92 LC running rich (High CO and HC) failed emissions...

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Well the FPR works a bit it drops it from 45psi to 40psi (is this normal?) when i apply the vacuum... haha i wasnt careful and i pulled the hose off after i had thought i depressurized it and WHOOSH! i was attacked by a stream of gas... :doh:luckily it missed me.
Today was not all bad though... I finally put on some 255 85 16's on the whale shark... now it doesnt look like its on roller skates anymore!
anyways... on to the compression check and bg44k...
 
Ok heres another quirk of this truck...
There are 3 vacuum switching valves (VSV) under the hood in a group. Red blue and grey. The grey one seems to intermittently click really fast, maybe 8 or 10 Hz. But it doesn't do it all the time. I did notice that if I bypass the grey VSV and apply a vacuum directly to the Air Switching Valve ASV that my O2 sensor dropped it's voltage dramatically!!! Could this be the problem I have been looking for??? From what I can tell the ASV brings in fresh air to the exhaust for further oxidization and reduction before it hits the cats??? Maybe?

My question is that I am not sure what this thing is for because there is not much info on this grey one but if someone could help me troubleshoot this I would be most grateful!!!
 
Compression checked out OK... here's the numbers in ascending order...

146
141
139
134
137
145psi

One semi low one... I think they should all be within 7psi of each other... But I'm not too worried about it.

I did find something else interesting today, there is a loud clicking coming from the fuel rail/injectors or something connected to them. I used a big metal file to pinpoint the loudest spots, which happened to be the fuel rail and injectors. The clicking increases in freq. with the rpm of the engine. Any ideas?

Im also checking the O2 sensors per the flow diagram in the FSM. The strange bit is that I'm getting inconsistencies and conditiions not described in the manual. Paulichie is sending some O2 sensors that he had laying around so I cant wait to put them in and see what happens. Thanks Paul!
Somewhere in the flow chart diagram is a "replace ECU" block... I hope I don't have to go down that road but I am determined to fix this tank of a vehicle.

Anyways, I will keep posting what I find...

Cheers
 
The ticking sound is the injectors firing. Normal sound. The 3FE is as quiet as ball bearings in a centrifuge.

ECUs don't fail on these trucks. The fact that your truck is running tells me that the ECU is just fine.
 
jonheld said:
The ticking sound is the injectors firing. Normal sound. The 3FE is as quiet as ball bearings in a centrifuge.

ECUs don't fail on these trucks. The fact that your truck is running tells me that the ECU is just fine.
Click to expand...

Yea I suppose, it just doesn't make sense why its running rich... And it's easier for me to start pointing fingers when I don't understand whats going on... :p It's like it's stuck in open loop or something... It has to be something simple but it is driving me crazy! :bang: The more I work on this truck the more I'm falling in love with the thing even though it's being a huge PITA. I have found many things that need to be fixed along the way (which is a good thing) for example, the brake booster doesn't hold vacuum, so I need a new one (I plugged the leak don't worry). The joints in the axles needed grease really bad, those things were bone dry. I replaced many hoses that were cracked and just in horrible condition. I have also done my share of breaking fragile plastic parts that are more expensive than I would like them to be. I broke the thermal time switch when I was trying to access the temperature sensor. Oops... And I fried an O2 last night...

Waiting on a pair of O2 sensors... That will be my next step. Good thing Paulichie is sending them because, like I said, I fried one last night when I was trying to measure the main O2... I shorted the signal wire with +V... oops, blew my ECU 15A fuse immediately and now my O2 doesn't output anything... :doh: There's no cure for stupid! Haha, just kidding, I don't have any self esteem issues... yet... I need to figure out this damn thing, it's consuming my life!

Thanks for all your help guys
 
One more interesting thing... I saw an EGR temp. sensor (I think) last night, I didn't thing I had a CA vehicle... maybe someone moved there and the car ended up here in CO. I thought that it would say under the hood if it was a California vehicle or not but I didn't see it.

Just thought someone might read this and say "oh, check the such n such thingy"...

Cheers
 
CJF said:
Good gawd...

Swap out the O2's and get back to us.
Click to expand...

Yup. You do seem to be going round and round without replacing the items that need to be replaced in order to solve the problem.

The O2 sensors are what gives the ECU feedback on the mixture. If they are old and crusty, then the ECU is getting false information. That's why EVERYONE has told you to replace them.

The more you try to solve this without actually solving the problem, the more facepalms you're gonna get. These are pretty simple systems, but parts wear out over 20 or so years. You're going to spend some money to get a neglected 20 year old truck back into shape. Better come to grips with that right now.

Stay OEM under the hood or you'll wind up replacing things twice.
 
jonheld said:
Yup. You do seem to be going round and round without replacing the items that need to be replaced in order to solve the problem.

The O2 sensors are what gives the ECU feedback on the mixture. If they are old and crusty, then the ECU is getting false information. That's why EVERYONE has told you to replace them.

The more you try to solve this without actually solving the problem, the more facepalms you're gonna get. These are pretty simple systems, but parts wear out over 20 or so years. You're going to spend some money to get a neglected 20 year old truck back into shape. Better come to grips with that right now.

Stay OEM under the hood or you'll wind up replacing things twice.
Click to expand...

Fair enough... I guess I was looking for more of a reason than just "its old". I understand things wear out, but I thought they were still operational from the signal they were outputting....

Point received... Replacing O2's
 
OK... New O2's installed, still running rich... I get about 5 or 6 mpg... It's freaking terrible! WTF is wrong with this LC?! I pulled the fuse and reset the ECU after I replaced the 02's and before I drove it so it could adjust... No luck. Any Ideas guys? thanks

Ive been driving it for a week and a half to see if it will ever get better... Im seriously about to fill it with ethenal and take it to the emissions place and be done with it. But i want to fix the damn problem! I mean 5-6 mpg is terrible! btw i dont smell any fuel leaks...:mad: is it possible it is a tooth off in the cam timing gear? i could adjust the timing correctly but i saw this was a problem on older 4runners.... just an idea... Man this is frustrating...
 
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Pull the vacuum line off the fuel pressure regulator (assuming there is one, dunno for sure on a 92). If there's gas in it, or if it smells like there might have been, change the regulator.
My buddy has a little ranger pickup that had a bad regulator, throwing O2 related codes. Yep, we changed the O2 sensor to no avail. Then, I noticed the vacuum connection looked like crap over at the throttle body. Pulled it off and some gas ran out. New fuel pressure regulator and the thing ran great and the check engine light went out. And, his fuel mileage went back up to where it should be.
The regulator will probably regulate pressure with a slight leak. But that slight leak will dump raw fuel in at the throttle body. The system will try to compensate for it and might throw a code for running too rich.
Good Luck fellow Coloradan!
 
blkprj80 said:
Pull the vacuum line off the fuel pressure regulator (assuming there is one, dunno for sure on a 92). If there's gas in it, or if it smells like there might have been, change the regulator.
My buddy has a little ranger pickup that had a bad regulator, throwing O2 related codes. Yep, we changed the O2 sensor to no avail. Then, I noticed the vacuum connection looked like crap over at the throttle body. Pulled it off and some gas ran out. New fuel pressure regulator and the thing ran great and the check engine light went out. And, his fuel mileage went back up to where it should be.
The regulator will probably regulate pressure with a slight leak. But that slight leak will dump raw fuel in at the throttle body. The system will try to compensate for it and might throw a code for running too rich.
Good Luck fellow Coloradan!
Click to expand...

Thanks, I appreciate it. I pulled the vac line and it smelled slightly like gas but wasnt wet. I plan on replacing this soon because its a little bit out of spec but I dont believe its whats causing the main issue.

Cheers
 
Got some new info here... OK, so I re did the O2 diagnostic per the FSM, this run through of the flow graph I received zero drops in the voltage between terminals te1 and e1. The FSM suggests replacing the ECU... great... NEW INFO: I was in the cab holding the engine at 2500 RPM and I noticed a code came up on the dash, code 51!!! Oh boy! The strange bit is that it only shows up when I am pressing the gas... and goes away when it goes back to idle, and it does not store.... i didnt notice this before because I would pull the throttle cable with my hands in the engine compartment during the previous tests I have done... I just happened to be extra lazy today and sit in the cab and do it and wholah! It also throws the code (and stays) if i put it into drive or reverse.... Seems like the computer is getting stuck in open loop mode when it is driven... weird...

Per the FSM this code 51 is:

system -switch signal

Diagnosis - No "IDL' signal or "NSW" signal to ECU, with the check
terminals E1 and TE1 shorted.

Trouble Area - TPS sensor circuit, TPS, Neutral Start switch, Acceleration pedal and cable, ECU...

Going to start with the easiest, the cable.... I did the TPS a couple weeks ago and I believe I got it to spec but I will check again as well...

Thanks guys...
 
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Haha anyone have a working ECU they're willing to let me borrow so I can see if that is the issue or not? :D
 
Isn't there a FSM test procedure for the ECU
 
if there is a test procedure for the ECU can someone post please?
 
I've read your thread hoping to immediately pinpoint your problem, but I'm at a loss.

The only suggestion I haven't heard (and it might be a dumb suggestion) is the fuel pulsation dampener located on the drivers side of the valve cover near the firewall.

I haven't messed with it myself, but I've read reports of it improving gas mileage. Perhaps it has something to do with your rich burn. (search 'magic screw')

Desmond
 
Check your throttle position sensor. I can see where it might think your throttle was further open than it really is, and dump a ton of fuel in there.
You might want to use a meter and go through the whole range of throttle positions. You might have a bad spot in the middle or something.
Good Luck!
 
Mixelplix said:
I've read your thread hoping to immediately pinpoint your problem, but I'm at a loss.

The only suggestion I haven't heard (and it might be a dumb suggestion) is the fuel pulsation dampener located on the drivers side of the valve cover near the firewall.

I haven't messed with it myself, but I've read reports of it improving gas mileage. Perhaps it has something to do with your rich burn. (search 'magic screw')

Desmond
Click to expand...

Thanks Desmond, I do plan on replacing the FPD when i replace the FPR, but i dont think they are the issue... I have adjusted the magic screw as well... I timed it, adjusted the idle to where it idles at 650 (not 100% smooth but around 95% which isnt bad). Im starting to think more and more its an ECU issue or maybe bad wiring somewhere... IDK

:cheers:
 
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