crynop

I have a 2004 Scion xA model. It randomly shuts down no fault codes nothing!! I noticed it normally shuts down at lower speeds lets say I'm about to turn a corner or slowly coming to a stop in a traffic light those are the most dangerous areas for me!! I'm thinking of replacing the Fuel Pump, if that fails after reading some where it could be the Torque converter they claim it acts in place of the clutch as in for automatic cars so it could be faulty or its solenoid related part! I guess will have to change the whole transmission on this ! to avoid complications.. if that fails I may have to change the ECU. I'm already in the processes of changing Fuel Injectors..already changed spark plugs.

Just before I forget...and YES if I want a couple of minutes say 5 - 15min my cars starts up fine. No miss fires nothing! No loss of power highway / uphill! Very weird and dangerous! It has around 135,000Km of mileage.

So did anyone manage to resolve the problem??? If YES what was the culprit?


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RichBinAZ

Is the idle speed very low? Enough to make the engine shake? If so, you may want to check for carbon build up in the idle Air Control Valve. It's part of the throttle body.
If you google "scion xb IACV" a few video's pop up. It can be cleaned rather than replaced.

2stroked

First, you need to stop throwing parts at the problem - especially since you're starting to talk about some very expensive parts. Start with the simple stuff first: Air, Fuel and Spark. That's all an engine needs to run. I doubt you're not getting air, so that leaves fuel and spark. (Notice, the transmission wasn't on that list.) When it dies, does it turn over? If it cranks but doesn't start, does the fuel pump run? Are both battery cables tight and clean. Are the main cables in good shape from end to end? If you put a code reader on it when it's dead, what does it show? Let's start with those.

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DannoXYZ

yes, you need to troubleshoot and diagnose using tools, not guessing. Replacing perfectly-working parts with brand-new perfectly-working parts changes nothing and symptoms persist.

Need to identify exact problem area first. Measure and come up with numbers and compare standards in manual. That will tell you if a part is good or bad. Even then, it may not be actual part itself, but surrounding stuff like wiring. So gather some data:

1. battery voltage with everything off. Voltage = ???
2. battery voltage while cranking. Voltage = ???
3. measure intake-manifold vacuum at idle with warmed-up engine. Vacuum = ???
4. measure vacuum at FPR at idle with warmed-up engine. Vacuum = ???
5. measure MAF-sensor output voltage at idle with warmed-up engine. Voltage = ???

crynop

This is clean. I had a quick open of the top cover /cylinder head gasket area..there is no sludge/heavy carbon oil up there.. engine appears clean internally

crynop

Hi ! thanx for ur logical responce !

1. The air is fine as the throttle body is perfectly working with no problem and no carbon build up, air cleraner is also fine and car is powerful when u rave and while driving ! As mentione it has no miss fires even when driving uphill there is no loss of power ! remember this happens in low speed only

2. Fuel is plenty in the car ! the fuel filter is not dirty either
3. I just changed my spark plugs and kept new ones

reagrdiing urr question This is what i need to monitor next..also one mechanic i talked to he mentioned once i keep the car on SWITCH ON mode the dashboard lights such as check engine, oil, temp etc etc should light up as usual if they dont it could be an ECU issue ...so need to keep an open mind on that

reagarding ur questions I purchased a new high quality battery already and cables are tight and clean atleast on the battery side.. but i maybe have to trace the other end of the cables which connect to the body. Regarding puting a code reader when car is dead i havent put it because i dont own one and normally will be far off from the mechanic..and the problem cannot be reproduced ! i can drive a whole week without the issue happening..maybe i may need to buy my own car code reader

crynop

Thanx for the response I will try to get these details

RichBinAZ

Looking in the wrong area.

Check out this video for the where this part sits on the throttle body


(not a helpful video other than that
Then check out this video for a close up of the part after it's removed at 1:39


and again at 2:47 where he talks about carbon clogging.

The second video gives you a better clue as to what needs doing.

Carbon clogging in this valve (even slight) will lower the engine rpm and can make it shake then stall the engine.
It only affects idle because the throttle valve is closed at idle. It will work fine at other Rpms or engine loading.

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crynop

Guys, Thanx for your responses. I finally figured out what was the problem. my problem got far worse to the point when the car shuts down even if i waited for 5 - 10 mins as before the car wouldn't switch on....so I did a Fuel Pump swap this didn't solve the issue. Then we found out the Ignition relay was already weak so we replaced that and the car worked for a couple of days without an issue. but then the problem happened again. Now usually there is a wire harness with a connector from the car switch/key area going to connect another connector which then takes the wires to first fuse box near/under the steering wheel of which some of those wires will run towards the external fuse box near the battery compartment..which completes the full ignition system... In my case we found out that the previous owner may have had an alarm/security system installed of which logically would stand in between the key/switch cable and the fuse box so it can monitor and do advanced controls like shutting down the car etc etc... now this device has now been removed out/disabled for some reason so the key /switch harness was connected to the connector of the alarm system even though its not there or disabled ... my electrical mechanic just then unplugged the key/switch connectors from the alarm connector and back to the original connector which goes back to the internal fuse box etc etc..meaning by passing the alarm/security system all together. This resolved the car issues now I have been driving over two weeks with no issues

Another tip is if you are stuck somewhere and u think the relay is dead u can swap the horn relay with the ignition relay as they are same..in specifications.. but if the car still doesn't startup there is a little trick we attempted which made the car switch on by jumping/by passing the relay but this
is not advisable. U should unplug the ignition relay from the external fuse box under the hood and connect a wire as shown in the picture this will connect the ignition system directly ....only use this to get u out of a bad location and to a mechanic but not as a daily driver see picture.



Hope this helps others out there with Toyota IST / Scion xA cars and maybe similar models too.

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