What should I start looking for?
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 902
Likes: 0
From: Glen Allen, VA
CI 3-4-6-8-9 Veteran
What should I start looking for?
'94 stock LT1 Auto with ~68k miles. Here's the problem:
At idle in drive, after the car warms up (after about 30-45 minutes of driving), I notice my oil pressure drops below 20 PSI and the battery gauge drops at the same time. The idle revs from 600 RPM to around 1,200 RPM like the engine is trying to pick up the oil pressure and the battery back up to normal. Not making any clunks, bangs or other strange noises and the car runs fine otherwise and no codes are being thrown. Normally does it after the temp reaches 230 and the fan kicks in.
Only had the car about 8 months and it started about a month or two ago. Not really getting worse or better. As far as I know, stock opti.
Any suggestions what I may be looking at for the non-mechanically inclined? Thanks. :cheers:
At idle in drive, after the car warms up (after about 30-45 minutes of driving), I notice my oil pressure drops below 20 PSI and the battery gauge drops at the same time. The idle revs from 600 RPM to around 1,200 RPM like the engine is trying to pick up the oil pressure and the battery back up to normal. Not making any clunks, bangs or other strange noises and the car runs fine otherwise and no codes are being thrown. Normally does it after the temp reaches 230 and the fan kicks in.
Only had the car about 8 months and it started about a month or two ago. Not really getting worse or better. As far as I know, stock opti.
Any suggestions what I may be looking at for the non-mechanically inclined? Thanks. :cheers:
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: What should I start looking for? (TimC)
Sounds normal. The alternator voltage regulator is not well temperature compensated and the alternator voltage will fall as it warms. Mine starts out cold at 14-14.3 and falls to 13-13.3 when it warms up. As long as it is above 12.0, it is charging the battery. When idling and with heavy electrical loads, the voltage may fall to 12.0 to slightly below because the alternator cannot generate full output at low rpm during idle. Not to worry, when you get underway, the voltage will climb and the battery will be charged. Also, the oil pump cannot deliver full pressure at low idle speeds and as long as there is measureable oil pressure at low idle, your engine is protected. The ECM attempts to maintain a certain idle speed and there is an idle speed motor that adjusts the idle speed . It hunts and you can expect this. Too much hunting and a tuneup is indicated. Cleaning out the soot that collects around the throttle plate has the largest effect on idle hunting.
Thread Starter
Burning Brakes
Joined: Jul 2001
Posts: 902
Likes: 0
From: Glen Allen, VA
CI 3-4-6-8-9 Veteran
Re: What should I start looking for? (jfb)
Cool...thanks jfb. Just wanted to catch it early if it was a problem. Glad to hear it's normal.
I'll clean out the soot around the throttle plate to see if it lessens. Probably does have some build-up since it didn't used to do it...this bad. A tune-up is already on the schedule before the cruise-in :cheers:
Thanks for taking the time to help. :cheers:
I'll clean out the soot around the throttle plate to see if it lessens. Probably does have some build-up since it didn't used to do it...this bad. A tune-up is already on the schedule before the cruise-in :cheers:
Thanks for taking the time to help. :cheers:
