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‘93 240 +T setting 1-4-3 code

Nill_Wrench

New member
Joined
Nov 5, 2022
Hey all, I recently “finished” my 240 +T, and ran into a couple of issues along the way which I solved and it progressively ran better and better. However, it will still set the 1-4-3 code and I can feel it pull timing at anywhere above 2,800 rpm. I’ve done a lot of troubleshooting and am running out of ideas. So far;

Verified good fuel and injectors, brand new FPR, 93 oct
Verified ignition and cam timing, tested very advanced and very retarded on both, no change
Verified good ignition coil, (maybe plugs) and gaps at 0.28
Brand new knock sensor torqued at 15ftlbs

Only thing i might think of on this list is the fuel pressure regulator may not be working properly, although testing that i think requires buying a fancy gauge that may not yield me any useful fix

Current specs are;

13c with 1bar wastegate
Redblockpowered ecu and ezk chips
Bosch 0280155759 red top 850t injectors
A cam with adjustable gear
Sucky loud open downpipe but definitely free flowing

I have heard that possibly the pcv can spew too much back into the intake and lower the octane causing pinging/knocking? Don’t really think thats causing it that bad but its one thing I haven't really figure out a way to verify. If anyone has any experiences to share or ideas to try i’m almost at my end. I’m sure it’s something stupid obvious that I’m missing but have zero clue as to what is causing it at this point.
 
Hello!

I'd check the knock sensor wiring for continuity and any corrosion at the connector. It might also make sense to verify the knock sensor part number. I've never run one that isn't original Bosch so don't know if the aftermarket ones are totally fine or complete junk (like MAFs tend to be). Make sure the threads on the knock sensor bolt as well as the mounting pad on the block are very clean.

Knock sensor stuff can be fairly sensitive and unfortunately all this stuff is getting to be pretty damn old.
 
I would think a 13c would be blowing a lot of hot air at 1 bar pressure. Also the exhaust housing isn't very high flowing. I would want to test the intake air temps and see if they are too hot for good combustion. Are you using a stock Volvo intercooler? They are decent at low boost but have a issue with higher pressures and the efficiency isn't gonna be good.
 
Check the knock sensor harness connector and wiring, specifically that the connector pins are still in the right location (not shoved back into the connector) and that the contacts are not spread apart. The EZK monitors the knock sensor signal at lower speeds to have something to compare to at higher speeds. If the signal is missing completely, it will post a 1-4-3 when hitting higher rpm & load.

There's not a simple measurement to check the knock sensor itself - it's a piezoelectric, so it will measure infinite ohms across the pins. On an unplugged EZK box, I measured ~20K ohms across the knock sensor pins (12&13). If you check the resistance across the 2 pins at the knock sensor connector in the harness, you may get the same ~20K value, or maybe somewhat less since all the other circuits are plugged in.
 
The code decodes to signal missing or faulty. Usually, those definitions are accurate. Meaning, you are not looking for lean mixture etc. The signal just plain isn't getting to the EZK at times, or, all the time. The only time I have gotten that code was when I replaced a head gasket and started the car up without remembering to connect the knock sensor. Do what others above have told you. Check the harness between the sensor and EZK. It is possible you have a bad EZK.
 
Got home and tested the wiring. It does seem to have good continuity, and the resistance measures exactly the same at the sensor as it does at the EZK plug. Not sure if thats right, and my cheap meter seems to be reading 4.8 megaohms, which I don’t think is right either. I might try putting a voltage supply on them if they are indeed two continuous wires running only to those two places, just to make sure.

I don't believe this car has/had a cold start injector, and it never had an EGR, so no other plugs to mix up.

A bad EZK is a good suggestion, since thats one thing I changed between non turbo to turbo that could have never been working in the first place.

I will educate myself better on how to measure resistance and continuity and test to make sure thats all good. If it is, sounds like I am looking at a bad EZK and not a lean or knock condition.
 
Try measuring just the harness. No knock sensor or EZK hooked up. Pins at knock sensor end to pins at the EZK harness. You should be in the 1 ohm realm.

Even if the car never had EGR it has the EGR harness integrated into the engine harness and it is right next to where the knock sensor is located. It is possible to mix the two up. See if there is a harness connector clipped to the flat steel manifold support. It will be right next to the IAC.
 
Page just updated and I saw dl242gt’s post. It pulls great, better than I would have hoped, up until it thinks it detects something bad and pulls timing and lights up the CEL. I was running it on the stock non turbo injectors AND my in tank fuel pump was not running at all, and it was indeed making that crackling noise under load. After fixing fuel the plugs no longer went white and it runs great before it sets the code. I have not tested intake temps, but with cooler temps here in texas and a decent cold intake and open downpipe, I have a hunch those arent my issue, as i would think they would cause a noticeable noise/issue. If all else fails thats on my list now though XD
 
how would I go about measuring at sensor and EZK end? Extenstion jumper wire? Or would that add too much resistance to be accurate?

No jetronic plug on that metal support, however I have spotted some sensor in the head farther towards the firewall under the intake that has a same style plug. Whats that?

Another note, the wire that I currently think is for the knock sensor has a green protective shielding around it. Is that a good marker for it being the correct plug?
 
As suggested disconnect the knock sensor and the connector at the EZK. Then use a paper clip unbent so you can connect both contacts on the knock sensor end. Then you should measure what 2manyturbos wrote above for the reading. Be very careful with the contacts so you don't bend or damage them.
 

Then backprobe, do not FRONT probe, the correct terminal at the EZK and make sure the circuit isn't high restance or open circuit. Tip to tip.
 
I've had a bad Bosch knock sensor out of the box. It would run fine until I passed 3k rpms then it'd trigger the code and pull a ton of timing. It sounds exactly like a dud knock sensor to me. Blue connector is cold start injector, white is coolant temp, black is knock sensor on my '90.
 
Do you have a spare injector kicking around? If so, measure the injector resistance directly, then plug in into the knock connector. Unplug the EZK and measure resistance across the knock pins 12&13. It should be about the same as just the injector, or maybe 1 or 2 ohms larger.
 
how would I go about measuring at sensor and EZK end? Extenstion jumper wire? Or would that add too much resistance to be accurate?

No jetronic plug on that metal support, however I have spotted some sensor in the head farther towards the firewall under the intake that has a same style plug. Whats that?

Another note, the wire that I currently think is for the knock sensor has a green protective shielding around it. Is that a good marker for it being the correct plug?
I just looked at my 1992 940 Turbo and the knock sensor cable is green.
 
Welp, I got a bad ezk. Tested resistance on the knock sensor wiring, and it checked out. What I then did was desolder the daughterboard from the 140 EZK I bought, and transplanted it on my stock 169. Ran like a charm and even got a bit quieter when getting on it.

Thank you all for your help, I was near ready to quit!
 
Good fix. I have never seen a knock sensor or the wiring fail on these cars, but I have seen the control modules throw bunk codes.
 
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