SC400 with occational bog

over40driv · 08-05-09, 06:48 PM

I have a full tune-up, fresh fuel filter, air filter, ground cable replaced, no CEL, new battery, new center cat. conv., cleaned MAF. The car runs excellent 9 times out of 10 when you pull up to a stop sign and go through the gears aggressively. The 10th time it bogs like its out of gas till it catches up and then will run perf. for 100 mile drive. Im out of ideas except that the injectors have not been out and pulse cleaned.

over40driv · 08-07-09, 07:21 PM

Just wanted to remind everyone, that a test that should be ran, is to paint a line across the harmonic balancer then drive and see if the rubber cushion is bad. So far mine is not, at 136,000.

UpInTheLex · 08-07-09, 07:59 PM

Just some food for thought.

I just disassembled my 198K mile 1uz and I noticed a few things.

A lot of the plastic connectors near the block such as knock sensor connectors and fuel injector connectors were VERY brittle.

The most alarming thing is the 2 wiring harness connectors from the cam angle sensors and the front of the motor that run under the plastic cover next to the 1st injector on the drivers side of the motor had melted down at some point and when disconnected I found burned wires and the plastic connector crumbled into many peices.

Also notable were where my injectors seal on the lower intake. These seals were very hard like plastic, not rubbery at all anymore. I'm wondering if air was able to pass by around the injectors seals under high vacuum conditions such as sudden throttle tip ins.

No CELs, Clean intake ports and injectors and I would get the slight hesitation that the SC400 seems to always have.

over40driv · 08-07-09, 08:05 PM

Thanks for the info. I just repl. my engine temp. control sensor, and it seemed like the plastic was pretty weak. One of these days Ill get the nerve to pull the intake manifold. Where did you get your new o-rings?

UpInTheLex · 08-07-09, 08:17 PM

See my other thread here for the job I just went through.
http://www.clublexus.com/forums/perf...ml#post4746811

I put 95 upper intake plenum/fuel rails/wiring harnesses onto a low mile 97 engine. It's a half a point more compression, has some lighter weight internals, and slightly more aggressive cams as compared to the 95 also.

To answer your question about the seals, I used the ones off of the 1997 1uz as it only had 27K miles on it and the seals were still fresh. Otherwise I would have called some injector cleaner services or the dealer or something to source the seals.

sc-driver · 08-08-09, 04:22 AM

maybe its ecu related?

http://www.clublexus.com/forums/perf...mely-rich.html

UpInTheLex · 08-08-09, 02:34 PM

Interesting! Where did you otain your new ECU?

over40driv · 08-08-09, 07:50 PM

Ive made the comment before that my car runs worse warm. I left work this morning and it ran great, then after 10 miles i slow down and make a 90 degree turn into my sub division, went to slowly take off and it just didnt want to pic up.

sc-driver · 08-09-09, 12:31 PM

i got my ecu from aliga (Gazi) here on the forums. There is also a website that rebuilds them too.
http://siaelec.com/index.asp?PageAct...S&Category=380

If its your ecu, you're going to notice that there will be white smoke coming out through the exhaust when the engine is cold. But more noticeably when it is very cold outside. It has something to do with the atomization of the fuel molecules. You can smell that it is pure fuel.

Another clue is that your car is very fast when the engine is warming up. As soon as you hit the normal operating temperature, it starts to slow down. This is because the cold start fuel injector has shut off.

So in essence, I knew my ecu was bad because it didn't know how to control the fuel injectors properly. lol. It was dumping fuel when it wasn't supposed to.

over40driv · 08-09-09, 02:39 PM

My 95 does not have a cold start injector, also has no smoke when cold.

sc-driver · 08-09-09, 03:49 PM

it has a cold start injector....trust me. Check the manual too.

Well I guess if you don't get any white smoke or that fuel smell then it might be something else. Good Luck

ihiryu · 09-06-09, 11:47 PM

actually only the early models have them, I think the middle of 95 (which was sold as a 96) didn't have a cold start injector.

disc400 · 10-25-09, 08:04 AM

Did replacing the engine temp. control sensor, ever solve the hesitation?.

BostonSC4 · 10-26-09, 04:35 PM

here try this. i had the exact same symptoms. buy a bottle of Techron Fuel cleaner. it MUST be techron! nothing else works with my car. get the 20 gallon treatment and throw it in there. they sell a 12 but the concentration might be too low to make an effect. so get the 20 gal. run it through and you should notice it runs perfect til that very gas tank is empty.