February 19, 201412 yr Hey, so I have a 2.2L engine from a 1999 legacy L swapped into my 1984 vanagon. But from day one, I get a flashing CEL after about 5 secs after the engine starts. On ecuexplorer it show a P0328 code. So I checked out the knock sensor/wiring and its all good, 2.8V when running. Also tried another knock sensor that's in spec and another ecu with no success. Reset the ecu and within 5 secs the CEL is flashing and P0328 is back. My friends scanner also picked up a P0302 code, cylinder 2 misfire. So checked the leakdown on the engine and changed the plugs. wires are new.... Engine idles smooth, but on ecuexplorer I can see its pulling most of the timing out when accelerating. Which makes sense since it should be in limp mode. I changed the timing belt before putting the engine in the van, but I double checked and believe its good. Any Ideas what would make a Flashing CEL come in so fast?? and no matter what I do P0328 keeps coming in??? Thoughts? idea?
February 19, 201412 yr Do you have 2.8 V at the sensor when its plugged in? (Back-probe the connector) Flashing CEL indicates a constant misfire, but it SHOULD be setting a code for which cylinder is misfiring. Kinda seems like you may have an ECU issue.
February 19, 201412 yr Author Do you have 2.8 V at the sensor when its plugged in? (Back-probe the connector) Flashing CEL indicates a constant misfire, but it SHOULD be setting a code for which cylinder is misfiring. Kinda seems like you may have an ECU issue. -5v off the ecu and 2.8v when its plugged in. -1999 models seem to have a hard time communicating with a lot of obd2 readers... found that out after I got this one as a donor. have to try my friends expensive scanner again -I got a second ecu from pnp and it does the same thing.... so either its a common issue with the ecus or I have a funky wiring issue i'm thinking. All the grounding looks good, every voltage I've checked looks good... -all the plugs looked abit lean too when I changed them. maybe I should check fuel pressure. its a new pump, but maybe the regulator is wonky. Edited February 19, 201412 yr by Vanagoon
February 19, 201412 yr I would be interested to see what the scanner says. Could be running too lean, pinging and driving the knock sensor crazy, which makes it pull timing. Lean also causes misfires at idle. If it pings at idle that can make it set codes for the knock sensor. What kind of fuel pump are you running? Have you checked fuel pressure to see if its in spec? Should have 35psi at idle. About 45 if you pull the vacuum hose off the FPR. Entirely possible you just have the cam timing a tooth off, might double double check that again for gits and shiggles, even if you already have.
February 19, 201412 yr I think Fairtax4me has a good idea on the timing belts. Doing a compression check might show the issue.
February 19, 201412 yr knock sensors are cheap. Is yours cracked? anyway, if you replace it, it can be important to orient the part so the cable dresses away at the same position as stock. Some people have put them on and the casting pushes on the bottom where the cable comes out and cracks it again.
February 19, 201412 yr Have been finding that the knock senser grounding is critical I file the block bottom of senser and bolt to make sure 100 grounded also check main engine harness conectors pins are all pluged in good
February 20, 201412 yr Author I have 3 knock sensors to choose from, all in spec and all the same issue. 100% sure its not the circuit or sensor. adjusted the valves and changed the valve cover gaskets/seals. Then changed the plugs, no oil to be found. The pump is the stock bosch vanagon pump, which worked flawless with the old engine. I'll be checking the timing belt and fuel pressure asap. Thanks for the ideas so far.
February 20, 201412 yr Author well timing belt is definitely good, was almost hoping it was off. But that would of been to easy.... Fuel pressure looks good too, wasn't the best gauge but im sure its good... when ecuexplorer is talking to the ecu, I can see that the knock sensor isn't pulling timing. but the ecu must be in limp mode, because there is very little timing when under load. still have to check the harness connectors, ill do that tomorrow.
February 20, 201412 yr Timing can drop back significantly under load. Back to around 10-12 degrees in some cases. A while ago Presslab (I think) posted a graph showing base timing and another showing maximum possible advance beyond base for the whole RPM range. It was for a phase 1 (92 or 94 IIRC) Ej22, but it would be similar for the 99. At least similar enough to give you a general idea of where ignition timing should be. Do you have a vacuum guage? Does your setup have a MAP sensor? Could look at MAP values to determine vaccum.
February 20, 201412 yr carbon build-up in the cylinders could lead to knock - but if the sensor isn't pulling timing, it isn't knocking. one experiment to try, clear the computer with a battery disconnect after filling with high octane. maybe try a coupla tankfuls. If the problem seems better, may be a 'real' knock issue. but from what you say - ECU seems suspect doesn't it? Or the connector to it w'ever
February 21, 201412 yr Author so almost no resistance on any of the ecu grounds to the engine, then I turn the ign on and I get close to 40ohm of resistance! then I turn off the ignition and the resistance stays at 40ohms for abit before dropping down again. bad connection thats getting warm and increasing resistance?
February 21, 201412 yr well, I don't know what instrument you're using but, an ohmmeter supplies its own current and isn't used on a powered circuit. Sounds like the meter is just confused with the power in the line and the slight drop across the connection? kinda weird as there shouldn't be a lot of current with the ignition just at ON. I'd be tempted to do all my resistance testing with the neg batt connection removed. Also, try reversing the leads on your testing. Sometimes corrosion can act like a diode. not commonly, but possible. Edited February 21, 201412 yr by 1 Lucky Texan
February 21, 201412 yr Even with the key On there should be little or no resistance on the ground side because there should be no potential (voltage) on the ground. Check for voltage on the ground side. More than 0.1V means you have a bad ground. Preferably you want your meter grounded to the battery negative post, so make a jumper wire to attach your meters black lead to the battery if it isn't long enough to reach. The ECU originally grounds through the wiring harness to the intake manifold. Not sure if you kept that when you made your harness, but if so make sure its clean and tight. Also make sure the engine is well grounded to the frame. You might even add a ground wire from the manifold to the battery.
February 21, 201412 yr Author Even with the key On there should be little or no resistance on the ground side because there should be no potential (voltage) on the ground. Check for voltage on the ground side. More than 0.1V means you have a bad ground. Preferably you want your meter grounded to the battery negative post, so make a jumper wire to attach your meters black lead to the battery if it isn't long enough to reach. The ECU originally grounds through the wiring harness to the intake manifold. Not sure if you kept that when you made your harness, but if so make sure its clean and tight. Also make sure the engine is well grounded to the frame. You might even add a ground wire from the manifold to the battery. I'm going to have to check for voltage again, there is a bad connection or something in the harnass. The resistance is from the ecu to the ground on the engine. Its in the harnass some how. The engine harnass is unchanged and the ecu to engine connectors have had very few cuts. Its mostly removing the unused stuff and just hooking the power, ign, and those items back into it. I'll dig into it again tonight. and no the ecu case isnt grounded, but I did try using a jumper and grounding it once and it never made a difference. T Edited February 21, 201412 yr by Vanagoon
February 21, 201412 yr If the ECU is bolted down to something metal then it is grounded. The ECU case should be grounded to prevent RFI from being generated by the case.
February 22, 201412 yr The reason you can't take a resistance reading when power is applied to a circuit is because the meter supplies power to it in order to make the test. Adding additional current in the circuit will throw the reading off. Checking for voltage across a suspected bad ground connection while there is a load on the circuit is the best way to find a ground problem. I suggest you try testing the circuit operation for the knock sensor. Remove the connector to the sensor and install a 510k ohm 1/2 watt resistor on the connector end in place of the sensor. If there is a singe wire going to the sensor then you will have to ground one end of the resistor. See if the CEL light goes out then. If it doesn't then the ECU may have an internal problem with that circuit, though having the correct bias voltage is encouraging.
February 23, 201412 yr Did you use the venting stuff from back of car ? on 98 they ran power and signal to rear of car for gas tank venting control must be in wire harness or defaults was 4 or six wires to rear of car fuel temp senser / vent valve / vacume signal senser
February 23, 201412 yr Did you use the venting stuff from back of car ? on 98 they ran power and signal to rear of car for gas tank venting control must be in wire harness or defaults was 4 or six wires to rear of car fuel temp senser / vent valve / vacume signal senser Yeah....mine runs fine without that stuff. Throws codes for Fuel temp/pressure and a "Mnfctr. Cntrld. Emmisions" whatever that means. Just a though......Did you plug in the "test" connectors? Green plug from ECU? it should be disconnected or else the ECU will be in a constant test cycle. That could be the flashing light.
February 24, 201412 yr Author I have a little board that gives the proper voltages for the unused circuit so I don't get codes. I went to pnp and got another ecu to engine harnass and swapped it in. No more limp mode or p0328 cel! when I get a chance i'll be ripping the old harnass apart and see if I can spot something. thanks for the ideas and help Edited February 24, 201412 yr by Vanagoon
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