Just picked up this Geo last week and I'm trying to troubleshoot the general misfire. I usually replace the normal tuneup parts on every vehicle I purchase because I never know its true history. So, in trying to figure out the misfire, I have replaced the cap/rotor, plugs, and fuel filter. The previous owner installed a Doug Thorley header and a K&N air filter. I'm not a fan of K&N, but will replace it once it gets dirty.
I've cleaned out the MAF and verified a good clean spark through the use of a spark tester. My next step is place a NOID light on each injector plug and check for good signal from the ECU. If that looks good, I plan to test each injector and possibly do an injector balance test. I also intend on testing the fuel pressure at the rail with a gauge. I don't currently own a fuel pressure gauge, so I'm wondering if anything else could be used if the threads match up? I do have a compression tester, but I don't know if that will work. Also, I plan on doing a compression test to each cylinder. Beyond these steps, what else am I missing?
Random misfire, so more than one plug is being affected - yes, fuel pressure, spark plugs (are they gapped properly at .028"), battery voltage, etc. Maybe if you advise exactly how the car is running, how it starts up from cold start, what cold idle is, how it drops to warm idle, what warm idle is, etc. it might point to a certain direction. Presumably you have a scanner, no? First thought is to actually clear the P0300 and then see if it actually comes back (or if the code is just in the computer's memory). You can also drive with the scanner hooked up, and it will pick up real time values that might be helpful.
Thanks for your help, Bex. I have a ScanGauge II that can be used to assess sensor readouts and DTC's, but it cannot display graphical information, nor be connected to a laptop. When I first bought the Geo, the CEL light did not appear to function upon vehicle startup. I now believe that it has been removed because of this misfire. PO said that the engine was recently replaced by a professional mechanic, but I have no way of verifying this information.
First scan showed p0505 and p0300. I cleared them, and only the p0300 continuously returns. Perhaps the p0505 was just in the memory and not active? I went through the first two tanks of fuel in approximately 300mi (each tank), and did nothing to it other than adjust tire pressure. Now that I'm on my third, I've been tinkering to get rid of the symptoms and code. The car starts and idles very nicely, yet the exhaust spits a little carbon until warm. Cold-Fast idle is about 1400rpm, then comes down to about 800rpm when warm. No misfire is audible at idle, and no code,either. Once moving down the road, the code appears. The car gets up to normal operating temps (180F) and stumbles off-idle through WOT in all gears. In spite of this, I get no lean or rich codes, nothing for the IAC, EVAP system, nor EGR. Other than the stuble/misfire, the car runs very well and consistently returns 24-28mpg.
I've spent the last few hours on this forum trying to research what my next step should be, but I think I may have found something. Cylinders are numbered 1-2-3-4, starting from the radiator to the firewall, correct? And on the distributor: #1 @ 1 o'clock, #2 @ 5 o'clock, #3 @ 7 o'clock, and #4 @ 10 o'clock? If so, the PO has the spark wires jacked up. I replaced the rotor and cap this morning, with no difference in driveability. I replaced the wires exactly how they were previously arranged.
So, if the firing order is jacked, I'll need to verify that the timing isn't also jacked. Looks like I'll be pulling the timing cover, no? I did notice that the distributor is rotated all the way advanced. Hmm........
Sorry, I had a fit of typos. You are correct, and I've found the proper firing order and distributor pic online to help my misunderstanding.
So I had some more time to diagnose this morning. I can't find a rental fuel pressure gauge that will fit the big 19mm plug on the fuel rail. I'm going to have to make one, I suppose. However, I was able to compression test the cylinders and each is pulling 178-184 @ WOT. I couldn't get my hands down into the #4 injector harness, but a noid light on cyl #1-3 were fine. The light intensity and flicker rate increased with RPM, as they should. I looked at the spark plug routing from the distributor and confirmed that the PO did route them wrong, but it won't fire when I reroute them in the correct 1342 firing order. I even changed the rotor positions and it still wouldn't fire. When talking with the previous owner, he states that his mechanic installed another 1.6L from a 96 Suzuki "sedan." Am I to assume that this is the Esteem? If so, I'll need to find out the firing order of that engine. The only way that this vehicle will run at all is if cyl #1 is routed to 10 o'clock, #2 is on 1 o'clock, #3 is at 7 o'clock and #4 cyl is routed to 5 o'clock. There is also a white mark where the rotor is supposed to point to #1, however, there is also another white mark where the "new" #1 cyl is currently pointing to (10 o'clock).
I'm thinking that if this motor is from another Suzuki, that would explain the odd distributor layout. Time to do some more research.
Condition of all 4 plugs:
Evidence of different firing order. 10 and 1 o'clock both have white marks painted:
Confirm that your rotor can only go on one way. There are knockoff rotors that can drop in 3 different ways which shouldn't be used on this car.
And yes, it would be good to confirm what engine this is. You may want to upload a photo of it.
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