Vehicle's computer Issue

Tiny
MONTE BROWN
  • MEMBER
  • 2002 HYUNDAI ELANTRA
  • 2.0L
  • 4 CYL
  • FWD
  • MANUAL
  • 155,000 MILES
I bought the car and it had a broken timing belt. This had bent the valves in the number four cylinder and so what I did was to go and purchase a used head from a wrecking yard that came out of a 2001 Hyundai sedan. I had that head cleaned and then I stripped it down and remove carbon residue from the valves and soaked the hydraulic flat tappets in diesel and then also lapped the valves, cleaned the cams and inspected for wear etc. Installed in car with all new gaskets torqued everything as per shop manual installed everything back as per shop manual.
Upon starting the engine for the first time right away the idle would fluctuate from 1600 to 3600 rpm and so when I took it out for the first time and gave it gas it wanted to take off like a race horse and then when I went to second it leveled off then third fine then forth fine, but then when I gave it more gas it wanted to run down the highway as fast as it would go I could not stop it so I turned the key off and then brought it back home very carefully. Now this morning when it was cool I started it and for the first forty seconds it idle just fine at 2000 rpm's and then it started the same pattern 1600 to 3600 rpm's when it warmed up. So I gave it a compression check and the cylinders all came in at 150 psi, I thought that low so added a few drops of oil in each cylinder and psi did not change. So I wanted to check and make sure the head gasket was not blown so I used a compressor and filled each cylinder with air and opened the radiator cap to see if I was getting air in the coolant passages but all checked fine. The compression check seems to point to the valves not closing as best as I can tell. So my question is can the hydraulic tappets keep the valves from closing which would fool the computer in to all kind of things which would explain the radical behavior?
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Monday, June 6th, 2016 AT 2:29 PM

4 Replies

Tiny
HMAC300
  • EXPERT
This may be a simple thing, try cleaning throttle plate and iac hole with choke cleaner as the plates get gunk on them and will do what you are describing. Also check for a vacuum leak like a line off/broken etc. Finally make sure air duct to throttle plate from MAF is on and no holes if after all of this and it still does scan for codes which an auto parts can do for free or if you have a scanner do it yourself.
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Monday, June 6th, 2016 AT 3:04 PM
Tiny
RENEE
  • ADMIN
Hi Monte,

Here is a link to an article that features written step by step instructions and pictures explaining how to do the scan yourself, also I have included a link to our YouTube channel with a how to video on code scanning. Most scanners are inexpensive to purchase, you can purchase one online from sites like Amazon.com. Once you have the codes please get back to us so that we can further assist you. We are always happy to help.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

https://youtu.be/YV3TRZwer8k

Thank you for visiting 2CarPros.com.

Kindest regards,

Renee
Admin
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Monday, June 6th, 2016 AT 5:05 PM
Tiny
MONTE BROWN
  • MEMBER
Well first off I would truly like to thank those who gave wonderful guidance with such quick attention to my issue that I had laid out. A site such as this one gives so many people such as I who have ran out of places to go for advice a glimmer of hope ! Although upon writing and sending in my complex issue I went outside to look once more at what could be the problem and would you believe that the problem was staring right at me the whole time it came to be a bad throttle cable. I noticed it was out of where it should of been in its metal cup and was jamming in an open throttle mode. So I just pulled back on it and it popped right back in place so I went and started the engine and it purred like a kitten right at 753 rpm so I took it out for a spin and it ran wonderful no problems ! I had replaced the tps the iac ran computer scans with the OBDII code reader and kept coming up with nothing. I had spent a total of 3 days trying to figure out what was wrong and there it was right under my nose the whole time ! I think I am guilty of falling into that human trap of making everything to complicated. Also I had done all the head work from start to finish and really didn't have any confidence in myself ! So for anyone out there wanting to try and fix an engine do what I did and go by the book and do everything step by step right down to every detail and you should come out alright! Remember if it doesn't then at least you did your best! I also added some pictures of where the problem was, in the first picture is where the cable had slipped out from the metal cup, the second shows where the cable was attached, forth picture is where the computer was connected and this is where it was fooling the computer, so the computer was constantly trying to keep up with what the false cable was telling it! Now my brain computer can relax and so can my car computer boy what a relief will sleep good tonight!
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Monday, June 6th, 2016 AT 8:07 PM
Tiny
HMAC300
  • EXPERT
You might want to keep an eye on this if it came out once it may come out again and it may be the cable is worn causing this to do that.
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Tuesday, June 7th, 2016 AT 5:37 AM

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