Qwertyui1

My 1995 sc400 was running fine with its previous maf but it was throwing codes for the maf as well as a rich code and unplugging the maf had no changes in the performance of the car so I figured the maf to be completely dead. I bought a new one and installed it and now the car can't rev past 2000 rpms, so this one must be working but malfunctioning right? Also unplugging the maf, the car runs fine. Are there any tests I can do on the two maf sensors? I have a multimeter.

SC400slide

iTrader: (11)

Here ya go.

Qwertyui1

Wow so I tested it and it passed. I reset the Ecu and drove around town with the maf plugged in and the engine light came back on. I tested it and the only code I'm getting now is 71 for my egr. It seems the maf code and my rich and lean code have disappeared. Could a faulty egr cause my car to not be able hit 2k rpms or floor it?

SC400slide

iTrader: (11)

Unique username BTW...lol

Your ECU is the culprit. Pull it out, pop it open and look at the capacitors for leaking/bulging/oxidizing/ect.

Qwertyui1

How do I go about that? Disconnect the battery, and just unbolt it? And it's by the passengers feet isn't it?

SC400slide

iTrader: (11)

Yeah just remove the carpeting and the pkastic cover and you'll see the ECU. I made a DIY awhile back. Have it professionally rebuilt, it'll cost you around 150 bucks.

Qwertyui1

Update: I'm about to pull the ecu but I have some new symptoms that may help narrow the problem. Last night I drove the car with the maf disconnected because I missed the power and my battery cable came loose( guess I didn't tighten it enough) reconnected it and later when I went to start it again the car wouldn't crank just a electrical starter noise for as long as I held the key. Got out reconnected the maf sensor and it started right up but died as soon as I let go of the let the only way I got it to start was hold the gas until the idle stabilized, took it down the block and the car stalled at the next stop sign. Later these problems were gone. I'm suspecting the ecu more

SC400slide

iTrader: (11)

Yeah, definitely have the ECU professionally rebuilt. Search up "lexus sc400 ECU repair" on eBay. Daryl in Cummings GA does the rebuilds. $150 last I checked, just send it to him, and in a matter of days it's sent back to you freshly rebuilt with a lifetime warranty. I used his service for my 92 SC400.

Qwertyui1

Well pulled out the ecu and popped it open and it looks pristine. Had it looked at by an experienced mechanic who's soldered ecus. He found the smallest leak on one of the caps but they all look solid. What's my best move to solve this issue.

SC400slide

iTrader: (11)

Any imperfections are a red flag. The caps shouldn't be leaking, if any are, I'd definitely have that thing rebuilt.

Qwertyui1

Okay, I'm game. I just need to know what caps are needed so I can order the genuine caps. Then have them soldered to hopefully solve my issues

Elchapo7

what ever happened did it work?

sparkyguy

Don't be shocked if you simply have a bad ignition coil on one side, or a loose high-tension wire between a coil and one of the distributors.
I had a similar problem. Car would easily start and appear to idle well but the power was REALLY zilch. Each coil & distributor serves 4 cylinders but each serves 2 even and 2 odd numbered cylinders. That lets the SC400's run in "limp" mode surprisingly well even while running on only 4 cylinders. I found my culprit by starting with the basics. I dusted-off my old vacuum gauge and was shocked that it was rock-steady at idle, but vacuum was way, WAY down at about 10" of vacuum. THAT ruled out all valve train issues, etc. I ultimately verified that pulling the coil wire on one side did not create ANY difference (that was the bad coil), but when I reinstalled the first side and then pulled the other coil wire I found the car wouldn't even start (since the car was actually running ONLY off that coil).