1988 Toyota 4Runner Engine loading up

Tiny
WILLIAM MOREAU
  • MEMBER
  • 1988 TOYOTA 4RUNNER
Engine Performance problem
1988 Toyota 4Runner 6 cyl Four Wheel Drive Automatic

I have a problem with the engine misfiring and loading up. Although it starts properly, after about a minute it starts to load up (similar to the older carberated engines that wererunning with the choke still on) Once the engine has been run for a while (about 15-20 minutes) the problem diminishes but never goes away. If I push the throttle all the way to the floor, it will excellerate rapidely (normally). At about 3000 RPM an obvious smoothing/increase in power is heard and felt. Also, what may be a seperate problem, the engine runs obviously worse in damp wet weather with clear misfiring and backfiring. I do not have access to a code reader so cannot supply any codes that may be available. If this were an older carberated engine w/o electronic ignition, my first guess would be a two fold problem of an ignition shorting out, and choke not functioning incorrectly. However with fuel injection and computer controled ignition, I am at a loss without just starting to replace parts randomly untill I find the problem. The shop manual has not helped.
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Wednesday, February 10th, 2010 AT 4:50 PM

4 Replies

Tiny
RASMATAZ
  • MEMBER
You don't need a scanner -just find the check connector in the engine compartment and jumper Te-1 to E-1 to pull code/s and count the flashes, its gonna be a flash pause flash flash this equates to code 12

Check the injectors to include the cold start injector and fuel presure regulator if they leaking also include in your check the coolant tempearture sensor-
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Wednesday, February 10th, 2010 AT 5:00 PM
Tiny
WILLIAM MOREAU
  • MEMBER
After reading your response I did get the following codes: 21, 25, 26, 42. A faulty oxygen sensor (or circuit) seems to be the most common link between codes. Given the remaining symtems (an obvious RPM factor, the change from cold start to warm run, and the humidity factor), an unrelated oil leak in the valve cover gaskets, and overall miles; I chose to go the "whole route" of a full tune-up, oil and filter change, replacing timing belt (idlers and related parts), valve cover gaskets, coolant temp. Sensor, and oxygen sensor. During this work I noticed what appears to be a two conductor wire harness that leaves the main harness on the left side fuel rale area, and passes down between the intake manafold and head between the number four and number six fuel injector area. This wire appears to have some missing insulation. I can not find any reference to any sensor under the intake manafold in my Hanes amnual. It is going to be hard to repair without removing the intake manafold. Given the humidity factor, I would like to know what this wire harness goes to (and if it could be a factor in the over all problems) before making the decision wetherr to remove the manafold or just make a best as can repair in place.
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Monday, February 22nd, 2010 AT 4:41 PM
Tiny
RASMATAZ
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Its hard to say where its going can you ID the color of the wires and I'll try my best to track it-
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Monday, February 22nd, 2010 AT 5:45 PM
Tiny
WILLIAM MOREAU
  • MEMBER
I am unable to gain access to the wire where it passes throughthe manafold. However, where it leaves the larger harness that feeds the fuel injectors, it is a coaxial wire with black insulation. There is about three inches of it to a plug that is two conductor and then about an inch to the manarold. Hope that helps. Thanks for your promt reply and help
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Monday, February 22nd, 2010 AT 5:58 PM

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