I have been having idling issues (it would rev on its own when in park or neutral up to 2000rpms and would sit at 1200 rpms in drive or reverse pulling the car) and my car would stall sometimes when I got to a stop. Not to mention the engine “coughing” sometimes when driving at lower rpms. Since these issues began I changed my spark plugs and wiring cleaned my MAF and attempted to clean my 1993 ICV. When I reinstalled the ICV I believe I left it too extended because when I went to run the car the idling issues were constant; the plunger tip was misshapen. I ordered a new ICV assembly and upon its arrival I instantly noticed it was for other SC and LS years. The mounting plate and electrical connection are the same and 3 of the 4 hoses fit the same so the only difference I can make out is the 1 vacuum line coming from the intake to bypass the throttle body at idle and the mounting plate lines up the same but is slightly different.

My question is will the later model ICV be compatible? Thanks for ur time

 

It's been too long since I've played with IACV's to remember clearly, but I don't believe the early and late styles are compatible.

Have you cleaned & adjusted the TPS yet? That sounds like it could be part of your problem.

 

thanks for your input, I ended up returning the newer model ICV and put the original one back and my car was driving perfect for most of yesterday than ended up idling poorly again and wouldn’t start by the end of yesterday. I’m gonna go back and clean the throttle body today. I have wanted to take off the entire upper intake manifold to clean it but am afraid that’s a bit more advanced than I should take on alone.

 

Try zip tying the IACV connector tight against the housing. I found in troubleshooting IACV issues that gravity is likely to blame. The connectors don't hold very snug when they get old, and the orientation allows them to sag enough to have an intermittent signal.

 

You aren't supposed to clean 92-95 maf's. they are karman vortex kind (KVF) and if you spray maf cleaner into them it will mess them up, usually a warning on the side of the maf cleaner can.

 

^^ Heed Ali's warning, NWSC. He's spot on. Cleaning your MAF unit will damage it (the sensor) beyond any possible repair. You can clean your actual throttle body if you wish to (bolted directly to your Y-intake manifold) but do not under any circumstances clean your MAF sensor that gets bolted to your factory air filter box or aftermarket cone filter and which has the rubber intake tube connected to its rear.

 

NWSC,

I experienced similar symptoms to those you describe with my '93 SC4 (260k miles) over the past 12 months - intermittant idle surges to 1000-1200 rpm, cutting out/stalling when starting out from a complete stop, but able to restart after sitting for 5-10 minutes. My mechanic cleaned the injectors, throttle body, IACV, checked the TPS, and replaced the air intake boot, but the symptoms persisted. I then had my ECU rebuilt, but still experienced the idle surges, and on one occasion after an extended drive, couldn't start the car (cranked, but didn't turmn over - turned over on the first attempt the following morning). I was ready to 'give up', but remembered the recommendation to check and replace worn vacuum hoses. I found a couple that were cracked slightly at one end and others that seemed to slide on/off too easily. I replaced all the vacuum lines illustrated on the diagram on the top of the hood. Car started up and idles perfectly with no surges experienced in the 100 miles I've driven since.

Now I can't say that the vacuum leak was the cause of car's problems (seems to simple and inexpensive). Full disclosure, the only other actions I took prior to replacing the vacuum hoses, was 'topping off' the engine coolant (based on another CL member's recomendation, and disconnecting the negative battery terminal which remained in that state for about two weeks while I was away on vacation.

FWIW, I have no regrets about replacing the ECU - the original capacitors on the circuit board have a limited life span and will cause problems, especially if they leak and damage the tracings. Fortunately, my ECU circuit board was relatively "clean" and only required minor remediation.

 

Well after replacing plugs and wires and cleaning my intake and throttle body and buying a new air filter, cleaning IACV, cleaning MAF sensor (I did this before anyone mentioned not to do it thanks for y’all’s wisdom) it was my coolant temp sensor. Also had a bad O2 sensor (right bank downstream) found a 20$ replacement on Amazon that’s working great. Car is running perfectly but she’s gonna sit until I can get more money to build her. Will occasionally take the beauty out on a ride when I’m feeling down but I just got my CD009 and am collecting parts for the swap. Thanks for everyone wisdom and I hope you all enjoy your sexy Lexus’s!