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Discussion Starter #1
I couldn't get an answer on probetalk, maybe you MX6'ers will be more forthcoming.
I just installed a rebuilt engine. After the 500 mile break-in period, I finally romped on it. I was SOOO excited! WEll, it was great, really strong and smooth up until 4000 rpms, then, it's hard to explain what it does. It's like the revs get really rough, and it's choking.. I lose power, and it doesn't wanna rev any higher, although I can get it to redline. It does it more under load than it does while sitting and me revving the engine. Okay, for more details, I have a 2.25 inch exhaust with NO cat and NO muffler. When I pull trouble codes, it does one long flash, followed by 8 short flashes, which would indicate a trouble code 18. Well, 18 doesn't exist. It stops at 17, and I believe continues at 25. I've recounted and recounted and it's 8, not 7. Although it doesn't return a trouble code, the EGR valve is stuck and won't move more than about 1/4 of a inch. I don't know if that would cause my problem or not though. Anyone got ANY ideas? I'm really hurting here, I spent well over a grand on an engine that still won't run right :(
Any suggestions at all would be very appreciated.
 

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I can't tell u for sure,but I think maybe u don't have the correct back pressure in the exhaust due to having no muffler or cat. In my experience w/ small engine (Less than 8cyl)cars when u r having problems in the upper rpm range,but works fine in the lower range,then the exhaust has too much(plugged cat),or not enough back pressure.(no cat/muffler)I know that incorrect back pressure can have adverse effects on an engine,possibly cause it to cease function all together.
 

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Discussion Starter #3
Hrmm, I don't see why it would be that way, BUT, I'm not saying you're wrong either. The engine that I pulled out never had any problems like that though, and that exact exhaust setup was on there for over 10K miles. One other thing, I was burning oil on deceleration on the old engine, and I thought it was valve seals, well, the new engine is doing it too. Could a bad seal on the turbo be causing oil to burn on decel?
 
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How do you determine that oil is burned on deceleration? Suppose the seal was bad in the turbo and it let oil thru- the pressure would be greater at higher rpm vs lower (decel) rpms. If your intake/TB has oil traces in it then the turbo seal is bad and may cause a problem at higher rpm as you spoke of (4K+). Injesting oil isn't too good, I've had to clean out the intake manifold after the turbo seal went on my 280ZX. Messy job!

But reading your first post it almost sounds like the TPS may be out of adjustment slightly. Or possibly could be dirty injectors if they were reused from the old engine.

Large exhaust on a small engine will hurt low rpm torque due to loss in backpressure and over time may burn out the exhaust valves, but the engine should rev happily under load. But seeing that you've got a turbo, that should create addequete backpressure to keep the engine happy. I wouldn't worry about the exhaust (in fact on turbo its better bigger).
 

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Discussion Starter #5
Okay, another idea, see what you think of this.
BTW, yes, I DO have oil in the intake, so, I believe a seal on my turbo is bad.
But, problem with it missing at high rpm's started AFTER the new engine was put in. So, I started thinking, the ONLY thing that wasn't new, or put in from the old engine, is the distributor. Gonna pull it ASAP and put the one from the old engine on and see if it makes a difference. My friend who helps me work on the car said it seems as if the timing is getting thrown off at higher rpms, like the timing isn't getting advanced/retarded like it should.
Anybody know if that's possible>?
 

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I had a similar problem but reversed. It would barely idle, sounded like crap and had no power until about 3000 rpm then it would take off as strong as ever. Problem was I did my timing belt and somehow when putting on the new one I must have misaligned it. So I took it off and carefully put it back on and it ran fine... so maybe yours is off the opposite direction mine was? doubt it, but worth a look.
 

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Discussion Starter #7
Hrm, you're the second person to suggest the timing belt. I'm gonna try the distributor first, cause it's easier to get to. If that isn't it, I'll check the belt again.
 

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I had the same problem as you did, 1st gear would redline ok, 2nd gear would start to hesitate after 3k rpm. I wasnt sure what it was!
I trouble shot the problem:

1. Petrol filter, didnt fix the problem. It must be electrical!
2. Check the spark plug gaps. Didnt fix, so replaced them.
3. Sparkplug leads and new distributor cap.

I did this last step together so I am not sure if it was the leads or dizzy cap. Problem has gone though, pulls like a train again!

P.S. It feels pritty shit trying to drag someone when your car keeps missing at high rpm.
 

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Discussion Starter #9
I can't redline okay in ANY gear though, not even with the car in neutral or the clutch depressed.
Also, plugs and wires, distributor cap and rotor are all new.
 

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Does the motor sound like its starving for fuel. If so try a fuel injector cleaner or even replace your fuel filter.

The problem could be related to air. Maybe you accidently left a sock in the airbox. Make sure that there is no restrictions in air flow!

Fan belt too tight?

These are all just suggestions, i am not a mechanic. I am just a civil engineering student.
 

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I'de say your ignition module (the ignitor) is done for. (or a connection has gone arye)... it happens to the best of us! I mean if you can't redline easily even in neutral, it cant be a fuel problem (well, it most likely isnt). Are your crank angle sensors in good working order?? *could*, in a remote chance, be the timing belt, but then you would notice the lower RPMs to make the car run like a dog as well.

good luck
 

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Discussion Starter #12
Okay, just for clarification. I perform routine maintenence very religiously. Fuel filter is new, fuel injector cleaner is used every 10000 miles or so. I just finished using a bottle of Sypower fuel injector cleaner in the last tank. There is nothing in my air box but a brand new filter, which I replaced Tuesday. The PCV valve is new. The EGR valve could probably stand to be cleaned, but, I pressed on it with my fingers and it moves freely. Spark plugs are fairly new NGK's. The wires are new.
As for the ignitor, I don't know how to check that. Is it the same as the coil? As for the Crankshaft position sensor, it SHOULD return a trouble code if it goes south, and I'm not getting a code for it. Not to say it may not be bad, but.. As for the timing belt, I'm not getting the bad revs at all rpms. I just replaced the distributor with another old one, and as soon as I time the sucker, I'll see how it runs then. I'll post and keep everyone updated. And thanks for the responses, you guys have been great! :D
 

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Hey Tex,

the Ignitor is right beside the stock ignition coil and this seems more than likely to be the culprit. It is responsible for shoting the park out and at different times based on RPM and load. I dont know how you can check it... but you can change it with one from another car (maybe a 6 from the junkyard or something) or get a new one.

let us know how it goes!!!

BTW - the ignitor looks like a .... uhh... something square!!! It shoud say "Ignitor" on it!! And it has one of those connectors that looks like a MAF connector on the top, but its a few pins shorter of the MAF connector.
 

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Discussion Starter #14
Yeah, I found the ignitor. I got a mechanic to use his code scanner. It showed the VAF sensor and air temperature sensor to be bad.
I got another one from a junkyard and put it in. No dice, I performed all the checks the Haynes manual showed, and everything checked out on both. Do you know how much a new ignitor is? Wow! $169.99 from Advance Auto, no telling HOW much from the dealer. Gonna try and find one from the junkyard though. I got to looking around and found the ignitor on my own :p
<sigh> money, money, money...
 

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You can have the one off my 626 Turbo for free if you pay shipping.
 

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Discussion Starter #16
Let me see how much the junkyard wants, if it's gonna be outrageously expensive, I'll certainly take you up on that, and thanks very much! I'll contact you by email if I need it.
 

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Discussion Starter #17
Okay, plugged the new ignitor in. Made no difference whatsoever. My friend this weekend is going to look into fuel pressure issues, because we've pretty much ruled out anything electrical. That and we're gonna double check to make sure the vacuum hoses are all correct and such.
:(
 

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BOOOOO!!!!!

I was so sure of that too... ah well.

Hey Tex, does the sluggishness kick in imediately? or does it gradually become more and more sluggish as the RPMs rise??
 

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Discussion Starter #19
Immediately, as if someone flicked a switch.
And then the power loss stays constant until redline, if I choose to try and make it to redline.
 

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if thats the case, it really sounds like engine management or something that 'happens' at the RPM it kicks in... I know that injector spray pattern changes immediately at around 4000 rpm or something... hmm I dunno... does anyone know if the FPR is controlled by the ecu????!
 
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