How to Fix Check Engine Light in an Older Car (Pre-1996)

How to Fix Check Engine Light in an Older Car (Pre-1996)

one, two, three, four! Rev up your engines! It’s time for the Scotty Kilmer Channel today it’s time to repair an oldie, but a
goodie, I’m going to show you how to fix a 91 Mazda rx-7 rotary engine that runs
bad, once it warms up and starts running it won’t go very fast, won’t rev over
about 2,000 rpms, but at least the check engine light is on, so you’ve got
something to start out with now, you can forget trying to use a modern scan tool
because this is obd one it’s not going to do anything with the scanner, these
scanners only work on cars that are 1996 or newer, and this is a 91, so in this
case we’re using dinosaur technology, a little piece of metal, and jumper cables,
and this 91 Mazda, you just go to the single green clip, then you stick a piece
of wire in it, then hook up one end of your jumper cable to it, then the other
end of your jumper cable here, goes on to the negative battery terminal, then the
check engine light starts flashing, it’s got codes, one long four tens, and one
short four ones, and in this case it has two codes, it went long long and then
seven shorts, which is twenty seven and it went long and then seven short, which
is seventeen, so it has trouble code seventeen and twenty seven, so look it up
on my handy dandy little book, and it says, seventeen heated oxygen sensor
front or rear bank, but just don’t go out and buy heated oxygen sensors, because
there’s lots of things that can cause it and the book shows that too, it shows the
probable causes as, either bad spark plugs, air leaks, oxygen sensor, or a bad
main computer, so let’s start out simple and check the spark plugs, I pull going
on voila, it’s already broken into pieces so that’s at least some of the problem,
and as you can see these rotary spark plugs are kind of weird-looking, they
also have to use one for the trailing and one for the leading, make sure you
get the right sets of plugs, because if you don’t in a rotary engine, all kinds
of stuff can go wrong, but as you can see, they have numbers on them, so just match
the numbers off and get the same number for each hole, you see that
one pair is B U R 90 QT and the other pair is B U R 70 QL, the T
stands for trailing and the L stands for leading, that’s just which way the rotor
spins inside the engine, don’t mix them up, because they’re different heat ranges,
now these crazy rotary engines are different than any other engine ever
made, but I can show you one thing, this is one of the plugs and you can see it’s
all black and it’s got a lot of carbon buildup on it, and that’s pretty typical
for these rotary engines, the seals on the tips of the rotors often go bad, so
as long as they run okay, most guys just keep changing the spark plugs, because an
engine overhaul it’s four times the worth of the car, so let’s start her up
now and see what happens, we’ll punch it and she’s singing along now, no problem
taking off now, so if you’ve got an old car that’s
acting up, why not fix it yourself, and remember if you’ve got any car questions
visit Scotty Kilmer .com you

About the Author: Michael Flood


  1. I have a 2002 Toyota Sienna and replace both O2 sensors (Bank 1 and Bank 2) codes were P1135 and P1155.  After replacing them I am still getting the codes.  I did the negative terminal off for 2 minutes and still getting codes.  Any ideas? Thank you for any help.

  2. hey @Scotty Kilmer, I have a 2001 Nissan maxima popping with a above threshold bank 2 code. P0430. Will this trick help with the clearing of the pre-cats too or am I going to have to fork over the money to replace them.

  3. I think you're great, Scotty. You know so much about auto mechanics and you are an excellent teacher. To see this car go from where it was to where your fix took it is an inspiration to give self-auto repair a shot, even if one has little auto mechanics experience. Your devotion to helping your fellow man is very admirable. Thank you. All the best to you.

  4. Hey Scotty,  wish I had watched you before I bought a used Mercedes.  It is currently in the shop and my guy thinks its the transfer box.  Car was fine from one day till the next when I ran a short errand and noticed some knocking sounds while pulling in and out of parking space.  Seemed fine driving straight.  Mechanic also says that sometimes changing the fluid in the box seems to help according to some of his sources.  My thinking is it is either going out or it is not.  Although, at 93,000 mi.  I'm sure it needed changing anyway.  Any advice O Great One?

  5. My engine lights comes on when i drive past 120 km/h …it stays on until have killed the engine. 
    when i start it up it the engine light wont come on untill i pass 120km/h.
    what would it be . 
    i allready change O2 sensors of the engine
    Its a toyota tercel 4e fe 1.3   engine

  6. Pretty good, but by the symptoms you don't even need a computer to figure out you should check the spark plugs. Of course there could be more problems, but I'd rather at least check the plugs if my car has trouble going over 2000rpm, than decipher morse code from my dash.

  7. hello scotty i have a question my O2 sensor show me before cat 945c after cat 70c and car more than 24 hours not started. if i clean it maybe its works or need replace it ?

  8. I had the oil change for my car yesterday, that stupid mechanic used a broken funnel which he knew it was broken, to fill up the oil. As you know what happened next, huge amount of oil pouring down alone the engine all the way to the floor and contaminated the oxygen sensor and other parts. The engine light is on today, and the problem was oxygen sensor. That guy said it was not their fault, it was the sensor itself goes bad, and they're gonna charge me $150 to replace it. But I've been driving my car for 4 years without any issues. Thing's just gone wrong after they spilled the oil. I was so mad, but couldn't do a thing. Now I ended up driving a stinky car with a broken sensor.

  9. I got same problem I have acura rsx base model it laggs on driving or on up hills sometime it feels like if it want to turn off not sure if it gass problem or sparkplugs or leak or transmition

  10. Hey Scotty,

    My parents have a 1994 ford thunderbird which has had the check engine light on for a while now. My dad has done a lot of time searching through the engine of what could be wrong. I want to give him a bit of help because the check engine light has been on (I don't know for how long). Any suggestions?
    P.S: I love your videos Scotty! I know nothing about cars but I am starting to become interested in learning more of fixing in the future! you are awesome!

  11. Old cars and their "computers", mine doesn't even remember what's wrong if I turn it off. So if I'm going to check it, I have to drive it until it shows an error and then check it on the spot while the car is still running.

  12. Hey Scotty I have a1990 Silverado and the service engine soon light comes on will this be the same method to do on the truck because like you said these years don't have a obd ll port for the scanner

  13. Hey Scotty I got a 2002 Honda Odyssey the check engine light and TCS light came on and my car shakes now and seems like it wants to turn off any advice on wat it is?

  14. will it work on my 88 turbo coupe my check engine light goes on and off every once in a while if you know of a problem it would help alot!

  15. Hey scotty, i have nissan maxima gxe sedan 1994 its automatic, every morning the engine light is on and the car shake the rpm goes up and down all the time but when it warm up the engine light is gone and the engine is stable. I check the spark plug is fine, i change the fuel filter, i cleaned the throttle it was very but not inside the throttle body got no tools for those. What seems to be the problem? Also my gas is like eating too much and it smells gas. Hopefully youll read this and help me. Thanks scotty.

  16. i have a 1993 corolla with no check engine light on at all. i check the little bulb behind the dash is working. but when turn key on no ckeck engine light on at all.

  17. Hi Scott. I've watched a lot of your videos and I just found this one. Nice to see you work on a rotary – mechanics around here won't touch them. I tore mine down and completely rebuilt it a few years ago.

  18. Here's hoping… I've got a Lancia Thema 3.0 v6 from 1993, and the ''Check'' light starts out blinking, and then turns solid.. Using the method for getting fault codes (pumping the gas pedal 5 times while key turned but not started), I get the code 4-4-4-4, which means ''No code stored''.. I had the code 1-2-1-1 before that, that meant ''Incorrect battery voltage'', but I changed the battery and it went away..

  19. I have watched several videos on fixing the engine light-on problem for
    Toyota 2003 Corolla for I have had the problem for many years. This time
    I changed my mechanic to Shell service station, Bellerose, NY 11001. He
    tested the engine with the diagoniser, and changed the top mount
    gasket, and that immediately solved the p0171 and p0770 problem. The
    engine light-on has been off since then. You may want to try this

  20. Thanks, Scotty! Wish you include some more articles on Mazda RX7's as there are very few mechanics that know how to work these kinda cars.

  21. my car p0340 keep coming up. i replace both senter cam and crhank senter. i reset the ecu. but code keep comeing back.

  22. hi scotty I got a question my check engine light comes on and flashes went I get on the highway and go speeds of 60 mph then when I get off the highway it goes off in a matter of seconds the only signs I get that something is wrong is the engine light and a shake and loss of power only at highway speeds do you have any idea what it could be I can't use a obd because the light dosent stay on long enough

  23. Hi scotty,
    Thank you so much for your help and support.

    Your website did not work! Can you please link it here.


  24. Mr
    Scotty Kilmer
    I have a Dodge avenger 2008 2.4l
    Iyo I want to know how to fix the oxygen sensor, and change them but I still give the same code, the engine check is still on

  25. scotty I have a 2005 madza rx8 when I turn it on when the engine is cold it turns on fine but when the car is warm its starts and then it turns off immediately wat do u think it could be

  26. Scotty, LOVE this, remember I have the 81 Turbo Trans Am and it give us codes the same way, got to separate the blinking lights to get your code numbers..Hard to believe my 81 is ran by a computer,,

  27. Scotty I have a Ford Explorer sport track and It says to change the oil but when I change it it still says to change it and I press reset but it still won't reset after restarting the engine

  28. Scotty
    Your videos are great. I have a question. I owned a pontiac sunfire 2004. I spent over $1000 to replace parts at the shop in a year. The engine light is coming every 2 or 3 months. Now its is on for 2 weeks straight. I dont know what to do. I replace the gas cap, filters, battery, battery plugs, and other stuff had been change. What would you recommend? The car is running fine so far.

    Please help.
    Happy New Year

  29. Of course though, the procedure for pulling OBD 1 codes do vary from vehicle to vehicle. My truck is a 1995 nissan Pickup. In my truck's case, you need to get access to the ECM in order to pull the codes. The ECM is under the passenger seat. Once the passenger seat is removed, there is a diagnostic screw on the ECM that is turned. After that, the check engine light will flash codes as normal.

  30. my car is a hyundai santro euro 2 1999 model from india.
    today i started my engine its starts very smoothly overall no problem in car. but check engine light is on its not going off.
    what should i do?

  31. I have a 2007 Sequoia that has the vas, track off and engine light on.Changed gas cap, removed battery terminal but did not solve the problem.How can I solve this problem.

  32. Hi Scotty, I was amazed when I saw your Utube videos. Wow what such experiece you have.
    Sorry to bother you, but I really appreciate your answer.

    I have a Ford F-150 5.8, year 1993. Lately when I drive it , stops all suddenly. it kind of startles and then i just let it parked. about one hour later i start it again . But has soon i drive it , happens again. CAN YOU PLEASE HELP ME, I DONT HAVE MONEY TO PAY A MECHANIC. AND I LIVE IN MEXICO NOGALES SONORA. I would love your answer and fix it my self please show me how to fix it. ive fixed before just by watching your videos. but i couldnt find a video today cause i dont know exactly whats wrong with. thanks so much for your time. May God continue to bless you and give you wisdom to keep helping others.
    Blessings to you and loved ones.

  33. What happens when 02 sensors weld brakes off is better to buy bung clamps if one don't have a tig welder or just take to shop have them weld new one on?..

  34. My speedometer is at 0 and odometer not working. Could this be reason for check engine light. for 1992 Nissan Sentra E.

  35. key off , key on , key off , key  on  , key off ,key on ,  3  times  will  activate obd-1 codes  .

  36. I love these videos. My new favorite is when he decodes pre-1996 vehicles Check Engine Light using a paperclip and a couple of wires with alligator clips. Too cool!

  37. Scotty I have a 07 Toyota Carola le with a check engine light that just went on it has 103 thousand miles car runs great any idea what that can be can it be nothing just because it has over 100 thousand miles ?

  38. ⬇️Scotty’s Top DIY Tools:

    1. Bluetooth Scan Tool:

    2. Cheap Scan Tool:

    3. Professional Socket Set:

    4. Wrench Set:

    5. No Charging Required Car Jump Starter:

    6. Battery Pack Car Jump Starter:

    Things I used in this video:
    1. Ratchet and socket set:
    2. Mechanic’s Tool Set:
    3. Disposable Gloves:
    4. Common Sense
    5. Full HD Camera:
    6. My computer for editing / uploading:
    7. Video editing software:
    8. Thumbnail software:

    🛠Check out my Garage to see what I use every day and highly recommend:

    ❗️Check out the Scotty store:

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  39. Scotty, I really like your vids. You know your stuff based on a life time of wrenching and that's impresses the heck out of me. Plus you cut to the chase and don't waste of a lot of time showing us useless stuff like your stereo, you kids new braces or an old pen that writes upside down that has nothing to do with the titled subject matter. Most of these guys, i just stop and go onto the next video. Plus too many of them are doing whatever they are trying to teach others, for the first time!!! To which i say….Morons!!! Keep up the good work and thanks a ton for your sage advice.

  40. Do you know where the conector is located for a 1992 (generation 4) honda prelude? I think by watching youtube it must be located somewhere on the passengers site but realy want to find out where exactly.. i havent found the blue connector yet 😣 .. please someone? My engine light goes on after like a 10 to 20 miles driving…

  41. An Actron CP9690 code tester works on OBDI and OBDII. It checks live, graphing, record, emissions test, oxygen sensor tests, code connect to diagnose codes, and MORE! It works from 1983-2013 and is updatable. EBAY has it.

  42. Hey Scotty, i have a 95 honda accord v6 and i wanted to know why my speedometer isn't working and the abs and brake light is on but no check engine? Any lead or clue on what that could be?

  43. I have a 89 Tbird that the check engine light comes on at start and goes off when put in gear. It idles ruff as if a miss is there, has new plugs cap and rotor. Can you help?

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