Hello,I presently own a 91' firebird with the L98 350. A few weeks ago I drove the car with the radiator cap loose . About 50 miles or so. Yeah,I know. Anyway, I smelled coolant and pulled into the nearest service station to get water. Temp said 240. Well, while I was on the beltway the cars temp said 160 or so. So, i thought it was fine. I Left it running while I added the water. Turns out the coolant escaped in the form of steam of course. Cars temp hit 240,like i said. I added the water at the service station. Cars temp went down to 220 ,then gradually lower. Anyway the car now runs really rough under acceleration. It does not run hot, no white smoke,no oil in the coolant,nor any coolant in my oil. The dipstick looks fine. Idles normally too. Now,it does have a different exhaust note though. Sounds hollow. More high pitched under acceleration? Just doesn't sound like the same car. I checked for codes,none to be found. Car runs at 160-185 degrees. Really bogs down upon acceleration. Does have a thermomaster thermostat and chip. Should be running at 160. However,after the event of driving with a loose cap and loosing all of my coolant, it has been running a little hotter.(185 max) I noticed blowby on the lower manifold around the pcv hose. Wasn't there before. Cleaned the pcv. Checked the fuel filter(a little dirty). Checked the distributor cap and rotor (not bad,a little corrosion) so i cleaned it up.Car runs a little better. Now this is the kicker, when the car is really low on gas (eigth of a tank or lower) It runs great upon acceleration and good all around! WTF is happening here? I am almost thinking I might have a bad fuel pressure regulator? knock sensor? I need help with this one.

 

Well for starters ide check the timing. Timeing thats off can make a car hesitate/sound different/run hotter. Actually ide really take the whole ignition system apart because if it got wet from boiling over it can do some funny things. Plus the ignition moduals dont like heat or water anyways may want to have it tested. Something else you might want to not is running a car down at 160 i dont know if thats even hot enough for the car to go into closed loop operation may wanna bump that up to alteast 180. Now a bog is usually caused by bad ignition timing or a lean mixture so ide have a look at that fuel pressure. Also although probably and hopefully it will be a waist of time, ide also run a compression test. Reason being if when the car leak antifreeze the cars temp readings may not be accurate so you may have been alot hoter than you thought you were. Also air pockets can cause hot spots which can cause cracked heads ect. Since you dont have any smoke or water in the oil i wouldnt be too concerned but its something ide be curious to check especially since you had so much blow by you didnt have befor and the higher temps. You have an interesting one thats for sure it will be interesting to get to the bottom of this.

 

Make sure you do a compression test and may even want to do a leak down test. My car had overheated twice on my new motor after I kept loosing my belts for the water pump. That problem had been solved, but I think it did more damage on my motor then I thought. My rings in a couple of cylinders are shot detected after I did a leakdown test and thank god it didn't ruin anything else. I am in the process now of taking my motor back to the shop that built it and have new rings installed. Bearing and everything else in the engine is still new and the builder said all he wil more than likely have to do is just replace the rings, rebalance the lower end and clean up the block.

 

Hey man, Well, i disconnected my knock sensor today and the problem amplified! Remember how i said that under acceleration it kind of felt like the power wanted to come through but was being blocked, almost like when you have a bad wire or plug. Well, disconnecting the knock sensor amplified the way the car acted under acceleration. Actually, it barely ran with the knock sensor disconnected. No power. Felt exactly like I had forgotten to hook up like three plug wires and drove the car! Can you imagine? I think you know what i mean. Well, I am starting to think it may be an ignition module? or computer may be bad. Tell me what you think. Where is the damn ignition module on the 350 TPI's? or is it controlled by the computer? Please let me know something. Later