92’ SC400 Cuts out at 3000 rpm.
11-25-20, 06:49 AM
#1
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
92’ SC400 Cuts out at 3000 rpm.
1992 SC400 NO CODES SHOWING.
When it’s dead cold it will run great for 5-10 minutes. Goes up to redline driving in lower gears.
After warming up my SC400 starts cutting out at about 4000 rpm.
After about 30 minutes more on the freeway it starts cutting out about 3000 rpm. 70-80mph
After about a hour more any grade it starts cutting out (2800-2500) and a big hill I’m struggling just to get over it. 60-65 mph or lower.
If I let it sit for 15-20 minutes it cuts out a little over 3000 rpm and I can continue on for another hour or so at close to 75 mph then it starts slowing. If I hold the peddle on the floor it just slows down. I have a gradually re-apply to drop down the the RPM it feels like running at.
On Vegas trips from San Bernardino to Vegas (200 miles) if I don’t stop and let it do it’s thing (cool off,reset its self ?) It’s a struggle to keep up with freeways speeds, I can barely get past 1500 rpm when I pull into town on city streets. Struggling to get up to 35mph.
If I let it sit for a few hours it all starts over.
Chasing this problem I have replaced the computer a few times, I had 2 rebuilt, 1 I tried rebuild myself, I just bought one from Tanin’s Electrix. No change other than shifting points.
I replaced the timing belt, spark plugs, new coils, caps & rotors, plug wires, TPS, fuel pump, bypassed fuel pump, cleaned the tank, replaced to fuel pump, replaced fuel filter twice, Cleaned IAC, looked at the fuel lines for being brittle or cracked, looked for vacuum leaks. All fluids changed, un-hooked the button under gas peddle.
Still no change. Still no codes.
Next on list.. O2 sensors, Cats, cam sensors, FPR, knock sensor. I just find it so frustrating to not have some codes to point me in a direction.
It sounds good, runs great for a few minutes, idles smooth, good sound (doesn’t sound plugged) I have dumped enough money in it to have bought a new car. New tires, brakes, struts, stereo, speakers, climate control, window tint, all fluids changed, new serpentine belt, new headlights, tail lights.
ANYONE know anything other than guessing ?
To me it stills sound like a problem with the ECU and if anyone has a good running 1992 SC400 in So Calif. I will pay gladly to do a switch to knock that out of my mind..
When it’s dead cold it will run great for 5-10 minutes. Goes up to redline driving in lower gears.
After warming up my SC400 starts cutting out at about 4000 rpm.
After about 30 minutes more on the freeway it starts cutting out about 3000 rpm. 70-80mph
After about a hour more any grade it starts cutting out (2800-2500) and a big hill I’m struggling just to get over it. 60-65 mph or lower.
If I let it sit for 15-20 minutes it cuts out a little over 3000 rpm and I can continue on for another hour or so at close to 75 mph then it starts slowing. If I hold the peddle on the floor it just slows down. I have a gradually re-apply to drop down the the RPM it feels like running at.
On Vegas trips from San Bernardino to Vegas (200 miles) if I don’t stop and let it do it’s thing (cool off,reset its self ?) It’s a struggle to keep up with freeways speeds, I can barely get past 1500 rpm when I pull into town on city streets. Struggling to get up to 35mph.
If I let it sit for a few hours it all starts over.
Chasing this problem I have replaced the computer a few times, I had 2 rebuilt, 1 I tried rebuild myself, I just bought one from Tanin’s Electrix. No change other than shifting points.
I replaced the timing belt, spark plugs, new coils, caps & rotors, plug wires, TPS, fuel pump, bypassed fuel pump, cleaned the tank, replaced to fuel pump, replaced fuel filter twice, Cleaned IAC, looked at the fuel lines for being brittle or cracked, looked for vacuum leaks. All fluids changed, un-hooked the button under gas peddle.
Still no change. Still no codes.
Next on list.. O2 sensors, Cats, cam sensors, FPR, knock sensor. I just find it so frustrating to not have some codes to point me in a direction.
It sounds good, runs great for a few minutes, idles smooth, good sound (doesn’t sound plugged) I have dumped enough money in it to have bought a new car. New tires, brakes, struts, stereo, speakers, climate control, window tint, all fluids changed, new serpentine belt, new headlights, tail lights.
ANYONE know anything other than guessing ?
To me it stills sound like a problem with the ECU and if anyone has a good running 1992 SC400 in So Calif. I will pay gladly to do a switch to knock that out of my mind..
Last edited by Nikad92395; 11-25-20 at 07:22 AM. Reason: Clarified
11-25-20, 09:31 PM
#3
Driver School Candidate
Join Date: Mar 2018
Location: new jersey
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
I have a 92 SC400 that was cutting out on me. I got all sorts of remedies from everywhere. I was told I needed a new gas tank, New fuel pump timing sensor, ECU and so on. It turned out to be the 12 volt wiring plug going into the upper ignition coil. Try jiggling it wile the car is running and see if it cuts out.
11-26-20, 10:40 AM
#6
To the op, I have a spare 92 ecm i took out of a parts car while back, it was reported to be running fine then the timing belt snapped and it was junked so i got tons of parts off it. Im in norcal bay area oakland berkeley area so if your ever around here pm me and we can hook this ecm up to see if it works, cheers
11-26-20, 11:15 AM
#7
What brand coils did you go with? SC400's are real sensitive to coils, for some reason. Trying a used OEM set would be worthwhile, if you went aftermarket. That's a long shot, though. I would guess you've got some bad wiring or connectors somewhere. Have you checked the driver's front wheel well for wiring harness rub through up top?
Trending Topics
11-26-20, 12:36 PM
#8
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
MAF. After reading about cleaning it, (some had results, some had ruined results)
I HAD RUINED RESULTS ! It stumbled, coughed, ran like poop..
I ordered one from RockAuto and I ran to PickUrPart and bought another..
Runs exactly the same as it did before..
I will go unplug it right now and try it..
Un-plugged it and No change other than runs like poop off idle.
Last edited by Nikad92395; 11-26-20 at 02:32 PM.
11-26-20, 12:42 PM
#9
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
To the op, I have a spare 92 ecm i took out of a parts car while back, it was reported to be running fine then the timing belt snapped and it was junked so i got tons of parts off it. Im in norcal bay area oakland berkeley area so if your ever around here pm me and we can hook this ecm up to see if it works, cheers
I have pulled 2 from pick your part, I bought cheap capacitors off eBay and tried replacing myself (no change) had one rebuilt by a ECU rebuilder, and bought a $600.00 one off TaninElectronix the #1 guy most use. No change.
Thank you for your offer !
11-26-20, 12:46 PM
#10
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
What brand coils did you go with? SC400's are real sensitive to coils, for some reason. Trying a used OEM set would be worthwhile, if you went aftermarket. That's a long shot, though. I would guess you've got some bad wiring or connectors somewhere. Have you checked the driver's front wheel well for wiring harness rub through up top?
I looked at the wheel wells for rubbing and no signs.. I guess I better take a little apart and inspect it closely..
11-26-20, 07:14 PM
#11
ok next get zipties and unscrew both o2 sensors and ziptie them to something so they dont dangle and drive it if you have power then your cats are bad. if that doesnt change anything do a compression test and make sure your timing is good. if all that checks out i would do some serious wire loom inspections
11-26-20, 08:15 PM
#12
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
ok next get zipties and unscrew both o2 sensors and ziptie them to something so they dont dangle and drive it if you have power then your cats are bad. if that doesnt change anything do a compression test and make sure your timing is good. if all that checks out i would do some serious wire loom inspections
Please explain. Do cats get more clogged the more you drive it and un-clog if you let it sit for 20 minutes ?
cats getting hot and 02 sensors messing up ?
Same with timing ?
I can see a/the sensor, wires/wire loom getting hot and be a cause.
11-27-20, 01:25 PM
#13
Bad wire look wont change due to hot and cold. It can only effect open and closed loop functions which is cold and hot running temp which is controlled by ecu and sensors.
11-28-20, 11:24 AM
#14
Driver School Candidate
Join Date: Mar 2018
Location: new jersey
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
On the 92 SC400's the ignition coils are on the driver's side in the engine compartment. One is above the other. The 12 volt plug going into the ignition coil was shorting out which it was causing my car to cut out suddenly. Somebody on this site had the very same problem.
11-28-20, 02:07 PM
#15
Driver School Candidate
Thread Starter
Join Date: Nov 2020
Location: Ca
Posts: 11
Likes: 0
Received 0 Likes
on
0 Posts
On the 92 SC400's the ignition coils are on the driver's side in the engine compartment. One is above the other. The 12 volt plug going into the ignition coil was shorting out which it was causing my car to cut out suddenly. Somebody on this site had the very same problem.
On my 92 Sc400 I have one on the side of the block (drivers side) and one up by the timing belt cover (passenger side)
I replaced both of those. Mine doesn’t just cut out while driving, like hitting a bump, turning,etc. Just won’t accelerate after a good amount of time driving as explained.
Thank you for explaining !