Car runs like crap after thermostat install

[KevinLee]

1993 Z28, Automatic

I've had the car for a few months now and its always taken a long time to heat up among other problems. ( like, over 30mins of driving ) so I figured the Thermostat was stuck. Also, the Temp guage never went above the 1st peg after 100 so I figured it was just broken.

My other issue is that the car backfires very hard sometimes when I give it too much throttle too fast ( 75% and up from very low throttle ) and when I'm on the highway. These are always preceded by a complete loss of throttle response and the car begins to slow as if I had let off the pedal completely. It also sounds like it is misfiring so plugs and wires are going to be done soon. ( Don't have a lot of time to work on the car )


Today I finally decided to get one since I was sick of freezing my ass off on my days where I open up at work.

Drained the coolant from the Radiator, took off the T-Stat housing and immediately I notice something off. THERE WAS NO THERMOSTAT
I place the new one in ( Duralast 180 degree ) made sure no coolant leaked out and onto the opti, place some anti-freeze back in the system and start the car. It heats up rather quickly ( which is very odd since its 20 something degrees outside and somewhat windy )

I notice the temp guage going past the halfway mark. Ok, theres no coolant leaking, a tiny bit is dripping out of the fill neck so it must be starting to circulate. I check the fill neck and the coolant is bubbling. Ok, the car is all warmed up, lets take it for a short spin. The air-dam is there for a reason so I figure the car just had to get some air to cool down.

The temp guage gets VERY close to the red area but drops every so slightly a couple times during my 2 minute drive. I get home, and going up my driveway, it backfires hard. I park the car and it dies. Start it up again and it starts like crap ( as it has been doing since it got cold out. ) and dies right away. One more start, I give it a little Rev to 3 grand, it backfires hard again, I let off and it dies. I started it a final time ( to which it started like crap for a 3rd time and let it idle on its own ( I usually give it a little bit of throttle to keep it at 1k rpms for the first couple of minutes I drive it and then it idles fine ) and the idle is bouncing between 700-500 every second ( as if I was tapping the gas ) and I shut her down.

During the restarts, the temp guage was in between half and 100 and didn't raise up.

My first thought is the 02 sensors are completely shot. Ign Coil is brand new. Other than that, I'm leaning towards the Opti-spark.

I'm more than likely going to remove the T-Stat later tonight so I can at least drive it back and forth to work. If it will still run without one that is.

What are your guy's thoughts?

[steveo]

a car that runs without a thermostat for an extended period of time will build up carbon in the top end like you wouldn't believe. that much carbon can easily cause crazy popping/backfiring when it heats up, as hot carbon is perfectly capable of pre-igniting fuel.

i would highly reccommend a full seafoam treatment to see if it improves anything

the temp gauge getting that high? either you got the wrong type of thermostat (common mistake) or you didn't bleed it properly.

there has to be a reason it was run without a thermostat, too. you have to think about that.

[Workman]

Good advice man! Also if you didnt know this, You need to request a thermostat for the LT1 your brand and model, dont get the one for a sbc off the rack at your auto parts store!!! Theres a bleeder screw on the side of the water neck, put something Like a shop towel or two there around the neck/t stat housing crank her up and loosen that screw a little bit, when you see antifreeze/water start to come out you should be good. Thats what i did to mine when replacing the t stat and no probs at all!! WIsh you luck man let us know how it goes.

[KevinLee]

Small update : Started it up again ( started like crap as usual, revved it up and the idle evened itself out at 1k )

Let it run for a few minutes, was heating up much slower this time. The temp guage got 1/4 of the way up and I decided to give it another spin. Got out of my driveway and halfway down my block before it backfired. Went back home, parked it, tried revving it again and it got close to 4k before it backfired very hard again and stumbled extremely hard and I shut it off immediately.

@ steveo I bought the car at the end of summer and the PO only had it for a month. The owner before him is the one who did the " modifications " to the car. Terrible wiring under the dash, wires leading to nothing in the engine bay, etc. If anyone, it was that idiot who took it out for the summer, probably in a attempt to keep the car running cooler. ( I know the guy was an idiot because he traded this Camaro to the guy I got it off of for a Mitsubishi Eclipse )
Also, could you show me what kind of thermostat goes in the LT1? I have a feeling that the $10 one I have IS a generic SBC T-Stat.

[shoebox]

For $10 you probably got the wrong thermostat. It should look like this. Your running problem sounds ignition related. Could be opti, but you should check for trouble codes. Opti codes don't turn on the check engine light.

[cocobolo95]

You can get 93 wiring diagrams at BBB Industries- Premium Alternators, Starters, Power Steering Products
Your 93 has much different wiring than later lt1 cars. If you pm me with your e-mail address, I'll send you a copy of 93 pcm pin outs. It can be helpful. Also I'll send you scanner readings and what they mean. One of the essential tools for modern cars is a scanner that not only reads codes but does running sensor scans. Your 93, you can read codes using a paper clip, but a data reading scanner is still highly recommended.

[KevinLee]

@shoebox. The T-stat I got matches the one on the bottom right of the pic you linked. I'll check the codes tomorrow and report back with findings.

@coco I know how to use the paperclip method so I'll just stick to that for now.

[KevinLee]

Update : Well it appears that my SES light is broken now. Odd because I KNOW it worked when all this was going on because every time the car died, I saw the light and new it was off.

Light isn't turning on at all.

[sleepyTA]

Your coil may be taking a crap or you may need to change O2 sensors. You also could have gotten water into your opti.