1991 Toyota Celica intermittent miss

PWRODGERS1

MEMBER
1991 TOYOTA CELICA
4 CYL
FWD
AUTOMATIC
198,000 MILES

Hi, I have a 1991 Celica GT convertible (calif), 5SFE engine, automatic trans with a strange miss after warming up. There is a cut out (bucking) when accelerating and the car lacks power. It would barely climb a hill. This problem occurred 3-4 days after changing the oil and getting fuel. For oil, I went from 10w40 to 10w30. I use ethanol-free gas. So far, I've replaced the injectors and seals, pump strainer, fuel filter, both o2 sensors, map sensor, TPS, coil, igniter, coolant temp sensor and plugs.

I've ohm checked the distributor (and checked gap and no oil inside), cold start injector, EGR VSV, ISC and plug wires. I vacuum checked the EGR valve and looked for vacuum leaks. Also looked for bad ground. All are good. Fuel pressure was within spec.

Last night, I replaced the distributor and cap (rotor and wires only 1 yr old) and strangely the power is mostly back. Especially on take off and it will climb a hill without much problem. The miss is still there but seems to be showing up around 40mph. The lack of power is not as bad as before. I can actually pull out in traffic but there is a bucking when accelerating.

Before all of this happened, the car ran good but would vibrate when stopped at a light and in drive. Sometimes worse than others.

Could a fuel pump cause these issues? The pressure was good and it's never left me stranded.

Any ideas? Help!

3 Replies

MMPRINCE4000

MECHANIC
8,549 POSTS

I would first perform a compression test to rule out/in a headgasket/valve problem.

If OK, I would have the TCC (torque convertor clutch solenoid) checked for sticking.

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Wednesday, April 14th, 2010 AT 7:59 AM

PWRODGERS1

MEMBER
2 POSTS

Thanks for your suggestion. I did a comp test not too long ago and I never saw white smoke or anything else that seemed like a blown head gasket or piston ring.

Believe it or not, I found the problem just after I posted the question. The problem was aftermarket plug wires purchased at AutoZone purchased not too long ago. That's why the power came back with a new distributor but the miss was still there. Although it ohm tested and gap tested good, the old 200K mile distributor was too weak to handle the higher resistance of the wires. When the wires were cool, they ohm checked to spec. Apparently the resistance rose as they expanded from heat and the spark was intermittenly weakened causing a miss, go figure. Since they had a lifetime warranty and I was basically at the end of my rope, I decided on a whim to trade them for a new set and see what would happen. I'll be purchasing a factory or Denso set soon.