If any of you have replaced one or more fuel injectors or the fuel pressure regulator, or the fuel pump (specifically because of a rough idle and/or stumbling while idling and making slow turns), can you tell me the symptoms that led you to replace them?

I'm asking because my '92 SSE supercharged has always had a rough idle since I've owned it but it seems to be getting worse by the day. There are no error codes.

Lately the idle has been so bad (when the engine is warm) that it sometimes increases boost automatically, to roughly the first mark from the bottom, and keeps it there while the RPMS increase to 800 or so while this happens (kinda like the boost increase that occurs when the AC is on). I doubt it'* a dirty throttle body because the boost needle reads the same after I quickly press the throttle and release it, and I removed and cleaned the throttle body again roughly 20,000 miles ago. And the problem doesn't stop if I put it in park or neutral and then back into drive again.

While starting and driving, there are no other symptoms - no stumbling or hesitation, stalling, hard starting, or anything else except for shuddering while idling and making turns while idling. There is no shuddering or stumbling under load either, even under heavy boost. No fuel comes out of the vacuum fitting on the fuel pressure regulator when the hose is removed. The engine starts right up whether the engine is cold or hot. Fuel economy is good. The plugs and wires were replaced about 20,000 miles ago - the wires measure from 4 to 7 KOhms, and all 6 plugs (Delco, stock) look the same but all are grayish white; the electrodes look normal and there is no oil fouling or other damage. I've recently replaced the PCV valve (Delco), TPS sensor (Delco), IAC sensor (Delco), MAF (Delco), the digital EGR valve (Delco), all 3 coil packs (Delco), the fuel filter, and the O2 sensor (Delco). I've checked and rechecked all vacuum lines; note that I sometimes hear the fuel vapor canister solenoid chattering - why is that? The catalytic converter was recently replaced just because it was the original and I thought it might have been partially plugged, but according to the muffler shop owner the old one was still good and the engine had been running clean.

The engine was rebuilt shortly before I bought it, and I've driven it around 50,000 miles since then. I looked at the timing on the #1 cylinder at idle, and the mark didn't jump around.

Could a bad injector cause this symptom? I don't see how that could be because the engine doesn't stumble under load or at freeway speed, and all 6 plugs look the same.

Could it be a bad fuel pressure regulator?
A bad fuel pump?
A fuel pump sock that fell off or a tank baffle that came loose?
A bad ignition module?
A bad boost solenoid?

Can anyone help?

What do your plugs show?

A dead injector would make the 02 show lean and richen the hell out of the car. a slow pump would make the pcm richen, but it would actually be the right burn so the plugs would be normal.

Fuel issues are pretty hrad without a scantool.

Mine is kinda similar. I've replaced/reconditioned/checked/rechecked the entire fuel delivery system and ignition system in the last year.

This car has had a rough idle since I bought it used, and I've replaced plugs and wires a couple times and the rough idle remains. I think I hear the fuel vapor canister solenoid rattling sometimes, and I don't think that'* supposed to happen.

Last night I replaced the air filter and the o-ring around the pcv valve. I also performed a scan with my Actron scanner and OCT MindReader scanner. Although I've owned these scanners for quite some time, this is the first time I got around to using them . Here'* some data taken at idle while the engine was hot and my foot was on the brake:

Actron CP9110 with CP9111 cartridge (software v2.0):
Batt: varied from 13.4 to 13.7 volts
BLM: varied from 142 to 149
BLM Cell: 16
Coolant: 208 degrees
EGR sol 1: off
EGR sol 2: off
EGR sol 3: off
ESC counter: 0
Exhaust o2: varied between lean and rich
IAC posn: 30
Idle Req. rpm: 625
Integrator: 127
Knock Ret: 0
Loop Status: clsd
MAF (gr/*): varied from 1089 to 1110
MAT: 115 degrees F
O2S: quickly varied from 300 to 800 mv
O2S Crosscounts: varied from 11 to 17
Quad Driver 1: bad
Quad Driver 2: good
Spark Adv: 24 degrees
TCC Applied: no
TCC Brake SW: on
TCC Slip RPM: 256
Throttle (%): 0
TPS Sensor: varied from .39 to .41 volts

OTC Mind Reader 3750:
A/F Ratio: 14.8
Batt: varied from 13.3 to 13.6 volts
BLM: 144
BLM Cell: 16
C/C Error: 1
Coolant Temp: 98 degrees C
Driver SS: Norm
EGR sol 1: off
EGR sol 2: off
EGR sol 3: off
Engine RPM: varied from 626 to 671
IAC: 31
Idle rpm: 62 x10
Integrator: 131
Knock Retard: 0
Knock Signal: no
Loop Stat: clsd
LV8: varied from 38 to 41
MAF: varied from 4.19 to 4.28 g/*
MAT: 47 degrees C
O2 Cross: varied from 16 to 21
O2 State: varied from lean to rich
O2 Volts: quickly varied from .28 to .76 volts
O2S Crosscounts: varied from 11 to 17
PRNDL Switch: INVLD
QDM 1(A): high
QDM 2 (B): low
RAW Servo: 54
SHT Wire A: high
SHT Wire B: low
SHT Wire C: low
SHT Wire P: hi
Spark Adv: 23 degrees
TPS: .38 volts
Troubl Code: no
Vats Sys: Yes
Weak Cyl: None

It seems the MindReader provides a little more data, and it'* odd that the MAF readings are so different between the two scanners. According to the factory shop manual, the MAF readings should be around 4.2 g/*. I also noticed that the Actron reported Quad Driver 1 to be bad, but I read on this newsgroup that this appears to be a software problem with that scanner. Would anyone care to comment on what this data in regards to the rough idle problem?

It just dawned on me, though, that I also need to check the supercharger base gasket for a vacuum leak under the nose side. I've read that those gaskets sometimes leak on the nose side, and that might cause idle problems.I'll take a look at the gasket tonight. :( :(

I think that the quad driver is switched to bad on mine as well when i push the brake. Try hooking it back up and see if it changes when you let go of the brake. Also I dont think that your tps voltage should vary if you do not touch the gas pedal.
Someone correct me if I am wrong, I am pretty new to this scantool stuff

QDM faults when the brake is pressed is a known bug. Ignore it.

Okay, Either your 02 is dead and you're filty rich, or your fuel delivery isn't up to par.

Check fuel pressure, and there'* a test for injectors, deals with ohms and things.

I checked the resistance on each injector a while ago, and they all measured roughly 17 Ohms if I remember correctly.

I'll try to find a fuel pressure gage and measure the pressure at idle, but at this point the first thing on the list for me to check is for a possible vacuum leak under the supercharger base gasket. If I spray carb cleaner in that area and it affects the idle, then there must be a leak and I'll fix it...but I don't want to remove the supercharger just to replace the gasket unless I'm sure there'* a need to do that.

By the way, I have another fuel pressure regulator, but I've never replaced one. I see the retaining ring on the back and I know how to remove that, but once that has been removed, is the regulator then unthreaded to remove it, or is it simply pressed into the opening?

I could be wrong (electical problems are not my strong suit) but aren't the tps readings a little high for being at idle? Probably has nothing to do with the problem and I'm probably completely wrong anyway :?:

TPS seems right. The FPR just pops out once you remove the snap ring. Give it a good pull, maybe a twist.