22RE ECU compatibility

[WarDamnEagle]

Every now and again, the 22RE in my 85 4Runner will surge a bit while idling. This normally occurs after a long hard run on the interstate but isn't consistent at all. I put a DOA Racing engine in last year and an LC Engineering header and stainless cat back exhaust system. I did not replace the original O2 sensor.

I swear I recently read a post on a similar issue where I thought Pappy said the first EFI ECU's had an inherient fault which sometimes caused this phenomenon. The solution, as I recall, was to go to a later ECU. I searched both subject and under his name but came up empty.

Roger Brown's website does a good job of documenting the various ECUs and he says that the 86/87 ECU (part number 89661-35070) will work in the 85 (OEM part number 89661-35020). Link to website:

Toyota 4Runner Technical Information

I am going to replace the O2 sensor but I thought I would also pick up an 86/87 ECU and see if that helps as well.

Can anyone confirm that this will help with the occassional idle surging or otherwise confirm that I'm wasting my time?

 

[pappy]

Not sure it will help your problem. The issue I had with the early ECU was at around 2000 rpm under light load the check engine light would come on. I seem to recall the code pulled was Ox sensor. I was told this was a problem with the ECU, and I am running one from a newer truck. I don't remember which. I have had no issues since.

I also seem to recall there were two ECUs used in 1985. I have a Nov 1984 truck, and a buddies Dec 1984(?) used a different ECU.

Idle surge sounds like Ox sensor. I've had this problem before.

 

[WarDamnEagle]

Thanks. I think I'm going to pick up an ebay ECU anyway and try it and also replace the O2. Won't be able to do this for a couple of months but will report back if it helped at that time.

 

[WristPin]

ECU should be the last thing on your mind

check the grounds at the manifold.
check make sure the battery cables are ALL tight.

 

[WarDamnEagle]

ECU should be the last thing on your mind

check the grounds at the manifold.
check make sure the battery cables are ALL tight.

Oddly enough, I just ordered a new set of cables (positive, negative and engine ground) a couple of days ago. Not sure technically why you say to check the above but it looks like I will be doing that when I install the cables.

FWIW, the engine check light also comes on sometimes coincident with this surging but, of course, I haven't tried to decipher the code when it's on.

 

[Downey]

I could be dead wrong, but I think your idle-up problem is normal in all of Toyotas ECU's. Part of the emissions system is designed to idle-up to burn off excessive fuel in the intake manifold. This would particularly be the case when decelerating for your freeway off-ramp from higher freeway speeds. All of the sudden the intake manifold has more fuel in it than is required during deceleration. If not burned-off, it becomes emissions!!!!!

 

[pappy]

Oddly enough, I just ordered a new set of cables (positive, negative and engine ground) a couple of days ago. Not sure technically why you say to check the above but it looks like I will be doing that when I install the cables.

There are other grounds to check. There is one at the back of the engine going to the firewall. Mine was toast, and while it would seem redundant with all the other grounds, replacing it actually did seem to make a difference on my truck.

 

[Bogo]

Oddly enough, I just ordered a new set of cables (positive, negative and engine ground) a couple of days ago. Not sure technically why you say to check the above but it looks like I will be doing that when I install the cables.

FWIW, the engine check light also comes on sometimes coincident with this surging but, of course, I haven't tried to decipher the code when it's on.

A bad ground can really mess with analog sensor data. If garbage data goes into the ECU then garbage commands come out of it. Ergo, a badly running engine.