Cruising and car suddenly changes tone

[desolateboosted]

Ok I'm cruising on the highway at around 60mph. The whole time just listening to some music. All of a sudden my car's RPMs drops from 3000rpms to 1500rpms while staying the same speed! The car's exhaust tone changes and it feels like I'm running on 2 or 3 cylinders. I have absolutely no power. Boost won't come on only like 2 psi. I'm like WTF just happened?! I pull off the nearest exit and pull over to a gas station. As I sit there the car is idling at 350 rpms! It has never idled so low before. I have 272/272s in and I know that if the rpms idle around 600 or less the car will die. But my car now is idling at 350rpms and there are a lot of vibrations. I decide to come home and diagnose it.

I get into the garage, open hood, everything seems fine. I check all the connections for electrical and hoses. tps, mas sensor, cas, isc, plug wires. They are all plugged in. Ok maybe my spark plugs took a shit. Changed those out start car. I still have the problem. Car is still idling low and I have no power. The rpms are acting very strange too. Like if I'm in 1st gear it will go up to 30mph and I will be at 3000rpms. It should be near redline! Next I do the plug wires. That didn't fix it. Coil Pack. Nope. Checked the timing belt and checked to see if I skipped any teeth. Nope all is correct. ECU is next. Nope not ECU either. Opened up valve cover. All rocker arms are still intact and head/cams looks fine. Ok I'm stumpped now. I don't know wtf is going on and I don't know how to fix it. I need help. I've tried just about everything I can think of.

 

[spshocker61]

I would want to say check your fuel options....like maybe injector clogged....but the 3k rpm at 30 mph isnt explained by that. It sounds like you have an interesting problem...how do you plan to check the ECU? If you can I would seriously consider getting ahold of a scan tool....if it threw a code that could be some good help. Just a few cents i found between the cushions of my brain. good luck

 

[desolateboosted]

I replaced the ECU with my old one I had laying around. I have a logger but friend is borrowing it right now. Will check to see if any codes comes up tomorrow. Although the Check Engine light has not lit up this whole time.

 

[desolateboosted]

I forgot to add I also did a boost leak test to see if I had a huge leak. Results came up with nothing more than the usual small pin hole leaks I had before when I didn't have this problem.

 

[spshocker61]

k....if you replaced the ECU make sure that you run the car so that it can relog the code...that is hoping that it is logging one. Hope that it sheds some light on the problem. I dont understand how the car can idle at 350 rpm....I assume it sounds like it is struggling a lot to keep on its feet at idle? I mean if it had a dead cylinder at that rpm then it wouldnt stay alive...thats too much dead weight on the crank to keep it going. It seems like it almost has to be a computer/sensor/ vacuum problem...but that still doesnt explain how the idle is possible WTF

 

[desolateboosted]

I did drive it around a little bit after the ECU installation. Check Engine light didn't come on. But I'll check it with the logger tomorrow. I don't understand either why it can idle at such a low rpm. At that rpm it just sounds like it's chugging... chug chugh chug chug... Only thing I havn't done is a compression test. Last time I did it (bout a week ago) it was 180 all across and 165psi on cylinder #2. I'm asumming it has to be a computer/sensor problem also. The thing that throws be off so badly is the rpms ratio to speed. It has changed like I'm running very very tall gears or something. I can't figure what would cause that.

 

[94Jettameowpsst]

check your transistor pack by ur coil pack it may have come partially unplugged, the same thing would happen to my 90 and if i would just hold it to the floor, it would throw a few nice big fire balls. Also it threw a cel

 

[desolateboosted]

I checked it also. It only has one plug right? Long about 2 inch rectanglish looking? If so that's plugged in. I pulled it out and plugged it in again. Started it up, still having the problem.

 

[desolateboosted]

Does the transitor pack send rpm signals to the tach/ecu? If so I might have a bad transitor pack then? That's the only thing I havn't changed yet.

 

[spshocker61]

Even if it did send the signal...its not bad b/c the signal must be right based on how your car is running...at least i would think.

 

[desolateboosted]

OK FOUND out the mot$#@herf$king problem! It was the power transistor. That bit$#@ch died on me.

 

[blackGSX2g]

Yep, I woulda guessed that as well. Same thing happened to me last week, same scenerio as you on the highway. My CEL popped right on for a misfire and I cleared it and figured it was the 6-bolt swap plaguing RM code, but it didn't go away. Once I noticed the tach weirdness I knew exactly what it was. Grabbed a spare from my garage and it drove 100% again. Don't know what caused it to go out like that, but it hasn't happened since.