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Discussion Starter #1
So it all started last weekend when I noticed that driving on the thruway I was getting up to 9 psi. Well I thought it was odd but it didn't seem like a "bad" thing at that point. Then no noticeable problems til last night. I was driving to the track on a country road and the car starts bucking and I couldn't rev over 4K. Under hard acceleraton very bad. When accelerating slower, boost would stay around 5-6 psi and would barely do it. It feels like hitting a rev limiter or maybe fuel cut? Later at the track and on the way home when coming to a stop, the engine would stall. It restarted without a problem. Driving today, 1st gear is OK but when accelerating somewhat hard, then shifting, boost would go up to 9 psi (maybe 10) and the car would start bucking pretty bad and wouldn't accelerate any more until letting off the gas and then resuming at maybe half throttle. But some times it does it when just cruising along at 20-30 psi of vacuum. So it seems like it might be misfiring. I read the "bucking" post in the engine section, could some of this apply to the 7M? The fuel pump is the original with about 114K miles on it. Probably somewhat tired at this point especially with the increased demands the 7M is putting on it. The filter is the one that was on the old 5M. It's a Toyota filter with about 5K on it. I'm going to order a new one tomorrow, I was planning on replacing it anyway. The engine (and injectors) had about 85K on them before the rebuild. And I've driven the car maybe 500 miles since. The wires are new NGKs. The plugs are new Denso Iridiums. I've run only 93 or 94 octane gas since the swap. I couldn't find any loose or disconnected vacuum lines, intake pipes, etc. I'll try and find a different ignitor, TPS, ECU to try. Also my EGTs don't go up when the bucking occurs which made me think it might be a misfire problem and not a fuel delivery problem. I have no boost controller that could be malfunctioning, just the stock wastegate. I don't have any cats that could be clogged, just 2.5" pipe and a straight through muffler. I'd appreciate any suggestions.

Thanks,
 

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Discussion Starter #3
onedic said:
check that first all the ic piping and you vacume hoses including the wastgate actuator.
You mean the wastegate actuator itself could be leaking? Internal diaphragm/seal? I have an extra one I could try.
 

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I'll lay you dollars to doughnuts it is an IC pipe leak. It will be fairly small if you can still boost. You need to take it all apart and inspect every piece of your IC set up very closely.

Did the same thing recently and it took me a week to find the leak because of where it was. Without taking every piece of piping out I would never have found it.

Leslie
 

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It's either a TPS or some other type of ignition issue. If it were a fuel pump or filter you would be pinging like a mother f*er under boost.

Run your ECU codes before you start tearing things off. If it's a TPS then remove it from the throttle body and clean the spring & catch lever with WD40. Sometimes they tend to gum up like mine did. The TPS eletronics almost never fail.
 

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its posibull its just a balloon that fills with air to move a arm but id check the lines first some times you have a crack that you only see when hot. if you have seen your boost # go up for no resson with tock settings then you have a bov / wastgate / ic / vacume problem the balloon fills up so and boost tays at 6 to 8 psi if your geting 9 to 10 then something is or was rong now the problem got bigger so you now buck and stall --- its like if you have a bov that vent atmisfer you can tall you motor by letting it blow of then drop to idel -- you will stall cuz the mas saw the air come in so it adds fuel but you let the air go so you have toooooo much gas and stall. get how it works you could have the same thing going with a crack or loss of air.
Dave
 

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Discussion Starter #7
Leslie, what did you find wrong with your intercooler pipes/hoses that you could visually identify?

I'll try the CEL thing but that will take a bit of doing, since that wire is not currently hooked up. 82s didn't have a CEL so even though I have an 85 cluster with the CEL I don't have that terminal in the connector. So that's why I didn't splice the MK3 CEL wire into anything. Maybe I'll just hook it up to an LED for now.
 

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Williamb82's car was doing the same thing. unplug the TPS and see if it still does that. if it does then you have a bad TPS, that's what william's ended up being. same exact simptoms.
 

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white_mk_2 said:
Leslie, what did you find wrong with your intercooler pipes/hoses that you could visually identify?

.
I literally blew out both of the IC hard plastic pipes. They are not one single piece they are both 2 pieces that are sealed together. I blew out the seals in both of them. Until I took them out I couldn't tell the seals were blown at all. Once I took them out, they pretty much fell apart.

hth

Leslie
 

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Also, make sure that your accordian hose (between afm & turbo) is in good shape (no cracks or leaks). Check fpr, too (not sure how you can do that without fuel pressure gauge).
 

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Discussion Starter #12
I literally blew out both of the IC hard plastic pipes
I didn't use the plastic intercooler pipes on my car, but that's pretty interesting how yours came apart.

make sure that your accordian hose (between afm & turbo) is in good shape
Yeah, I had heard from many people that these go bad so I got a new one
when I rebuilt the engine (well, that and just about every other hose).

At work there's a SST to check for intake air leaks which I used to find... several. I fixed them, but on the way home it stalled once coming up to a toll booth and it's still boosting to 9 psi and bucking a little. I'll try the TPS thing. Won't having the TPS disconnected cause other problems though?
I'll check my TSRM for more info on the TPS in general. I have another coil pack I can try but not another ignitor. I'm going to see about getting more spare parts this weekend. I have lots of spares for the old 5M but almost nothing for the 7M. Even if I don't end up needing them now, I will sooner or later. Thanks to eveyone for all the suggestions so far (keep 'em coming). I'll keep you all posted on any progress.
 

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I had similar problem for a time with my 91 mk3T and I found leak in ic piping. It was actually easy to find after awhile. If you have a leak it will send a fine spray of oil out which will collect dust and turn into a mess on the surface of the pipes around the leak. Look for crud on and around piping - it will indicate leaks.
 

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knock sensor

not familiar with how 5 or 7m computers deal with detected knock, but maybe it's an oversensitive (broken) knock sensor? pulling timing or cutting fuel or cutting spark or whatever the hell it does? maybe disconnect the knock sensor in a troubleshooting effort?

please post back when you find out what it is!

shiva
 

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i dont think its the tps. if it was it would be bucking before boost too. the fact that it happens over 6psi tells me you have a busted i/c hose, and i would put my money on the first hose off of the turbo. pull that hose off the car so that you can closely insopect it on all sides. just looking at it from the top with it installed may reveal nothing.
william
 

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Discussion Starter #17
williamb82 said:
i dont think its the tps. if it was it would be bucking before boost too.
Actually it does do it when not boosting. Sometimes just cruising with 20-30 psi of vacuum. Speaking of TPSs, would a '90 TPS work with my '88 harness/electronics? How could a faulty/malfunctioning TPS cause the overboosting though? And if it's not, what could?

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well, then its most likely the tps. unplug it and see if the bucking stops. if it does thats your problem. as for the over boosting, the vacum hos from the turbo outlet to the wastegate actuator prolly has hole started. it is close to the exhaust manifold and eventually will melt or deteriorate from the heat.

as for a replacement tps, andy 4wire tps from 85-88 should work fine, n/a or turbo. as for 89+, im not sure, havent looked at one closely so dont know. if you have a spare 85 tps it should work. just be sure to reset the ecu first.
william
 

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Discussion Starter #19
williamb82 said:
just be sure to reset the ecu first.
william
OK, well I have an '85 TPS laying around, and I got a '90 TPS yesterday really cheap so if it doesn't work then no biggie. How do you reset the ECU? Just leave the battery disconnected for awhile?

Thanks,
 
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