Rough idle at low RPMs
04-27-08, 03:04 AM
#1
Rough idle at low RPMs
Car is an 89 vert with a S5 JDM 13B swapped into it. N370 ECU and N/A harness which has had pins swapped by the rotary tech who did the swap. 3" RB exhaust w/presilencer and FCD, custom 3" or so TID, air pump and ACV are removed with blockoff for the ACV. Koyo radiater with OEM clutch fan and dual belt alternator pulley. I've got an FD fuel pump.
Been getting CELs of 3, 17, 33, 38...a little while ago I also had an 18, but fixed that.
The idle got bad and performance went south also. The exhaust has been at times thick and sooty particularly under heavy acceleration and the car has smelled like gas occasionaly. At times the smell of gas would be kind of strong (could smell it in traffic), but still intermitent.
When I first started tracking down my problems I went to CEL 18 and have repaired the TPS I have repeatedly tested the TPS (as recently as today) with the resistance method and it's within FSM specs on both TPS sensors and at both idle and thru gingerly going to WOT. Here is a link of my repair on the TPS
TPS thread
17=feedback system I've been told is probably the O2 sensor
I've been having on going issues with my OEM O2 sensor and get occasional CEL on the highway. Many years ago the wire from the ECU to the sensor harness got pinched in the UIM when getting bolted down. I had a "good enough" crimp on there for a while but have since repaired the spliced wires better..however the shielding on the wire had to be cut back in order to splice the wire back together. I've replaced the O2 sensor recently and I wouldn't think that the non-shielded wire would pick up interference going from the front passenger side of the engine to the O2 sensor. I've let the O2 issue go out of plans to get a wideband.
CEL 3 CAS
This also has been an ongoing issue. Been getting this CEL since the swap was done. I've checked resistances per the FSM and it's within specs. I've replaced the CAS with a known good one and still have the CEL. When replacing the CAS I set the timing and then retested the TPS. Though at the time I didn't know about taking the cover off and checking the gears inside. Will be doing that soon. This part is rather noobish, but I'm not sure how to check for continuity on the CAS. I've got the FSM and have read which pins to check, but am confused on how I setup my multimeter to do it. I know that is a basic electronics skill, but I've never needed to do it in the past.
CEL 38=AWS which I have never had on my JDM. I've had this CEL since the swap also
Just a couple days ago I saw a thread with someone instructing to splice the wiring after doing ACV removal and I believe the person said to do it for AWS removal also. I've been looking for it on and off for a couple days now and can't seem to find that thread again. I believe the person said to do it so that CELs for those items would not come on.
CEL 33= port air bypass solenoid
This one is more recent and I thought it was pointing me to my OEM BOV (port air bypass valve as Mazda calls it). I picked up a brake bleed vaccum kit and used it to test both my BOV and my boost pressure sensor. They are both working.
While I had the UIM off I tested and cleaned the BAC. I've read the BAC can cause poor idle. The resistance was 11.4..within FSM specs. I applied current to it and heard it pop. Per 1300cc.com I cleaned the BAC by spraying openings with carb cleaner. Two things I'm iffy about. The spray cleaner did not flow thru the BAC, it didn't look like there was a means for it to travel thru the BAC. Also my BAC is an N374 (JDM), maybe this is typical of JDM BACs, but mine has no adjustment screw where FSM says there should be one. I can't tell if it was sealed at the factory as part of a JDM difference, or if there is in fact a screw buried in there but so stripped that it looks flat.
Also while the UIM was off and I was testing my BOV and boost pressure sensor, I replaced the vaccum lines. I inspected my ACV blockoff plate and it seems to be holding solid. When putting it on I cut a gasket to fit and used sealant too boot...I paid attention to the upper corner where leaks are apt to happen.
One possible issue a couple weeks ago I scrubbed and cleaned my TB springs. After using a tooth brush to clean them I sprayed them all pretty good with WD-40. The TPS needed re-adjusting after the cleaning. I never touched the flapper plates in the TB, but perhaps they are off a bit now also. At the time I didn't notice this but did today. The dashpot on the rear of the TB doesn't make any contact with throttle mechanism. I didn't have time to mess around with it as it was getting late. From what I've read so far the dashpot controls deceleration and a bad one or one needing adjustment causes backfiring and such.
One other issue I'm unsure of but trying to read up on. Low voltage and it's effects on the engine. I've got the OEM alternator and did have a decent sized stereo wired in. With everything wired in, lights on, etc I was very low on voltage..just about on 10ish, which to my understanding is basically running off the battery alone. Earlier in the week I disconnected the power going to both my amps and have had power off on the headunit. Voltages are back to where they should be 13-14. I'm going on educated assumption that low voltage can throw off ignition..can it then throw off the CAS? In my searching I found info on fuel pump rewiring and will be doing that soon. I reset the ECU by leaving the battery disconnected while doing work. Still had CELs though.
Wow did this turn into a long post, but I think I covered it all. Any advice is greatly appreciated.
One thing I forgot to add. I inspected the thermosensor on the back of the water pump, it has dry rot on the insulation where it meets with the sensor and a touch of corroded wire is exposed. I'll be ordering a new one tomorrow.
Been getting CELs of 3, 17, 33, 38...a little while ago I also had an 18, but fixed that.
The idle got bad and performance went south also. The exhaust has been at times thick and sooty particularly under heavy acceleration and the car has smelled like gas occasionaly. At times the smell of gas would be kind of strong (could smell it in traffic), but still intermitent.
When I first started tracking down my problems I went to CEL 18 and have repaired the TPS I have repeatedly tested the TPS (as recently as today) with the resistance method and it's within FSM specs on both TPS sensors and at both idle and thru gingerly going to WOT. Here is a link of my repair on the TPS
TPS thread
17=feedback system I've been told is probably the O2 sensor
I've been having on going issues with my OEM O2 sensor and get occasional CEL on the highway. Many years ago the wire from the ECU to the sensor harness got pinched in the UIM when getting bolted down. I had a "good enough" crimp on there for a while but have since repaired the spliced wires better..however the shielding on the wire had to be cut back in order to splice the wire back together. I've replaced the O2 sensor recently and I wouldn't think that the non-shielded wire would pick up interference going from the front passenger side of the engine to the O2 sensor. I've let the O2 issue go out of plans to get a wideband.
CEL 3 CAS
This also has been an ongoing issue. Been getting this CEL since the swap was done. I've checked resistances per the FSM and it's within specs. I've replaced the CAS with a known good one and still have the CEL. When replacing the CAS I set the timing and then retested the TPS. Though at the time I didn't know about taking the cover off and checking the gears inside. Will be doing that soon. This part is rather noobish, but I'm not sure how to check for continuity on the CAS. I've got the FSM and have read which pins to check, but am confused on how I setup my multimeter to do it. I know that is a basic electronics skill, but I've never needed to do it in the past.
CEL 38=AWS which I have never had on my JDM. I've had this CEL since the swap also
Just a couple days ago I saw a thread with someone instructing to splice the wiring after doing ACV removal and I believe the person said to do it for AWS removal also. I've been looking for it on and off for a couple days now and can't seem to find that thread again. I believe the person said to do it so that CELs for those items would not come on.
CEL 33= port air bypass solenoid
This one is more recent and I thought it was pointing me to my OEM BOV (port air bypass valve as Mazda calls it). I picked up a brake bleed vaccum kit and used it to test both my BOV and my boost pressure sensor. They are both working.
While I had the UIM off I tested and cleaned the BAC. I've read the BAC can cause poor idle. The resistance was 11.4..within FSM specs. I applied current to it and heard it pop. Per 1300cc.com I cleaned the BAC by spraying openings with carb cleaner. Two things I'm iffy about. The spray cleaner did not flow thru the BAC, it didn't look like there was a means for it to travel thru the BAC. Also my BAC is an N374 (JDM), maybe this is typical of JDM BACs, but mine has no adjustment screw where FSM says there should be one. I can't tell if it was sealed at the factory as part of a JDM difference, or if there is in fact a screw buried in there but so stripped that it looks flat.
Also while the UIM was off and I was testing my BOV and boost pressure sensor, I replaced the vaccum lines. I inspected my ACV blockoff plate and it seems to be holding solid. When putting it on I cut a gasket to fit and used sealant too boot...I paid attention to the upper corner where leaks are apt to happen.
One possible issue a couple weeks ago I scrubbed and cleaned my TB springs. After using a tooth brush to clean them I sprayed them all pretty good with WD-40. The TPS needed re-adjusting after the cleaning. I never touched the flapper plates in the TB, but perhaps they are off a bit now also. At the time I didn't notice this but did today. The dashpot on the rear of the TB doesn't make any contact with throttle mechanism. I didn't have time to mess around with it as it was getting late. From what I've read so far the dashpot controls deceleration and a bad one or one needing adjustment causes backfiring and such.
One other issue I'm unsure of but trying to read up on. Low voltage and it's effects on the engine. I've got the OEM alternator and did have a decent sized stereo wired in. With everything wired in, lights on, etc I was very low on voltage..just about on 10ish, which to my understanding is basically running off the battery alone. Earlier in the week I disconnected the power going to both my amps and have had power off on the headunit. Voltages are back to where they should be 13-14. I'm going on educated assumption that low voltage can throw off ignition..can it then throw off the CAS? In my searching I found info on fuel pump rewiring and will be doing that soon. I reset the ECU by leaving the battery disconnected while doing work. Still had CELs though.
Wow did this turn into a long post, but I think I covered it all. Any advice is greatly appreciated.
One thing I forgot to add. I inspected the thermosensor on the back of the water pump, it has dry rot on the insulation where it meets with the sensor and a touch of corroded wire is exposed. I'll be ordering a new one tomorrow.
Last edited by JustJeff; 04-27-08 at 03:24 AM.
04-28-08, 10:46 AM
#4
Low voltage can definitely cause some issues with idle.... I'd look into an upgraded alternator. As for all those CEL's, they probably trace back to one common source that is throwing them all off... although I don't know what, lol. It's unusual for the CAS to go out though... you may have a short in your wiring harness somewhere?
just as a warning though.... have you ever had OMP problems? My ECU was fried cuz of it and "forgot" some CEL's.... like the knock sensor. I had to replace the thermosensor to see the OMP was out and replace the OMP to see the knock was out, ya dig? Maybe something, maybe not. Good luck.
just as a warning though.... have you ever had OMP problems? My ECU was fried cuz of it and "forgot" some CEL's.... like the knock sensor. I had to replace the thermosensor to see the OMP was out and replace the OMP to see the knock was out, ya dig? Maybe something, maybe not. Good luck.
04-28-08, 01:19 PM
#5
Thanks for the heads up.
I did have problems with a bad ECU I bought for my swap. Some chump on this site sold me an ECU with fried MOP/OMP, unfortunately it took me so long to actually complete the swap and use the ECU for me to go back to the seller became pointless.
I was getting CEL for the metering pump also, though I never went into limp mode. I swapped a known good MOP/OMP on the engine and still got the CEL. I then bought a good ECU and havent' had any issue with MOP/OMP or ECU giving those particular codes. I've read about a bad MOP/OMP frying the ECU, but can the bad ECU I was using reverse directions and fry the sensors?
The 17 and 3 codes have remained constant through the use of both ECUs. Though again the 17 code is sporadic and when it does come up it is only during highway driving.
As you suggested, I'm very suspicious of the wiring on a larger scale than just the CAS wiring. The rotary tech who did my swap left much to be desired. So far every spliced line he crimped has fallen apart in my hands...literally. The boost solenoid that sits near the oil filler neck was one of them. I found the crimp disconnected on that one, then the TPS I provided a link to was fouled. For the longest time I thought my reverse lights were out and after doing some searching I found that my reverse/5th gear wires aren't connected. That part is only partially his fault as my JDM tranny is missing the plugs...though he could have given me a heads up. While the UIM was off I found an unplugged ground coming off the top of the rear housing. There was a ground wire with a single plug harness on the end going to nothing. I removed the wire but have it set aside so that I can match it up with what should be plugged into it.
I'm in the process of getting better grounds on the car. The car audio hobby people have something called The Big Three. Basically it's matching the gauge of your ground wires to your power wire going to your amps.
1)grounding the engine to chassis
2)grounding the battery to the chassis
3)alternator to the battery (+)
But for now I've got my stereo disconnected. Once I've upgraded my alternator I'll reconnect and listen to music. As long as my stereo is disconnected I get solid readings of 13-14volts. I'm also reading up on grounding the ECU better.
I've got a USDM TII harness that I'm working on removing mods from the previous owner. I'm trying to decide which is better to completely remove my N/A harness or simply find the incomplete work and improve on it. Granted it is a 20year old car and it could be a simple failure, but given my history with this tech's work I'm not out of bounds in being suspicious.
I thought I was going to have some time today to ****** a thermosensor off a junkyard RX. Though this is probably for the better, I'm better off spending the big bucks for the $30 replacement for a new one.
I did have problems with a bad ECU I bought for my swap. Some chump on this site sold me an ECU with fried MOP/OMP, unfortunately it took me so long to actually complete the swap and use the ECU for me to go back to the seller became pointless.
I was getting CEL for the metering pump also, though I never went into limp mode. I swapped a known good MOP/OMP on the engine and still got the CEL. I then bought a good ECU and havent' had any issue with MOP/OMP or ECU giving those particular codes. I've read about a bad MOP/OMP frying the ECU, but can the bad ECU I was using reverse directions and fry the sensors?
The 17 and 3 codes have remained constant through the use of both ECUs. Though again the 17 code is sporadic and when it does come up it is only during highway driving.
As you suggested, I'm very suspicious of the wiring on a larger scale than just the CAS wiring. The rotary tech who did my swap left much to be desired. So far every spliced line he crimped has fallen apart in my hands...literally. The boost solenoid that sits near the oil filler neck was one of them. I found the crimp disconnected on that one, then the TPS I provided a link to was fouled. For the longest time I thought my reverse lights were out and after doing some searching I found that my reverse/5th gear wires aren't connected. That part is only partially his fault as my JDM tranny is missing the plugs...though he could have given me a heads up. While the UIM was off I found an unplugged ground coming off the top of the rear housing. There was a ground wire with a single plug harness on the end going to nothing. I removed the wire but have it set aside so that I can match it up with what should be plugged into it.
I'm in the process of getting better grounds on the car. The car audio hobby people have something called The Big Three. Basically it's matching the gauge of your ground wires to your power wire going to your amps.
1)grounding the engine to chassis
2)grounding the battery to the chassis
3)alternator to the battery (+)
But for now I've got my stereo disconnected. Once I've upgraded my alternator I'll reconnect and listen to music. As long as my stereo is disconnected I get solid readings of 13-14volts. I'm also reading up on grounding the ECU better.
I've got a USDM TII harness that I'm working on removing mods from the previous owner. I'm trying to decide which is better to completely remove my N/A harness or simply find the incomplete work and improve on it. Granted it is a 20year old car and it could be a simple failure, but given my history with this tech's work I'm not out of bounds in being suspicious.
I thought I was going to have some time today to ****** a thermosensor off a junkyard RX. Though this is probably for the better, I'm better off spending the big bucks for the $30 replacement for a new one.
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