Rough idle, running rich. Can't figure it out - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

NiSilS14 · 10-22-2010, 04:47 PM

My gf's car started to acting up with the fuel pump not turning on. In short I replaced the fuel pump and the relay. The car already had a walbro 255 in it so I just replaced it with another one. After I got the car running it was running really rough, idling very bad with black smoke out of the exhaust. I figured it was a fuel pressure issue, installed a fuel pressure gauge. Gauge read 46psi at idle with vac. I installed a AFPR and readjusted it to 34psi with vac. Car ran fine for about 15-20mins and just crapped out. I thought it would be a coolant temp sensor. i tested it out and came out good, but replaced it anyway. No effect. I also replaced the MAF, injectors, O2 Sensor, cap, rotor, spark wires and plugs with known good ones or new, and cleaned out the IACV. I got to run a little better but it still stutters pretty badly. I dunno what else to check other then the TPS and/or ECM. Weak ignition maybe?

Cliffnotes:
-Car won't turn on fuel pump
-Replaced fuel pump and relay
-Rough idle and running rich
-Readjusted fuel pressure with afpr and gauge
-Runs fine and craps out 20mins later
-Installed CTS, MAF, O2, Cap, Rotor, Spark wires, Plugs, with known good items or new.
-Runs slightly better, still stutters.
-TPS, ECM, Weak iginition?

NiSilS14 · 10-22-2010, 10:09 PM

Waaah, nobody?

HPKMotorsports3 · 10-22-2010, 10:25 PM

is the maf new or used? if used clean it real good... then if it still does the issue check tps

KrazyS13 · 10-22-2010, 10:51 PM

If this is a Pre OBD2 model you should perform the ECU's self diagnostic procedure. Many people overlook this simple yet affective procedure and it can be very helpful(not all the time though).

Also, do a compression check... Always good to rule that out.

Bigsyke · 10-23-2010, 01:00 AM

I would check the timing, but make sure you check it correctly or else it wont show the correct reading.

1st make sure the chain hasnt skipped and its properly timed. next make sure you get the car to idle around 650rpms, if its above a certain point the timing is going to be horribly incorrect. I thought i had my timing correct however I would squease the IACV hose and the timing would increase when the idle dropped. Set the idle with the TPS subharness unplugged at 600 rpms warm. If you have bypassed your IACV coolant lines, you want to take the car for a long drive, then let the car idle with the hood closed to enduce heat soak to the IACV. Then unplug the IACV and make sure the idle is at 650 before checking the timing. The adjuster bolt on the distributor should be a tad more towards the firewall side of the distributor house slot. If its not, then your distributor is off a tooth, or your knock sensor is faulty.

If the distributor is too far off (off a tooth) then this would create a possible wear spark scenerio since the distance from the center of the rotor to the cap pins has increased. Did your old distributor cap have alot of corrosion on the inside pins? When a spark has to jump it will create alot of corrosion on the pins.

Do you still have a catalytic converter?

NiSilS14 · 10-23-2010, 01:44 AM

Although timing isn't something I've checked yet, I don't see how anything ignition related could've caused a exxcessively rich condition. I don't see how the car could've jumped timing so bad to be idling as rough as it is. Car drove fine not too long ago. But to answer your questions, there was no corrosion on the cap and rotor. Yes it still has the cat. I'm gonna pull the codes first, should've done that first.

klits562 · 10-23-2010, 10:44 AM

Quote:

Originally Posted by NiSilS14

Although timing isn't something I've checked yet, I don't see how anything ignition related could've caused a exxcessively rich condition. I don't see how the car could've jumped timing so bad to be idling as rough as it is. Car drove fine not too long ago. But to answer your questions, there was no corrosion on the cap and rotor. Yes it still has the cat. I'm gonna pull the codes first, should've done that first.

weak spark can cause a rich condition by not burning the fuel properly and it'll then dump into the exhaust into the o2 sensor
Check to make sure your dizzy is not off a tooth, mine was on 180* backwards when i bought it and it had similiar problems running.
Also since you were having a trouble earlier with a rich condition and high fuel pressure and all that you could have clogged the cat causing the engine to run really rough.

Bigsyke · 10-23-2010, 09:08 AM

Timing being off just 1 tooth on the distributor can cause these conditions, Its happened to me.

10-22-2010, 04:47 PM	#1
NiSilS14 Zilvia Junkie Join Date: Sep 2003 Location: Denver, CO Posts: 569 Trader Rating: (20) Feedback Score: 20 reviews	Rough idle, running rich. Can't figure it out My gf's car started to acting up with the fuel pump not turning on. In short I replaced the fuel pump and the relay. The car already had a walbro 255 in it so I just replaced it with another one. After I got the car running it was running really rough, idling very bad with black smoke out of the exhaust. I figured it was a fuel pressure issue, installed a fuel pressure gauge. Gauge read 46psi at idle with vac. I installed a AFPR and readjusted it to 34psi with vac. Car ran fine for about 15-20mins and just crapped out. I thought it would be a coolant temp sensor. i tested it out and came out good, but replaced it anyway. No effect. I also replaced the MAF, injectors, O2 Sensor, cap, rotor, spark wires and plugs with known good ones or new, and cleaned out the IACV. I got to run a little better but it still stutters pretty badly. I dunno what else to check other then the TPS and/or ECM. Weak ignition maybe? Cliffnotes: -Car won't turn on fuel pump -Replaced fuel pump and relay -Rough idle and running rich -Readjusted fuel pressure with afpr and gauge -Runs fine and craps out 20mins later -Installed CTS, MAF, O2, Cap, Rotor, Spark wires, Plugs, with known good items or new. -Runs slightly better, still stutters. -TPS, ECM, Weak iginition?

10-22-2010, 10:09 PM	#2
NiSilS14 Zilvia Junkie Join Date: Sep 2003 Location: Denver, CO Posts: 569 Trader Rating: (20) Feedback Score: 20 reviews	Waaah, nobody?

10-22-2010, 10:51 PM	#4
KrazyS13 Zilvia Junkie Join Date: Aug 2009 Location: Murfreesboro, Tn Age: 40 Posts: 464 Trader Rating: (28) Feedback Score: 28 reviews	If this is a Pre OBD2 model you should perform the ECU's self diagnostic procedure. Many people overlook this simple yet affective procedure and it can be very helpful(not all the time though). Also, do a compression check... Always good to rule that out.

10-23-2010, 01:00 AM	#5
Bigsyke Zilvia FREAK! Join Date: Jun 2008 Location: NA Age: 40 Posts: 1,342 Trader Rating: (0) Feedback Score: 0 reviews	I would check the timing, but make sure you check it correctly or else it wont show the correct reading. 1st make sure the chain hasnt skipped and its properly timed. next make sure you get the car to idle around 650rpms, if its above a certain point the timing is going to be horribly incorrect. I thought i had my timing correct however I would squease the IACV hose and the timing would increase when the idle dropped. Set the idle with the TPS subharness unplugged at 600 rpms warm. If you have bypassed your IACV coolant lines, you want to take the car for a long drive, then let the car idle with the hood closed to enduce heat soak to the IACV. Then unplug the IACV and make sure the idle is at 650 before checking the timing. The adjuster bolt on the distributor should be a tad more towards the firewall side of the distributor house slot. If its not, then your distributor is off a tooth, or your knock sensor is faulty. If the distributor is too far off (off a tooth) then this would create a possible wear spark scenerio since the distance from the center of the rotor to the cap pins has increased. Did your old distributor cap have alot of corrosion on the inside pins? When a spark has to jump it will create alot of corrosion on the pins. Do you still have a catalytic converter?

10-23-2010, 01:44 AM	#6
NiSilS14 Zilvia Junkie Join Date: Sep 2003 Location: Denver, CO Posts: 569 Trader Rating: (20) Feedback Score: 20 reviews	Although timing isn't something I've checked yet, I don't see how anything ignition related could've caused a exxcessively rich condition. I don't see how the car could've jumped timing so bad to be idling as rough as it is. Car drove fine not too long ago. But to answer your questions, there was no corrosion on the cap and rotor. Yes it still has the cat. I'm gonna pull the codes first, should've done that first.

10-23-2010, 09:08 AM	#8
Bigsyke Zilvia FREAK! Join Date: Jun 2008 Location: NA Age: 40 Posts: 1,342 Trader Rating: (0) Feedback Score: 0 reviews	Timing being off just 1 tooth on the distributor can cause these conditions, Its happened to me.