2000 4.3 - misfiring, bad idle, hesitation, rich smell
#11
06-01-2010, 10:14 PM
Another update-
I took it to the store and back tonight to see if it would perform better since I put the new plugs in. I put the MSD 6AL-2 back on to see if it had any effect. I had to harvest it from the '91.. the 6AL I had sitting out had the wrong ring terminals on it. No noticeable effect so I suppose a weak ignition system isn't the culprit.
I tested the fuel pressure again-
56 psi at idle, 64 psi when the throttle is snapped open. Doesn't seem to leak down with the engine off - at least not during the couple minutes I watched it.
It was still feeling sluggish off the line, had to use more foot than usual to get it moving but it was running smooth and wasn't chugging or misfiring. I got a code as I was getting off the highway - let off the throttle fully from about 2500 RPM as I began to coast to reduced speed for my exit when the light came on:
P0154 - O2 Sensor no activity (bank 2 sensor 1)
and two pending:
P0151 - O2 Sensor volts low (bank 2 sensor 1)
P0154 - O2 Sensor no activity (bank 2 sensor 1)
Since that's the same sensor I replaced with the heater circuit fault, I figured I must have buggered up the plug somehow. I pulled the connector to check the pins, everything looks good. I couldn't find any frays or burns when I traced the loom back to the PCM under the hood. Unfortunately - my multimeter broke a few months back so I can't check the damn voltages myself!
I copied down the freeze frame info for the active code:
DTC that caused freeze frame : P0154
Throttle position : 0.0%
Engine RPM : 2050 RPM
Load value : 7.8%
Air flow rate : 13.61 OR/Sec (what the heck is or/sec?)
MAP sensor : 27 kPa
Coolant temp : 199°F
Short Term Fuel Trim1 : 0.0%
Long Term Fuel Trim1 : 0.0%
Short Term Fuel Trim2 : 0.0%
Long Term Fuel Trim2 : 0.0%
Short Term Fuel Trim3 : 50.0%
Long Term Fuel Trim3 : -38.3%
Long Term Fuel Trim4 : -46.2%
Short Term Fuel Trim4 : 67.8%
Vehicle Speed : 69 MPH
Fuel System 1 : Open2
Fuel System 2 : Open2
Data from an Actron OBD II AutoScanner.
Any clues where to look first? Am I destined to drop some more coin on a new DMM? I went ahead and cleared the code, hoping to get some fresh data from the next cold start. Does it need two cold starts to fail an O2 or just one?
Edit 6/2-
Gave in and bought a new DMM. Tried to get some useful readings from the sensor and harness - with hopefully some success. Trouble is I'm not quite sure how to digest the data I collected.
Testing the resistance between the brown wires (the heater circuit?) gave me 15-16 ohms (varied a bit each time I tested it) on the new sensor. Testing these on the sensor I removed last Friday yielded 4.5 ohms. The spec I saw was 3.5-14 ohms?
Testing continuity from the tan wire to ground (terminal D?) on the new, installed sensor yielded 4.0 ohms. Testing from the tan wire to the threads on the old sensor gave 0.8 ohms
No continuity from the purple wire to ground on the new or the old sensor.
Testing for current across the black and pink wires of the harness showed 12.00 VDC. If I read right, that's the O2 sensor heater power?
Given that these 4 wire O2's are still a somewhat new science to me - spoiled by years of a single wire OBDI O2 sensor - is this data of any value in determining the cause of the P0154 and P0151 DTC's? Any other data collecting I need to do from the sensor and harness?
I intended to test continuity from the sensor connector to the VCM connector... but I had little luck determining what terminals I need to probe at the computer end. I only have a few hours each night for diagnostics so any advice is welcome.
I took it to the store and back tonight to see if it would perform better since I put the new plugs in. I put the MSD 6AL-2 back on to see if it had any effect. I had to harvest it from the '91.. the 6AL I had sitting out had the wrong ring terminals on it. No noticeable effect so I suppose a weak ignition system isn't the culprit.
I tested the fuel pressure again-
56 psi at idle, 64 psi when the throttle is snapped open. Doesn't seem to leak down with the engine off - at least not during the couple minutes I watched it.
It was still feeling sluggish off the line, had to use more foot than usual to get it moving but it was running smooth and wasn't chugging or misfiring. I got a code as I was getting off the highway - let off the throttle fully from about 2500 RPM as I began to coast to reduced speed for my exit when the light came on:
P0154 - O2 Sensor no activity (bank 2 sensor 1)
and two pending:
P0151 - O2 Sensor volts low (bank 2 sensor 1)
P0154 - O2 Sensor no activity (bank 2 sensor 1)
Since that's the same sensor I replaced with the heater circuit fault, I figured I must have buggered up the plug somehow. I pulled the connector to check the pins, everything looks good. I couldn't find any frays or burns when I traced the loom back to the PCM under the hood. Unfortunately - my multimeter broke a few months back so I can't check the damn voltages myself!
I copied down the freeze frame info for the active code:
DTC that caused freeze frame : P0154
Throttle position : 0.0%
Engine RPM : 2050 RPM
Load value : 7.8%
Air flow rate : 13.61 OR/Sec (what the heck is or/sec?)
MAP sensor : 27 kPa
Coolant temp : 199°F
Short Term Fuel Trim1 : 0.0%
Long Term Fuel Trim1 : 0.0%
Short Term Fuel Trim2 : 0.0%
Long Term Fuel Trim2 : 0.0%
Short Term Fuel Trim3 : 50.0%
Long Term Fuel Trim3 : -38.3%
Long Term Fuel Trim4 : -46.2%
Short Term Fuel Trim4 : 67.8%
Vehicle Speed : 69 MPH
Fuel System 1 : Open2
Fuel System 2 : Open2
Data from an Actron OBD II AutoScanner.
Any clues where to look first? Am I destined to drop some more coin on a new DMM? I went ahead and cleared the code, hoping to get some fresh data from the next cold start. Does it need two cold starts to fail an O2 or just one?
Edit 6/2-
Gave in and bought a new DMM. Tried to get some useful readings from the sensor and harness - with hopefully some success. Trouble is I'm not quite sure how to digest the data I collected.
Testing the resistance between the brown wires (the heater circuit?) gave me 15-16 ohms (varied a bit each time I tested it) on the new sensor. Testing these on the sensor I removed last Friday yielded 4.5 ohms. The spec I saw was 3.5-14 ohms?
Testing continuity from the tan wire to ground (terminal D?) on the new, installed sensor yielded 4.0 ohms. Testing from the tan wire to the threads on the old sensor gave 0.8 ohms
No continuity from the purple wire to ground on the new or the old sensor.
Testing for current across the black and pink wires of the harness showed 12.00 VDC. If I read right, that's the O2 sensor heater power?
Given that these 4 wire O2's are still a somewhat new science to me - spoiled by years of a single wire OBDI O2 sensor - is this data of any value in determining the cause of the P0154 and P0151 DTC's? Any other data collecting I need to do from the sensor and harness?
I intended to test continuity from the sensor connector to the VCM connector... but I had little luck determining what terminals I need to probe at the computer end. I only have a few hours each night for diagnostics so any advice is welcome.
Last edited by Matt 4.3 TBI; 06-03-2010 at 08:31 PM. Reason: More additional info
#12
06-03-2010, 08:32 PM
Risking mod intervention to bring this back up from page 3 since edits don't seem to reflect when I add new information...
Drove it on the highway again tonight, about six miles or so. Light didn't come on but the same codes are stored as pending-
P0154 and P0151. What else can I do to try to determine what the culprit is? I tested the resistance from the tan wire on the sensor to the negative battery terminal while the sensor was hot - got 35 ohms. I wasn't able to find much in terms of voltage from any of the pins, even with my DMM set to the 200mV range.
Do I swap back in the old sensor? The P0155 code related to that sensor has cleared up but these new codes are no better. I have noticed an occasional sulfur (rotten egg) smell around the outside of the vehicle when I bring it back from a test drive - but no smell from the exhaust.
Drove it on the highway again tonight, about six miles or so. Light didn't come on but the same codes are stored as pending-
P0154 and P0151. What else can I do to try to determine what the culprit is? I tested the resistance from the tan wire on the sensor to the negative battery terminal while the sensor was hot - got 35 ohms. I wasn't able to find much in terms of voltage from any of the pins, even with my DMM set to the 200mV range.
Do I swap back in the old sensor? The P0155 code related to that sensor has cleared up but these new codes are no better. I have noticed an occasional sulfur (rotten egg) smell around the outside of the vehicle when I bring it back from a test drive - but no smell from the exhaust.
Last edited by Matt 4.3 TBI; 06-03-2010 at 09:22 PM.
#13
08-15-2010, 12:24 PM
tell me i have a 95 with similiar problems such as bad idle, misfire code,but it runns nice on highway .just changed distributor cuz of broken screw hole for cap hold down thinking that was problem.still same.napa says its running code for running rich bank 1. just replaced 02 sensor with no luck still same idle n codes.would i b having same problem as u
#15
08-13-2012, 09:33 PM
Hey, looks good, Thanks for the pics that is a huge help. I have a 1998 4dr 4wd that needs this done. I am new to this stuff, so my question is : How hard is it to remove the upper intake to get to the spider? I have to clear the fuel pressure first, correct? I got the haynes guide but it is pretty vague.... Thanks again man
#16
10-14-2012, 12:00 PM
Hey, looks good, Thanks for the pics that is a huge help. I have a 1998 4dr 4wd that needs this done. I am new to this stuff, so my question is : How hard is it to remove the upper intake to get to the spider? I have to clear the fuel pressure first, correct? I got the haynes guide but it is pretty vague.... Thanks again man
#17
10-14-2012, 03:58 PM
Well you seem to know what your doing
Thisthread should help ut alot of other people with the same problem.BTW how much did the new spider and injector assembly cost you?
#18
10-14-2012, 06:14 PM
I paid $189 for a Delphi FJ10565 MFI conversion off EBay thru Mach5 Auto. When I removed the old spider it was leaking from the regulator, #5 cylinder intake runner was washed clean from it leaking for a while.
#19
12-31-2016, 06:02 PM
I'm not certain if this subject belongs in this forum or in the Engine/Trans forum - mods feel free to move it if you feel it would be appropriate.
This is a problem with my 2000 Blazer ZR2:
This just cropped up this morning while leaving for work - the idle is very rough and sits about 500 rpm with the AC off. Acceleration is sluggish, pushing on the pedal gives no immediate response. The engine didn't try to stall or feel like it bogged down when I hit the gas, it just doesn't seem to react without a delay. Fuel level is between 1/4 and 1/2 tank. I had to sit at a railroad crossing for a few minutes, the idle felt rougher than my 91 with its Edelbrock cam. I ended up taking it back to the house and driving the Malibu instead. These things always seem to happen when you're already running late! The last time I drove it was on Sunday and it ran normally - mix of city and highway on that trip. I'm not sure what's changed since then.
It definitely sounds and feels like a misfire. Took it down the highway to the gas station and back. When cruising it is resistant to acceleration until it downshifts. Still accelerates well under hard throttle. Doesn't sputter and try to stall when snapping the gas open from a stop or letting off the gas quick from full throttle.
-Plugs are about two years old, air filter around last October, replaced the charcoal canister and both valves last winter. Alternator was tested earlier this year when I replaced the battery.
-Plug wires appear to be in place properly. I attached my timing light to each wire as well - each one caused the light to blink in about the same pattern. So, distributor and cap/rotor appear to be good. Very quick strobe when the light is attached to the coil wire.
-Exhaust has a strong gas smell - normally no odor at all, like smelling a running hair dryer. Tailpipe shakes noticeably, distinct 'chugging' sound as it idles.
-Engine visibly shakes under the hood.
-Vacuum read 18 in/Hg but I could only find ported vacuum so it didn't act right when I tried snapping the throttle.
-PCV valve rattles. You can feel the stopper snap back and forth by covering and opening the hole with your finger while the engine is running.
-Oil is relatively fresh, only about 300 miles since the last change. Light amber color, no visible chunks and doesn't feel gritty. Didn't feel any pressure coming from the PCV valve port in the DS valve cover.
Still no MIL codes. I'm open to any suggestions at this point. This ZR2 still feels relatively 'new' to me as I drove my 91 Blazer since it was new up until 2008 when I purchased this one. As I'm new here I'll explain the name to clear up confusion - I registered with this name on a number of S-Series forums over the past eight years when my 91 4WD Blazer was my daily driver. To keep things simple (and due to a lack of creativity) I just keep using the same name.
Thanks for any help you guys can offer.
I finally got a code last night - P0155: O2 sensor heater circut malfunction (bank 2 sensor 1).
Installed the new O2 and cleared the code. So far no difference. Still chugging and shaking at idle, exhaust smells like gas and bad hesitation when you hit the gas. Surging seems even more noticeable now when holding the throttle steady.
A bit more info-
I don't feel comfortable trying to do a full ODBII drive cycle - I really don't want to take it on the highway to get it up to the required speeds. I started it up and let it idle in D with the AC and rear defroster on for over two minutes - I let it go until it reached operating temp. It was idling noticeably rough as expected. I then put it in P and gave part throttle to get the RPM's up to 3000 - no audible misfires, backfires or sputtering. I let off the throttle and then shifted back into D and let it idle. Now it was idling extremely rough, shaking the vehicle visibly. I let it keep idling like this (RPM's about 500). It sounded like it was straining to keep running. Sooty smoke was visible coming from the exhaust - along with the gas smell. Obviously there's a very rich condition going on here but I'm not sure what to check. No codes yet. I'll try this one more time once it cools off so it can do a full warmup cycle.
It still starts up with no trouble so it doesn't seem like the fuel pressure regulator is leaking. I haven't got any misfire codes so I don't think the poppets are sticking (but I don't really know all the symptoms).
Unfortunately I called the local shop to see if they could lend a hand - they have no one on staff to do diagnostics until after the holiday weekend.
As I mentioned, I have the MFI spider kit but I've been avoiding the chore of installing if until a problem arose with the CSFI injectors.
Any other investigation I can do to help narrow this down?
This is a problem with my 2000 Blazer ZR2:
This just cropped up this morning while leaving for work - the idle is very rough and sits about 500 rpm with the AC off. Acceleration is sluggish, pushing on the pedal gives no immediate response. The engine didn't try to stall or feel like it bogged down when I hit the gas, it just doesn't seem to react without a delay. Fuel level is between 1/4 and 1/2 tank. I had to sit at a railroad crossing for a few minutes, the idle felt rougher than my 91 with its Edelbrock cam. I ended up taking it back to the house and driving the Malibu instead. These things always seem to happen when you're already running late! The last time I drove it was on Sunday and it ran normally - mix of city and highway on that trip. I'm not sure what's changed since then.
It definitely sounds and feels like a misfire. Took it down the highway to the gas station and back. When cruising it is resistant to acceleration until it downshifts. Still accelerates well under hard throttle. Doesn't sputter and try to stall when snapping the gas open from a stop or letting off the gas quick from full throttle.
-Plugs are about two years old, air filter around last October, replaced the charcoal canister and both valves last winter. Alternator was tested earlier this year when I replaced the battery.
-Plug wires appear to be in place properly. I attached my timing light to each wire as well - each one caused the light to blink in about the same pattern. So, distributor and cap/rotor appear to be good. Very quick strobe when the light is attached to the coil wire.
-Exhaust has a strong gas smell - normally no odor at all, like smelling a running hair dryer. Tailpipe shakes noticeably, distinct 'chugging' sound as it idles.
-Engine visibly shakes under the hood.
-Vacuum read 18 in/Hg but I could only find ported vacuum so it didn't act right when I tried snapping the throttle.
-PCV valve rattles. You can feel the stopper snap back and forth by covering and opening the hole with your finger while the engine is running.
-Oil is relatively fresh, only about 300 miles since the last change. Light amber color, no visible chunks and doesn't feel gritty. Didn't feel any pressure coming from the PCV valve port in the DS valve cover.
Still no MIL codes. I'm open to any suggestions at this point. This ZR2 still feels relatively 'new' to me as I drove my 91 Blazer since it was new up until 2008 when I purchased this one. As I'm new here I'll explain the name to clear up confusion - I registered with this name on a number of S-Series forums over the past eight years when my 91 4WD Blazer was my daily driver. To keep things simple (and due to a lack of creativity) I just keep using the same name.
Thanks for any help you guys can offer.
I finally got a code last night - P0155: O2 sensor heater circut malfunction (bank 2 sensor 1).
Installed the new O2 and cleared the code. So far no difference. Still chugging and shaking at idle, exhaust smells like gas and bad hesitation when you hit the gas. Surging seems even more noticeable now when holding the throttle steady.
A bit more info-
I don't feel comfortable trying to do a full ODBII drive cycle - I really don't want to take it on the highway to get it up to the required speeds. I started it up and let it idle in D with the AC and rear defroster on for over two minutes - I let it go until it reached operating temp. It was idling noticeably rough as expected. I then put it in P and gave part throttle to get the RPM's up to 3000 - no audible misfires, backfires or sputtering. I let off the throttle and then shifted back into D and let it idle. Now it was idling extremely rough, shaking the vehicle visibly. I let it keep idling like this (RPM's about 500). It sounded like it was straining to keep running. Sooty smoke was visible coming from the exhaust - along with the gas smell. Obviously there's a very rich condition going on here but I'm not sure what to check. No codes yet. I'll try this one more time once it cools off so it can do a full warmup cycle.
It still starts up with no trouble so it doesn't seem like the fuel pressure regulator is leaking. I haven't got any misfire codes so I don't think the poppets are sticking (but I don't really know all the symptoms).
Unfortunately I called the local shop to see if they could lend a hand - they have no one on staff to do diagnostics until after the holiday weekend.
As I mentioned, I have the MFI spider kit but I've been avoiding the chore of installing if until a problem arose with the CSFI injectors.
Any other investigation I can do to help narrow this down?
#20
01-01-2017, 06:13 PM
This thread is awfully old, I had to check some other threads to recall what the fix was. In this instance, it was a bad PCM. Once the PCM was replaced the issues resolved and I had no further drivability issues until the new transmission went out (the TCC would not unlock so it would stall when coming to a stop) and then the fuel pump went out (it died going through an intersection and would not restart).