[Northish]

Hey long time no post ^^

Yesterday my heart skipped a beat, for the first time ever the engine check light came on while I was on the way home from uni. The Vienta has been such a reliable car since I've had it, the only issues have been age related and easily fixed apart from the headgasket.

In any case I got it home and used the paperclip trick to read the engine codes and I was given these:

21 – Main Oxygen sensor signal fault
24 – Intake air temperature signal fault
31 – Air flow meter circuit or vaccum sensor signal failure
41 - Throttle position circuit fault
55 – Knock Sensor fault

I was told that I needed to clear the codes, warm the car up again and the get the codes again and these will be the ones I need to fix. I reset the EFI, went for a drive to warm the engine up again and then went to read the codes and they were all gone.. I'm happy for that but now I'm worried that the problem is still there and that all I've done is just clear the codes. Can anyone shed some light on this?

Aside from this the car has been going great. When I've finished my studies I'm planning on dropping the stroked engine in and then working on a rear mount turbo. I really didn't want to have to get another set of headers made for the car since the whole exhaust is custom anyway so I figured this would keep it simple while keeping the heat out of the engine bay and not cramping it up more than it already is!

 

[mcgowaw]

can you give us the maintenance history?
specifically, when was the last major maintenance done?
did you replace/clean any sensors like o2/maf-map/iac/cts/egr tmp, etc?
did you clean the intake/tb/egr/iac with seafoam?
have you driven at least 100 miles since the reset and did any codes come back?
tony

 

[Northish]

Last major thing done was changing the timing belt about 5,000 kms ago. Since then though I've had the intake out to change the sparkplugs and anytime I have to take it out I clean everything there with throttle body cleaner. I've never changed any of the sensors in my 3 years of owning it either. I've only driven about 20ks but I do about 100 kms a day so I'll keep an eye out for if the light comes on.
Thanks for the quick reply

 

[BMR]

Hey, good to hear from you again Northish!

Man, that is a bunch of unrelated codes! Sometimes when that happens it's the ECU going bad.

 

[mcgowaw]

yep, seems to be unrelated. that's why i said to drive it and check again as these are probably old codes that haven't been cleared since he bought a new battery years ago. obd1 is a pain to get any useful info out of. it'd be nice to see if he has any systems not ready or see the ltft's but maybe no codes will come back assuming he's done the cigar smoke test and ensured no vacuum hoses are leaking, and the pcv valve has been replaced sometime in the recent past and the regular maintenance has been kept up.

op, has this car ever died on your unexpectedly?

tony

 

[Northish]

I haven't had internet for about 7 months so getting on here has been hard haha.

I've driven about 130kms and haven't had the light come back on, I tried replicating the event when it first showed and it didn't come on either. Pcv gets cleaned fairly regularly because I'm paranoid about it getting clogged. I will try the cigar test tomorrow and see if I'm leaking anywhere, maybe I've left a hose loose somewhere while pulling stuff apart.

I've only ever had it hiccup briefly when cornering especially tight and quick but I put that down to it being starved of fuel due to the cornering. The car has always been reliable and consistent ^^ He behaves himself quite well for a car named after the God of mischief (I might be a little too attached to my car)

I appreciate all the help, it's a shame to see the forum mainly dedicated to posts about Camry trouble and not diy's and projects :/

 

[Northish]

Ok, so I've done another 2000 kilometers since the codes were wiped and yesterday I had two codes return:

41 - Throttle position circuit fault
55 – Knock Sensor fault

I'm a bit worried about the last one, does this mean that the sensor is faulty or that the sensor has detected a knock or something? Sorry to pester you guys about this.

 

[71Corolla]

Usually the harness going to the knock sensors get cooked but the sensors themselves are fine. The dilemma is are you willing to risk taking the top of the engine apart and not replacing the sensors then find out there are bad. Here's a great thread on knock sensor diagnostics -
http://www.toyotanation.com/forum/1...nosing-replacing-knock-sensors-3vz-fe-v6.html

For the other code your TPS is probably worn out or it may need adjusting have you ever removed it?

 

[DFBonnett]

I did the bypass on the knock sensors last year on my wife's grocery getter. We only use premium gas so knocking is not an issue. Hope this helps. Last post in the thread. http://www.toyotanation.com/forum/1...ock-sensor-work-around-93-camry-3-0-v6-2.html

 

[tedmich]

A little math!

If I have a 1993 car that has gone 200k miles (400k km) it has probably been running between
A) 6667 hr with an avg. speed 30 mph (48 kph) LEADFOOT
and
B) 20000 hr with an avg. speed 10 mph (16 kph) MORE REASONABLE

Thus every electrolytic capacitor in the ECU is at least 2 fold over their typical rated service life of 3000 h

They become electrically leaky way before they actually leak electrolyte, and the 1990's was characterized by a huge amount of counterfeit caps which fail way before their promised lifespan (see www.badcaps.net).

In addition any 1993 car has ECU caps that are 200,000 h old and no sane EE would use caps this old if they had ZERO miles.

Luckily these ECUs have big beefy Mil spec PCBs with through hole components and good lead solder, they are a breeze to work on!

Spend ~ $5 at a reputable electronics online retailer (Digikey/Mouser/Allied/Newark/Farnell) to buy identical value EL caps (at or above the old ones rated voltage) with a temp rating of minimally 105C and specific LOW ESR designs made by top shelf cap manufacturers:

• United Chemi-Con /Nippon Chemi-Con
• Nichicon
• Sanyo/Suncon
• Panasonic
• Hitachi
• ELNA

(service lives of 12,000 h or more are now readily available!)

Then watch some online tutorials on using a temp controlled soldering iron ($15) and a solder sucker ($5) with good rosin core no wash electrical grade LEAD solder ($5) and replace all of the old EL caps.

The ECU will then last another 23 years! No more code-alanches, better mpg, better performance etc. etc. :thumbsup:

 

[Silent Runner]

Gee Tedmich,

I'm going to have to pull my 71' 340 Duster out of the barn to get around this capacitor thing now.:wink:

 

[mcgowaw]

ted's suggestion is what pushed me to finally, after 2 years, replace my ecu. glad i did. i still got the old one and i'd recap it but the braindead PO had replaced the ecu before i got the car trying to fix a dirty intake/iac/egr problem cause he was a parts replacer. he used the wrong number. probably thought they were all interchangeable. to wit, the oil filter from a recent oil change was for an I4!
the correct model ecu is in there now though so i'm happy - better shifts, mpg's and no unexpected stalls or codes.
tony