Help a newb figure out what mods are on 91gt

v8muscle

New Member
Jun 18, 2005
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I bought a car from a girl knew nothing of what was done to the car. I knew it was a pretty good deal, but a little bit of a hack job too.

The car is absolutely equal in acceleration with a c5 from 2nd thru 4th gear (tested repeatedly), but the engine runs a little funny at idle, bucks at cruise.

So far I've searched these forums and checked the car.

I need to know what to look for because I see very few mods of consequence to make this fox hang with a vette and I want this car to run correctly 100%. Help a new stanger solve this mystery of why this car is quick and what to look for...

What I know is done to the car:

1) It has a tremec of some sort for the tranny, but I can't tell which it is while under the car. How do you tell?
2) 3.55 rear end
3) shorty headers and 2.5 dual exhaust
4) Moroso CAI
5) Removed AC/PS
6) Aftermarket electric fan
7) Lowered susp
8) Chassis supports welded on
9) Stock ECU

Everything else looks and sounds stock.

It is also giving me a code 22 (map out of range)
ECU gives codes for Primary and Secondary air systems not functioning.
Timing doesn't move when throttle is opened up at idle. (every other car I have checked does)
Fuel pump is lound and whiny, sometimes the engine pings when under throttle.

Please help, this learning curve is impossible without spending months surfing old posts.
 
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take some pictures of the engine and post em up!!!!!!!!!!!
c5's arent really that great by the way. it's not too out of place for a worked 5.0 to hang or beat one. the zo6 on the other hand is a monster........
without pics to go by, it's really hard to guess.
the biggest things you need to look at in the engine are the heads, and the intake manifold. any part numbers? brand names etc.... those are the main visible parts to guess at what you're running, without taking things apart...
or take it to a dyno, and see the #'s.... not precise, but it'll give you a better idea of what you might have.....
 
Post up a couple pictures of the engine bay:nice:

What color are the fuel injectors?

Open up the oil filler tube and see if you can see roller rockers...

If aftermarket, many will trim or remove the oil baffle.

Congrats on the car:)
 
The car looks pretty decently average... I'll get some pictures up by Sat if post is still alive.

Engine "looks" stock and gets 17-19mpg city + hwy
Injectors are orange, I ran the codes on google, and they appear to be 19lbs

Engine has some tapping going on for sure though. I will check the filler tube thanks.
 
If you're hanging with a healthy C5 then someone has done something. They are mid 13 cars.

Pinging usually indicates a lot of timing. You may want to check and see if the spout is installed. Look at the cable coming from the dizzy. There should be a short connector coming off of it with a grey plug stuck in it. That's the spout. When it's removed the timing is locked. That would explain the lack of advance when you rev the engine.
 
Spout connector is in. Throttle goose test didn't reveal any trouble. I guess I'm not a complete noob, but I don't know where to go from here.

The c5 ran a 13.7 at the track, and 12.8 on the 100 shot.

If you guys think these mods will make mustangs that fast, then say so, cause I don't see it happening... but then again I was a dsm guy before.
 
The code 22 can have a significant impact on performance.

Code 22 MAP (vacuum) or BARO signal out of range. The MAP or BARO sensor is pretty much the same sensor for both Mass Air & Speed Density cars. The main difference is where it is connected. Mass Air cars vent it to the atmosphere, while Speed Density cars connect it to the intake manifold vacuum. Its purpose is to help set a baseline for the air/fuel mixture by sensing changes in barometric pressure. The MAP or BAP sensor puts out a 5 volt square wave that changes frequency with variations in atmospheric pressure. The base is 154 HZ at 29.92" of mercury - dry sunny day at sea level, about 68-72 degrees. You need an oscilloscope or frequency meter to measure it. There is no way you can use a common cheap voltmeter or DVM to accurately measure the output signal.

The MAP/BARO sensor is mounted on the firewall behind the upper manifold.

Baro or MAP test using frequency meter - run the test key on engine off. The noise from the ignition system will likely upset the frequency meter. I used a 10 x oscilloscope probe connected from the frequency meter to the MAP/BAP to reduce the jitter in the meter's readout.

If it is defective, your air/fuel ratio will be off and the car’s performance & emissions will suffer

Some basic checks you can make to be sure that the sensor is getting power & ground:
Note that all resistance tests must be done with power off. Measuring resistance with a circuit powered on will give false readings and possibly damage the meter.
Check the resistance between the black/white wire on the MAP/BARO sensor and then the black/white wire on the EGR and the same wire on the TPS. It should be less than 1 ohm. Next check the resistance between the black/white wire and the negative battery cable. It should be less than 1.5 ohm.

The following power on check requires you to turn the ignition switch to the Run position.
Use a DVM to check for 5 volts on the orange/white wire. If it is missing, look for +5 volts at the orange/white wire on the TPS or EGR sensors. Use the black/white wire for the ground for the DVM.

Tremec transmissions:

photo_tr3550.jpg

Tremec 3550/TKO


photo_t5.jpg

Tremec T5

See http://www.ttcautomotive.com/ for a full listing ot the TKO variants
 
Just take pictures of everything and post them up. There are guys here that can rattle off mods just by sight alone.


Get in close to the heads and other areas of the engine as well.