To anyone with an erratic idle issue,
Writing this to give a hand to other SC/XR7 owners that might be experiencing a "difficult to diagnose" erratic idle issue.
I have a '91 SC 5-Speed with 130k on the motor/car. Early August she finally blew the factory head gasket, passenger side rear breach, which wasn't so bad as it needed some other work done as well. Motor mounts, exhaust manifold gaskets, cats, plugs, ect. I also had the occasional CEL coming on, so I figured there might be a sensor or two that needed to be replaced. So I did the top-end rebuild replacing the following.
-All gaskets from the heads up
-Motor Mounts
-Catalytic Converters
-O2 Sensors
-Upper Control Arms
-IAC Valve
-Injector rebuild/reseal(seals and hat)
-180 Thermostat
-Plugs/Wires
-Belts
Prior to when the gasket blew, it did have a slightly low idle, and would especially drop low when I would initially turn on the A/C, but in no way idled erratic. Occasionally I would notice a quick on/off CEL, but would never stay on longer than a 45 seconds.
After the rebuild, I started it up and she purred. Everything seemed normal for about the first half hour of running time. So I took it out for the first drive and about 5 mins into it, I noticed the CEL come on. Shortly after, the motor started to idle low a couple times almost to a stall at a stop sign, or low speed turn. So I brought it back to take a look and it only got worse. Erratic idle started. It would lope from about 1100 rpm to an almost stall back to 1100. Looking under the hood, I would jump the throttle a little and it would even out for 15sec or so, than start to lope again, several time almost coming to a stall. When I would turn on the A/C, it would help, but not completely take it away. Also the drag on the motor from the power steering being turned would drag it down quit a bit, and if it was in the low of a lope, stall it. Keep in mind that when driving or giving throttle, it seemed to run well but not 100%. During this I also noticed it seemed to be running a little hot considering the 180 stat, would kick the fan on at the end of "M". As the evening progressed the lope only seemed to get worse. The last time I drove it to get some gas(about 5min from home), its stalled at almost every stop. I would have to double foot the clutch and gas to keep it going. That night I ran the codes and the first one up was 565(Canister Purge Circuit Failure). I really didn't think much of it as several more came up, but it was getting late and I was finished for the night, pretty frustrated.
The next day after work, it was time to go at it again. During the day, I read the SCCOA forums when I could looking up all terms of low, poor, erratic idle I could. Most all focused on vacuum leaks and the TPS/IAC system, which makes total sense. But I was sure that I did not have any vacuum leaks from hoses or poor assembly. The IAC was new and I was going to check the TPS that eve. None that I read mentioned the canister purge valve being the culprit of the erratic idle. Only one or two out of the many I read even mentioned it as a code they needed check into, and one mentioned replacing it but that it did nothing solve the problem. So I go to work that night and just out of the side of my head, remembering that it was the first code coming up, think I should at least take a look at Canister Purge Valve. To my surprise the first thing I see is the rubber line off the valve going to the canister is twisted. I start to think there might be something with this. So I go to pull the line and valve(best way I found was to pull the lower air box housing, remove the air silencer(which meet the "land of the misfit parts"), and stick my hand through the air box inlet hole). I get it unplugged noticing it's somewhat corroded. Take a look at the line, its twisted and collapsed. So I proceed to pull the valve off the line going to the engine. To my total surprise, this tar black oil/fuel mixture starts pouring out. I would say 4-7 tablespoons. It was nasty stuff, made my hands COMPLETELY black. After it stops draining, I decided to see what else was in the line by sucking on it. I don't necessarily recommend this, but it's what I did. BTW, tasted like S%@T. I must have gotten another 2-3 tablespoons of this liquid out of the line. Once it clears I realize this line goes right to the PCV line in the back of the motor. After clearing the line, I turn my attention to the purge valve itself. The "to engine(small arrow pointing)" side is plugged with this tar. I proceed to clean the valve though both tubes(carb cleaner). At first it's plugged, but after several soaks of the cleaner, I can start to suck air through it. So I let is soak for bit more, clean the terminals and plug, then re-attach the unit with new vacuum lines on both ends. I also replace the rubber portion of line from the tank to canister to be on the safe side. Lastly, I go get a new PCV valve to ensure that it's not causing this issue. Re-assemble the air box and go to start it up. Problem Solved!!!! Not one lope, idled perfectly smooth! I go take it for a drive, its running cooler(mid O), has much better responsiveness, and more power. CEL has not come on since. I really couldn't believe it, but am a believer now.
I apologize this post is so long, but I feel more details the better when it comes to giving this type of information. If anyone is having erratic idle issues and can't seem to find the problem, it might be worth taking a look at the canister purge valve/lines. If this helps just one other SC/XR7 owner, than it's done it's job. Any questions, let me know.
Good Luck!
Chris
Writing this to give a hand to other SC/XR7 owners that might be experiencing a "difficult to diagnose" erratic idle issue.
I have a '91 SC 5-Speed with 130k on the motor/car. Early August she finally blew the factory head gasket, passenger side rear breach, which wasn't so bad as it needed some other work done as well. Motor mounts, exhaust manifold gaskets, cats, plugs, ect. I also had the occasional CEL coming on, so I figured there might be a sensor or two that needed to be replaced. So I did the top-end rebuild replacing the following.
-All gaskets from the heads up
-Motor Mounts
-Catalytic Converters
-O2 Sensors
-Upper Control Arms
-IAC Valve
-Injector rebuild/reseal(seals and hat)
-180 Thermostat
-Plugs/Wires
-Belts
Prior to when the gasket blew, it did have a slightly low idle, and would especially drop low when I would initially turn on the A/C, but in no way idled erratic. Occasionally I would notice a quick on/off CEL, but would never stay on longer than a 45 seconds.
After the rebuild, I started it up and she purred. Everything seemed normal for about the first half hour of running time. So I took it out for the first drive and about 5 mins into it, I noticed the CEL come on. Shortly after, the motor started to idle low a couple times almost to a stall at a stop sign, or low speed turn. So I brought it back to take a look and it only got worse. Erratic idle started. It would lope from about 1100 rpm to an almost stall back to 1100. Looking under the hood, I would jump the throttle a little and it would even out for 15sec or so, than start to lope again, several time almost coming to a stall. When I would turn on the A/C, it would help, but not completely take it away. Also the drag on the motor from the power steering being turned would drag it down quit a bit, and if it was in the low of a lope, stall it. Keep in mind that when driving or giving throttle, it seemed to run well but not 100%. During this I also noticed it seemed to be running a little hot considering the 180 stat, would kick the fan on at the end of "M". As the evening progressed the lope only seemed to get worse. The last time I drove it to get some gas(about 5min from home), its stalled at almost every stop. I would have to double foot the clutch and gas to keep it going. That night I ran the codes and the first one up was 565(Canister Purge Circuit Failure). I really didn't think much of it as several more came up, but it was getting late and I was finished for the night, pretty frustrated.
The next day after work, it was time to go at it again. During the day, I read the SCCOA forums when I could looking up all terms of low, poor, erratic idle I could. Most all focused on vacuum leaks and the TPS/IAC system, which makes total sense. But I was sure that I did not have any vacuum leaks from hoses or poor assembly. The IAC was new and I was going to check the TPS that eve. None that I read mentioned the canister purge valve being the culprit of the erratic idle. Only one or two out of the many I read even mentioned it as a code they needed check into, and one mentioned replacing it but that it did nothing solve the problem. So I go to work that night and just out of the side of my head, remembering that it was the first code coming up, think I should at least take a look at Canister Purge Valve. To my surprise the first thing I see is the rubber line off the valve going to the canister is twisted. I start to think there might be something with this. So I go to pull the line and valve(best way I found was to pull the lower air box housing, remove the air silencer(which meet the "land of the misfit parts"), and stick my hand through the air box inlet hole). I get it unplugged noticing it's somewhat corroded. Take a look at the line, its twisted and collapsed. So I proceed to pull the valve off the line going to the engine. To my total surprise, this tar black oil/fuel mixture starts pouring out. I would say 4-7 tablespoons. It was nasty stuff, made my hands COMPLETELY black. After it stops draining, I decided to see what else was in the line by sucking on it. I don't necessarily recommend this, but it's what I did. BTW, tasted like S%@T. I must have gotten another 2-3 tablespoons of this liquid out of the line. Once it clears I realize this line goes right to the PCV line in the back of the motor. After clearing the line, I turn my attention to the purge valve itself. The "to engine(small arrow pointing)" side is plugged with this tar. I proceed to clean the valve though both tubes(carb cleaner). At first it's plugged, but after several soaks of the cleaner, I can start to suck air through it. So I let is soak for bit more, clean the terminals and plug, then re-attach the unit with new vacuum lines on both ends. I also replace the rubber portion of line from the tank to canister to be on the safe side. Lastly, I go get a new PCV valve to ensure that it's not causing this issue. Re-assemble the air box and go to start it up. Problem Solved!!!! Not one lope, idled perfectly smooth! I go take it for a drive, its running cooler(mid O), has much better responsiveness, and more power. CEL has not come on since. I really couldn't believe it, but am a believer now.
I apologize this post is so long, but I feel more details the better when it comes to giving this type of information. If anyone is having erratic idle issues and can't seem to find the problem, it might be worth taking a look at the canister purge valve/lines. If this helps just one other SC/XR7 owner, than it's done it's job. Any questions, let me know.
Good Luck!
Chris