shurup

Well, afler the engine died on me last yaer when I was on one of my trips far, far away from home, I decided it was time for a rebuild. I pulled the engine out and sent it to an engine shop (didn't have time to rebuild myself) and sent the tranny (5spd) to another shop. After putting everyting back together and test driving a truck, I noticed that I didn't gain much power after the rebuilt. Actually I think it even run worse comparing to what it was a year or two before it broke down. Everything I said so far is engine power at low and mid RPMs. Before rebuild I hardly ever run the engine past 3K RPM and only once or twice took it up to 4K (the truck is old, with about 250K miles on it - was afraid to brake something ). After the rebuit it starts working really smooth and quieter and I did rev it up to around 6K (when on neutral), it gets up to speed fast without any troubles and creazy noises, but when on a highway, I don't feel any power gain after around 3-3.5K RPMs. It is like if I want to pass someone, I might as well stay on 5-th or 4-th because it won't make a big difference if I downshift and RPMs will go higher.
Now, here are the things that add to the problem, but I am not sure to what degree.
- I have 31x10.5 mud tires on a stock truck. I know it rubs my power, but that should be on all RPMs, not just on high.
- I didn't adjust the timing with timing lights (don't have one), but I know that I am pretty close to the right position of the distributer. Will fine tuning the timing make big difference (or any difference)?
I know the timing needs to be fine tuned also because if I use regular gas, I am getting check engine light with a code -knock sensor- when engine goes just past 4K RPM when under load. I don't see this problem if I use better fuel.
- I have a crack in the plastic air tube right where it connects to the trottle body. I was going to replace it with a new part, but the Toyota Diler I went to was closed for some stupid holiday, so I ended up wrapping a roll of black tape around the end of that tube. I don't know for sure if it is still leaking air from that crack, but if there is some air being sucked through that crack, that means that air flow sensor would sent the incorrect signal to computer and it would screw up my air/fuel ratio. The question is - would it make such a big difference on engine power? I know it would make a HUGE difference on turbocharged engine but not sure about a normal (no turbo) one.
- What else might be wrong? What else can I check?

Jay351

check your cat. Might be plugged.
And I would fix the leak on your intake asap. These engines HATE any kind of air leaks.

neilan

definatly get a timing light a little bit can make a huge difference. Are you sure your distributor isn't one tooth off?

Black tape should seal an intake tube quite well but take some starting fluid and spray it around to check if there are vacum leaks. If there is a leak the fluid will be drawn in and the engine will rev.

Check you cat but its not likely its plugged if you have good low end still.

Jay351

How could having good low end rule out having a blocked cat?

shurup

Oh... By the way, did I post into the right forum?

Jay351

I wouldve posted in the 89-95 forum as it gets MUCH more attention.

shurup

OK, I bought a timing light and checked for timing. It was 5* only and sticker under the hood says it should be 10* so it wasn't too far off but I changed it to 10* and after a short test drive to 15*. It did make a little difference.
Also before I bought a timing light I punched out the cat (I know it is not a really good thing to do but here in Alberta we don't need to do any emission checks or anything). Now it is not plugged for sure and I don't think it was since it didn't make a big difference.
Together these 2 things I did add a little bit of power but I think it is still not enough on higher RPMs.
I will fix that leaking plastic tube too.
Any other ideas/suggestions on what else to check?

Jay351

do you have stock 4.10 gears? or 4.56 ?

shurup

I am all stock except for lift and tires.
I also did some modifications to my intake (will post some pics later). It added a bit of power. Overall my truck performs way better than what it was, but it still has week hi end torque.

How do I move this tread to other forum? I e-mailed one of the moderators asking to move my tread, but nothing happened yet.

shurup

Here are some pics of my intake. There is NO vac leaks anymore.

What other suggestions you guys have on what else to check?

TNRabbit

Was the knock sensor replaced? If not, and it's bad, the computer will retard timing during driving to 0 degrees. If you're getting knock sensor code, I'd think it was the sensor or the wire between it and the wiring harness. Very common failure point.

shurup

Before the rebuild I didn't have ANY CEL (Check Engine Light). After the rebuilt it was showing CEL all the time (knock sensor). It turned out to be the wire that connecs sensor with computer. After I replaced it, the problem went away except for the case when I used regular gas and the engine was under load with RPMs over 4000 - the CEL would come up again with the same code. CEL wouldn't come up if I use better grade fuel. I was blaiming incorrect timing for it. Since I bought a timing light, I checked it and it was a bit off. My gas tank is almost empty now so I am going to fill it up with regular and see if it is going to come up again after everything I did to my truck.

shurup

Is there a way to check a deffective knock sesor using a timing light? I think I read it somewhere that you can check it with a timing light.

Another thing I just remember. When I was checking my timing, the timing mark was supposed to move slowly in the opposite way of the engine rotation (counterclockwise) if you start opening up the trottle (I also read it somewhere ) and in my case when I start opening up the trottle it wasn't moving at all untill some point when it just jumped out of view (far to the left I think). Is that the way it supposed to be? How does that timing mark acts with you guys? Could some one ckeck to see if it does the same thing?

shurup

Run it until EMPTY FUEL LIGHT come up and filled it up with regular. Drove it about 120 Kilometers yesterday pushing it sometimes past 4-5K RPMs - no CEL so far so My guess was right - it was timing related. Also noticed a little decrease in performance on all range of RPMs - cheap gas - will go back to something better.

Any commnets on my previous post?

TNRabbit

I only run 93 octane on mine; it's happiest & has the most power. if you're at 15* btdc I'd be surprised if you DIDN'T get pinging. TPS & knock sensor would be my next guesses.

Maybe you have a distributor going bad??

shurup

I believed I replaced a distr cap and rotor.
Don't think that I had pinging. But then for one thing I have bad hearing problem. For another - my power stearing pung is noisy enough to mute all the other sounds. Before the rebuild I was able to hear ticking noise (valves) through all other noises, but after the rebuild the engine is really quiet and smooth. I was going to replace my power steering pump but it is so far away in my list of to do things that I don't wory about it right now.

You think TPS may affect the performance on different RPM range? I will check it. And if it a knock sensor wouldn't it show a CEL if there any problems?

Anybody has any comments on my timing mark moving around (read above).

TNRabbit

[quote=shurup;50601748]I believed I replaced a distr cap and rotor.
Don't think that I had pinging. But then for one thing I have bad hearing problem. For another - my power stearing pung is noisy enough to mute all the other sounds. Before the rebuild I was able to hear ticking noise (valves) through all other noises, but after the rebuild the engine is really quiet and smooth. I was going to replace my power steering pump but it is so far away in my list of to do things that I don't wory about it right now.

You think TPS may affect the performance on different RPM range? I will check it. And if it a knock sensor wouldn't it show a CEL if there any problems?

Not necessarily.

Anybody has any comments on my timing mark moving around (read above).

Again, it might be the DISTRIBUTOR vice cap/rotor...[/quote]


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