PismoJoe

Easy enough to look in there with a flash light to see if the fuel filter looks new, sort of a PITA if you don't need to replace it...

BajaRunner

Ha, yeah I hear you. I was going to take off the plenum anyways to paint it, and to check the injectors... I still haven't found it though. haha.

americanmcss

Slight popping like that could definately be a valve thing, you might also be running rich or lean as well. Running lean more than likely. Have you checked to make sure your injectors are all working as they should? Not sure on standard procedure for testing, but Im sure someone does. Too lean would definately account for power loss as well. BTW where did you get that intake? Custom made?

BajaRunner

Thanks for your input.

Well unfortuently, I am not sure how I would test the fuel output of the injectors without the SST's. There is probably a method for the at home mechanic. Maybe I'll try that magical search button

Who is the most reputable person shop to send injectors to get serviced? I think that might be a good idea.

Yes the intake is custom made. Its fit is perfect. The PO said he had his hot rod builder friend make it for him. It uses a K&N cone filter and obviously incorporates the AFM quite nicely. Honestly, I can't feel a difference when I put the stock one back on (for inspection).

BajaRunner

Update. After reaching operating temperature I went in and adjusted the valves. All the intake valve clearances were spot on.

The exhaust valves were all tight! I re-adjusted to spec.

Here's some pics of the rocker arms... Notice one exhaust arm seems to have burnt oil on it, or what looks to have got hot. That exhaust valve was the tightest of them all with little to no clearance.

Also, I'm still uncertain what I am looking for in the timing chain to inspect for wear or a skipped tooth? It seems tight to me and what I can see, the guides don't look worn.





And while I wait:
Duplicolor high temp aluminum. Stuff went on like butter! Wow!

BajaRunner

Well now I'm really stumped.

Just ran compression test (dry) under operating temperature, and was surprised to see:
160, 160, 165, 160. (Give or take a few psi, my gauge doesn't have a great resolution).

I should have run a compression test before I adjusted the valves, but oh well.

The fuel filter is indeed new, and its OEM! Still shiny.

Next I guess are the fuel injectors. Who's the best to send them to? Thanks.

americanmcss

Nice work with the paint. When it comes to the timing chain, I believe that there is a plastic tensioner device down by the crank shaft on the left hand side that can wear out and cause problems. Not sure if thats what everyone is talking about but I have heard of it causing problems.

BajaRunner

After doing some reading, I think I'll replace the O2 sensor. Mine "looks" old.

Rockauto.com has Denso O2 sensors. Of course, I don't know which one to buy. They list a few... Since I only have 1, and its before the cat, I assume I just buy a "front O2" sensor.

BajaRunner

After talking with my mechanic buddy on the phone and then just reading this thread which I seemed to have never seen (https://www.yotatech.com/forums/f116...60/index2.html) I am fairly certain that it is EGR related. My mechanic told me to block the EGR off completely from the intake manifold and see if that helped.

I ended up cutting up an old brake backing plate (thin metal) and placing it between the intake plenum and connecting tube from the EGR (where the temp sensor is). Rather than blocking off the flow completely, I made a 1/4" hole so I wouldn't throw a CEL 71.

I was noticing a lack of power with an increase in engine temperature.... The stock tube size into the intake plenum is about 3/4".

Another thing I've been noticing is the abundance of carbon deposits! It is everywhere...I just cleaned off the temp sensor 2 days ago, and already its black with carbon.

ra33it

Subscribing. I'm very curious to see where this takes you. Good luck Baja!

BajaRunner

Oui! I didn't notice any help with the hiccup/misfire.

I decided I wanted to replace the gasket on my IACV, and in doing so needed to undo the coolant lines. Super high pressure, and coolant spat everywhere. That was weird.

Tried to burp system afterwards, and just tons of coolant came out from radiator...its like there is no pressure pushing coolant down through the radiator. I think its clogged with RTV since i been finding good sized pieces of it after the PO did put a new water pump on. How big are the tubes within a radiator? Small enough to get clogged with 2" pieces? I may try and pull the bottom hose off, and just flush the radiator with a garden hose.

BajaRunner

So I had my buddy (mechanic) come over and check out the truck finally.

He feels that my lack of power is due to the aftermarket exhaust and lack of backpressure. Seems logical due to the fact my truck has headers that go into a 2.5" pipe all the way out to the tailpipe exit. High flow cat and a flowmaster muffler.

So tomorrow I'm going try and restrict flow by putting a half soda can with holes it it at the end of the tail pipe.

Are there any ways around from getting a whole new exhaust? Is there anything I can place inline with my current system to increase backpressure without putting in all new piping!?

BajaRunner

Took it to another mechanic. (Toyota truck specialist)

First one to drive it BTW....

Power he said is GOOD. Misfire, since only under no load conditions is probably the TPS.

Where do I get a new TPS? Worth getting a Toyota part I'd imagine?

I did see a hike in ohm's when I cycled the throttle :/

americanmcss

Back pressure is a common misconception that people all over this forum swear that our trucks need. Totally FALSE!!! Do some research. A good buddy of mine is a graduate from UTI in engine performance and all that other garbage. He said its not about back pressure, its about exhaust velocity and scavenging. Putting a pop can in the end of your tail pipe is not going to give you more power. Cutting your exhaust pipe size down to 2" before the muffler and then stepping up to 2.5" after may help solve your problem. 2.5" exhaust pipe is for engines running 250-300 horsepower...

BajaRunner

Yep I hear you. I totally agree. I'm actually in a class right now where we are analyzing head loss in piping systems. I should have just used my own knowledge to figure that one out.

Sometimes though, when you are really stumped, you'll take any advice and try it.

Anyways, I feel stupid to say that the entire exhaust system is actually 2". I used my calipers and measured. Once again, someone else told me it was 2.5" and I took their word. hahah!

A genuine TPS from Toyotapartsales.com is cheaper than a NAPA one. Crazy!

Testing the TPS when static (using feeler gauges) everything checks out ok. My idle is great at 850 RPM. When I hold it steady at 2500 RPM, is when I get a misfire.

However when I do a dynamic test, and sweep the throttle valve open while observing the multimeter, I get some weird resistance spikes. For example, when I move the throttle valve, the ohms jump up pretty quick. When I stop moving, they will jump back to where it "should" be. Is this normal?

I also tested the AFM and the readings were all good as well.

One last key detail which I seem to always forget to mention, and is probably extremley important to anyone who can help problem solve is that the misfire only occurs when there is NO LOAD. Driving it is totally fine (or at least I can't notice it). When in neutral is when I get a problem.

BajaRunner

Here is the temp sensor after only a week of driving:

Carbon buildup!??! Doesn't this mean its running rich? Can the TPS be sending a faulty signal creating a rich or lean mixture? (I know I should really be judging from the spark plugs).


And since I was bored, here is a picture of the painted valve cover.

americanmcss

Yeah that looks like some serious carbon buildup. I wonder if it may be the gas you are using. I read in the owners manual that gas with 10% methanol can cause some problems. Ethanol seems to be ok though, since I use a gas that is 10% ethanol and get 23.5 mpg mixed driving. I was thinking about this earlier too, that since you have a header and a flowmaster muffler, you are more likely to hear engine noises like slight backfires and stuff like that. Perhaps what you are hearing is typical for this engine, its just louder due to the lack of muffling...? Its funny about the exhaust pipe thing though. I just put some new exhaust pipe on my truck today. I had 2" from the manifold to the cat, then stepped down to 1 3/4" for the stock exhaust which was rusting and leaking badly so I replaced it with fresh 2" and a cheapo thrush turbo muffler. I dont think I gained or lost anything with my "butt dyno" readings, but its definately quieter. I would prefer the header and flowmaster sound but Im hesitant because that 4 banger sound with the FM mufflers gets annoying after a while.

I was just looking at your distributor too and noticed something. On my truck, the distributor is rotated a little bit further towards the front. Just an observation.

Nogarage

This misfire/power problem, did it begin with the installation of the brand new head?

BajaRunner

Americanmcss:
I have thought of that...due to the exhaust system itself, maybe I am hearing more than I am used to? Both mechanics I took it too didn't seem to say anything of that.

Interesting note on the distributor. Timing for the engine is correct however.

Nogarage: I have no idea, I just bought the truck!

Speaking of the new head, I found out that it has a bigger cam, and "bigger" valves. Don't know if that would change anything on my end to make it work?! Of course I have no paperwork on the cam.

Anyways right now my main points of interest are:
1) TPS
2) Injectors
3) O2 sensor

Can anyone else verify when checking the resistance (TPS) while opening up the throttle body, the readings will spike as you move it, then once stopped it will go down to a steady reading?

americanmcss

Yep I think you may have narrowed it down to the culprit there.