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Enes, VOLVO Master Technician
Category: Volvo
Satisfied Customers: 4911
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2001 s40 1.9t Volvo idle rough at startup then settles down

Customer Question

2001 s40 1.9t Volvo idle rough at startup then settles down after about one minute and runs fine. replaced the MAP Sensor, new air filter, cleaned the MAF Sensor, STP injector cleaner, and checked for vacuum leaks. Same results idle rough for one to two minutes and then runs good with lots of pep. the first code I got was P0237 P0336 and now also P0171...what next? it was running fine and climbing a 5K mountain pass in Oregon and it made one big cough and lost turbo boost passing speed and went to totally almost no idle or acceleration power. then after the work I did it now idles when warm but runs ruff on startup.
JA: Is the power loss consistent, or does it fluctuate?
Customer: fluctuates in idle for maybe one to two minutes...then runs fine
JA: Are you fixing your S40 yourself? What have you tried so far?
Customer: yes myself and as I noted in the first email I replaced the MAP Sensor and cleaned the MAF sensor and put in a new air filter and STP injector clearer and check for vacuum leaks ... none that I can see. looked over the Turbo boost Solenoid up by the air cleaner but didn't replace it
JA: Anything else you want the mechanic to know before I connect you?
Customer: it a 2001 S40 1.9t with 92K miles and has been garaged from the time it was bought new
Submitted: 8 months ago.
Category: Volvo
Expert:  david craig replied 8 months ago.

hi im david, pull the iac

Expert:  david craig replied 8 months ago.

and clean it out

Customer: replied 8 months ago.
David...The IAC stand for what and where is it located at on the engine...
Expert:  david craig replied 8 months ago.

idle control

Expert:  david craig replied 8 months ago.
Customer: replied 8 months ago.
I just change that Idle Control expensive part 1.5 years ago that you noted when I turned the car off and then went to turn it on and it wouldn't start and stay running so changed that IAC to a brand new one and ut fixed the start and no idle and die. I will check it tomorrow and let you know hoeever. However i had as noted a computer number of P0236 and P0237 in my problem info i sent so do you think it could be that (Turbo Boost Sensor or some say its called the Barometric Pressure Sensor) on the make up air that black tube and it looks like the MAP sensor but is list as the two names above. Or maybe the Turbo Boost Solenoid over by the MAF Sensor and aur filter. Just a thought.
Expert:  david craig replied 8 months ago.

let me know tomorrow if you still have those other codes once you determine the idle is ok.

Customer: replied 8 months ago.
David...Cleaned the Idle Control Valve and the roughness in idle settled down. However, as before i still have the Check Engine Light Code P0236 Turbocharger Booster Sensor and P0237 Turbocharger Booster Sensor and P0171 Number One Lean. So I know where the Turbo Booster Solonoid is with 3 vacuum hoses but where is the Turbocharger Booster SENSOR? 2001 Volvo S40 1.9t and i have installed a new MAP Sensor and cleaned the MAF Sensor and Cleaned the Idle Control Valve and a new Air Filter and STP Injector Fluid added. So the common thread looks to be the Turbocharger Booster SENSOR would that cause all this idle and at times acceleration problem? Should I replace it and where is that sensor. Gil
Expert:  david craig replied 8 months ago.

absolutely would cause all of that, let me get you that location........

Expert:  david craig replied 8 months ago.

see if this helps

Expert:  david craig replied 8 months ago.

do you still need assistance?

Customer: replied 8 months ago.
The parts location diagram you sent on the last contact yesterday said; the Boost Pressure Sensor could be my idle problem. I see the Parts numbered 19 and 8 are both are noted as Boost Pressure Sensors but shows NO part number but look the same. One happens to be on the Manifold (MAP changed) and the other up high on the air tube by the handle of the oil dip stick is too listed as Boost Pressure Sensor. Are they both the same type of sensor and are they interchangeable?
Expert:  david craig replied 8 months ago.

let me find out for you

Expert:  david craig replied 8 months ago.

yes, they are interchangeable. same part numbers different functions....weird.

Customer: replied 8 months ago.
OK i will work with that as i have a spare one and get back... Just didn't know if i could. use it.
Expert:  david craig replied 8 months ago.

sounds good. keep me posted.

Customer: replied 8 months ago.
David...Same ruff (Volvo 2001 S40 1.9t) idle at start up for maybe 3 to 4 minutes and until the engine warms up and check engine light always stays on Saying; P0237 Turbo Charger Sensor. Have changed the (1) MAP SENSOR to a new one and check the (2) Turbo Booster SENSOR (same as the MAP part just noted by you). (3) Cleaned out the IDLE CONTROL VALVE, which was only one year old (4) Cleaned the MAF SENSOR and put in a new filter. Also found NO vacuum leaks. See next paragraph:Ordered a TURBOCHARGER CONTROL VALVE sometimes called the TURBOCHARGER BOOSTER SELENOID (It is NUMBER 1 on the Volvo Parts Chart you sent me, as an attachment and has 3 vacuum line connected to it and is key to the turbocharger engine use and could be part of the problem.The part noted above was not in stock and won't be in for a couple days and due to Thanksgiving and with that causing me a problem by running into my 7 days of free time with you I have pay $25.00 on line already to get to you, but I don't want a monthly relationship and continuing account charges. Does this $25.00 I have paid go on account for a run over for one month? I don't want any more months support service after that, as I will get rid of the car before I continue to put money into new parts hoping to find the right one eventually. Do you have any additional ideas other then this part I have ordered that I should be aware of? Sincerely ***** *****
Expert:  david craig replied 8 months ago.

i have no idea how the billing or free trials or subscriptions work. i only answer questions sir. try the sensors you have ordered and then open up a new question if that doesn't fix the problem, or i can opt out now, and see if another tech has run across this issue and will be able to give you a better idea.

Customer: replied 8 months ago.
David...I just as soon work with you, at this point, rather then start over again... but if you can check around with other staff on the Volvo Ruff Idle at Start Up and a continued Check Engine Light for Hand Computer: Turbocharge Booster Sensor that would be great too. I will put the new part on as soon as it gets here and let you know. Volvos Parts are hard to find in stock here. Thanks Gil