Hi folks, hope y'all can assist me...

93Z28, over 165K miles on it, had the opti cap/rotor kit done @ 141K, during the past week my car has been runnin kinda crappy...

Here's what has happened during the past week. Been using Chevron gas for the first time in a long while, prior to that I have used Mobil exclusively.

the past 3 days I have noticed that, once the car warms up, the damn thing stammers real bad between 1000-2000 rpm, once past 2100rpm it seems to smooth out. On the freeway, doing 60-80 mph, if I'm in 6th & floor the pedal, the car feels like it's only running on 6-7 cylinders, the thing stammers, coughs, THEN once the rpm's get over 2300 rpm, it starts to smooth out--ONLY if I keep the rev's up!

I cleaned the K&N stock filter replacement last saturday, I was thinking that maybe that might have caused some problems?

Gosh, I dunno, I checked my recent dates, had the fuel injection system cleaned out via Jiffy Lube September 2002, only 10,000 miles ago. Fuel filter & plugs changed 10/19/02...

???

Someone today told me maybe my EFI needs cleaning, told me to buy Outlaw Fuel System Cleaner, so I did & filled up the tank with Mobil premium, & wifey & I took it out for a spin...

It was fine! Until the car got warmed up, then the same stinking thing! How embarrassing it is to try to make a left turn from a standing start & the car literally coughs so bad that it almost stops, then skreeches away???

By the way, when the A/C is off, it runs much smoother, I found out that apparently the A/C clutch is not disengaging all the way, so do y'all think that maybe this has something to do with it?

Tomorrow I'm going to Jiffy Lube & have them do their fuel injection cleaning thang.



I'm irritated right now, if y'all have any suggestions I would GREATLY appreciate it.

Thanks.

 

You are probably wasting your money on the fuel injector cleaning, but who knows? You might want to change your fuel filter, though and also check fuel pressure with a test gauge.

Gut feeling is the opti or the ignition control module (ICM). Either can give heat related troubles. If there was a way to operate it with a scan tool connected, that might lead you in a particular direction. You could have a sensor acting up after you have gone into closed loop.

 

have you replaced the plug wires lately? Wifes car did something similar, her's is a 3.8L though. She had a spark plug that was arcing at the plug. Seems like you are only getting the stammer maybe only under high load situations?? I dont know though.

Jason

 

Thanks for your responses guys.

Hmmm...I changed to 8mm blue wires when I changed the plugs back in October, so they're fairly new...
My gut feeling is that it's the Opti as well...

 

Carlos, let me know what you come up with on your car. I am experiencing a similar problem with my 94...

 

TTT

 

I have your EXACT same problem. In regards to turning off your A/C. Is it just when A/C is on that you have the problem? Or when you have heat turned on as well. Because regardless of whether heat or A/C is on, mine does it as well. It's not a repeatitive problem. Very intermittent. Always happens under 2000 RPM, and usually when coasting in 4th. Feels like a quick hiccup or something. Takes about a second where it hesitates, and all is normal again. If I shut off the environment controls altogether, then it's completely fine. I noticed a few months ago, that at idle when the car is warmed up, I can here something turn on, like a click sound, idle fluccuates for a second, then goes back to normal. I beleive it's this sound that is the cause of the problem. A buddy of mine however told me the sound was normal, and was just the A/C compressor. I really don't think it's the Opti, because of the fact, tuning off enviro controls seems to fix the problem. Only thing is I can't leave them off, because 1) It's pretty cold where I am still, nad 2) I can smell coolant from the heater core, when I shut of the controls. Get's to be a little annoying!

 

I have some more info regarding the problem. Hooked the car up to the laptop yesterday, and ran Datamaster to see if showed anything abnormal. Let it idle for like a good hour. Things I noticed....

1) When I hear the click sound, MAP Pressure, and A/C Pressure Increse. My normal MAP pressure is about 30-31kPa. After the click sound, it shoots up to about 34-35. This lasts about 3 or 4 seconds, then you here the click sound again, (Sounds like it shuts off) MAP pressure goes back to 30-31.

2) Turn the enviro controls off, no more click sound.

3) ECM is reading the outside Air pressure wrong. Pressure around here is about 101kPA on any given day. My ECM reads it at 93ish usually. Is this normal, or odd? Should the ECM be that far off?

4) Fans are acting weird. 1st fan turned on at 111 degrees, and shut off at 146. Came back on at 168, and second fan kicked in at about 184. Both stayed on and tem stas at around 185.

Don't know if any of this helps, but I think the problem is definately related to the A/C somehow. My A/C pressure also went way up, to about the 100's After the On click sound. When it shut off, the A/C pressure went back down to about 60 or lower sometimes. ANyone know what this value should be at? SHould it be fluctuating this much? Is it not holding the pressure it's supposed to?

 

Hate to say it but I'm having the same problem. I thought it was my opti too since I've never had it off. However, my car has the same symtoms as all yours. It seemed to have started when my A/C started cooling off. After some checks I've got a bad valve on the evaporator. It is not equalizing the pres so the high side temp goes up and press and it is just a chain reaction from there. The PCM DOES control many things in the a/c and uses engine to control it.

Bottom line is I need to replace the valve block and dryer.

I also have the 1-2k stumble and thought it was bad gas, fuel pres, ign and so on. It comes down to the valve block on the evap.

My .02...

 

I live in orange county (los alamitos)California too and my car started to run rough after we had all those windy days blowing dust and dirt allaround last week.

I wonder if we are both having similar problem as a result to something in our engines getting dirty or clogged.

I have a similar thread on this forum too since I replaced my opti and water pump about 8 months ago and it has been running perfect up until late last week.

 

ZRAG man, if that is the culprit, YOU ARE THE MAN! How do I go abouts confirming that is my problem as well now? Other than taking it to some A/C place for a big Bill! Is there a fuse to pull or something? Any idea how much to replace this "Valve Block."? Damn A/C. I never even use the thing. I knew it was going to be trouble some day. Anyone else here use datamaster? What is A/C pressure supposed to be at? And should it be constant?

 

Is it possible that if the AC sucked in a lot of dust and dirt it could cause it to go on the fritz?

 

Ok guys. Mine only does it when hot and A/C on. Last week we had some record highs down here.

The thing is it is a bit complicated. The ac has a high and low side, basicly hot and cold. As temps go up in engine bay and high temps outside the ac needs to work harder. Theory is it is much more difficult to keep the freon compressed (cold) due to hotter freon going into the compressor. Thus it needs to work harder. As a result when the evap valve block is not working right, balancing the pressure of incomming freon and hot freon exiting the hot freon builds up faster than the condensor can cool it. So the high side pressure will go up to 400psi highside in my case and 15psi low side. Remember the compressor is turning with 400psi that must put on a load. Ideally it should be 45psi lowside and 150psi on the high.

I figure it is having a problem at a transition from 1-2k rpm when psi is up. That is when the PCM determines to turn off and on the compressor according to idle speed and temp.

I am also going to insulate the ICM from the hot temps to see if that helps.

I'm by no means an expert but an ac check up can run $20-60. Your call.

Good Luck

 

For the most part my car is running fine when the AC is off but as soon as I turn the AC on the car start to idle rough and sometimes stall at stop lights. So right now Im just keeping the AC off until I can get the car in the shop to get the AC fixed.

Does anyone know how much it will cost to fix this whole AC thing?

 

OK FIRST OF ALL I HAVE HAD THE SAME PROBLEM FOR A WHILE ON MY 94 Z. LOTS OF TIMES YOU NEED TO HOOK UP A SCANNER SEE IF ANY CODES COME UP . I HAVE REPLACE THE CAP AND ROTOR AND OPTI AND SPARK PLUGS. STILL RAN ROUGH IN FACT ROUGHER THAN BEFORE. HAD THE INJECTORS CLEANED VIA PRESSURIZED CLEANIN NOT THE CRAPPY VACUUM INSTALLED WAY THESE QUICKLY LUBES USE. THIS MADE A HECK OF A DIFFERENCE. HOWEVER I WAS STILL LACKING POWER. AFTERWARDS DOING THIS MY SERV. ENGINE SOON LIGHT IS COMING ON........ GUESS WHAT GUYS THE EGR VALVE AND SOLENOID. THIS CAUSES THE CAR TO HESITATE SPUTTER LOSS OF POWER BACKFIRE AND MAKE THE CAR DIESEL AFTER SHUTTING IT OFF. WE ALL SEEM TO THINK OF THE OPTI SPARK FIRST BUT WE FAIL TO REALIZE THAT WHEN THE OPTI SPARK GETS SO BAD THE CAR USUALLY WONT RUN AND OR WILL NOT EVEN REACH A HIGH RPM. I HAD THE EGR FIXED AND RUNS GREAT . SO BEFORE YOU PAY OUT THE YING YANG FOR THE DISTRIB. KIT LOOK INTOTHE CODES OF YOUR CAR CHECK TO SEE IF YOUR EGR IS FUNCTIONING PROPERLY .... SOMETIMES THE OBVIOUS IS EXACTLY THE OPPOSITE: