Check engine light on and off, runs bad when it is on

Tiny
CMCGALLION
  • MEMBER
  • 1993 TOYOTA PICKUP
  • 4 CYL
  • 4WD
  • MANUAL
  • 117,000 MILES
We bought this truck and ran great, one owner, original miles. Half way home it shut off at 70 MPH. Towed home and finally found O2 wire melted to muffler. Fixed that but now engine light goes on and of again. But when it's on it runs bad and has no power at all wont run over 60 MPH. When light goes off it has great power and goes 75 MPH or more. Help please!
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Monday, December 28th, 2020 AT 10:46 AM

6 Replies

Tiny
AL514
  • EXPERT
Hello, sorry to hear of your issues there. The engine computer is seeing an intermittent fault. There should be a diagnostic trouble code stored in the ECM (engine computer). Here are the instructions for retrieving diagnostic codes for truck. Let us know what codes you get from watching the check engine light flash. Also be sure to check all the fuses. With wires being shorted out like that, there may be a blown fuse. Here is our YouTube page as well, there are many videos that might help you: Edit I'm adding the list of codes and their definitions.

https://www.youtube.com/results?search_query=2carpros

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing
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Monday, December 28th, 2020 AT 11:44 AM
Tiny
CMCGALLION
  • MEMBER
We don't have a code reader!
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Monday, December 28th, 2020 AT 4:47 PM
Tiny
CMCGALLION
  • MEMBER
I put a wire on the e1 and e1. And the engine light stays on. No blinking at all.
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Monday, December 28th, 2020 AT 5:03 PM
Tiny
AL514
  • EXPERT
Did you follow the instructions closely? the engine must be at operating temperature, all accessories off, and vehicle in neutral and the pins are TE1 and E1. This might take a couple tries. Was the damaged oxygen sensor replaced, and all the fuses checked? The first 2 diagrams show where the fuse boxes are, one in the engine compartment and one in junction block 1, to the left of the steering column. The oxygen sensor may be damaged, which could have happened when those wires shorted out on the exhaust. I have included the bottom 3 diagrams to check for the correct voltage at the ECM connector. If any of these tests fail, most likely the ECM was damaged during the short of the oxygen sensor wiring. These checks should be done with a multimeter. I'm including some guides to help with testing. But the solid check engine light means no codes are stored. The oxygen sensor probably should have been replaced. It may only take the ECM warming up for the problem to show. I'm adding one more guide for Toyotas.

https://www.2carpros.com/articles/toyota-trouble-code-definitions-and-code-gathering-method-1990-1995

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-a-car-electrical-system-works
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Tuesday, December 29th, 2020 AT 6:42 AM
Tiny
CMCGALLION
  • MEMBER
We replaced the o2 sensor, knock senser, fuel filter, and still no change.
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Thursday, January 7th, 2021 AT 3:25 AM
Tiny
AL514
  • EXPERT
Okay, I'm sorry to hear none of that helped. So let's refresh a little, you're driving and all the sudden you lose power and it won't go over 60 MPH. How often does this happen, once a week, twice a week etc? How much fuel is in your gas tank when the problem shows up? is it only at highway speeds? do you notice any other sounds or smells during the event (we'll call it that)? can you feel a shake in the driver's seat? any additional information you can provide me will be a huge help. Even if you think it's not related. This truck is quite old so that's why we're having issues figuring this out. Plus I'm not with you at the vehicle, so I can only go by what you say. So details are important. When you lose power does it always shut off, or will it stay running, just poorly? And please try to answer every question as best you can. I'd really like to get you through this and get it running correctly for you. If it stays running during the "event" try opening the hood and if possible shoot a quick video of the engine running rough.

Two more questions. how many wires does your oxygen sensor have and how many oxygen sensors can you find? There definitely should be one in front of the catalytic converter and possibly another behind it to monitor the catalytic converter efficiency. One more quick question. do you have a multimeter and know how to use it?
I do have a test plan for you. I want you to check for spark when the problem shows up. Can you do that? Also are you still having the no start issue or did that clear up with the fixed oxygen sensor? If is still a no start, try unplugging the mass air flow sensor during this time. It's on the air intake boot.
https://www.2carpros.com/articles/how-to-test-an-ignition-system
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Thursday, January 7th, 2021 AT 4:57 AM

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