raptor510

Hello everybody!

1994 4Runner V6 Auto 4x4

So about a month ago my check engine light came on. Code 25. It went off a few minutes later and disappeared for almost 2 weeks. Came back on. First move was replace the O2 sensor which did not solve the issue as it came back on (I cleared the code) about 3 days later. Searched for vacuum leaks and found non but while fiddling around under the hood with the engine running the CEL went off. I was perplexed but happy until it came back on the next day. I checked the plug wires and ended up replacing the distributor cap and rotor but it was still on. To rule out the distributor installed a new one and like I though, that didn't make any difference. I had my mechanic poke around and since the engine was rocking back and forth a bit he started pulling plug wires until he found cylinder #3 to be dead. When he pulled the spark plug it was bone dry and didn't smell of gas or anything so he said I had a bad fuel injector or maybe it was really clogged. I ordered a set from TeamYota and installed them yesterday. Truck runs noticeably better and the CEL went off! For 30 minutes and now it's back! I am at a total loss and have no idea where to go from here! Please help a brother out. Many thanks ahead of time!

ZUK

iTrader: (1)

25

air/fuel ratio lean indicator--lean signal sent to ecu from o2 sensor

--injector fault(s)

--fuel pressure

--oxygen sensor

--airflow meter or map sensor

--ignition

--ecu


sounds like you have a lean condition....too rich. Is the tailpipe black?

inspect the air filter....is it extremely dirty which would limit air flow.

Do you have a K&N air filter? The oils tends to clog the airflow meter/map sensor

Just before this happened, did you change anything about the truck? Any performance items like air intake snorkel or K&N or a new cheap set of neon spark plug wires....maybe an off brand of plugs. Maybe an exhaust change of some sort? Anything under the hood?

raptor510

Thanks ZUK.

I have installed new fuel injectors yesterday and they clicking away like champs.

Have not checked fuel pressure (Don't know how to do so).

New Denso O2 sensor.

AFM is only a couple years old but I suppose I could clean it somehow...

Just left a shop that specializes in Yota's and they set timing to 10 degrees and reseated my intake hose (I had it on a wee bit off) and then they pulled the EFI fuse to clear the code. They said to keep an eye on over the weekend and see if the CEL comes back on. Drove it home and the CEL did not come on.

I am hoping it stays off but I am afraid it may pop back on again any day now!

Should I have the fuel pressure checked? Will that rule out the fuel pump?

Odin

Yes, unless it's an intermittent electrical problem or dirty, corroded connection.

scope103

Zuk - a "lean condition" is the opposite of too rich. Raptor had too much air, not enough fuel. The stuck-closed injector allowed one cylinder to pump nothing but air into the exhaust. The leakage around the intake hose added unmetered air.
I don't see how that could help, but I could be wrong.

The fuel pump pumps fuel at a certain RATE, which if sufficiently restricted could reach 100psi or so. But it's not that restricted; instead the fuel pressure regulator "dumps" the pumped fuel at exactly the right rate to keep the rail at about 38psi (depending on throttle opening). If the pump can't make the necessary rate for idle, the FPR will shut completely but the rail still won't make it to 38psi, and the engine will stall.

A WEAK fuel pump might not make full flow; enough for idle, but once the RPMs come up and the injectors are open longer, it can't keep up. Then the fuel pressure might drop under a lot of load and throttle opening, and that would throw a code.

So testing the fuel pressure at idle should tell you nothing. You'd have to work out some way to check the pressure under heavy load.

raptor510

I agree with you. It makes logical sense that if the fuel pump were not working properly I would have more than one issue manifesting itself and more likely than not the ECU throwing a code. My idle is peachy now and holding at 780rpm nice and steady. I do get less than desirable mpg but I am running 33's. I am hunting down an exhaust leak today that my mechanic said wouldn't really be to blame for the issue but the sound is driving me nuts. I still have not seen the CEL come back on but I am going to drive a lot over this weekend and keep an eye on her. I wish I hadn't spent $100 on a new O2 that wasn't the problem to begin with!

ZUK

iTrader: (1)

Had a moment there
I got it 100% turned around

raptor510

So the sage continues!

Fired her up this morning and within 300 yards the check engine light came on again! Pulled over and checked the code and this time it is NOT 25 but 52!
Decided to drive her to another shop close to my house and the entire way she was driving like a tired dog. No power at all and the exhaust leak is getting louder. I am at a loss...could an exhaust leak cause the engine to knock? TO make matters worse, while in the parking lot of my mechanics shop she dumped a cup or two of coolant. Appeared to be coming from the rear of the engine but after 10 minutes with a flashlight inspecting all the hoses by the firewall I couldn't see anything. It looked like it was dripping down from somewhere and coming down the tranny then onto the drain plug of the front diff. WEIRD. Limped her home and looked underneath to find the leak had almost stopped but I see coolant all the way up the front driveshaft all the way to where it connects to the transfer/transmission. What is going on with my poor truck???
Thanks for everyones help so far...we killed the code 25 but I need help with this coolant leak and the damn code 52, PLEASE.

scope103

I don't know where you get your Code information, but where ever it is, you must read the whole thing. http://personal.utulsa.edu/~nathan-b...85diagnosi.pdf

Code 52 has NOTHING to do with whether your engine is knocking. Nothing. The code means the ECU CAN'T TELL if it is knocking. If the engine IS knocking it can quickly blow a hole in a piston, so to save the engine the ECU dramatically retards timing. Retarded timing => tired dog.

The MOST likely cause of Code 52 is a fried knock sensor "pigtail." It's in a hellish environment and transmits a tiny signal; after 15-20 years the insulation fails and the signal is lost in the noise. Replacing the pigtail is cheap but otherwise non-trivial (you have to remove the lower intake manifold), but there is no other way to get around the Code.

I have no idea what's going on with your coolant.

raptor510

Scope, thanks for the explanation. I am having it towed to my shop Monday morning and letting them tackle the knock sensor issue, exhaust leak as well as the coolant leak. I know I could change the pigtail for the knock sensor harness myself but if they are going to be tearing into it I would rather just let them handle it. Besides, it's been sweltering out lately!
I will keep you guys posted though and thanks for all the good input! Have a good weekend.

raptor510

So I was fiddling around yesterday and while trying to find the connector for the knock sensor under the TB I noticed the coolant line by the fuel rail would leak when I touched it. Moved it a bit more and there was a split in the hose. Great. Put 2 and 2 together and realized while I had fixed the code 25 issue being the 100th time I've had the intake plenum off the hose must have just had enough flexing and gave out and was leaking all over the knock sensor connector, filling up the valley then leaking down the back of the block to the exhaust crossover then down the pipe and also the bell housing. I was going to be damned if I was going to tear the plenum off AND the lower intake to replace a wire. Grr.
Today my neighbor and I took off the manifold again and when it was off we noticed that coolant line was completely disintegrated where it attached to the back of the block too. Grabbed a new piece of hose at the auto parts store and replaced it. I also sprayed the knock sensor connector and cleaned it with a toothbrush and some q tips as well. Put everything back together, but as Murphy would dictate, lost one crush washer for the cold start injector and somehow managed to pop the lcv hose off the lcv valve on the valve cover. ARGH. Ordered 2 new crush washers from the dealership and will be trying to get the intake up just enough to get the hose back into place. Hopefully we won't have to take the whole thing off again. That bracket going from the EGR valve to the block is a PITA to work with!!! Hopefully this may serve as a FYI for people who are maybe having a code 52. Check that TB coolant line and make sure it isn't leaking on your knock sensor connector!
Wish me luck tomorrow...I'm hoping this will end my problems! (Although, I still have to track down the exhaust leak on the passenger side.) Will keep everyone posted.

raptor510

Got my 4Runner put back together this morning. She idled great. Made sure everything was fine but the second I drove her down the street the code 52 popped right back on. I cleaned the crap out of that knock sensor connector! Any ideas? Is that knock sensor wire harness shot? Am I going to have to replace it?

scope103

Maybe.

"cleaning" an electrical connector that has been exposed to a lot of water is iffy at best. If you leave the smallest amount of ionic salt, just the moisture in the air can cause a short. Since this is a shielded connection with a very tiny signal, it doesn't take much.

You could try ohming out the wires (conductor and shield) from the ECU to the connector, and then with the connector together to ground. But that's not going to pick up a "degraded" connection.

Your biggest problem isn't the pigtail (that can be replaced cheaply but with a bit of work), it's the harness-side connector. It too was wet. I might try soaking and rinsing that connector in DISTILLED water, carefully dry it with your hair-dryer, and see if that makes any change.

raptor510

Tried everything I could to clean the contacts but nothing worked. I decided to take her to my shop and have the sensor and pigtail replaced. $850. OUCH. I know I could have done it myself but I don't really have a place to work on it in the shade and it has been brutally hot here lately. The shop will give me a year warranty on their work and new plenum and intake gaskets will be installed (of course) and they may even check my valve clearances for free!
I will keep everyone posted on how she drives tomorrow when I pick her up!

raptor510

Guys, I got my truck back today and after $900 she had a new knock sensor & pigtail harness, gaskets and some coolant lines she sounded and ran like a champ. For about 15 minutes. Then the code 25 popped back on again! Help me out, guys! What am I missing? No vacuum leaks, new O2 sensor, and replaced all injectors. Help!

Blue_petersen77

Hey guys,
Pertinents: 02 Tundra 4.7 4x4 (324,248 miles)
replaced wheel bearing and all seals on pass rear axle (checked and triple checked abs tone ring position and replaced sensor and reset codes...
I have a strange problem! Now when the truck is running at idle and NOT moving, the abs light is flashing... as soon as I start driving it goes away and stays off... then as soon as I come to a stop... (everytime) it keeps flashing until I move again

Things checked: fuses, diff oil, reservoir fluid, sensor and tone ring positioning, cleanliness of tone ring and sensor, new brake pads, Ebrake adjustments....

Any help would be appreciated!

scope103

Blue-petersen77 -

I'll bet you'll have much better luck if you post to a forum (on this site) followed by folks with Tundras. I sure don't know anything about them new-fangled shiny trucks.

Blue_petersen77

Wow! Sorry broseph!
I used to be here regularly about my 94 4 runner lol. I'll take any grief associated with "not searching"... I put in my specs and it brought me back here... too many Coronas I'm sure lol. Bone head move on my part.... carry on!


P.S....... I would kill to get my old 3slow back

Charchee

You mentioned an exhaust leak. Where is it located?

southbound yota

Following this thread--any luck with a solution? I've gone through an almost identical series of problems.