5 seconds (+~1.2sec)
Silver 93 MTX SHO: 6.4-6.8 seconds (+~1.3sec)

My brother calculated that the silver one is down 20 WHP.

 

[93rev2sev]

Rear calipers are not sticking. I have felt that in the black one. The silver car will settle into cracks in the concrete at stops. Rolls real easy.

 

[SHOtime2511]

Pull codes
Check fuel pressure
Check plugs/wires
plugged cats
bad thermostat
MAF
O2's

do this stuff and you will find your problem

 

[93rev2sev]

FIXED!

The SHO is Super again!

I cleaned the MAF with no change and moved on to wires and plugs. I was about to swap O2 sensors when it started to get worse. I unplugged the MAF and it was better. I put a known good MAF on there this morning and it's night and day.

I have all my powah back!