I have a Volvo 1993 Volvo 850 glt that won't idle. It cranks starts runs for about 5 secs then dies. If I try to give it gas it dies even quicker. It has good spark, good fuel pressure, and good compression. I can't seem to figure it out

 

Does it not run at all (after 5 secs) or just not idle? Two different things.


Any notable event precede this one? Any codes, etc.?

 

It only runs for 5 secs then dies has no codes

 

You checking for codes here?

 

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Ok so I did that and only got one code from A6 I got a 2-1-4 that's the crankshaft sensor right?? I just replaced that sensor with a new one

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Did you clear the code and try again?

 

Yes but code keeps popping back up could this be my problem?

 

May have gotten a bad sensor.

Move the coil wire as far away from the crank wire as possible, see if that helps.

 

So it goes from having no codes (post #3) to a 2-1-4 code that won't reset, and you ask, "do you think that could be the problem"???


You guys know the ECU sets the codes, right? So, if the sensor is known to be good (yes?) then what do you think problem could be? The wires connecting the ECU to the sensor possibly?


From the 1995 850 Manual (underlined are my edits):
=====================================
1-3-1 (VSS Signal Absent) & 2-1-4 (VSS Signal Intermittent)
1) Connect measuring unit to ignition ECU. See MEASURING UNIT
under SELF-DIAGNOSTIC SYSTEM. To check VSS signal, connect voltmeter between measuring unit terminals No. 1 and 2. Operate starter motor (using a remote starter switch would be best).


Voltmeter should indicate 300-400 millivolts with ignition switch in START position (cranking) and about one volt with engine running.


2) If voltage is not present, turn ignition off. Connect an
ohmmeter between measuring unit terminals No. 1 and 2 (A1 &A2 at ECU connector). Resistance should be 200-400 ohms, depending on temperature. Connect ohmmeter between measuring unit terminals No. 2 and 20 (pin A20 is ECU ground pin). About zero ohms should be present.
=================================================


I.e. you're cking that the VSS sensor impedance should be 200-400 ohms when measuring it statically (no engine rotation) and output a bit less than half a volt at starter cranking speed and about 2x that at idle speed. Note above instructions are using a Volvo break-out box so I would pull the ECU (make sure the key is off when R&Ring the ECU!) and ck resistance between A1 & A2. Should be 200-400 ohms and should get 0.3 - 0.4 vac with the starter cranking.


My guess is you may have a corroded connection in those VSS sensor wires somewhere..

 

Moving the wires apart didn't solve anything I'm going to try testing the harness connection

 

Also test the sensor. It's rare but there is always a small chance you have a bad new part. Check the connector too !! Might be some corrosion in there or a bent connection that isn't making a proper connection. Same with the pins on the ECU. If you go that far be careful with it but there is always a chance you're having some corrosion on it's pins too.

 

Ok I checked the harness on the connection between the ECU and the crank sensor and everything matched up it was getting the correct amount of voltage. I tested the sensor with a voltmeter and got the right resistance value. Thank you for the suggestions. Is there anything else I should check?

 

I have a question is there is an issue with the crank sensor then wouldn't I not get any spark to the plugs?

 

In most cases if the crank sensor is bad or the ECM isn't getting a signal there would be no spark.

 

So in my case I am getting spark so shouldn't it at least run?

 

Have you checked your vacuum lines? My s70 wouldnt idle after I replaced the starter because I was forced to do it at night, and didnt realize I had pulled a tiny vacuum line towards the fan. Caused me a lot of headache, thought I killed the MAF because It idled without it.

 

How would I check the vacuum lines?

 

Visual. Look for bad elbows at connections mostly.

 

So I figured it out the car would not stay running due too bad gas and fouled spark plugs it idles yet but cylinders 1 and 2 are intermediately firing. Also if I touch the gas it floods and kills the engine. I think I might have a damaged flywheel is there any way to test it?