StevieA

Hi guys

First poste here, done some searching around last few weeks looking for some input on an issue I have looking for some asvice/feedback pls - first some background:

93 LS 400
231,000kms (Nova SCotia, Canada)
car sat 2 years after having body repair until I purchased for $2,500 3 mths ago. Undercoated and quite solid car - love it!

Since purchased have done the following:

Dash and climate control fix (the typical issues posted in this forum dash lighting issues sticky guages unreadable climate control LCD)

Used Y-Pipe

Used alternator

Passenger front O2 sensor

ECT Sensor replaced

Here's the issue:
Last Wednesday, day before installing O2 sensor, car's performance was A-1. Acting like a 250HP V-8 should, plenty of fun. Then I went for a 3 hr drive and car sometimes would hesitate badly when floored, sometimes not, mostly just seem about like a Hyundai Pony with 1/3 normal power. It would take like forever to reach redline in 2nd gear. However still start & idle smooth. All performce issues were at full or 3/4 throttle. So I figured replacing the O2 sensor would fix it. It didn't, it just eliminated the check engine light, car still performed poorly.

So today we replaced the ECT sensor from reading these forums. Car seemed a little better but still not where it was or should be.

Tomorrow we're going to try a new fuel filter.

Anyone have any similar issues or ideas? - there are no codes showing or ck eng light on etc.

Thanks love the car & especially the V-8 so want all the horses I can get underperformance bugs me. - Cheers!

Bill Dowd

this is a shot in the dark try cleaning your MAS sensor with comerical cleaner made just for it you can buy MAS cleaner at most car parts stores such as PEP boys ETC.

PureDrifter

iTrader: (10)

get it maintained properly before anything else.

when was the last time you did plugs/wires/caps/rotors?

StevieA

Plugs/wires/caps rotors - no idea. Just bought it 3 mths ago. Will be on my list of to do's if performance doesn't soon return. I have a great patient mechanic working for me with years of training experience on Mercedez & other foreign/imports incl. Lexus so I'm sure he'll suggest these items at some point for now he's saying lets try a fuel filter after he test drove it today.

Experiencing some additional issues now - when full throttle shifting it really falls flat when shifting like the fuel is cut for a second or more between shifts. Much more exaggerated of a hesitation than when I first got the car....it nearly moves your body off the seat it hesitates so much

Tried unplugging MAF as I read elswhere in this forum someone claiming huge short term increase in performance. Well, for me no difference, except caused ck eng light to illuminate so I plugged back in.

Will try unplugging EFI fuse tomorrow and doing a few full throttle runs with trac control shut off see if it behaves differently. Then at 2PM replacing fuel filter. If it's real dirty maybe I have a fuel pump issue..?? From the car sitting causing rust/residue in the tank?

Also intrigued by all the chatter about these cars having ECU issues solved with a rebuild

StevieA

I'll test a few 0-60MPH runs in the AM to compare - I believe 8.2 seconds is the norm. Will post the results

StevieA

This morning 0-60 runs

1st with car off, unplugged 7.5A Engine fuse, 15A ECU-A & 15A ECU-B waited few minutes. Plugged them back in.

Trac off, O/D off, power shift on here's the times - severe surging, underpowered even shifted at around 5,000RPM at times.....

15.03
11.98
15.68
17.55
15.61

Obviously not performing as the standard for this car is 8.4 seconds. Car starts & idles fine no engine lights on only works poor under full or 3/4 throttle and up until a few days ago performance was top notch for 3 months since I bought it

StevieA

Changed fuel filter today. It was filthy - see pic below with residue in coffee cup an indication of what came out of the filter - it was like burnt cappacino coffee with water beads. Put about 10km on since and performance is showing signs of improving. Added methyl hydrate and Lucas fuel treatment as well to the tank. Will report again in a week or so if this fixes the issues.

Bradster

Have fuel injectors professionally cleaned/flushed and full throttle body cleaning.

StevieA

Update - about a week since fuel filter change - performance only slightly better - obviously a problem with fuel delivery I believe. Will go 1 more week then see my mechanic again for next step. For 300km engine light was on then went away - I'll have him diagnose next week. Again anything other than 80% to full throttle car works fine - only under full throttle-ish does it die & not perform.

Will update next week

If I had the cash I'd replace the tank, fuel pump, filter and have the injectors and throttle body cleaned by my mechanic but being cash-strapped we'll do one step at a time & let the board know when the issue is fixed.

Actually, if I just drove like an old man I'd have no issue, but I want it to perform like it used to which was pretty quick & fun for a heavy car

kristano

I just purchased a 93 ls400 for my son and we have a similar problem with the acceleration. did you ever solve the problem?
Thanks, Kristano

LiCelsior

iTrader: (32)

do a full tune up and post back. spark plugs, wires, throttle body cleaning, fuel filter change, air filter change.

StevieA

Well, it's been a couple weeks or so since we changed the fuel filter as my mechanic instructed been running Lucas fuel conditioner through it.

Still same issues except today when I took it to him again it appeared to be getting better. He did fuel pressure test and it was fine and fuel was clear he said he pumped a litre out of it.

When I drove it home punching it at 100kph it worked decent actually.

Then I tried shutting off TRAC and OD and setting power shift on and it was a slouch ran like ******. Then I put all settings back to normal and did 0-60MPH...............16 SECONDS.

So next step is we could do the plugs/wires/ throttle body air filter as suggested but...........seems funny it went from rocket to slouch from one day to the next - I'm thinking of trying another ECU. Bought the car from a friend who has a successful used auto parts business he has a 91 and a 94 LS400 junked so I know he'll let me try an ECU off one of them if it fits. Will post any improvements I find

3UZFTE

Put a turbocharger on it.
x2 for tune-up. No, but in all seriousness, your fuel filter was ok, and save yourself some $$, a dirty air filter likely won't cause this issue unless it's repeatedly dirtying the MAF. You should try plugs, wires, caps and rotors. If your fuel pressure is fine, its likely not fuel related. I doubt its the ECU as it drives fine until you get after it or go WOT. Another place to check would be the EGR, if it's opening at WOT it could be stumbling if it's malfunctioning. All in all, take it to someone who knows what they're doing. Don't forget to clean the MAF sensor when your doing the throttle body.

StevieA

Thanks - I was quite proud of my mechanic but now he's kinda throwing his arms up and saying go to Lexus - think that's the right move? for a '93 that I paid $2,500 for? Will I walk out with a $5,000 bill and no better performance or do you think they'd be the answer?

StevieA

Question for everybody.

Car performs OK if I stab it at hiway speeds with OD on and ECT on, pulls decent but I still think it used to have more.

If I try 0-60 its a real dog off the line and records 11-17 seconds consistently

Now here's the real question. If I shut off ECT and OD and put on power shift and step on it the thing REALLY STUMBLES HARD. Has about 30% normal power, shifts too early, surges off and on......takes like 10 seconds or more to go from 4,000rpm to 6,000 rpm in 1st gear.

Since turning on or off the electrical performance "enhancers" has such a dramatic effect on performance I was thinking ECU.

Anyway, so many of you have recommended plugs, wires, caps and rotors plus cleaning MAF and throttle body (maybe EGR too) so I'll have that done and report back.

Just wanted some of you to consider my comments above