1993 Camry 4 cylinder Losing Power Under Load

[frafreg]

The car was running fine until I needed a new battery. I replaced the battery and shortly after, I noticed the car would have a miss and idle rough intermittently after putting it in drive. It's an automatic transmission. I took it out for a ride and when I tried to go up a hill it could barely make it. The car has about 90 K miles on it but it is very well maintained. It has new plugs, cap, rotor and wires with less than 10 K miles on the parts. I pulled the plugs and they looked good. I cleaned the throttle body and the IAC but it didn't help. There is no check engine light on. Not sure if I will get any codes. Out of gear it idles fine. I can rev the engine out of gear with no problem. It seems to be load related.
Also, can I download the service manual for this car from this site someplace?
Thank you for your help in advance.
I appreciate it.

[Brian R.]

Try replacing the ignition coil. They are known problems in this engine. Send me your e-mail for a FSM if I can find one.

[frafreg]

My email address is [email protected]. Do you think a cold check of the coil with an ohm meter show any problems? I can check the winding if I know what it should read. Thank you very much for your help.

[Brian R.]

A resistance test of the coil would only tell you if it's bad, not if it's good. The coil operates under very high voltages and if it is bad, a low voltage test like with your VOM will not necessarily detect it. If the coil is out of spec at low volts, then you can be sure it's bad.

[Brian R.]

check your e-mail

[Brian R.]

Also, check if there are any codes stored in your ECM

[frafreg]

Thank you very much for the service manual and advice about replacing the coil. I will get to this as soon as possible and let you know the results.

[frafreg]

Hi Brian. I finally got around to replacing the ignition coil last night but there was no change. While the car was fully warmed up, I watched the car idle out of gear and I noticed an occasional misfire but when I put it in gear it stalls. I took it out again and I tried dropping it down to low gear when going up a hill and I was able to get up the hill. This all happens after being fully warmed up. When I originally cleaned the IAC I did it on the car by spraying into the two hole in the intake manifold. I didn't remove the IAC. Is it possible that the IAC is still dirty or maybe the throttle position sensor? There are still no codes. Any help much appreciated. Thank you!

[Brian R.]

Check the ignition timing in "N" gear, shorting TE1 and E1 terminals of the data connector. Should be 10 btdc at idle and operating temperature.
Check your fuel pressure in pinched-off return hose with ignition on, shorting FP and +B terminals of the data connector.
Check spark in all cylinders, should be bright hot snap and jump 1/2 inch.

These are the starting points from Basic Inspection on page EG1-310 of your maintenance manual. Follow that troubleshooting procedure. These are for a no-code situation. See also EG1-327.

[frafreg]

Brian, thank you very much for your response. Since we spoke, I purchased the TOYOCOM device which enables me to see live OBD1 data. The timing is correct at idle, the ECT temperature looks good and spark is a bright hot snap. The only information I couldn't see that might be an issue was the O2 data percentages because I didn't have it set up correctly. I was told that oxygen feedback should be on when the engine is warm and the engine load is not heavy like cruising around town or just idling. It should indicate a value from 0% to 15%. A solid 20% means the system is out of range and inactive. I am going go back to make sure the percentages are correct. I noticed after warm up, the car idles fine in park but almost stalls when i put it in drive. If i disconnect the TPS, it idles good. I tried driving the car with the TPS disconnected but the hesitation under a load going up a hill is still there so I don't think the TPS is the problem. It is just compensating for something else I haven't identified yet. Also, i can see that the TPS operates smoothly without any skips while opening the throttle by hand. Appreciate any feedback you may have at this point. Thanks again!

[Brian R.]

Check fuel pressure and volume.

[frafreg]

Hi Brian. I am going to rent the fuel pressure tool as you suggested but my local Autozone did not have one on hand this weekend so, I have to wait until someone returns it.
In the meantime, I took your advice and I went back to check the ignition timing again. The TOYOCOM make it easy to see the timing without a timing light. The timing is going up and down at idle from -2 to +5 in Park. The idle is moving up a and down also. I cleaned the IAC on the car and was wondering if I need to remove the throttle body and do a more thorough cleaning of the IAC since it may still be dirty. What could cause such an unstable timing? Thanks again for you help. Much appreciated.

[Brian R.]

Bad distributor, loose distributor, bad distributor cap/rotor. See if there is play in the distributor shaft. When is the last time you changed the timing belt tensioner? Crank position sensor. Crank position sensor star wheel may be marred. I'm not sure what level of damage to the star wheel will cause it to indicate bad on the sensor.

Still thinking...

[frafreg]

Thanks for your reply Brian. I appreciate your help. When I replaced the coil I didn't notice any excessive play in the distributor shaft. The car has 79K miles and has had oil / filter changes every 3K to 4K miles. I swapped out the cap, rotor, wires and spark plugs to try to diagnose this problem a few weeks ago. Nothing made any difference. The plugs are Bosch. Not sure if that matters. Is there a way to test the camshaft position sensor? Thank you.

[Brian R.]

Bosch plugs are marginal. Use DENSO or NGK only. They are unlikely to be part of the problem since changing them had no effect. I wouldn't buy Bosch for your engine. DENSO and NGK only should be used for all ignition components.

I guess you mean the crankshaft position sensor. I don't know of a good way to test it. I would make a point of checking the distributor shaft carefully. Check for rotational play and side-to-side play. Make sure that it's tightened down correctly.