89 4x4 hesitation, I got codes

[Dnice]

Hi,
I have an 89 4x4. Recently I noticed some occasional hesitation at freeway speeds. Then it got progressively worse within 5 drives or so. It doesn't accelerate well and hesitates/bogs. I pulled the codes and got 2-1, 5-1, and 7-1.

I'm hoping to get some help ad to where I should start. Also if it matters, my van tends to run on the cold side for quite a while after starting and running.
Any suggestions on where to begin?
Thanks. This forum is great.

[djshimon]

The codes are in your manual or on the library section of this website you can look at them or download them-According to the codes 21 says O2 sensor(get a new one), 71 is EGR(does it look melted?) and 51 says Switch signal -tps maybe-I'd worry about this after the cat is checked. I'd look into your Catalytic converter-might be clogged by the symptom of it bogging down more and more.
When did you last change your spark plugs?
Take my views with a grain of salt-I usually figure things out the hard way.

[Dnice]

Thanks. It's definitely been a while since the plugs were changed. I've had the van for about 11 years but prob only put 50k on it since then. I'll try to take a look at the Cat and the Egr. Change plugs and O2 sensors as well. Will the damaged EGR be obvious? Sounds like I've got some work to do.
Thanks again.

[timsrv]

Hi & welcome to TVT!


The codes are in your manual or on the library section of this website you can look at them or download them-According to the codes 21 says O2 sensor(get a new one), 71 is EGR(does it look melted?) and 51 says Switch signal -tps maybe-I'd worry about this after the cat is checked. I'd look into your Catalytic converter-might be clogged by the symptom of it bogging down more and more.
When did you last change your spark plugs?
Take my views with a grain of salt-I usually figure things out the hard way.

:whs::thmbup:

When the primary o2 sensor fails the ECU goes into a "limp" mode as it doesn't have the information it needs to correctly mix the fuel. Running lean can create serious issues, so the limp mode is set to make the van run a bit rich. Running rich will make the economy & the power go down. If left in this mode for very long it can plug up the cat converter. When the cat converter plugs up, this will create exhaust back pressure and the result is serious power issues and over temp issues with exhaust components (EGR included). The TPS (Throttle Position Sensor) is also an emission device designed to help the ECU provide the correct fuel mix (based on position of your throttle). If the ECU doesn't know throttle position, this can exasperate the problems created by a bad o2 sensor.

Replacing the o2 sensor(s) is easy. Here's a link to a thread that gives part numbers: http://www.toyotavantech.com/forum/showthread.php?415-Oxygen-sensor-part-number

Replacing TPS is a bit more involved. You'll need to remove the throttle body to do that one. While it's off it's a good idea to clean it up. Here's a thread where this is discussed: http://www.toyotavantech.com/forum/showthread.php?1242-Article-Cleaning-the-Throttle-Body

Replacing cat with a CA approved unit can be quite expensive. Because of this I'd probably do the other things 1st, clear the codes, then see if code 71 comes back. If you still have power problems, and if code 71 comes back, then it's likely the cat converter is toast. Depending on how much corrosion is on the cat mounting bolts, replacing that can be easy or hard. If the bolts are badly rusted, you may decide to take to an exhaust shop and let them do the work.

And definitely take care of the other tune-up issues. Be sure to use high quality platinum spark plugs. I prefer Denso #P16R, but others will work here (I don't like Bosch). Be sure to replace the fuel & air filters too. OEM spark plug wires last a long time, but the van is getting old. If you don't know when or if they have ever been replaced, then probably a good idea to do those as well. Same goes for the distributor cap and the rotor. Drive train fluids should be replaced in 60k mile intervals, and engine oil S/B replaced every 3 - 5 k miles..........but I'm sure you already know that. Tim

[Dnice]

Thanks Tim,
Do you think the 5-1 code- EGR system could cause this issue as well? Should I address this last, after 02 sensors and TPS?
Also, do you have a link to a good source for a new TPS?
Thanks for your help.

[timsrv]

As previously discussed, code 51 is most likely your TPS. Code 71 is your EGR temperature getting too hot. It's possible it's getting hot due to the extra contaminants the cat is burning off, so I'd wait and see how it does with the other issues fixed. I'm pretty sure that in the throttle body thread (linked above) there's a link to a new TPS. When I need just one (and nothing else), I'll usually purchase from Amazon (about $35 w/free shipping). Rockauto.com has them for $28 or $29, but the shipping will usually make up the difference. Sometimes I make large orders from rockauto & will get 5 or 6 of them (then the shipping is worth it). As discussed in that other thread, I've been using Bech Arnly units (made in Italy) and I believe they are quality units. If you can afford Toyota, they will want roughly double the price, but not sure if they are any better. Tim

[Dnice]

Thanks for the input. I'm starting to understand this more and more!

Another question- Anyway to check the CAT easily? The bolts look pretty locked up. I suppose I will have to break them and look in, then replace with new ones?

Thanks again.

[timsrv]

You can check flow out the back while somebody revs the van and make sure it gets a good blast of exhaust, but this will only help identify the really bad ones. You can also inspect the EGR modulator (plastic disc thing behind the throttle body) for heat damage. Back pressure increases stress on this part often causing it to crack or melt. This can be a telltale sign the cat is failing or has failed. With today's technology, I'm sure there are other ways to tell, but the only way that I know of (to be sure) is to remove the cat and hold it up to light. You should be able to see through it (like looking through a screen mesh). If it's plugged or has broken out pieces of mesh, then it should be replaced. While off, I will usually take the vehicle for a quick test drive to verify the power issue has been improved. The vehicle will be loud and obnoxious, so be weary of cops and sensitive neighbors (if you drive with it off). There are places that sell "catalytic converter test pipes". This is basically a piece of pipe with flanges welded to it for "temporarily" replacing the cat. It's only legal for them to sell as as test equipment (so you can go for a quiet test drive), but realistically, nobody buys something like this unless they intend to install permanently. Considering your location, it's not likely you'd get away with doing something like that (and not something we endorse). Tim

PS: Depending on the type of TPS failure you have, since the TPS is part of your electronic advance system, having that fail can disable the electronic advance. If the electronic advance is disabled, the exhaust WILL run hot. So definitely fix these other issues before getting serious about code #71. Tim

[dennisdcarty]

I too have an 89 4x4 ....Ive been throwing a lean code (25) off and on for a while.
the car is rough / sputter y at idle and if I am sitting there talking on the phone for instance, the check engine light will come on. turning car off turns off light though...I haven't cleared code yet.
Occasionally the check light will come on going down the highway

I replaced two oxy sensors and TPS so it seems I should head for the cat next ?
It is old for sure. Tune up has been maybe 20K with a new rotor in the middle someplace
My mechanic cleaned the throttle body when installing the TPS.
Runs down the road well enough..smooth etc....Fuel pump a possibility even if pressure is OK ?

Is there a place that that rebuilds throttle bodys as there is CPU etc?

Thanks to all !

[timsrv]

Very 1st thing I would have recommended would be replacing o2 sensors, but since you already did that we can rule those out. I wouldn't worry about the cat on a code 25. Code 25 is more likely a problem with injectors or perhaps low fuel pressure. Considering age, a faulty ECU is also a strong possibility. Considering the PITA of the other possibilities, I'd probably start looking on eBay for a spare ECU. There are different ones out there (especially on 88 - 89 vans), so I would get the part number off your existing one and use that number for searching. Only get one with a matching number. Prices vary greatly, but over the years I've purchased 2 extra ECUs for all my vans. Average price was ~$20, so if your timing is right, these are cheap.

If code #25 comes back with a different ECU installed, then I'd start digging into the fuel delivery system. Good luck. Tim

PS: Code #25 could also be a faulty Air Flow Meter or even a plugged up air filter, so if you haven't been replacing that every 30k miles, then it could be that simple. Tim

[dennisdcarty]

I have another computer in case of break down which bit it isn't the right part #...would you say put it in and try it for a hundred miles or no ?

[timsrv]

I don't know. Depends on what it is for. 88 - 89 ECU's need more inputs to function correctly. CA spec ECU's also need an EGR temp sensor input. Typically you can dumb down the van by putting an earlier and/or non CA spec ECU in it, but if you go the other way (more advanced ECU) there will be problems. A more complex ECU will be looking for sensor readings that won't be there, and this will cause it to go into limp mode and/or throw codes. A simpler ECU (86 - 87) will function fine but the front o2 sensor (88 - 89) is not compatible with an earlier ECU. If you have an 88 - 89 van and install an ECU designed for 86 - 87 then you'll need to remove the cover plate from the exhaust manifold and put a single wire o2 sensor there. Then you'd need pull a wire from it to the ECU and hook it up to the correct ECU pin connection. Another interesting and fun fact is Toyota swaps around some of the ECU pins on different ECUs. On vans, this typically only happens if you're swapping ones from different years (Example: installing an 86 - 87 ECU into an 88 - 89 van). Even though the ECU connectors are the same, some pin locations are not, so if you swap in an earlier ECU, you'll need to map out and swap around some pin locations (been there done that). This is why it's recommended to stick with ECU with the same part number. Q: Can other units be made to work? A: Yes. Q: Is it worth it? A: For testing reasons, probably not. Tim

[Dnice]

Update:
So I replaced the front O2 sensor with a new one. I could not get the rear one off. After some research I think this one might not affect the system?

Anyway, the van runs better than before I changed it but still has some issues with a lag, hesitation, and weaker acceleration. Is the Egr valve the next thing I should check? Or the TPS? I never took the Cat off but it seems to be flowing ok.

Any suggestions? Thanks
Dennis

[Burntboot]

"I could not get the rear one off. After some research I think this one might not affect the system?"

Generally speaking, Car companies aren't in the habit of wasting great gobs of money, installing systems that have no purpose.
It provides feedback to the ECU about how well the engine is burning the exhaust, so it can and will affect the system.

Suck it up and replace the rear o2, THEN see how it runs.
Maybe it solves your issues, maybe not, but at least you 'll know you haven't taken any faulty short cuts.

[dennisdcarty]

"I could not get the rear one off. After some research I think this one might not affect the system?"

Generally speaking, Car companies aren't in the habit of wasting great gobs of money, installing systems that have no purpose.
It provides feedback to the ECU about how well the engine is burning the exhaust, so it can and will affect the system.

Suck it up and replace the rear o2, THEN see how it runs.
Maybe it solves your issues, maybe not, but at least you 'll know you haven't taken any faulty short cuts.


ANYONE KNOW HOW TO COME UP WITH MY ECU PART #


THANKS

[dennisdcarty]

Its worn off the unit

[Dnice]

ANYONE KNOW HOW TO COME UP WITH MY ECU PART #


THANKS

Hey Dennis,
You should start a separate thread with your issues so it gets properly addressed instead of buried in this one that I started.
Will probably benefit us all including the guys kind enough to respond to our issues.
Thanks

[Dnice]

"I could not get the rear one off. After some research I think this one might not affect the system?"

Generally speaking, Car companies aren't in the habit of wasting great gobs of money, installing systems that have no purpose.
It provides feedback to the ECU about how well the engine is burning the exhaust, so it can and will affect the system.

Suck it up and replace the rear o2, THEN see how it runs.
Maybe it solves your issues, maybe not, but at least you 'll know you haven't taken any faulty short cuts.


Thats good advice. Thanks.
What about if I run the diagnostic and see if it comes back as O2 sensor again assume the rear is bad?
Or if the O2 sensor code doesnt flash, I can move to the item?
Either way, I'll try to get it off when I get some time.

Thanks