'97 Blazer sudden bunch of codes, bad idle
cathammer
11-18-2008, 08:40 PM
Hi folks,
Here's the deal...thought I would ask some others before I start tearing into things. I'll start from the beginning, even though some things may not be related to the current problem.
Have a '97 S10 Blazer with about 110K on it. 4.3v6, auto. It has had a very slightly uneven idle since I've had it (about a year)...never dies or anything, just not silky smooth at rest. Otherwise, no problems....figured I should get around to putting in new wires, etc. at some point.
About a month or so ago, I had a problem with the throttle plate sticking...cleared that up spraying & wiping the bore with some carb cleaner.
Last oil change was maybe 1000 miles ago (Walmart). A few days ago, on a fairly cool morning, it had a mild ticking sound on start-up that matched engine speed....sounded to me like a stuck lifter; guy at the parts store thought the same. Didn't seem to affect performance that I could tell & set no error codes. Oil pressure (about 50 at cruise, 35 at idle in gear when warm) & water temp unchanged. I put in a 12 oz bottle of Gunk oil cleaner stuff & after about a day later it stopped. At almost the exact time it stopped, I got a CEL & it started to run rough. This only lasted for a mile or so. My guess was that freeing up the lifter maybe threw off the ECM settings for a minute.
It ran fine for a day or so until this morning when the CEL came on again and the rough idle/run started back. It seemed to smooth out a little from time to time while I was driving home, but didn't go away. Again, oil pressure and water temp were normal. No evidence of water in oil, nothing weird coming out of exhaust. I stopped at the parts place & had them pull the codes:
P0300 RANDOM MISFIRE
P0141 O2 SENSOR HEATER CIRCUIT MALFUNCTION BANK 1 SENSOR2
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P1406 ...reader said something like "mfr control, aux em control", but I've seen other info that says this is a code for a bad EGR on a '97 GM
My immediate thought is that it's a bad EGR which is, in turn, causing the other codes....but I'm not a mechanic, so that's just my off-the-cuff guess.
Anybody have any helpful thoughts?
Thanks,
Bill
Here's the deal...thought I would ask some others before I start tearing into things. I'll start from the beginning, even though some things may not be related to the current problem.
Have a '97 S10 Blazer with about 110K on it. 4.3v6, auto. It has had a very slightly uneven idle since I've had it (about a year)...never dies or anything, just not silky smooth at rest. Otherwise, no problems....figured I should get around to putting in new wires, etc. at some point.
About a month or so ago, I had a problem with the throttle plate sticking...cleared that up spraying & wiping the bore with some carb cleaner.
Last oil change was maybe 1000 miles ago (Walmart). A few days ago, on a fairly cool morning, it had a mild ticking sound on start-up that matched engine speed....sounded to me like a stuck lifter; guy at the parts store thought the same. Didn't seem to affect performance that I could tell & set no error codes. Oil pressure (about 50 at cruise, 35 at idle in gear when warm) & water temp unchanged. I put in a 12 oz bottle of Gunk oil cleaner stuff & after about a day later it stopped. At almost the exact time it stopped, I got a CEL & it started to run rough. This only lasted for a mile or so. My guess was that freeing up the lifter maybe threw off the ECM settings for a minute.
It ran fine for a day or so until this morning when the CEL came on again and the rough idle/run started back. It seemed to smooth out a little from time to time while I was driving home, but didn't go away. Again, oil pressure and water temp were normal. No evidence of water in oil, nothing weird coming out of exhaust. I stopped at the parts place & had them pull the codes:
P0300 RANDOM MISFIRE
P0141 O2 SENSOR HEATER CIRCUIT MALFUNCTION BANK 1 SENSOR2
P0135 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 1)
P1406 ...reader said something like "mfr control, aux em control", but I've seen other info that says this is a code for a bad EGR on a '97 GM
My immediate thought is that it's a bad EGR which is, in turn, causing the other codes....but I'm not a mechanic, so that's just my off-the-cuff guess.
Anybody have any helpful thoughts?
Thanks,
Bill
old_master
11-18-2008, 09:15 PM
Always diagnose the DTC's in the order they appear on the scan tool. Repair the problem, clear the DTC's and do a complete drive cycle. http://www.obdii.com/drivecycle.html If the SES light comes back on, again diagnose the DTC's in the order they appear, etc etc. Always diagnose and repair the first code first. Don't pay much attention to any other DTC's as the first problem can set other DTC's.
In your case, if the P0300 was first, diagnose and repair the random misfire first. A good place to start looking for a problem is secondary ignition: Ignition coil, distributor cap, rotor, plug wires, and spark plugs.
Another thing to keep in mind, 97 is known for faulty ignition switches which can set DTC's randomly and cause other seemingly unrelated electrical issues.
In your case, if the P0300 was first, diagnose and repair the random misfire first. A good place to start looking for a problem is secondary ignition: Ignition coil, distributor cap, rotor, plug wires, and spark plugs.
Another thing to keep in mind, 97 is known for faulty ignition switches which can set DTC's randomly and cause other seemingly unrelated electrical issues.
cathammer
11-19-2008, 05:52 AM
Thanks OM,
Actually, electrical was my first thought before I had the codes pulled. The 300 code WAS first (I'm not sure about the rest, since I was trying to jot down the info quickly as the parts guy was flipping thru the codes several times, so I don't necessarily have the rest in order).
I think I'll go ahead & do the plugs, wires, etc. as you suggest, since they probably need doing anyway, & see what happens.
A couple of things I forgot to mention:
The car was hard to start the last time (leaving the parts store)...cranked OK but wouldn't fire up.
My son said the exhaust smelled funny (maybe a little rich) as he got out of his car behind me coming back from the parts place.
How would I diagnose a bad ignition switch?
Cheers,
Bill
Actually, electrical was my first thought before I had the codes pulled. The 300 code WAS first (I'm not sure about the rest, since I was trying to jot down the info quickly as the parts guy was flipping thru the codes several times, so I don't necessarily have the rest in order).
I think I'll go ahead & do the plugs, wires, etc. as you suggest, since they probably need doing anyway, & see what happens.
A couple of things I forgot to mention:
The car was hard to start the last time (leaving the parts store)...cranked OK but wouldn't fire up.
My son said the exhaust smelled funny (maybe a little rich) as he got out of his car behind me coming back from the parts place.
How would I diagnose a bad ignition switch?
Cheers,
Bill
Sin99
12-12-2008, 08:41 PM
Hi ! i have a 1999 GMC jimmy with 133k miles...4.3 v6 auto. my truck haves a slight uneven idle about 3 months now.once i pick speed about 30 mph truck runs great ... I'm getting engine misfire detected code p0300 and code p1875 4wd low switch....i change all spark plug wires, (spark plugs) new cap and rotor.
MT-2500
12-13-2008, 10:32 AM
Hi ! i have a 1999 GMC jimmy with 133k miles...4.3 v6 auto. my truck haves a slight uneven idle about 3 months now.once i pick speed about 30 mph truck runs great ... I'm getting engine misfire detected code p0300 and code p1875 4wd low switch....i change all spark plug wires, (spark plugs) new cap and rotor.
Welcome to AF.
On your truck is is best to start a New Thread/post and give all info and someone will help you.
Welcome to AF.
On your truck is is best to start a New Thread/post and give all info and someone will help you.
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