M/T Failing? Don't know how to determine . . .
 

For the most part my Engine seems to be running pretty well. It has a slight sputtering at idle, but I have been through every system I can think of. My timing belt skipped 17 teeth so I did a timing belt/water pump job, and the noisy engine thing is minimal now ('93 MX-3 1.8L V6 with the noisy exhaust cam washer thing). My primary problem is a seemingly HUGE loss of Horsepower. Poor acceleration, down 30-50% I would say. On the expressway, full foot to floor will get me a top of about 81 mph, and, with any slight incline, my speed drops down from that, so, I can barely maintain Highway speeds. Car has 265,000 miles on it, and owes me nothing, but I do need to figure out my main problem. My neighbor suggests a possible failing Manual Transmission. I can see his point; if the M/T is failing, there could be tons of extra friction within it robbing all the lost horsepowers. Thing is this: I have never experienced this kind of failure. Shifting is as good as it has always been for me, owning the car for the last 30k miles. Clutch is fine; nothing is behaving differently about the transmission, other than possible increased internal friction of some sort. Has anyone here had anything like this happen? Also, I have kept close tabs on my cylinder compression. All cylinders remain at + - 200 psi, still, even with so many miles on it. (By the way, the timing belt that came off looked totally OK, but I now understand that we have suspect automatic tensioners. The idlers were slightly worn, but, not enough to skip the T belt). I am currently trying to ratchet up my plans to do a JDM Engine and Transmission Swap because of my big issue. Whatever it might be, it is significant enough to worsen and strand me (again). Any input would be highly welcomed, and thanks in advance.

A few comments:

• A failing manual transmission is beyond unlikely given the symptoms. Think about it, to rob the car of that much power, the heat generation in the transmission would be so high it would cook the MTF (which would make shifting problematic).
• Given the engine seems to start and idle relatively well and has decent compression numbers, I'd start looking at the O2 sensors and the catalytic converter (I'm betting on the latter).
• How many miles between quarts of oil?
• Does the engine use any coolant?
• What is your fuel economy like?

Thanks for response Shipo. I didn't think it through that well, Yes, the friction would create tons of heat if the Tranny was the culprit. But BTW, what is the MTF? Now, before I did the timing belt job, I checked compression in four cylinders, and they were all down to 120 psi. That is what convinced me to go ahead with that job. Now that the timing is correct, I probably should do it again just to verify improved compression. Both O2 sensors are very new; Bosch brand (which I invested in after crappy results from eBay cheapo's_). The cat is basically new too, and I did take it off a couple weeks ago to verify not the problem, as that was suggested by two different people. Oil consumption hasn't been that bad, and has even improved since I started using AT 205 Reseal, but I can't give you numbers on miles / quart. Engine uses no coolant whatsoever. Fuel economy is definitely down. On the highway, I used to get 28 mpg going fast with the A/C on (in Arizona no less); now probably down to 23 mpg if I were to estimate, and I can't use the A/C basically at all right now as I just don't have enough power. I had read that possible issues could be the coolant temp sensors, but, I would think no because the lost power shows up immediately after cold starts. I would like to say that the onset of this problem was pretty sudden too. I was on the expressway, and maybe needing more foot into it than normal without realizing it, but when I switched on the A/C I began to lose speed, even as I mashed the peddle to try to keep it up. Had to turn off the air to get home, and the problem has been this way ever since. I will go out and check my compression right now.

• MTF = Manual Transmission Fluid (aka. gear lube)
• Bosch O2 sensors = crap, junk, garbage, whatever else you can say negative. (I have yet to find a brand of car which runs well on Bosch O2 sensors, I ALWAYS recommend either OEM or Denso sensors for the best results.)
• One other theory we might want to play with; when you did the timing belt job, did you replace the idler (if so equipped) and the belt tensioner? I ask because a belt which has slipped a tooth could easily be the culprit here.

Keep us posted.

Updated Compression readings: 1=205psi, 2=175, 3=205, 4=185, 5=205, 6=210. Other things I did include New Coil, New Fuel Pump (my neighbor's gauge gave me a false low reading; pump was fine), Recently changed all vacuum solenoid valves and vacuum hoses, and since I did get a TPS code I re-calibrated that.

Oh yeah, I did a complete Timing Belt job; the whole kit; all new pulleys/idlers, tensioner, and water pump. I think I detect you don't like Bosch; lol. Well, at least I don't get a code from them like the cheapo's gave me. And, I do agree with you that Denso products rule. Aisin is a great parts company too.

Also, I have the JP50 MAF; that thing will never go bad.

Are you 100% sure everything was aligned up when the timing belt was replaced. Evening being 1 tooth out will cause it to feel like you've lost 50% power.

I've seen catalytic convertors block up causing massive restrictions before too.