Damn, 3.4 DOHC problems already!

[GnatGoSplat]

I'm having problems with the 94 3.4 DOHC Cutty already.

It ran and drove fine. Then one afternoon, it idled rough, but ran and drove fine on the highway.

After sitting for a day, the car was difficult to start. After starting it up, the car would run for a second or two, falter, then die. Restarting it was the same problem. Thinking maybe it was an IAC problem, I had Penny (my wife) step on the gas just a little bit when it started to die. She did, and then the RPM's raced up to 3k or so and started coming back down slowly again, then raced up to 3k again.

 

Weird.

 

I'm gonna buy some carb cleaner to check for an intake gasket leak, but let me know if this sounds like it could be something else.

[SuperBuick]

Sounds like the IAC. I had a similar problem, took it out and cleaned it, and it worked OK. Check the O-ring and the pintle thingy. - Tom

[weisinator]

I'm having problems with the 94 3.4 DOHC Cutty already.

It ran and drove fine. Then one afternoon, it idled rough, but ran and drove fine on the highway.

After sitting for a day, the car was difficult to start. After starting it up, the car would run for a second or two, falter, then die. Restarting it was the same problem. Thinking maybe it was an IAC problem, I had Penny (my wife) step on the gas just a little bit when it started to die. She did, and then the RPM's raced up to 3k or so and started coming back down slowly again, then raced up to 3k again.

 

Weird.

 

I'm gonna buy some carb cleaner to check for an intake gasket leak, but let me know if this sounds like it could be something else.

 

My Lumina 3.1 did that after I had the car for 6 months. Turned out to be the ECM.

[GnatGoSplat]

Bummer, it wasn't the IAC.

I took out the IAC, cleaned it real good (it was covered with carbon). Lubed it up, reinstalled.

When the car started, it was up at 2k rpm then slowly drifted down to less than 500rpm, trembled, then revved back up to 2k rpm and did the same thing until it settled at about 700rpm and seemed to be fine, but sounded/felt like it had a bit of vibration and miss.

 

BUT, I know something is definitely wrong, because it has a "Service Engine Soon" light on, so the ECM is storing codes. The problem is this is a 94, so I can't pull codes, UGH!!!

 

The IAC was VERY black with soot, like exhaust. The exhaust was also very stinky, like it was running quite rich. I'm wondering if maybe I have an EGR problem? I sure wish I could pull the code. Does anyone know of an inexpensive scan tool that can pull codes from a 94 3.4 DOHC?

I'll also have to see if Diacom supports it (I doubt it) or maybe there's some software out there for the MAX232-based serial ALDL interface?

[LukeZ34]

Stinky exhaust? Might very well be an O2 sensor that's shot. The weird idling could be cause by a leaky intake gasket.. those are the 2 things I would look at.

[RedZMonte]

Bummer, it wasn't the IAC.

I took out the IAC, cleaned it real good (it was covered with carbon). Lubed it up, reinstalled.

When the car started, it was up at 2k rpm then slowly drifted down to less than 500rpm, trembled, then revved back up to 2k rpm and did the same thing until it settled at about 700rpm and seemed to be fine, but sounded/felt like it had a bit of vibration and miss.

 

BUT, I know something is definitely wrong, because it has a "Service Engine Soon" light on, so the ECM is storing codes. The problem is this is a 94, so I can't pull codes, UGH!!!

 

The IAC was VERY black with soot, like exhaust. The exhaust was also very stinky, like it was running quite rich. I'm wondering if maybe I have an EGR problem? I sure wish I could pull the code. Does anyone know of an inexpensive scan tool that can pull codes from a 94 3.4 DOHC?

I'll also have to see if Diacom supports it (I doubt it) or maybe there's some software out there for the MAX232-based serial ALDL interface?

go to a parts store they can pull a code for you.. once you get the code form them that will tell you what you need to fix. or you can also buy the code readers from a parts store for like $15.

 

RedZ

[DropTopOlds]

Mine was doing that and it was the lower intake gasket. Except in the morning mine would rev to 3k then lower slowly, then falter and die. only after it got warm would it run smoothly. Strange thing, though. If it idled too long (when cold) the SES light would come on, and if I drove it ~10-20 feet it would go off.

[cutlassdude96]

yea I would just goto Autozone and have them scan it.

[Guest blue68442]

I have not had this problem, but from all I have read on the engine.. It is a leaky intake manfold gasket..

[GnatGoSplat]

Yep, that's what it was. A leaky lower intake gasket.

[gtr252]

I've got the same problem with my '94 3.4L Cutty, haven't even tried to fix it yet. Possibly the lower intake gasket? I might try that one sometime. A buddy at work told me it was something called the "Idle Control Module", but I'm not sure if thats also known as an IAC or not. Is the lower intake gasket hard to check or replace? I haven't really looked at it too much.

 

Took my front valve cover off today, stripped the powdercoating off and painted it in that new aluminized red paint, looks VERY sexy. Can't wait to clean up the rest of the engine, it'll be looking really nice after I get done I hope. I'll get some pics up for you guys sometime.

[GnatGoSplat]

By Idle Control Module, he must mean the IAC because there's not much else.

The lower intake gasket is extremely easy to check. Just get some carb cleaner from Wal-mart (only 78-cents a can), start up the car, and spray around the lower intake gasket and plenum gasket. I think the lower intake gasket is more likely than the plenum gasket. If RPM changes, then there is a leak in the gasket. On mine, it almost stalled the engine every time I sprayed.

 

To replace is not so bad, but many things have to come off. Enough that you could miss something on reassembly and have to take it all apart again. I have mine apart and just got the gasket today. I'm REALLY hoping I don't end up with extra parts. I also did a pretty trashy fix to my oil pump drive O-ring leak and I'm hoping that will hold up or I'll have to take things apart again.

[ctx46]

No, I believe the idol control modual is what control the IAC.....

[GnatGoSplat]

The PCM controls the IAC. There is no intermediate module.

[GnatGoSplat]

Hahah, almost a month later I finally got around to replacing the intake gaskets. The car gave me a great scare... idled great until it warmed up enough, then it wouldn't warm idle at all. It surged several times and then died. I couldn't keep it idling. I pulled the yellow 20A ECM fuse, put it back in, and it STILL wouldn't idle. Suspecting maybe there was still a leak, I sprayed carb cleaner everywhere, and nothing changed. I held it at about 1500rpm for awhile, let off the gas pedal, and suddenly it smoothed out and idles fine. Now it seems to run great. Took it for a spin, seems to run and idle perfectly. If it stays like this, I'll be happy.

 

One thing I noticed, the temp gauge only goes up to the 1st tick mark above cold. My 89 Cutty and I believe my GP goes almost, but not quite to the middle. Maybe the 94 just has a different scale on the temp gauge? I noticed the 2nd tick mark is bold and has the label "200", but it isn't even halfway. Do I have a thermostat stuck open or something? I'm pretty sure I bled the system correctly, only coolant comes out of the T-stat and heater bleeders. The radiator hose feels hot. I checked and the harness is plugged into the sensor on the head, so I think it's hooked up. Any ideas?

[ctx46]

I ment the drivers in the computer that controls the IAC....... I didnt mean another component at all...... I glad to here its working ok now....

later

[rmac24vdohc]

My 94 DOHC is the same way with the thermostat. Stock 195 but sits right at that second bar halfway between 100 and 200. Also, I have noticed that if I take off on a hard start and leave it floored through 1st and 2nd gear the temp goes up near 200 then comes back down quickly. What causes that?

 

Mac

 

1994 Olds Cutlass Conv 3.4DOHC

2001 GP GTP

[gtr252]

my '94 cutty with the 3.4L almost always stays at 200. I used to have a 160 degree thermostat in it when I bought it but that didn't let the heater warm up enough during the summer, so I bought a 195 and put it in, stays at 200 just fine now. Your thermostat could be stuck open, not sure though.

[luminator94]

My thermostat went a little nuts on me to for awhile in my 3.1L, its still not right. I changed EVERYTHING and it still wasn't right. So I finally took it to a reputable garage to have the damn thing fixed, cuz I didn't want to do any damage to my engine. Here's what the put on my invoice printout:

 

"Customer states that car is overheating, mostly on hills. Customer has already flushed coolant, changed sensor on thermostat housing, thermostat and fan switches, states that fan does not seem to come on when it should. Checked for overheating, engine coolant temp on scanner range from 187 degrees to 192 degrees on highway and up hills. Needle on gauge reads 3/4 of the way up scale and in the red zone. Checked eletrical cooling fan operation-both fans operate as designed. Installed signal generator gauge temp sensor connector and sweep resistance. Gauge reads inaccurate, SENSOR PIGTAIL DAMAGED."

 

So whatever the sensor pigtail is must have caused this in my car. The gauge always reads hot, so I'll never not when my car is really overheating until the ole' steam is rollin' out from under the hood.

 

 

Aaron

[Guest]

yea I would just goto Autozone and have them scan it.

 

Mine is a 95..the put the key or whever it is on the thing and nothing, took it to gm, nothin/ I get no explanation on why i can get my service coeds and am told to replace the pcm...that sounds cheap Ahh...who really cares my car runs grrreat. Is there any way to try and read the codes with a paper clip of some sort?

[Guest]

I forgot to mention my hypertec 160 degree thermestat which was the biggest differnce i have made on the car....low 15s and it was cheap

[cutlassdude96]

yea I would just goto Autozone and have them scan it.

 

Mine is a 95..the put the key or whever it is on the thing and nothing, took it to gm, nothin/ I get no explanation on why i can get my service coeds and am told to replace the pcm...that sounds cheap Ahh...who really cares my car runs grrreat. Is there any way to try and read the codes with a paper clip of some sort?

 

If you have the 16 pin OBDII conector, then you are the second person that cant get there computer read. Some dude on GMF with a 95 Aurora has the same problem. You cant use a paper clip if you have the 16 pin conector.

[GnatGoSplat]

94-95 3.4 DOHC's are OBD-I and has the same OBD-I diagnostic connector (12-pin?) as 88-93. Only thing is the diagnostic pin is missing. I've checked schematics, and there's no diagnostic pin on the ECM itself either. It's a modified version of the 88-93 ECM but has more injector drivers for SFI. I can only theorize that they ran out of pins and dropped the diagnostic pin.

[brian89gp]

from what i have gathered 94-95 are an OBD1.5. Everything is different down to the ALDL communications. It also uses OBD2 SES codes. Strange

[GnatGoSplat]

94-95 3.4 DOHC ALDL communications are the same.

I hooked up an '89 Cutlass trip computer to the ALDL of the '94 and it read all the data correctly. It reads coolant temp, tach, and volts off the ALDL properly. I'm not sure about anything else though.