General info: 91 Deville

1) The odd time after driving the car (say once a month) after I park the car and turn it off it seems to like to boil over (ie: back fills into the overflow and spills out - approx 5 liters (roughly over 1 gal) needed to be added the last time to fill it back up).

Now is it possible that I still have a bubble someplace in the system? Right now I have ran the car with no thermostat, from cold to the point at where the fan turns on @ 201* takes roughly 15 minutes at idle. To me this seems fast despite there is no thermostat in the system. I haven't driven it since the last boil over and refill, but before the car seems to like to sit around the 210-215* range while driving - which seems high, yes? The cooling system has been flushed and there is a new water pump, new rad cap, etc.

2) Some other things I noticed today while on the scanner:

seems to run rich at idle - is this normal? I thought it should swap between lean/rich

other readings @ 201* closed loop

O2: 600-800 mV
throttle sensor: .64V @ 850 rpm (idle)
Inj pulse: 3.2 - 3.4
spark advance: 24-30*
Manifold air temp: 181.2*
barometric pressure: 3.82v
EGR Duty: 99.4% (when does this change, is it at a certain throttle position?)
CCP Duty: 0.0%
left & right rich/lean flag are both rich at idle, will move to lean if I tap the throttle.

it goes into closed loop status at 140* - no error codes present. Does any of this seem normal, or what should I be checking?

BIG thanks for any relies,
Tim

Are you getting good coolant flow at idle? I read that people with northstars have bad coolant flow at idle because of the longer lines or something, maybe it was the 4.9L too.

Does your heat work? if so, then that means coolant is in there. Other than that, I cant be of much help.

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84 Fiero Sport Coupe #1192 :: 86 Fiero Base Coupe :: 84 Chevette CS 4 Door

One other thing to check is get someone to watch the coolent hoses when you quickly rev the motor from idle to about 3000rpms. To look for a rad hose that might be getting sucked shut.

Make sure you have a good mix of 25% coolent to 80% water or 20% coolent, 75% water and one bottle of water wetter.

I changed over to NTK O2 sensors and the voltages seem to stay around 440mv all the time now.

As for running rich, refer back to my thread about the 4.9 Elderodo, applying power to the stuff they said to hook to solved all of my problems. I put 3 gallons of gas in the car 2 days ago and have not burnt it down yet.

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85GT 5spd MSD Everything,4.9 With Nitrous. www.captfiero.com

quote Originally posted by Capt Fiero: One other thing to check is get someone to watch the coolent hoses when you quickly rev the motor from idle to about 3000rpms. To look for a rad hose that might be getting sucked shut. Make sure you have a good mix of 25% coolent to 80% water or 20% coolent, 75% water and one bottle of water wetter. I changed over to NTK O2 sensors and the voltages seem to stay around 440mv all the time now. As for running rich, refer back to my thread about the 4.9 Elderodo, applying power to the stuff they said to hook to solved all of my problems. I put 3 gallons of gas in the car 2 days ago and have not burnt it down yet.

thanks for the suggestions:

I have power to those things meantioned. PBJ suggested connecting those up to me last year. Maybe I need to change out the O2 sensor, odd since it is new.

Hoses should be ok, they are all new.

Drove the car down the highway today, didn't take my scanner (should have) - anyways, the temp would climb up to about 105*C (according to the guage, so how accurate the gauge is - 105 is mid point on the guage where it should sit about 1/4 ways). If I turned of the heat inside the car, the guage would drop back down to less than 1/4. NOTE: I do NOT have a thermostat in the car right now. The car seemed fine a week ago, since it boiled over it wants to run hot. Maybe I am running too much coolant? I believe it's at 50% right now.

thanks,

your coolant tubes should be near perfect. I run a 180 degree thermostat, a v-6 radiator and about 80% antifreeze. if you have the small 4 cylander radiator wtih the air delete it will overheat.

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88 coupe 4.9 Izusu 5-speed Rockcrawl chip. True duels.No A/C .KYB GR-2 on all 4 corners Built to run.

I havent run a tech1 (scanner) on a 4.9, but a 99.4% duty cycle @ idle for EGR on most engines would not be right. I believe the duty cycle @ idle should be 0% or close to it. The EGR duty cycle would start to increase as you go off idle. That may explain why it stays rich at idle. An open EGR valve would make it run lean, and the ECM / O2 sensor is compensating for it by keeping it rich.

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Tim
Red 88 Formula Auto 2.8 100K+ Miles

I don't care how much money you have, free stuff is always a good thing.

quote Originally posted by FrugalFiero: I havent run a tech1 (scanner) on a 4.9, but a 99.4% duty cycle @ idle for EGR on most engines would not be right. I believe the duty cycle @ idle should be 0% or close to it. The EGR duty cycle would start to increase as you go off idle. That may explain why it stays rich at idle. An open EGR valve would make it run lean, and the ECM / O2 sensor is compensating for it by keeping it rich.

Ok, big thanks, I will have to look into that.

I just bought a 180* thermostat and will try that, running about 50% coolant, the rad is a 85 V6 with air delete, coolant pipes are perfect (not a single dent)

My car can sit and idle in 27C traffic for ever and will not overheat. Fan comes on at 204F and runs till about 190f and shuts off. Has not once ever got to 105C on the gauge.

Did you replace the water pump when you did the engine?

Sorry if you already mentioned it, I kinda skimmed the thread.

water pump is new/water pump inlet is new/thermostat new/caps are new/hoses are new...so far the engine has been running ok, it's just the once in a blue moon that it barfs up coolant. And the 4 times it has done it, I never saw the guage move past 1/4 (unless it did and dropped back down). I guess I still have a nasty little bubble in the system working it way around

Tim