brockhendo

Hi all,

I am only new to this forum, I recently (3 weeks ago) made the decision to buy a 1991 SC400/SOARER which is completely new for me. I have predominately owned 4x4's, so buying a V8 Jap car is way out of my comfort zone. Since Purchasing I have noticed a few issues, and would like to rectify them as long as the cost isn't greater than the value worth spending on a 5k car. I have been logging all the questions and issues I have with the car so that I can fix or adjust everything possible without spending too much money on it. So I am going to Cram allot of information into this thread. The reason I turned to this forum is because where I live in Brisbane Queensland, there doesn't seem to be too much familiarity with the 1uzfe soarers/sc400 from mechanics and the public, so I'm hoping to diagnose or learn more about it without spending lots of money. The car is booked in 5 days from now to have the tappet noise fixed and diagnose any power issues, but I am trying to do some process of elimination myself beforehand so I can make it cheaper and leave the mechanic with some detailed notes.

The car -

1991 Lexus SC400 (although has Toyota badge on top of engine?)
175,000 kms
Basic 2 1/4 inch exhaust from cat converters back. (No extractors or high flow cats)
19" Wald Duchatelet ii rims
No log book or service history, however noticeably maintained to an average standard.

The Body and paint is in excellent condition only a few very minor dints. The interior has normal wear and tear but has been well looked after, All the electronics work perfectly. The air con works beautifully. The engine seems ALMOST A1, Doesn't leak a drop of fluid (except very minor leak from 2 of the spark plugs and the rocker covers). Idles smoothly at correct rpm. Engine runs and sounds very smooth. There is however a tapping noise coming from around Rear of the Left hand spark plug bank near the 8th cylinder.

Main Issues and Concerns -

Tapping Noise - I have been told repeatedly not to worry about it because most 24 year old cars tick or tap. But it's annoying me so I have the car booked at a Jap engine specialist to have that issue fixed (whatever the issue may be) in 5 days’ time. I have asked a few different mechanics and people that are familiar with the 1uzfe (very few around my area) and keep getting mixed opinions e.g. noisy tappet on 7th or 8th cylinder - Noisy lifters - bent valve shims, apparently those are common problems with these.

Speedo - Will not hold a Steady speed reading on the digital dash, Jumps around constantly no matter how steady you maintain the speed. As a result, when using cruise control, the car constantly tries to adjust regulate speed so the car jumps forward and backs off really vigorously.

Acceleration/Power - This is my main concern, I have driven heaps of other V8's around the same age, newer and older, but all have been a 5L or bigger. I understand not to expect the same power from a 4litre V8 in a 1600kg car, but when I first purchased the car, it was sluggish and felt like it was dragging through the bottom end pick up. Since I have owned it the top end power has seemed ok but only improved after some adjustments, it's mainly the bottom end power I want to fix.

Acceleration/Power observations - Before any adjustments or repairs that I have done so far From a stand, when you take off in D or L with ECT on or off, the initial acceleration was very poor, it felt like it was starving or something was restricting electronically or slipping in the gearbox until about 3500rpm. Once you get moving and the revs start to rise, you can feel the power from the engine finally get to the wheels properly and then it suddenly picks up and takes off like a V8 should. Hitting corners sharp and accelerating hard would barely make the wheels chirp. From a stand and in D (only from a stand and only in D) when you accelerate hard and keep at the throttle, once it reaches 5000-5500rpm the engine starts to cut out a few times only for a moment until 2nd gear. If I throttle too much from a stand, any other car on the road would beat me until I hit 2nd, it feels like the engine is dragging. However if you carefully feather the throttle right and ease into it, you get a much better pickup (still not what it should be). Driving at night when it is cooler rather than the hot day results in a dramatic difference in power.

Power Related Adjustments and Repairs - First of all, when I replaced the fuel filter, I couldn't believe how old and how filthy the old one was. It was visibly ancient, I couldn't say how old exactly but it was very old, it was that dirty and clogged the fuel that was passing through it was coming out a merky muddy colour. After replacing the fuel filter I started running Fuel cleaner through each full tank (Only filled up 3 times since owning). Directly after replacing the fuel filter for the first 5 minutes of driving the engine was dying mid acceleration and flipping out on me, then it sorted itself out and the difference in power and torque was substantial. The Speedo stopped jumping around so much and was holding a fairly steady reading. However now 2 weeks on it seems as though it may be starting to block up again. Because of the state of the last fuel filter, I have purchased another fuel filter and after this tank with fuel cleaner in has emptied I will replace the filter again. When checking the spark plugs and lead, the spark plugs were not done up properly (not even hand tight) they seemed old and probably due for new ones (plug from cylinder 3 was black and sooty and looked older than the other plugs).The leads were pretty old but tested ok, I plan to get new leads and plugs shortly, however they are fairly expensive. Did a compression test and was confused with the results #1=215psi, #2=205psi, #3=160psi, #4=210psi, #5=215psi, #6=210psi, #7=205psi, #8=190psi (I was thinking #3 and #8 was lower because of either rings or valve stem seals) I was in a rush and needed to go somewhere so I didn't diagnose any further. For the mien time I ran a wire brush over the plugs and put them back in tight. I then noticed slack in the Kick down Cable for the Transmission so I adjusted that up to fully tightened ( I realize this is not how they should be adjusted, but I have read that transmission could be the cause of the lack of power). The result was like driving a new car, it was at night and fairly cool, but the difference in acceleration was like quite substantial (I think mainly because of the transmission adjustment). It still feels like initially it hesitates from takeoff, but taking off now was what you would expect from a v8. The pickup it has now is totally different and a massive improvement. However still slightly drags from initial take off but nothing like when I first got the car. Driving during the day........... And In D from a stand it occasionally cuts out briefly at top end but nowhere near as bad. Now easing into the throttle before planting it will get a pretty good take off. It still is not a full potential though.

General Observation -
Fuel pump - bypassed with a paper clip to avoid ECU control. Common issue apparently.
Tapping Noise - Doesn't make a sound when the engine is cold.
Engine Temp - once reaches running temperature it never fluctuates.
TRANSMISSION FLUID - Full and clean, however was a clear like oil, almost like engine oil. I was expecting it to be a red colour?

Questionable Observations -

The Toyota badge on the top of the motor? - I would have assumed even though Lexus is a Toyota product, that the entire car would be badged Lexus. Like I said, just an assumption

The guards have been rolled out around the wheel arches - the 19" rims that are fitted would not constitute rolling the guards for.

The Suspension - The car has independent coils all round. From what I have read, this model should have had adjustable air bag suspension.

The Radio - is a stock radio/cassette/CD player with both AM and FM frequency. From What I have read, the only models that came with this were the left hand drive model for the US market.

Traction Control - no relay for the traction control. There was a fuse for traction control, however the fuse had blown, replaced the fuse and it blew again straight away. No on/off button for traction control. (Not sure if this model came stock with or without)

The Previous owner - Seemed like he was generally naive with cars. However After the purchase was finalized, He slipped in another pitch trying to sell me a 'Torsen' Diff for the Lexus that he had and was trying to sell. He had also had some repairs done less than 5,000 kms prior to the sale at a place called Toyo Technics on the Gold Coast in Queensland. He mentioned that Toyo Technics are very familiar with these engines and that I should call him if I have any issues with it. Toyo Technics had told him that the tapping noise is a noisy tappet on cylinder 7. However upon reading the receipts and then inspecting the work that had been done, Toyo Technics seem to be very careless and sloppy with their work.

Toyo Technics Repairs as listed on the receipt -
Timing Belt Kit
Water Pump Kit
Front Crank Seal
Cam Seals
Raptor Arms
Good Used T/Belt Hyd Ten
Cooling Fan Pump Fluid
Engine Coolant
Degreaser
O Ring (Thermostat Housing to Manifold)
Thermostat Housing
Thermostat Housing Gasket
Hose Clip

Now the rocker covers are leaking less than 5,000 kms after these repairs and they are also sealed with gasket glue in a very messy fashion. If you rub the outside of the crank seal around the harmonic balancer, you get a very small amount of oil on your fingers which suggests it is leaking extremely slowly (considering the motor was degreased at Toyo Technics and I degreased the motor after purchasing as well). Those minor details lead me to believe they didn't do the best job and it sort of looks like it was slapped back together.

Repairs and Adjustments since purchase - p.s I went a little overboard
Right Steering Rack Boot - 2 x New Front Rotors (Original rotors were borderline illegal thickness) - New Bendix front Brake Pads - Brake Cleaner - Bled and Completely Flushed Brake Fluid and replaced with Penrite Super Dot 4 - Threebond Engine conditioner Intake Manifold and upper Cylinder Cleaner - Battery Conditioner - New Engine oil Penrite 10w 50 - New Ryco Oil Filter - Heavy Duty oil Stabilizer - New Radiator cap (old one didn’t seal properly) - New Ryco Air Filter - New Ryco Fuel Filter ( Big ISSUE! Read Other Notes) - Indicator, lower turning, rear number plate bulbs - Replaced Front left headlight (old one was too foggy) - New Drive Belt - New tensioner pulley and idle pulley bearings - Cleaned all electrical fittings and plugs with inox electrical lubricant mx3 aerosol - Complete engine bay, suspension and undercarriage degrease and clean - Lubed Auto Transmission Shift Linkages - Repaired front Brake L&R rotor backing plates - Adjusted throttle cable tension to remove slack - Cleaned Air Flow Meter with CRC air flow sensor cleaner - Cleaned throttle body, PCV and idle air control valve - Cleaned Power Window Switches - Checked and cleaned fuses and fuse box (inox mx3 aerosol) - Replaced damaged Injector Fuse - Checked Transmission Fluid (clean and full, See other Notes) - Topped up radiator with minimal amount - Checked all the hoses - Adjusted Kick down cable to full - Running Unleaded 98 with fuel and injector cleaners.

So I realize there is allot of information here, But while I am spending time and money on it, I want to get as much done as possible. Any Suggestions, tips or pointers would be appreciated. The trip to the mechanic next week I want to make as cheap as possible. This car is an all new experience for me, I'm used to big turbo diesel 4x4's so I'm trying to learn as much as I can. I don't know a great deal about engines, I know the basics so any help would be awesome.

Thanks.

t2d2

iTrader: (8)

If it's sluggish at the low end, look into: TPS adjustment, IACV cleaning, ignition coils, and vacuum leaks. The 1UZ is pretty sensitive to all of the above, it would seem. I finally replaced my coils last week and it seems to have cleared up the last remnants of hesitation. Once it's running healthy, consider the A/T solenoid bypass to free up quite a bit of the power.

https://www.clublexus.com/forums/per...-its-free.html

According to the somewhat local Lexus dealership, compression numbers are: minimum acceptable = 142 lb, good = 178+, and 240 range is great.