93 regal misfires (tail pipe explosions and smell)

[noclues]

i have a 93 regal that misfires - at least that's what i assume it's called when i hear tail pipe explosions and smell as if you're lighting matches. no smoke. the engine rpm varies a lot and sometimes cuts off. the whole car is shaking like one of those adventure rides!

it has done this twice in the past couple of weeks when i start it after a few days of sitting there. the strange thing is that it goes away after a few minutes of running or at the next start after it cuts off. so it's driving nicely as usually after the initial fits. it's not doing this while driving at least not yet.

last oil change was about 400 miles and about 2 months back.

i pulled the wires going to the coils and it's sparking so they appear fine. it's the same gas tank on both occasions (more than half used) - not driving the regal more than a few miles a week.

so i'm wondering is it dirt in the gas or a problem with the gas filter/pump? or could it be the oxygen sensor or smth else?

3.8 engine, 151000 miles - blinks code 17 when connected to A/B.

any help is appreciated!

[HotZ28]

Do you have any DTC's stored? 1993 can be checked by jumping ALDL terminal A&B to get the codes. Let us know the mileage of car also.

[noclues]

151000 miles - blinks code 17 camshaft. i wonder could it be "partly" broken so that it works most times but then some times the computer loses track and tries to go into failsafe?

BTW - when i plugged the AB paperclip and turned the key (not crank) the big fans in front of the engine started to rotate wildly and after disconnecting them (pulled the 2 relays) there was still a constant clicking coming from the driver's side of the engine (about where the ABS and horn are). any idea why? all this stopped once i pulled the paperclip.

[HotZ28]

Code 17 according to my book is; PCM did not detect any spark reference pulses within 240 fuel control reference pulses (80 crank revolutions) while engine was running below 1200 RPM. Spark Reference Circuit. ECM fault crank position sensor circuit.

BTW, fans will run and relays will click when in the diagnostic mode.

[noclues]

Originally Posted by HotZ28

Code 17 according to my book is; PCM did not detect any spark reference pulses within 240 fuel control reference pulses (80 crank revolutions) while engine was running below 1200 RPM. Spark Reference Circuit. ECM fault crank position sensor circuit.

BTW, fans will run and relays will click when in the diagnostic mode.

hmm i used the haynes book for the code.

so what exactly do i need to check and how?

[richtazz]

Does your car have a 3.1 or 3.8 engine?

[noclues]

Originally Posted by richtazz

Does your car have a 3.1 or 3.8 engine?

3.8

[richtazz]

I also show code 17 as a camshaft position sensor circuit problem. The ECM uses signals from the cam and crank sensors to adjust spark timing. Your problem could be either the cam position sensor itself, the wiring to it, or the magnet in the cam gear that the sensor picks up it signal from.

[HotZ28]

This can also be the crank position sensor (CKPS), or the ICM is failing to buffer the spark reference signal to the PCM. During normal operation, the PCM uses the spark reference signal to control ignition timing until the engine speed exceeds 1200 rpm, at which time the fuel control reference signal is used. If the window on the harmonic balancer is interfacing with the 18x Hall-effect switch, the ignition control module will ground the spark reference signal. When conditions exist for setting DTC 17, the fuel reference is used by the PCM to control ignition timing advance. This condition will cause module mode to be used for timing advance below 400 rpm and IC ignition timing to be degraded below 1200 rpm. If connections and harness are OK, try checking voltage on CKT 647 (terminal C - LT BLU/BLK) with a DVM while moving the related wiring harness and terminals with engine idling. This may help isolate the location of the malfunction.

[noclues]

thanks for all your replies!

next time it does this i'll check terminal 647. it reminds me of the TPS problem i had some time ago - when the sensor had a "bad" spot and it would only have the issue sometimes but work fine most of the time.

i've also found out that Murray's doesnt loan those Actron scanners anymore - for some odd reason... too bad they did help a lot.

[noclues]

i've been quite busy for a while but tonight i located the camshaft sensor and it's a pain to get to so i'm thinking of alternatives.

the car cuts off when idling at a light (or in the parking lot) but works fine when driving. it also surges sometimes close to 2000rpm then back to 800 or so as if it's randomly getting too little then too much air or fuel - also in idle mode only. also in idle if i rev the engine it sometimes stalls after the rpms come back down.. could it be the knock sensor or the IAC? just asking because i read the knock sensor causes the ECM to retard the knock and even cause rough idle if broken. same goes for the IAC... and they are both much easier to replace or test!

how do i test the knock sensor?

can i clean the IAC without removing it? i'd like to reuse it after removing because it's 60 bucks... is it safe to remove it or will it break considering the car is 15 years old?

thanks!

[noclues]

ok i got a spray can of throttle/carb cleaner and one of silicone spray for 7 bucks total. took out the IAC (a pain!) cleaned with carb cleaner on the pintle and the inside of the throttle body, then finished off with a spray of silicone. i also checked the resistance of the coils (55 ohms in AB and CD). at first i forgot to reset the computer and the car wasnt really starting. then i did the 5 second on/10 second off and it started just fine.

BTW to put the screws back in i tied them with beading wire (or other wire) and secured around the throttle body or wires in the area. this way i made sure they dont fall off if i dont screw them in properly.

the test drive was very promising. no more idle surging, just barely at the beginning when the engine wasnt warmed up. the idle is pretty much constant around 900 or so rpm even at the longer stops at lights. it's quite amazing because even though i did soil a lot of cotton swabs, it didnt look like a lot of buildup.

i hope that solved it...

[noclues]

NOT SOLVED... it died again when i stopped at a light. the engine just stops, no noises or vibration, its as if i turned off the ignition - and it can happen 5 minutes into the drive or just before i reach my destination 40 minutes later. started up rightaway as usually...

so i decided to replace the $2.99 PCV valve. old one looks full of gunk and barely rattles while the new one is moving a lot more inside. the test drive was fine (as usually) and the idle is stable around 900. now remains to be seen in day to day traffic...

if that doesnt doesnt work i read somewhere there's a re-learn procedure (disconnect battery and retrain car like here http://www.v6z24.com/howto/idlerelearn )... or adjusting the minimum air rate screw for the idle - although thats probably not the case.

if you have any other ideas of what to test i'd really appreciate it!

[noclues]

not fixed... stopping got worse. it's actually stalling just when i get close to a red light that turns green sometimes. so i have to stop all the way, park and then restart with ppl assuming i'd accelerate. almost got rearended

[noclues]

i removed the MAF connector and immediately got SES light on. codes are 34 (maf sensor) and 26 (quad driver) - i assume it was caused by the voltage surge when i removed the MAF.

the idle appeared to improve with it unplugged! when i plugged the connector back into the MAF the engine started choking. after revving it a bit it got back to around 1000 rpms but it wasnt an even idle.

i'm planning to change the Crankshaft position sensor first and if that doesnt do it then it's the more expensive MAF...

any other suggestions? please any help is appreciated as driving the car is becoming dangerous with all the stalls at lights.