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Help, There's a gremlin in my engine

2K views 11 replies 5 participants last post by  dblotii 
#1 ·
I'll try to be specific as possible on my issue. The car is running rough. It runs great when cold (rich?) even being able to get moderately hard acceleration without misfires. Once it warms up it has a hiccup at idle, you have to "clear its throat" riding the clutch to get moving, or the engine will stumble when accelerating from a stop. If you mash the throttle at any speed, it drops a cylinder, but doesn't always seem to be the same one. Doesn't like to accelerate under heavy load without misfiring. When accelerating and it misfires, you can back of the throttle until it picks up the misfiring cylinder

Everything is stock. The engine has 262k on the odo. Rebuilt after the classic failure at 162k. The car sat for about 10 months. To my knowledge the car was running fine when I parked it. At the time of being parked it did have codes P0456 and P0442 (evap codes).

When I got the car out of storage the alternator was seized, so I replaced it.

The engine seemed to be running fine at idle and acceleration, but if you pulled over 5500rpm it would misfire. The high rpm misfires progressed to becoming rough idle and misfires under acceleration. I assumed the evap leak could be contributing. Being unable to find the evap leaks I had my shop put it under a smoke test and found leaks in the gas cap and purge valve. Replaced both. Codes have not reappeared in 2 months time. I assume I have fixed this problem.

I am still getting P0301, P0303 and P0300 codes. Since it was still running rough and the engine has a habit of eating aftermarket MAF sensors, I swapped it for new (sensor under warranty). No change.

The issue seems to be an air/fuel mixture problem, and the car sat for awhile, I put in fuel injector cleaner and dry gas. The engine runs much better when there is fuel injector cleaner in the tank. (changes octane?) With fuel injector cleaner in the tank the st and LF fuel trims are within 2% lean/rich. If I force it to misfire continuously, the short terms will go about 15-20% lean. Which makes sense I guess since a lot of raw fuel is being dumped in the engine. Without fuel injector cleaner I was getting the blinking CEL.

I couldn't remember the last time I had changed the plugs, (probably when I rebuilt the engine at 162K) so I threw in a new set. The idle only has occasional misfires, acceleration problems persist, but at a higher engine load. When I pulled the plugs, gaps were pretty large (didn't have tool to measure at the time) the outer area was carboned, but the central ceramic cone was bright white looking lean. (see misfires/STFTRM).

I inspected air plenum, but haven't found any tears, (I would have expected them to leak during the smoke test if they existed). I haven't pulled the injectors yet, and I don't have a way to measure fuel pressure.


HELP! Suggestions?
 
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#3 ·
Can you please post your actual Trim Numbers at ~2K Idle not moving.. It will be four Trims..

With your Missfire Codes on Bank One and Bank Two, it's not likely a Single Fuel Injector Problem.. But the Trims Might give me a Clue ..

I agree a Hot Missfire might sound like a Lean when Warm.. but it could also be an Ignition Missfire, as you suggest when backing out of the throttle, the miss goes away.. It takes less voltage to fire a smaller charge which is what you are doing when closing the throttle.. and the ECU will do a Richer Mixture when in Open Loop WOT condition.. Mine was hitting 11.5:1 before I did the MAF Mod..

I'm leaning toward Ignition.. Can you check the Ign Grounds.. Or the IGN Relay.. or the Coil Plugs?..

Cap
 
#4 ·
I'll do a fresh pull later this morning on trims. My tank is clear of Injector cleaner so there shouldn't be anything masking what is going on. I'm not sure if my screen shots I have currently saved is with or without cleaner.

I did forget to mention, I had been running without the engine cover. There appeared to evidence of prior water intrusion in the #1 coil when I replaced the plugs and the engine had run the worst on a recent rainy morning. All coils have been replaced in the history of me owning the car.
 
#5 ·
Finally got a chance to pull fresh trims. I think you are onto something with the ignition diagnosis. Finally got some trim numbers. These numbers are after running for ~20 minutes at highway speeds. I had meant to pull B2S1 O2 numbers, but grabbed the wrong sensor.

At idle
ST FTRM1 0.8% LT FTRM1 -8.6% Fuel Trim B1S1 0.8% O2B1S1 0.080V O2B1S2 0.830V
ST FTRM2 1.6% LT FTRM2 -7.0% Fuel Trim B2S1 -0.8%
ABSLT TPS 11.8%

At 2000 rpm
ST FTRM1 -4.7% LT FTRM1 0.8% Fuel Trim B1S1 0.8% O2B1S1 0.760V O2B1S2 0.785V
ST FTRM2 -3.9% LT FTRM2 0.8% Fuel Trim B2S1 0.0%
ABSLT TPS 14.5%

Sniffing the tailpipe at idle, smells rich. I think I read that Bank 1 control cylinders 1 & 3? So swaping coils from 1&3 with those on 2&4 should move the issue around? The engine still has the hiccups. I am buying a different OBD reader that lets me data capture better. The one I have won't log, and won't let you connect if you aren't sitting still.
 
#6 ·
Bank 1 is Cylinder 1 and Cyl 4
Bank 2 is Cylinder 2 and Cyl 3

Smells rich.. Think you might have a Bad Cat Converter.. if its hot and working, the exhaust should not smell bad..

Cap
 
#8 ·
If you're looking to get a new scantool, I suggest Techstream. It has (among other useful functions) a function for monitoring the misfire count on each individual cylinder. This would help you to diagnose the issue in your situation, where everything appears normal on a generic OBD2 reader. It can also control the injector duty in real time. All this reduces the guesswork. About $50 on Amazon for the latest cracked version and clone cable.
 
#9 ·
Thought I should follow up. Life has been pretty busy so I didn't have the time to get under the hood myself. I took it to a garage to due a full sensor diagnostic. On thier recommendation I replaced coils 1 & 3. Replacement immediately solved the issue.

The shop knows I do my own work so they didn't try to sell me on anything, but mentioned that the resistance on all 4 fuel injectors is out of Toyota spec. Soooo... I've set the money aside for a new set from Toyota. If a failure doesn't cause me to replace them sooner I'll get under the hood in the spring when the garage is warmer.

I'll look into Tech Stream.
 
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