Rebuilt 7MGTE revving problem

[cyanide54]

Hey guys,

Over the past few months I have been battling a problem with my freshly rebuilt 7m. The motor will not rev past 3500rpm. When you get to 3500, and open the throttle more, the motor bogs and you hear the occasional pop from the intake. Idle is perfect, vacuum is strong, all sensors have been checked by my shop down to the knock sensors. Fuel pressure ruled out, no codes, afm replaced, injector clips replaced. Still nada. My mechanic is starting to think that the machine shop did something wrong in the valvetrain... The valves were ground and the head was disassembled completely and rebuilt with new stem seals etc. the machine shop already made a mistake when they installed the head to a decked block without taking the same 12 thou off of the timing cover. Idiots. Does a mechanical problem sound viable? Maybe when they fixed the timing cover the crank timing pulley had the belt installed a tooth or two off?
The motor also felt like it is making very little power when I took it out of the garage to flat-deck it to the shop.

Any help is appreciated. I have searched the web high and low for a similar problem after having checked all other avenues.

Located in Vancouver, BC if anyone would offer a hand or opinion, compensation is here for your help.

 

[toyotanos]

Standard diagnostic checks are in order.

Check for codes in the computer- connect terminals E1 and TE1 in the diagnostics connector and watch the CEL flashes- they will count out flash codes. Refer to your repair manual for what they mean and how to understand them.
Check cam timing, do a compression check, make sure the plugs are not fouled and are gapped correctly, wires connected to the proper cylinders.
Check your ignition timing, should be set at 10* BTDC with a timing light and E1-TE1 connected at the diagnostics connector.

Report back with results of tests!

 

[cyanide54]

As I mentioned, no codes being thrown. My mechanic checked all sensors and they are all working properly.
Plugs are brand new and were gapped properly. Wires are in correct cylinder positions. We have ruled out the basics, that is for sure.
Timing is also properly set to 10* btdc. Been quadruple checked.

 

[Suprapowaz!(2)]

Do you know how to work on your own car? If not it's going to be hard to help you. The most we can do is guess along with you.

 

[supraguy@aol]

Although you say vac is strong, it almost sounds like mechanical timing is off a tooth(not ignition timing).
I'd give the suggestion(a guess) to remove the timing cover, and check the cam position vs. true TDC on the crank, by placing a chopstick or something similar into spark plug hole #1.

 

[cyanide54]

I do. However I am no expert. Just self-taught.
I pulled the motor and disassembled it myself. I had the machine shop do the machining work and rebuild it into a longblock. Then I reassembled the rest of the motor and installed it into the car, I got the motor running, and tried to figure out the problem for quite a while. And the fact that now having been to two shops and both mechanics who are competent with toyota cannot figure the problem, we are starting to assume the machine shop has done something wrong with the rebuild. Honestly, at this point, I will take guesses. Lol

 

[cyanide54]

Although you say vac is strong, it almost sounds like mechanical timing is off a tooth(not ignition timing).
I'd give the suggestion(a guess) to remove the timing cover, and check the cam position vs. true TDC on the crank, by placing a chopstick or something similar into spark plug hole #1.

This is what I am thinking. Just want a communal majority opinion that it is the possible culprit.

 

[Suprapowaz!(2)]

Same here. Self taught not an expert by any means.
So get started And do exactly what supraguy@aol suggested. Take pics of the process and post them so you can have a dozen eyes looking for anything out of the ordinary.

 

[super51fan]

Have you checked valve clearance.

 

[cyanide54]

Hey guys,

Little update here.

The car has now gone from my mechanic back to the machine shop as they have a service department as well. They claim the timing is infact bang on... They also mentioned that exposing propane to the throttlebody area makes the car rev freely and smoothly, no more issue. They are suggesting fuel system upgrades because of the billet compressor wheel upgrade to the turbo. Would that upgrade to the ct26 alone allow enough extra cfm flow to cause a lean condition even under no load?

 

[Suprapowaz!(2)]

Well thanks for the update. Be sure to let us know all of your modifications so we clearly understand what's going on. We didn't know you had a bigger upgraded billet compressor wheel. What else do you have?

 

[cyanide54]

My apologies, forgot to mention it. Only modifications that the motor has are that billet compressor wheel, arp studs, metal headgasket, shimmed oil pump with aftermarket remote cooler setup, silicone intake (replaced accordian hose), and a k&n fipc. All else is bone stock.

 

[supraguy@aol]

Is this like a 57+ trim mod to the turbo?
If so, I could see a possibility of lean during high manifold pressures, but not in no-load condition.
If this is truly the case, then I would say something in the fuel system is under-performing. You said that fuel pressure was ruled out. How?
In past experience, i've found that a dying fuel pump can have this symptom- good idle, breakup in higher rpm. And you said the shop claimed timing was "bang on". WHICH timing? Mechanical, ignition, or both?

 

[cyanide54]

http://www.xsboostturbochargers.com/products/billet-turbocharger-compressor-wheel-toyota-supra-ct26/

That is the billet wheel instaled in the turbo.

The no load is what I find strange as well. Fuel pressure ruled out by checking pressure at the rail, it was 45psi.
The machine shop claims that the ignition and mechanical timing are both good.

Could the fuel pump simply sitting in the car unused for a couple years send it to the graveyard?

 

[supraguy@aol]

Possibly, but if it's the original 25+ yr old pump, it may have simply lived a full life.
A walbro 255/ AEM / Aeromotive pump are easy 3 hour swaps, that guarantee you good fuel pressure for years to come.
In addition, ALWAYS replace the fuel filter. It's location is just above and in front of the tank. During a pump swap, is the best time to access it.
And although they have a million mile rating, they can and DO get clogged. Lemme see if I can find a pic of mine...

 

[supraguy@aol]

My filter element.
Normally, its folded in half along it's length, then rolled up.

This filter had 190,000 miles.

The opaque section is solid dirt.

 

[cyanide54]

Well I guess I'll start with a walbro pump and a new filter. It is the original pump so I could see that being the issue. Thanks for your insight, man. Big help.

 

[jetjock]

Couple of thoughts:

1) The pump and filter can easily be checked with a flow test.

2) Neither of your two mechanics nor the machine shop appear competent.

 

[cyanide54]

How can I go about that? Tsrm? Could you link me or give me a brief description of what I need to do? Obviously it's preferable for me to be able to test it before I dive into dropping the tank and replacing the fuel pump.

Machine shop is shit. Used to be good. My buddy worked there for years and they were fantastic, that's why he suggested them, but since he has left it has gone to shit apparently.
The car's first stop was to racing greed. A local tuning shop that has built many high performance cars, since their shop rate is through the roof, and hearing that they have mucked around with some people's time, I took the car back. After going there i heard mixed reviews, some good some bad.
The second shop has been in business fixing japanese cars since the 50's. Their mechanic has been working on japs since the 80s. But they don't do much work on cars that have mods. Usually just stockers.
If you think that after this long, I haven't realized your point, you are captain obvious in the situation.

 

[Suprapowaz!(2)]

2) Neither of your two mechanics nor the machine shop appear competent.

This is why I urged him to do him own trouble shooting. Though he keeps sending it back to the mechanics that can't seem to find anything.

I'm afraid you might be getting hosed by your mechanics. It's best to do your own investigating, and see the results for yourself. I've dealt with mechanics in the past that would tell me everything is "bang on", but when I looked into it I would find their mistakes. There's no money in troubleshooting/fixing their own mistakes. They'll keep telling you everything checks out to avoid losing money. And don't tell me he wouldn't do that to you because he's your friend. My old mechanic that was hosing me was my friend, too. Just when you think you know somebody. When I called him on his lies he got pissed off and told me to find another shop to fix my car.
For the record, the only reason why I was taking my car to a mechanic was because I lived in these snobby apartments at the time that would not allow you to lift the hood of your car for any reason. No mechanic work performed on property. Not even checking your fluids.