Arrgh!

Here'* the history:

- 96 Bonne threw check engine light
- Mechanic checked code, MAF Sensor fail
- Replaced MAF
- Removed TB
- Checked UIM - no warpage, no holes/degradation of manifold
- Repalced TB Gasket (degraded)
- Mechanic also flushed coolant system, refilled, and replaced serpentine belt as well
- Got car back
- 3 days later, Car nearly overheats on way home. Coolant overflow tank is empty. Put more coolant in, get car home.
- Let car cool.
- Replace spark plugs with NGKTR55'*, Needed to be done anyways. Checked all plug wires, no corrosion, no arcing, no burns.
-Replace stock thermostat with 180* (been meaning to do it anyways). Run car up to operating temp, water pump kicks in thermostat opens. Top up rad and overflow tank.

- Car operates normally for a week. New operating temp about 82C

- This afternoon (was warm about 25C outside), I star the car, start driving, and it shudders as I press the pedal, like it'* misfiring or a cylinder isn't firing at all. Pushing down on the pedal makes it catch. As it warms up, the behaviour lessens, but is still noticable. Looking at the temp gauge, the temp is well above 90C. Manage to limp the car home without overheating the engine. Pop hood, coolant overflow tank is empty again. Add more coolant mix, keep running car, gurgling coming from overflow tank.

- No evidence of coolant leaks in engine bay that I could see

-Idle temp at 90 after getting coolant tank refilled.


I'm pulling my hair out trying to figure out what the hell is going on. This happened all of a sudden. The UIM appears to be intact, the ignition system isn't showing any errors.

Any advice would be greatly appreciated, I'm totally at a loss and need to get this fixed. Preferably without spending more money....
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SON OF A @#$@#$^@#$

So I get the vacuum line hooked back up, as below, and everything'* great for 2 weeks.

As I'm driving home from a friend'* house on Sunday evening, about 2 blocks away from my house, I start getting the shudder problem again. I think oh ****, what now. Pull in the driveway and park it (it'* almost midnight).

I look at it in the morning, and it'll fire, then die right away, like I turned it off.

I get the mechanic out today, and he puts a scanner on it. Scanner isn't reporting any codes, but the voltages coming back are wrong (reference 5V line coming back at 6.62V), and it looks like the injectors are pumping out full blast at start, and flooding the engine.

So, unless anyone has any suggestions (which I will GLADLY take), it looks like I need a new computer (PCM?). What'* involved in swapping this? I've searched for a few threads, but haven't come across any detailed stuff.

Any advice is gladly appreciated.

At a quick glance, it would appear that the coolant system wasn't filled & vented properly. As for the shuddering since the TB, and MAF were affected, I'd go back and look over those items again. Also check that all vacum lines connected.

Could it be that the lower intake manifold gaskets have failed?

LeifW

Mark, yer a genius. Dunno how I missed it, but a vacuum line had popped off. Probably was not quite all the way on after replacing the T-stat, and the hot weather popped it off from expansion.

Thanks again!

That'* great you found the reason for the roughness...but would a loose vaccum line make you lose coolant?

Seems that way. Probably boiled off some water into the overflow tank. Car got up above 100C easily.

Since your loosing so much coolent, I would check the oil level to make sure your not leaking coolent internally into the engine oil.

If the oil looks milky brown, you've got trouble.

Oil'* still the right color. No milk.

have you ever had the water pump replaced? because a couple years back before my dad had the water pump replaced it had those same symptoms, then we got the new water pump and it was good as new.

after you turn off your car does the coolant just spew out everywhere, and does it steam when it overheats, and can you smell coolant when your car is running, these are all tell tale signs of a bad water pump

Keep an eye on running condition and that coolant bottle. You shouldn't lose any or get up much over 100C w/o having issues.