ECM reset
Thread Starter
Racer
Joined: Mar 2008
Posts: 389
Likes: 2
From: Austin Tx
ECM reset
Quick question guys...on average, how long does it take for the ECM to set set everything (air fuel mix, idle speed, etc.) after a reset? Is it dependent on number of start/stop cycles, driving time, or a combination?
89 coupe (L98)
Thanks
Sam
89 coupe (L98)
Thanks
Sam
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
A couple of seconds really - actually it's constantly resetting with Long Term Fuel Trim retained in memory when you shut it off which means if it's developed a small vacuum leak, it's ready to correct for it when you restart it. If it isn't running right, scan, post the issue.
Thread Starter
Racer
Joined: Mar 2008
Posts: 389
Likes: 2
From: Austin Tx
A couple of seconds really - actually it's constantly resetting with Long Term Fuel Trim retained in memory when you shut it off which means if it's developed a small vacuum leak, it's ready to correct for it when you restart it. If it isn't running right, scan, post the issue.
Here's the issue:
My 89 failed the Texas emissions (Two speed Idle) test.
At 2279 RPM the HC(ppm) was 878 and the CO(%) was 3.50
At 834 RPM the HC(ppm) was 1120 and the CO(%) was 3.32
The standard for both is HC=220 and CO=1.20
I don't know what any of this means except that it's out of tolerance.
The guy suggested a can of CRC or a good tune as possible fixes before a retest in 15 days
Here's my thoughs as to what could have contribued to the problem. Yesterday morning I had replaced the battery. If I remember right, that resets the ECM causing it to try and find a good fuel/air mixture. Since I drove the car directly to the inspection station (about 6 miles from Wallyworld) could ECM still have been searching for a proper fuel/air mix and throw the test off?
If I'm going to spend money, I would much rather go straight to the problem than waste time chasing ghosts.
Thanks,
Sam
Last edited by samh; Aug 4, 2010 at 04:41 PM.
Melting Slicks
Joined: May 2010
Posts: 2,082
Likes: 3
From: Conowingo Maryland
going to try to help a little here your HC is out the window at low RPMs do you have a low idle miss? a bad or poor tune will cause high HC. plugs, wires, pvc, just make sure car is in good tune. now if your motor is in poor shape burning oil or something of that nature you are going to have a tough time in getting it to pass. CO is air fuel mixture. If were you I would take care of the HC then adress the CO it may come down when you get the HC fixed. I just noticed you said 6 miles was the car up to full operating temp? hope this helps some. One other thing how are yor converters if not functionaly right your CO will be high
Melting Slicks
Joined: Jun 2010
Posts: 2,528
Likes: 2
From: PA
Had a similar problem with my 91 Mustang, after driving it straight to the testing station (about 3 miles). The tester said to go out, drive it 10 or 15 miles, stay out say 20 or 30 minutes, push it a little, get the temp up, and come back. That was all it took to pass.
In your case your emissions are so far above the limit I'd definitely get a tune up too, but drive it for 20 minutes or so before heading over.
In your case your emissions are so far above the limit I'd definitely get a tune up too, but drive it for 20 minutes or so before heading over.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
It's rich. Rich enough to stink and to burn up the CAT. The ECM compensates for worn parts based on O2 input, so most socalled tuneups are waste of money until fuel delivery mucks up.
Scanning it would tell you where to begin, but I'd guess that it's sucking air pass the O2 and when the ECM gets a lean indicator, it's dumping fuel. Assuming a scan shows a Lean O2, you might check the header check valves by clamping off the hoses to see if the O2 returns to normal. Other causes would be a vacuum leak or a blown head gasket allowing coolant into the combustion chamber. Check cylinder #7 which is problematic for this Year.
Scanning it would tell you where to begin, but I'd guess that it's sucking air pass the O2 and when the ECM gets a lean indicator, it's dumping fuel. Assuming a scan shows a Lean O2, you might check the header check valves by clamping off the hoses to see if the O2 returns to normal. Other causes would be a vacuum leak or a blown head gasket allowing coolant into the combustion chamber. Check cylinder #7 which is problematic for this Year.
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