Hot start and overall power issues

[m3f_vmbray]

The sedan engine that I rebuilt is having a couple of issues. When cold it starts better but crank time is a little long, maybe a rev or two longer than normal. When hot it will chug and make knocking noises and then start, and if I give it gas it starts fine.


Overall power is lacking, particularly at low rpm but even at high rpm it sounds like not enough gas, lots of air intake noise but not quite the power it should make, maybe off by 20%.


Have tried swapping with spares I have:

Coils

Throttle pos sensor

Intake air sensor

Fuel pressure seems okay but need better test

Fuel pressure regulator

Fuel injectors (did help some)

Oil looks good, very clear after 500 miles (dumped break in oil already after 25 miles and due to dump this)


I tried jumping the fuel pump relay with a 20a fused jumper per Bentley and the fuse blew instantly.


Not sure if the symptoms of hot start and power are related. The icv was bad as it had water in it and froze, so the one I have is from the junkyard but I cleaned and the car idles fine.


Seems like next steps are:

Compression test (my tester died so I'm ordering one)

Better fuel pump test

Triple check cam timing (did this when assembling but who knows?)

Swap battery with my car (sedan battery sat up but charges fine)

Crank pos sensor

Cam pos sensor

Get my in pa computer working and check codes but I don't think there are any (cel on from swap)


Thoughts?




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[m3f_vmbray]

Actually when I got to work the hot start issue was present and giving it gas while cranking did not help. It just started at higher rpm after chugging a couple times. Idle is fine after this happens


Power seems better after flogging it a bit. Possibly some of the power issue is babying it during break in.


Also the vanos was rebuilt and tested with compressed air. Solenoid maybe?


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[m3f_vmbray]

Okay more after being more scientific today. After running and being turned off, engine consistently fails to crank and does sputter and knock and dies if I don't give it gas. Second crank it fires right up. Turning key to run for five seconds before starting does not improve matters. Does this seem like fuel pump issue with residual pressure? It does seem to lose pressure faster than spec bit not by too much. Was down 1 bar after 20 mins sitting, spec is .5 bar I think. Seems like a vapor lock kind of issue though.


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[m3f_fiveightandten]

Sounds like a timing issue or a fuel issue to me. It's not throwing any codes? Is fuel pressure within spec while it's running?


It could also be a bad vac leak. Did you double check all the hoses and connections under the manifold?


-Timing

-Fuel

-Vac leak

-Sensors/electrical connections


Odds are it's one of those things. If you've double checked all that, it can't hurt to move into compression/leakdown testing. But i'd be surprised if that's the issue. Did it ever run properly, post-rebuild? Has the car been driven?

[m3f_vmbray]

Sounds like a timing issue or a fuel issue to me. It's not throwing any codes? Is fuel pressure within spec while it's running?


It could also be a bad vac leak. Did you double check all the hoses and connections under the manifold?


-Timing

-Fuel

-Vac leak

-Sensors/electrical connections


Odds are it's one of those things. If you've double checked all that, it can't hurt to move into compression/leakdown testing. But i'd be surprised if that's the issue. Did it ever run properly, post-rebuild? Has the car been driven?

It's just passed 500 miles. Yes strangely it seems like it pulled fine at first but I was taking it easy so it wasn't as obvious.


I may pull the valve cover in the am and check timing. I did that once already while assembling it and just got paranoid and pulled it to check.


Don't think vac leak but I can easily smoke test it. It seems like fuel but a quick test showed pressure. Was trying to do the fused jumper to run the pump but it just blew my 20a fuse instantly and I was short on time.


Thanks for the thoughts!


Edit - wiring was labeled so I don't think wires are crossed. Was wondering about relays though, would be easy to swap fuel pump relay with the coupe.


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[m3f_vmbray]

Well this is annoying. Decided the timing was the probable issue so I took it all apart and redid it very carefully. Maybe made a tiny difference but all the issues remain. Tried my coupe fuel relay and didn't help.


Not sure if the fuel pump is the problem. If I turn the key to run for some seconds before cranking it makes no difference. Now one thing that it does occasionally that seems like it might be the pump, is at a stop light it will chug down and almost die or die, and then be okay. Runs like it's not firing a cylinder, and giving it gas makes it run faster like it's missing. Will do this for maybe 5-10 seconds and the idle normally.


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[m3f_vmbray]

Took some time this evening to get my inpa computer going, the old laptop died and the new one wasn't fully set up yet. Scanned the car and got a bunch of codes. 65 Camshaft with frequency 109 seems to be the culprit. Also have 251 Malfunction of evaporative control system, 20 malfunction indicator light, 242 misfire cylinder 5 and 212 vanos jammed.



Aside from the 65 cam sensor error, all the others have frequency 1 or 2. I'm ordering a cam sensor and seal. The vanos codes are probably from after pulling it today, pretty sure that the vanos jammed code is common after pulling the vanos.

[m3f_vmbray]

Swapped my cam position sensor in and power is restored! Car moves out just fine now!


Hot start issue remains so not related. Gonna clear codes and scan again tomorrow. Still don't think fuel pump because it happens after just five seconds of being off when hot.


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[m3f_Braymond141]

If your VANOS code persists, redo it but this time use air pressure to cycle forward and back a few times before locking down the exhaust sprocket. Hand operation is not reliable.

[m3f_vmbray]

If your VANOS code persists, redo it but this time use air pressure to cycle forward and back a few times before locking down the exhaust sprocket. Hand operation is not reliable.

Okay thanks. I did test it with air when the engine was assembled. I think you get that code when the oil comes out and has to be pumped up again. It said the code was not present so I will see once I clear and drive it.


Wondering if iac is the hot start culprit. At least power is good now. Pulling hard and running great.


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[m3f_vmbray]

Cleared codes. Coolant temp sensor was reading 96 F after hours of sitting, and intake air was what looked like normal temp. After running coolant temp was spot on so I don't think that's the issue. Ran around the hood and had no cel. Car pulled hard. Difference is not subtle, so cam pos sensor was definitely bad. Came back and cranked car three times to check hot start issue. Started pretty well two times, long crank but started and idled fine. Third time was a train wreck, sputtered, almost died, then made nasty starter gear noises (I guess) and stalled. Scanned again and got more camshaft codes, more vanos jammed codes, and one ews signal not present code. Can message 217 is the manual conversion where it can't talk to the auto computer I think. Looks more like a vanos issue I guess. I rebuilt vanos carefully with Beisan seal and rattle kit. Maybe vanos solenoid? Here are the codes for your enjoyment

[m3f_vmbray]

Well the vanos is mechanically fine. It looks like it's not getting oil for some reason. Hooked the air to it and the travel is perfect. I noticed when taking it apart that not much oil came out this time. When I activated the solenoid with the air fitting connected, it spat out some milky oil and did it's travel. The oil overall looks fine. It's not low on coolant or anything and coolant looks fine. Not sure I like all this, not sure what's wrong. Gotta go look some more, just got it apart and found all that.


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[m3f_jayjaya29]

Milky oil from vanos unit is just emulsified oil from the air pressure. Does not signify a coolant to oil situation.

[m3f_vmbray]

Milky oil from vanos unit is just emulsified oil from the air pressure. Does not signify a coolant to oil situation.

Thanks for posting, I'm just paranoid


Checked vanos piston, it's free as can be. I had a lot of oil from the line the first time I took it apart, I remember because the oil immediately dripped on the belt requiring all that to be cleaned. The last two times there's not enough oil to drip on the belt. Not sure if the line is supposed to hold oil when off or not.


I cleared adaptations and the codes but cel was back on at the second start. It seems like there are fewer occurrences of the error since it was up to 300 something frequency and after a 10 minute drive was only 9. Need to scan again today.


Wondering if the crank sensor might be the cause, since the error is caused when the crank and cam are out of position relative to each other, with the vanos accounted for. So if crank position was wrong or erratic but not completely bad maybe it can cause this?


Vanos operated very smooth with air and it's the third one I've done.


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[m3f_Braymond141]

Are you checking the vanos travel with exhaust cam locked down? My point was to leave it unlocked so you know the timing is set with vanos fully retarded (air pressure applied, voltage on solenoid off. Cycle on/off/on/off, lock down on off. Cycling the vanos with the exhaust cam sprocket bolted down is just travel check on the intake cam.