FingerMan20

When I had my truck I replaced the cat and o2 sensor and noticed a whole new engine behavior, also, and about 3 more mpg.

I hope the fix remedied your problems! Be sure to update us, J!

jandk2005

CRAP.........got it home from the smog shop, which PASSED ME with FLYING colors, most of the SMOG crap, the NO and the CO and the HC, were near zero which surprised me ...... anyways well i went to advance the timing......did so , ran it to work and back, NOOOOOOO POWER, i went from 10 deg, to 15 as LOTS of people have said brings power since its running so rich......... well it was a PAIN in the rear to get it passed 55mph down the road , not to mention i was in 3rd and 4th gear and it wouldnt go...........
got it home and put the timing back to 10deg .......... jumped it as well, and i honestly cant say if its gonna make a difference..........i went from having a great running rig, to a crappy one instantly............ anyone????

Crymson

Pull the EFI fuse or disconnect the battery for several minutes to reset the ECU, and see if your problem returns.

jandk2005

yeah, i pulled the fuse, and let everything reset for about half an hour......... i put it back in and went to sleep....gonna drive it to work tonight and see how she runs......hopefully a little better

jandk2005

ok, running horribly, drove a few blocks..saw a spark......drove home..GLOWING EXHAUST from headers to cat...... BRAKE LINES WERE on fire FLAMES ...........had to get the hose to put them out.... DID NOT OVER HEAT Radiator did not seem hot, just smoke from the headers and my carpet was a little melted......., shut it off, still starts and runs.......
DOes anyone think it could be that my brake lines near the Headers got hot, ( theyre about 1 1/2 to 2 inches away bent them when i put ont he Downeys) or maybe the E brake line is stuck...........the handle does spin freely when try to let the ebrake out ...expanded the brake fluid and cause my brakes to seize causing my motor to run really hard??? because THATS the only thing i can think of.......... still idles great seems to have power in the driveway????

jandk2005

Maybe a Throttle position sensor could that be the prob? Jiggled it around and it started running like crap again in the driveway....... does that control timing etc etc?

Flash319

TPS, TPS, TPS. Adjust that and your problems will go. Mine was out of adjustment and I was cracking exhaust manifolds. Exhaust temp gets really hot, also your timing will be out if your TPS is not adjusted when you do your timing. That would explain the no power. When you short the TE1 and E1 the idle should change. If not then the TPS is out of adjustment.

jandk2005

when i short the TE1 and the E1, there is NOOOOOO change......... also, i noticed that when i was trying to jump them, the TPS had to be fully closed.......well i actually had to push it down to make it seat and then the check engine light started flashing...... so with that in mind id figure that it is out of adjustment....... should i just adjust or get a new one?

regularguy412

I'd say anything is possible with the tight quarters in there. Maybe try some thermal wrap on the headers and on the brake line. If the exhaust temp is that hot, you may have a fuel delivery problem and the engine is running too lean. If it's fuel starvation , check these for starters: Fuel Pressure, Fuel Filter, AFM and TPS for proper adjustment and operation, fuel injectors ( dirty or clogged).

Mike in AR

Flash319

Just adjust the TPS. Get a mutli-meter and using resistance (Ohms) setting check the resistance between the idle pin and i forget the other, a manual will say(I think the top 2 pins). When it is at idle, there should be a low resistance (switch is closed, should be around 20 ohms) then when you start to turn the throttle just a hair the resitance should jump to infinate (switch open). It acts just like a switch. So make sure that when the throttle is closed that the switch is made. This talls the ECU that the truck is in idle condition. This effects the curve of the fuel delivery. It sounds like your ingnition timing was way retarded so raw fuel was getting into the header and making it very hot. When the TPS is not set right the timing will be way advanced (like 35deg) when you look at the mark. So you would adjust it back but in fact you were making it way retarded.

jandk2005

Long story short, it didnt look the same as it was in the FSM.......a few minutes of scratching my head and i figured it out..... the IDIOT who last messed with the truck prior to me buying it put the DAMN TPS in backwards........ everything was backwards!!!!!!
this was something i didnt touch when putting the heads/ headers on....... So i swapped it around and CRAP i actually have a FULL OPEN THROTTLE ...... So, i followed the FSM to a T and EVERYTHING was in specs. anyways, so put everything back together and JUMP THE TE1 and the E1 ports *the vacuum SHUT OFF as it was suppose to* ...and attatch the timing light and i pull the trigger........
****** 5 deg ATDC ********
no wonder i wasnt going anywhere...... so raw fuel was being dumped into the headers after it had already reached the top........so , i Adjust it, and i set it to 13 Deg BTDC. I test drove it NO pinging and what a difference...... NIGHT AND DAY....it actually had some get up and go! VERY smooth, and VERY Crisp! i could actually take off in 2nd gear!

NOW, lets do some Toyota Stealership TECH bashing....... what idiot works on TOYOTAS all day long and doesnt know how the TPS should go in? So let me backtrack and give you the history.......ORIGINAL had it for abou 190 k with no problems...... Finally his original head gasket blew, so toyota REPLACED the whole engine, no cost becuase it was covered in the warranty! So i got it, at about 15k after the motor swap, because he just bought a new Hummer and wanted a little more power........
So i buy it for 1500$ a steal........drove it home, tuned it up, and it just wasnt right, did compression test, finally figured out that the miss was a burnt valve, ripped off the heads, did some reasearch on these motors, took off the crossover, put some downeys on it. I have my LESSONS learned the hard way..... Now im thinking about it, and HOLY CRAP, what if the TPS caused the burnt valves, and all the problems associated with the new heads that i had to put on??? Well, luckily not to toot my own horn, but thank god im observant enough to figure this one out, cus the trained guys that do it for a living down there at the Toyota place in my town, are a BUNCH of morons......... Anyone got any opinions?

jandk2005

by the way, just put on the roof racks and my new wheels and tires....... Soft 8's 15 inch wheels, with 31 x 1050 x 15's BFG M/Ts......... looks bitchin

jandk2005

no opinions?

jandk2005

come on, someones gotta say somethin???

regularguy412

I think we're all just glad you found it.

rdharper

This explanation fits my own situation. '94 4Runner runs well if I advance the ignition to 25 degrees. I did check the TPS and found it reading open at idle. I adjusted it so it read 10 ohms at idle position.

However the problem remains unchanged, but it is possible my setting didn't survive the tightning process, so I'll recheck it tomorrow.

I do have a question. If the TPS does not detect the idle position correctly, then it must be detecting the throttle open position, right? Its effectively a switch, as you say.

My question is, why does the ECU want to advance the timing 30 degrees if not at idle. Does this seem right? I'm just curious here. Is that really where the timing wants to be with the throttle open?

One more related question. Why is the following happening when I disconnect the TPS? What happens is... the check light comes on of course, and, the truck has lots of power and no hesitation. Again, just trying to understand this.... (silly me).

Thanks for your post,
Richard Harper
Morgan Hill, Ca

CoedNaked

Just a question - can you advance the timing from 10 degrees to 11 degrees, or is that too small of an increment? Would 12 degrees be better?

regularguy412

You can adjust the time forward any amount you like, but you'll eventually run out of room on the slot that holds the adjuster bolt. That being said, the main limiting factor on base time adjustment is pre-ignition of the air/fuel mix. If you push the base time too far advanced, the mixture starts to ignite too soon and causes spark knock. That's why you usually have to run fuel with a higher octane rating ( like Midgrade or Premium ) instead of Regular, when running advanced timing. Higher octane fuel doesn't burn as easily.

Just creep up on it. Adjust the time with the Te1 and E1 pins jumpered and then go out and drive it. See if you get any pinging on part-throttle or full-throttle acceleration. Advance it until there is pinging, then back it off a degree. Remember , atmospheric conditions and fuel quality (winter vs. summer fuel, etc.) will affect this situation. You should really tune it conservatively, just in case you go on a road trip and you get different fuel, drive at altitude, different humidity, etc.

As engine RPM increases, the pistons rise in their bores much quicker. That is to say the come to Top Dead Center quicker. However the fuel only burns at a consistent rate; it doesn't burn 'quicker' as the RPM increases. Therefore, for the maximum force of the combustion to be applied at the most appropriate instant ( to actually push 'down' on the piston from TDC ), the burn process needs an ever increasing 'head start'. That's why the engine artificially advances the timimg of the spark event as RPM increases. It has been found that after about 30 degrees 'lead' on the spark event (total advance = initial base time + artificially advanced time), no additional power is gained, even though the engine speed may continue to increase. That's why the total spark advance is usually 'all in' by around 3,000 RPM. These figures will vary somewhat from engine to engine and whether an engine is set up more for racing or more for fuel economy.

Gonna make a guess here. I would suspect that there's a fail-safe mode in the ECU that allows the engine to run even if the TPS fails. I would suspect that the engine is running slightly rich, thus the improved power. However, I'd also bet that you would have poor fuel economy if you continued to drive with this situation. Others can please provide more input.

Mike in AR

rdharper

Thanks Mike. Understood the principle with respect to advancing the timing, but wasn't sure the 30 degrees made sense.. seemed excessive. Also, thanks for the details on rpm vs advance... makes sense.

I've an update on the whole thing. Firstly, my very new (May5th) '94 4Runner is now smogged and running beautifully... purring as the wife says. Passes Cal Dynamic Smog with numbers so low I thought maybe the Test-Only Smog Station had made a mistake..lol. No check lights.

All it cost me was a lot of times on these boards (this is the best I've found), and a TPS from ebay for $17.5 including shipping. Yesterday I had just about given up for now, when I got the sense from flash319 that my problem was still OBVIOUSLY the TPS, despite the fact I'd come to understand how the TPS works, what it does, and I'd correctly adjusted it.

Well, given all that, I thought I'd try one more thing. Since I knew the TPS was correctly going from high continuity (10.5 ohms), to infinite just as it should, I loosened the screws and, while the engine was running, adjusted the TPS by hand (after warm-up). Sure enough, the RPM jumped from 500rpm to 1100rpm. I'd played with the timing and throttle body idle screw, so it was running on the high side now. So I carefully set the TPS adjusted so it was just detecting idle, by this method, tightened down the TPS screws with a just-right phillips bit crazy-glued into a 1/4" socket.

An advantage of setting it this way is that you get immediate feedback by the rpm shift. Since the TPS is acting like a 0/1 (off-on) input to the ECM, the rpm shift is immediate and obvious. Makes setting the dang thing very simple, and quick.

The socket/bit adjust method allowed me to get the right distance and a right angle to apply enough torque on those very hard to get to, screws. Not as good as replacing the screws with hex type, but then I didn't have to wait for the hex screw kit to come in, or make a trip to town, or risk dropping one of the screws down where I couldn't get at it.

Anyway, then, while E1-TEI were still jumpered, I set the timing to 12 degrees, set the TB Idle Adjust so that with no load on the motor my rpm's were now at 800.

Buttoned it all up and test drove it. Power is smooth and strong. Beautiful. Fini. Done. I'm a happy boy.

Thanks to all who took the trouble to write on the idle/timing/TPS problem.. In particular flash319 and Mark... and Mike(you).

Ebay purchase price was 3k. 150.4K miles. Loaded and pretty.

I was prepared to put a lot more money into it, as basically, because of my experience with my '85 4WD SR5 long bed (which the wife also loves), I decided Toyota was worth investing in. Now I've got a truck when I need it, and a grocery/Great Dane hauler when we need it. All paid for.

Life is good.

Richard Harper
Morgan Hill, Ca