Hey guys! I'm a new user on here. Great forum by the way.

I've been having a problem now with my 850 base model. It does this weird surging under partial throttle or coasting at around 20mph, 30mph, and 50mph. However, if I give it more throttle around these mph ranges, it does not do this. I pulled some codes 143 (kickdown switch shorted to earth), 223 (throttle position signal too low), and 221 (A2, long term fuel trim). Any ideas on where to start?

 

What year is your car?

 

my volvo is a 1994.

 

Have you searched those codes? They likely have some effect on your problem. Sounds like the ecu it adjusting your timing or something to compensate for some other error going on.

 

Yeah, I've done some searching on these codes but will definitely keep searching for more info. Do you know if the kickdown switch is easy to replace?

 

Mt 01 S80 was doing that throttle body sent to bba reman they rebuilt it for 120.00 no more surge

 

No knowledge if the KickDown sensor/switch. But I don't believe the throttle body is remotely simular to the ones on the S80's.

 

Well thanks for all the suggestions. I will get cracking on it and let you guys know whats wrong when I figure it out.

 

I know this post is very old but did you find a fix for this? My 1994 850 is doing the same thing.

 

Check for loose clamp, or torn hose.

 

I agree with Robert that the FI system is trying to compensate/adjust - I'd start by inspecting vacuum lines (my experience is a torn line usually throws a code) as well as the airflow hoses/boots (ie the OTM (over the motor) tube connections/hoses, the connections into the intercooler and the intercooler itself as well as the hoses for the MAF and idle air valve. You may want to pull and see if there's any crud in the intake to the throttle body and if so, clean the idle valve and MAF with some MAF cleaner.

The 850s don't have the electronic throttle body the s70/s80s have, so its not the same cause/effect but does suggest the intake air volume/pressure is off leading to an incorrect mixture. Any other symptoms like cold/warm starts, hesitation, power at full throttle etc? Any odd behavior in the temp gauge (ie the ECT sensor could be off)?

 

I don't want to insult anybody's intelligence, but that might just be the a/c compressor cycling or even changes (for whatever reason) in alternator output. Surging is a funny thing to try to diagnose.

 

 

Thanks to all for input. Mine is not a turbo. things done so far.
1. Checked all vacuum line for leaks. Visually and by spraying carb cleaner while engine is is running to notice RPM change.
2. Removed and cleaned throttle body.
3. Replaced cam position sensor. (New)
4. Replaced ignition coil and module. (New)
5. Replaced crankshaft position sensor. (New)
6. Replaced distributor cap and rotor.(New)
7. Replaced spark plugs and wires. (New)
8. Replaced fuel pump and filter on pump in tank. (New)
9. Checked fuel pressure and regulator. (Within specs.)
10. Replaced fuel filter. (New)

Running out of options.

 

Do you have a good scan tool?

 

have you done a smoke test to recheck the vacuum lines? There's a few places (like into the PCV system components) that are hard to get to view and spray, including the line that goes all the way back to the evap canister.


Check out Robert's home made tester:


Since you've ruled out many of the fuel (all? short of the relay) and spark components , that you may need to check the MAF and MAP sensors as well as ECT sensor. (ECT is easy to test with a VOM - should be something like 3k ohms or so cold, less than 300 warm. Check out Volvotips for some procures and values.

 

Yes,but cannot use scan tool. This year and model has the SELF-DIAGNOSTIC SYSTEM.

 

I have installed a new fuel pump relay also. Did not think about the ECT sensor being that the dash temp has been working correctly. Does that gauge get its reading from a separate sensor? I will try Robert's test next, I like this guys videos. Also have been on Volvotips for some time now.