Danny Martin Posted February 9, 2013 Share Posted February 9, 2013 Hi first time post but been dreading your post trying to figure out why my 91 LS is surging between 800 to 1100 RPM's ? I cleansed the trottle body and trottle sensor , checked for broken vacume lines . I put sea foam in the tank & new air filter . Gettin ready to replace the fuel filter today . It's a 91 with 200,000 miles on it . Also where is the vacume canister located at? Thanks Danny Quote Link to comment Share on other sites More sharing options...
landar Posted February 9, 2013 Share Posted February 9, 2013 Hi Danny and welcome to the club! A couple of additional questions for you which might help the members determine the root cause. Any codes showing? Does the engine run better when cold or hot or does it make any difference? Does it run ok other than the idle? Here is how to check for any codes(you should try this even if there is no check engine light) -> http://www.lexls.com...odereading.html For the canister, see this thread -> http://us.lexusowner...e__hl__canister My initial thoughts were Idle Air Control Valve or the ignition coils. The coils are infamous for getting weak with age. The IACV for gumming up. Looking forward to more info. Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 The car runs fine for about 5 minutes till it warm up. Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 It showed codes 25 and 24 till I cleared them and now none yet . Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 It runs and drives great except for idle . Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 Is there a vacum canister ? Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 Iavc ? I'd air control valve location also ? Quote Link to comment Share on other sites More sharing options...
landar Posted February 9, 2013 Share Posted February 9, 2013 The car runs fine for about 5 minutes till it warm up. Hmmm...it sounds like a "closed-loop" issue. With codes 24(intake temp sensor) and 25(lean mixture), I would check the MAF sensor and temp sensor in the throttle body. Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 9, 2013 Author Share Posted February 9, 2013 We removed the trottle body and cleans it how do tell if its the MAF ? Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 10, 2013 Author Share Posted February 10, 2013 Thanks tomorrow I will clean the MAF and see what that does . Driving me crazy ( smile ) Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 10, 2013 Author Share Posted February 10, 2013 Hi someone said not to spray MAF cleaner spray on the MAF but to clean with alcahoe and cotton Swave . True or not ? Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 10, 2013 Author Share Posted February 10, 2013 Someone said you can't clean the MAF on a 91 ls400 if so I can't afford a new one $1200.00 heck that's more then the car is worth . Quote Link to comment Share on other sites More sharing options...
landar Posted February 10, 2013 Share Posted February 10, 2013 Someone said you can't clean the MAF on a 91 ls400 if so I can't afford a new one $1200.00 heck that's more then the car is worth . [edit] The air is a "hot" wire type where the air changes the resistance of the wire. There is also a thermal sensor to feed temperature info to the computer. Sometimes the little circuit board soldering gets messed up and disturbed by the cleaning. The MAF is very expensive from the dealer so the best bet is to buy a used one from a junkyard. I got one for my ES300 last year for $50 at the yard. Your symptoms and codes seem to imply a sensor is acting up and, at the moment, the MAF air flow and temp sensing is most suspect. If you are handy, maybe you can carefully pull the unit apart and check the condition of the connections and solder? I think there is a shop procedure to checking it. Will do a search later on.By the way, Danny, did you know that you can edit your existing post if you like? Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 10, 2013 Author Share Posted February 10, 2013 Took the MAT off and didn't see anyway to clean it it was enclosed in plastic . Reinstall and started the car unplugged the MAF and it didn't change anything still surging . So I took for 20 mile drive same thing but now the check engine light is not on . Does this mean the MAT is shot ? Quote Link to comment Share on other sites More sharing options...
landar Posted February 10, 2013 Share Posted February 10, 2013 The LS400 uses a "hot" wire air flow sense and not the "vane" type in the ES300, so I have corrected my previous post. It is very possible that your MAF sensors are shot but lets see if we can find an excerpt from a shop manual on how to check it. Stay tuned... Ok, I found this but it may be beyond typical equipment -> http://easyautodiagnostics.com/111/MAF-LOOK-UP/MAF-Lexus-lookup/Year-LS400.html Another question: was the engine running fine BEFORE you cleaned the MAF? Quote Link to comment Share on other sites More sharing options...
Danny Martin Posted February 10, 2013 Author Share Posted February 10, 2013 Thanks I'm gonna see if my son can do it . ( smile) Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 3, 2013 Share Posted March 3, 2013 OK I replaced the MAF sensor no change still surging . so now can I clean the IAC valve ? So far I cleaned the throttle valve change the air filer and fuel filter oh I also cleaned the throttle sensor and nothing has helped . Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 3, 2013 Share Posted March 3, 2013 The car runs fine with no codes . Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 3, 2013 Share Posted March 3, 2013 Is it even possible to clean an IAC valve ? A new one is about $600.00 Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 5, 2013 Share Posted March 5, 2013 I quite and gonna scrap it. I cleaned the air control valve today and change a thing . Thank you all for your help. Danny in Arkansas I on fixed income and can't keep throwing money into it . Quote Link to comment Share on other sites More sharing options...
Daniel091 Posted March 5, 2013 Share Posted March 5, 2013 check the tubes connecting the maf to the throttle body. make sure they're tight. look for cracks as well. is the IAC receiving a vacume signal? check connections on plug wires and coils also. hate to see this go to scrap. Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 5, 2013 Share Posted March 5, 2013 When I unplug the IAC it don't change anything . Quote Link to comment Share on other sites More sharing options...
zedanny1 Posted March 5, 2013 Share Posted March 5, 2013 OK I can unplug the MAF no change then I unplug the air control valve no change still surges . Do you thank then it could be the ECU ? Quote Link to comment Share on other sites More sharing options...
Daniel091 Posted March 6, 2013 Share Posted March 6, 2013 Its possible. Quote Link to comment Share on other sites More sharing options...
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