Whoops... I have a 1988 Trans AM GTA L98 5.7L

Hey... I really need some help pin pointing this problem. Another guy had posted a message up with the similar problem, but his engine was modified, mine is pretty much stock internally. I went to the drags last night.. and my car improved to an average of 15.7secs to the 1/4 mile, as opposed to last months 16.57sec time. But... I think the trans Am *** was looking over me.. cause I pulled up to spin the tires a bit to clean them up.. and to my surprise, there was power and the RPM's shot up like a bat out of hell, and I ended up doing a full blown burn out.. that run ended as a 15.08second run. What the heck went RIGHT for that run????!!!!! The car felt like I thought it was supposed to... I red lined it on that burn out, and I wasn't even trying.. I loved it!!! Finally some power.. BUT then it went back to slow after 2 nice runs.

Any ideas? Here's some things I have done already...

- 3" Mandrel bent exhaust with high flow cat and flowmaster muffler.
- MSD 8.5 Ignition Wires
- MSD GM Blaster Coil
- MSD Cap and Rotor
- Holley Airfoil
- Recent MAF sensor and relay
- Fuel system flush
- 160 degree thermostat
- Throttle Body Coolant Bypass
- And the obvious.. K&N Air Filter

Please give me some pointers... Here are my suspicions....

- Ignition Module
- O2 Sensor
- Timing
- TPS
- MAF AGAIN!!??

Later Guys.. Thanks ahead of time

Happy Racing

[This message has been edited by nblanchard (edited September 30, 2001).]

 

should probably tell us the kinda car u got and what engine it has

 

What was the temperature?

 

160 degree thermostat way to low! If you have a stock computer you are now going to be running to good with a 160 stat. Go up to at least 180.

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1989 Iroc-Z 5.7 350, Blue, T-Tops

Lightly Moded:
Edelbrock Headers, Rebuilt B&M 700R-4 Tranny, Higher Stall Torque Converter, Airfoil, K&N's, Ported Plenum
-- Blue LED Bakelite Dash
"Just some 17 Year old spending every dollar I make on my car."

 

bullsh!t. i guess all these 160 degree thermostats in my vette and iroc are causing my engines to run bad, since they run perfect.

 

Mine ran bad with the 160 until i put back in the 180 stat

 

a thermostat isnt going to make your car run bad. otherwise it would still run like crap when its warming up if you had issues where your car ran bad under 160-170 degrees.

 

why is running a 160 stat bad i am currently running one in mine and all it really did is mad the engine run much cooler sence i live in the middle of a desert i thought it would be a good idea to run a cold one anywayz how can it affect your engine (bad)

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CHRIS
1983 firebird transam
edelbrock performer rpm intake 360*k&n intake 160 theroostat gitting trans raced up and lots and lots of plans 4 the future

 

its not bad. in no way, shape, or form. the cooler you are, the more horsepower you develop. cant argue with a proven theroy.

 

I don't think you guys would understand it even when told judging from this conversation. It has to do with the temperature of the quench area in the cylinder and it's effects on the completeness of the burn of the intake charge. Do a search on this.

 

I am running a 160. And the temperature of the quench area only comes into play very early in the warm up process. So, in my opinion with a properly running TPI this is a non issue.

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1991 Firebird
350 L98 (was a 305 TBI),T-5,Edelbrock TES and cat back,Accel manifold
NOS,subframes,jegster torque arm,MSD Digital 6
AFPR,Lakewood lcas
Hurst linelock,SLP cam (206 212 .480 .486),relocated battery,cold air,Hypertech chip,centerforce df,clutch
poly bushings and mounts
AFR 190s
Harland sharp 1.5 rockers
autopower rollbar

12.33 @ 114.83 juiced uncorrected

13.510 @ 102 non juiced uncorrected

 

However.... a possible answer to his question is Temperature. At the track, a cooler engine (read warm, not hot), tends to make you run faster. If you didnt cool down between runs, you will run slower. Doing a correct burnout will help your ET, as you will hook better. Even with street tires.

A side note: keeping your engine hot at the track will make you run slow, but consistent. A must for bracket racing.

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Mike Metzler (Desert86Roc)[*] Check Out:SpeedWorldMotorplex.com[*] Check Out:Chevrolet F-Body Online Part & Illustration Manual[*] My 86 IROC 305 TPI Page (406 build in progress)

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.362 @ 88.238 mph (uncorrected, headers, no NOS)
<><

 

Yes, my engine was around 90 celcius, this was after an hour of cool down, then someone blew there engine after my 2 good runs. So the car cooled down for about 30mins... and I ran at the same temperature, and it ran slow. Does anyone think a bad knock sensor would cause this bogging at higher RPM?

Thanx for all your help so far... I don't think temperature has anything to do about it though... Not a .6 to .7 second diference.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Temp may not be a factor in your case, but it does make a difference. You could be getting a lot of knock retard. You need to put a scanner on it while doing some test runs to see what is going on.

Just as an example though...When engine temp is around 150* on a 80* night, I can run a 15.36. If I let the car warm up to over 160*, I will start running 15.7s & 8s, a good half second slower (and yes, I was in closed loop before WOT, and have fuel pressure adjusted for WOT).


[This message has been edited by Desert86Roc (edited October 02, 2001).]

 

I found out whats wrong!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Yippee!! Had my car at the dealer today for spark plugs, brakes, decarbonization, and fuel filter (I usually do all this stuff myself... but I have no time after work).. I got th emechanic to take it for a drive test with the diagnostic computer.. and guess what they found out... TPS voltage was down to 1.42 Volts at WOT, when it is supposed to be 4 Volts. Checked the TPS itself, and it was ok... so the mechanic checked the voltage from the computer and it read 1.42 Volts, thus, meaning there is either a short in the wire (Blue Wire) or the ECM is bad.

So, anyone else having a gutless after 4000RPM problem, check this out!!! It is cheaper than the hit and miss method.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)