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| 7.62mm Crusader |
1998 Buick 3800 non super charged. Plugs are new AC. Shes been at rough idle about a week now. I am hoping its not intake and plenum, even though thats not too costly. Doing a carb cleaner check tomorrow. I found a vac line diagram to follow. I actually hope its IAC valve or EGR. Had it scanned tonight but check engine light was gone and no stored codes. Anyone have knowledge of the 3800 ? | ||
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| 7.62mm Crusader |
She idles at 1000 to 1100 cold, 800 fully warm and 700 under load. | |||
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| 186,000 miles per second. It's the law. |
Have you checked the fuel filter? | |||
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| Member |
Try cleaning the air intake throat. 98 still has the aluminum intake? | |||
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| Page late and a dollar short |
Check coil packs, spark plug wires and spark plugs? I'm assuming you checked those first. Despite the fact that you just replaced them make sure you did not accidently crack one. I'm assuming you checked for arcing wires and coils also? No codes leads me to believe that it's in a non SES indicator sensed part. I don't remember if that is an electronic EGR valve, if not it could be stuck slightly open by carbon buildup and not throw a code. I doubt the IAC is involved, that should throw a code as it is fed thru the PCM. -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| 7.62mm Crusader |
I believe its aluminum and think the gaskets and plenum are only 2 years old. | |||
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| Man Once Child Twice |
Run any Tekron through it largely? | |||
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| Member |
A mechanic I worked with years ago diagnosed vacuum leaks with an unlit propane torch. He would set the flow rate very low and run the nozzle along vacuum lines. When the leak was located the idle would smooth out due to the mixture getting better. Don't know if this will work on later model vehicles but it sure made quick work of vac leaks back when. The “POLICE" Their job Is To Save Your Ass, Not Kiss It The muzzle end of a .45 pretty much says "go away" in any language - Clint Smith | |||
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| Member |
The black plastic intakes are known for cracking around the EGR tube. Then antifreeze goes in the intake valves. | |||
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| 7.62mm Crusader |
I can check the EGR tomorrow. I have new wires, Duralast. ACs on it now but they're ageing. I mentioned the IAC as its pintle gets carboned too. Oyyyy..fun. | |||
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| 7.62mm Crusader |
Ive heard smoke test too but will only have carb cleaner. | |||
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| Page late and a dollar short |
BTW, a little FYI. We had a 92 Bonneville with a 3800 that had the unnerving fault of stalling out while driving. Just shut down for no reason, no SES codes. I worked in a Pontiac dealership at the time, our techs could find no reason for the shutdown. Really fired up the wife as it shut down on her in the fast lane at her customary 80-85 mph on I-96 one morning. I found it one day after my wife got a new car and I took it over. Stall out, I pulled off the road. Car cranked normally, no fire. Cycled the ignition on and off. Second crank I am looking at the tachometer, no movement of the tach needle. Suddenly as I am watching the needle, it jumps up, car starts up. Got back to work, replaced the crank sensor, all good after that. That failure would not trigger a SES light as the crank signal was lost to the PCM. Acted like the ignition switch was turned off, PCM read this as shut down. This might save others some grief with diagnosis, I hope. -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| 7.62mm Crusader |
Only coolant loss is up front at a fitting or hose. I keep after that. | |||
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| Page late and a dollar short |
From memory I think that if the IAC is stuck open it increases the idle speed and sets a code as the pintile reading does not match the TPS. -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| 7.62mm Crusader |
Even the old cars are pretty smart. TPS sensor crossed my mind but I havnt a clue how it would act. Sort of sticking with vaccum or EGR for now. They sure got a load of sensors. | |||
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| Page late and a dollar short |
Also another FYI. If you have the plastic fittings at the front for coolant hoses, GM replaced those with metal ones. Get them. I don't know if the aftermarket has them available in metal too. -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| 7.62mm Crusader |
Thank you. I think I can rule out IAC then. I dont know how to test the coil pack. | |||
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| Page late and a dollar short |
I retired from GM dealership parts departments the end of June, I figured 47 years in it was enough for any person.......... -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| Page late and a dollar short |
Coil pack, look for arcing to ground with the engine running in the dark. May not be real visible, take your time. Also, a small grayish white "witness mark" may show on the coils or the wires where they arc to ground. Those coil packs were usually "go or no go". -------------------------------------—————— ————————--Ignorance is a powerful tool if applied at the right time, even, usually, surpassing knowledge(E.J.Potter, A.K.A. The Michigan Madman) | |||
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| 7.62mm Crusader |
Man their prices are high. I priced sway bar bushings today at Buick in Burlington, KY, I politely told them I will buy elsewhere. $80.00 for 1 end. Bolts are $5.00 each, WTH ? Auto Zone ordered me a kit with everything for $30.00 tax included. | |||
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