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B230f surging

Volv

New member
Joined
Feb 8, 2020
My engine is now surging from 2-6-800rpm. It does sometimes bug down a little bit on acceleration. Not always it does. But it runs better now. It?s driveable. Can drive without worrying about enginefault. On idle it?s the only problem, it?s surging.

- new IAC
- new Intake and throttle gasket
- New injectors, Rail, FPR
- New fuel pump, filter
- new distributor, dizzy cap, rotor, Leads, coil. MAF,
- New CPS
- new spark plugs
- new timing belt, (timed correctly, it?s fine ignition timing)
- New lambda, I?m on my third
- I have two ECU and EZK
- cleaned throttle,
- egr- delete
- sometimes trip teller lives it own life and shows between 1000-4000rpm when I?m not actually on that RPM.
 
Thanks :)

I haven?t tried to change my Coolant temp sensor.
I?ll measure it :)

What other problems can cause bad idling?
I have checked Throttle position sensor. It?s OK

Is it set correctly? If not, the ECU can not control the idle. It will surge. The most common cause of a surging idle is a failing AMM. And no, the ECU has no way of knowing the AMM is failing. The ECU does not throw a code for the AMM other than for a failed hot wire or bad connection.
 
Is it set correctly? If not, the ECU can not control the idle. It will surge. The most common cause of a surging idle is a failing AMM. And no, the ECU has no way of knowing the AMM is failing. The ECU does not throw a code for the AMM other than for a failed hot wire or bad connection.


AMM? The MAF? I have checked that and tried another maf. Didn?t help. So I guess my MAF works then.
 
You went right past my previous question without answering it. Is the TPS set correctly for sure? This doesn't just mean you put in on and hear it click.
 
You went right past my previous question without answering it. Is the TPS set correctly for sure? This doesn't just mean you put in on and hear it click.

Sorry
Yes it?s correctly adjusted. Butterfly valve is fine aswell. Checked it.
Clean throttle
0,15mm clearance?
 
Pinching the IAC hose closed with a large pair of needle nose pliers should result in the idle dropping to 400-600 RPM. That's when you know the throttle plate is set correctly, as long as you don't have any vacuum leaks elsewhere. You should check the hose that connects the AMM/MAF to the throttle body for cracks/holes. Leaks there can also cause a surging idle.
 
Sorry
Yes it’s correctly adjusted. Butterfly valve is fine aswell. Checked it.
Clean throttle
0,15mm clearance?

Still sounds like this is the problem. Idle will hunt if switch doesn't close and fuel ECU sees the closure. Time and time again folks say "yes the TPS is adjusted right" but then we find out the switch was not working, the terminal retracted from the harness plug, or the instructions were not understood.
 
^^

I'm with you on this. Trying my best to be tactful. I've seen this happen sooooooooooo many times. OP, you need to check with an ohmmeter whether the switch is actually closing and staying closed when the throttle closes. IOW, a completed circuit with very little resistance. The ECU can't adjust the idle without the throttle plate being set correctly and the TPS being set correctly relative to the throttle plate setting. The idle air valve is just there for very minor adjustments to the air flow. When things aren't set right initially it goes crazy trying to compensate.
 
^^

I'm with you on this. Trying my best to be tactful. I've seen this happen sooooooooooo many times. OP, you need to check with an ohmmeter whether the switch is actually closing and staying closed when the throttle closes. IOW, a completed circuit with very little resistance. The ECU can't adjust the idle without the throttle plate being set correctly and the TPS being set correctly relative to the throttle plate setting. The idle air valve is just there for very minor adjustments to the air flow. When things aren't set right initially it goes crazy trying to compensate.


I appreciate it :)

I?ll double check tps. How many ohm on closed and open position?
 
Infinite in the open position. Less than 1 ohm in the closed position. My Fluke usually reads .1-.2 ohm when I'm checking a TPS that is working properly. I've seen the readings as high as 5-10 ohms with contacts that are dirty/burned.
 
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