Hi guys, first post here. Tried doing a search for info on this problem, but couldn't find one that matched my symptoms. Here goes.

95 Camry, 5S-FE, Automatic, 150k miles.
Intermitently surges/hesitates upon accelaration upon reaching 25-30 mph. If gas pedal is released/eased up on it runs ok, but will not go any higher if pedal is depressed any further. RPM will not exceed 1500-1800, except when A/C is turned on, then it will go an additional 500 rpm more. Also, sometimes it just automatically clears up and then runs fine for days. Tends to do it more often if it's wet, or car has been left outside overnight.

No check engine light, or codes set, even when diagnostic mode is set!

Changed dist cap and rotor, plug wires, plugs, and fuel filter and checked timing.

Swapped in 2 other used ECU's and still had the same problem.

Checked IAC valve, ECT sensor, MAP sensor, IAT sensor, and TPS sensor,
dist pick-up and coil resistance. All are either in spec, or very close to it.

Replaced distributor (found small crack in face of fwd pick-up coil), reset timing.

She ran great for about a month after changing distributor, but started having the same problems a few days ago.

Any wisdom/suggestions will be greatly appreciated, Thanks.

 

If engine runs worse when raining or overnight (perhaps damp) would look at ign again.

A bad coil can cause these issues. The coil can crack, moisture then shorts it out.

If the coil is externally mounted watch for arcing on a dark night (plus look at the rest of the engine).

 

Started up last night outside in the dark and saw no signs of ark/spark.

Left outside all night (26deg), no moisture, got in this morning and drove perfect for 4 miles then had 1 stumble on accelaration approx 40 mph, feathered throttle and immediatly cleared up and drove perfect the rest of the way back (2 more miles) home. Hooked up scan tool and had zero codes.

Looked at distributor coil (internal) no cracks and resistance reading were still good. Visual check of igniter (external) good.

What am I missing? Don't have any hair left to pull out!!

Could the ECU have a glitch/hick-up in it?

I read in one of the other categories about clearing the ECU memory by shorting the battery cables (obviously after the cables are disconected from the battery) together for 10 minutes to discharge a capacitor in the ECU, then running at certain rpm's for a certain time/frequency to reset the values in the ECU. Could this help?

Thanks again for any advice!!

 

A computer problem on a 95 would be very rare.

Don't short the battery cables. Disconnecting the battery cables will clear the computer. 10 minutes should be more then enough time. The computer is has no learn mode, the software program is fixed.

Have you checked fuel pressure? The fuel system is not monitored by the computer. The system has a fuel pressure regulator screwed onto the fuel rail. The can filter seldom plugs up.

Is the coil installed in the distributor? If things worked OK after all the ign work would still be looking at the coil. Check auto yards for a el cheapo used one.

There is also a small capacitor installed in the DC power wiring for the injectors, ign, etc. This is to reduce radio noise. Might be near the drivers strut tower. On the off chance it has a problem, remove the wire going to it.

 

Appreciate the reply.

What am I looking for on the fuel pressure regulator?

Ignition coil is internal.

I'll chase down the wiring for the RF capacitor and try disconnecting it.

Thanks

 

Low fuel pressure.

Should be 38-44 psi ign switch on a fuel pump jumped (engine not running).

Disconnect vacuum hose from regulator and plug holes.
Start engine and idle, pressure should be same as above.

Connect vacuum hose. Pressure should be 31-37 psi.

When the problem happens how is the idle-normal or ?

Assume you changed the coil ign wire.