Engine Performance problem
1993 Geo Prizm 4 cyl Front Wheel Drive Manual 137000 miles
I have a 1993 Geo prism Lsi with 1.6L, Manual trans. With California Emissions Package, everything completely stock, no aftermarket modification. Before the problem started, the car was running fantastic, plenty of power (for a GEO lol). The problem started on the way to work, my car just died. I thought maybe I was out of gas, I called AAA to bring me gas, it did not start, I had it towed home. I had no spark, ran the tests in the factory manual, found a faulty ignition coil in my distributor, replaced coil. Car now starts and runs, IDLES great.
Now the problem is that I have horrible performance, and terrible gas milage. I get absolutely no power going up a hill at all, but can go about 70 mph if level or downhill, now getting about 15-20 mpg. Other symptoms: My intake is much louder, I can not rev the engine past 4,000 rpm even if I hold the throttle wide open in neutral. (I punch it, and it goes to about 4,200 rpm and goes down under 4,000). My new spark plugs are turning white, my guess from lack of fuel. The check engine light is not on, has not been on since I had the car, but I verified the light works.
What I have tried: I have replaced the spark plugs (correct gap, application, heat range). I have installed a new distributor cap, rotor, set timing according to the instructions: 10 deg before TDC with a jumper wire in the DLC terminals TE1 to E1. I have checked compression and have an even 170ish through all 4 cyl. I pulled the timing belt cover and verified the belt did not slip, the notches line up perfectly. I ran the engine diagnostic procedure, even though the light was not on, no active codes, no stored codes, nada. I have checked for vacuum leaks, there are none. I have checked every electrical connection, they are all plugged in. I have tried a new MAP sensor. I have gone through the testing of the main feedback sensors: MAP, TPS, Temp, Cam sensor (in distributor) and checked the ignitor, along with the air gap for the signal rotor in the distributor. I even tried switching with a junkyard distributor, no difference. I have strong spark, and the timing advance is working when I rev the engine. I have gone through the fuel pressure tests, and every test checks out fine. There is no blockage in my exhaust, clean air filter. I have triple checked my firing order. I have a pretty new alternator, replaced a year ago, charging sys. Works great. I put new plugs in it when problem first surfaced, I have put about 500 miles on the plugs, they are now white on the electrodes, leads me to believe the ecu is not monitoring fuel delivery properly above idle speed. I have unplugged the injectors one by one while running, they all work fine.
This is a problem that happened all at once, not one that got progressively worse. I have tried everything I know, and this problem is a little out of my league. The only thing I know left is to replace my ECU maybe. THe only thing I can think of is that maybe when the ignition coil blew, the residual voltage had to go somewhere and damaged the ecu. I hope I am wrong, and that I am overlooking something else, cause that ECU is a PITA to replace. Any suggestions are greatly appreciated.
Sunday, April 13th, 2008 AT 4:21 PM