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Discussion Starter #1
anyone know what could possibly be the problem?.....

i bought an 89 supra with a rebuilt engine that runs fine...but when it sits in idle and is warmed up the idle runs very weak..the engine light comes on followed by white smog (not a huge cloud just consistent smog)...then if i push the gas while in idle and let go the engine light turns off and runs fine...let it sit for a few minutes and the idle drops again the engine light comes on and the problem repeats in that way...i'm going to try putting new plugs and wires on it..but i haven't gotten an exact idea of what could be the problem....

i'd appreciate any experienced advice thanks
 

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man that sounds like it sucks. engines can be tricky so i'm not gonna waste your time with my ideas, but I hope someone can help with that.
 

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Well, it sounds to me like a sensor of some type is failing. If it indeed does run fine that is...

White smoke or semi white can be produced in several ways. One way is oil this is normally a whitish blue to blue smoke and has the apparent smell of oil being burned. Next could be antifreeze when it is being burned it has a sweet type of smell and tends to dissipate in the air rather quickly. Next is automatic transmission fluid which is normally found on automatic vehicles (of course) and its occasionally drawn into an engine thru a vacuum line via a defective transmission modulator valve or some other defective part. Transmission fluid is very apparent and billows out so bad that you can't see anything behind you (as does a common blown head gasket). Last (but not least) another type of smoke that is not white but black is the presents of to much gas/fuel being burned in the engine.

With the history of these cars (blown head gaskets galore) (I've gone through 2 peronally) I would personally start investigating if there's any oil in the coolant (take the rad cap off, and look at a near horizontal angle at the fluid. If you see that wonderful rainbow pattern, there's oil in the coolant.) If you change your oil, you may also find coolant there if it's indeed a blown head gasket issue. A compression test is another way of seeing if you've got HG issues.

Also, I'd have the computer flash back the codes to me. This will tell you (generally, since it's not even an OBD1 vehicle, the list of codes it can throw isn't too detailed) what could be wrong.
 

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Discussion Starter #4
the head gasket is a metal hks..the headgasket was replaced along with a rebuilt engine...so the head gasket is fine.....i will look into your advice along with my friends who know more about cars than i ever did....
 

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wonknown said:
the head gasket is a metal hks..the headgasket was replaced along with a rebuilt engine...so the head gasket is fine.....i will look into your advice along with my friends who know more about cars than i ever did....
Just because the HG is a Metal HKS HG doesn't mean much.

If it was installed with proper hardware (see ARP Head bolts or studs (Stock Bolts aren't great for MHG's) and on a motor that had the head AND block resurfaced, you've got a much much better chance however.

Metal HG's are notorious for not sealing properly unless all surfaces are machined. If only the head was done, it can very easily be blown. Likewise if only the block was done. On top of that, stretched (reused) stock head bolts and improperly torqued bolts/studs can cause similiar failures.
 
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