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YOUR RESEARCHengine fires but won't idle, run or hold RPM (after replacing coolant tank)
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Disconnect battery, let sit
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Performed · outcome unconfirmed · Original poster
I disconnected the battery, let sit for a bit, and reconnected, to reset any stored settings.
engine fires but won't idle, run or hold RPM (after replacing coolant tank)
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Leading evidence: 'Disconnect battery, let sit' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check either physically' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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engine fires but won't idle, run or hold RPM (after replacing coolant tank)
Install correctly
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engine fires but won't idle, run or hold RPM (after replacing coolant tank)
Run perfectly
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Performed · outcome unconfirmed · Original poster
Once I remove and reinstalled the plenum the car ran perfectly.
engine fires but won't idle, run or hold RPM (after replacing coolant tank)
Check either physically
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Suggestion · Original poster
Can you think of anything else I can check either physically on the car or with the durametric?
engine fires but won't idle, run or hold RPM (after replacing coolant tank)
Run cycles
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Suggestion · Original poster
I suspect that the few starts-but-doesn't-run cycles on the engine pumped all of the cold oil up into the engine and now it's very slowly draining back down into the pan.
engine fires but won't idle, run or hold RPM (after replacing coolant tank)
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17 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
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Just checked again and the bottom bar is solid now, so I'm guessing in a few hours the oil level will be back to normal.
2004 996.2 C4S 3.6L cranks and fires up but won't stay running. If I modulate the throttle I can keep it from dying immediately also can't really make it run either, doesn't hold an RPM and sounds like crap. If i let off the throttle engine immediately dies.
I'm hoping something like an electrical connection.
Precipitating event: car was running perfectly until last weekend when I started the job to replace the leaking coolant tank and the lower AOS vent line (the one that runs across the top of the engine). The car sat for a week with the coolant tank out, throttle body and 1st throttle plenum removed, and the lower AOS vent line removed. Intakes openings and AOS vent line holes were covered. Coolant hoses were left open. Everything went back together easily today and I was feeling pretty good until the engine won't start. Doh!
To get the coolant tank in/out I had to lower the engine until it was resting on the cross member. Engine was support all week by the cross member and with the jack on the boss at the rear of the engine (just aft of oil pan). I tried to make it rest on both points as much as possible (so not loading the suspension through the crossmember and not held up just by the jack).
I'm suspecting that either when I lowered the engine, when I was struggling to get the coolant tank out, or when I was feeding the new the AOS vent line through, I must've knocked some electrical connection. I've checked everything as carefully as I can and can see no issues:
- Durametric shows no codes
- MAF connector seems installed correctly.
- e-gas throttle connector seems good. Key on for 60s forces it to adapt and I can hear it clicking. Durametric shows throttle sensors responding when I modulate the gas pedal, so throttle body seems to be workng.
- all vacuum lines seem connected and not cracked
- injector connectors on the 1-3 side of the engine seem to have solid connection.
- all O2 sensors look good (their wires were tight but not overly so when the engine was lowered).
- tachometer works, so CPS sensor fine
I disconnected the battery, let sit for a bit, and reconnected, to reset any stored settings. No effect.
Can you think of anything else I can check either physically on the car or with the durametric? I admit I'm a total novice using the durametric and have checked everything I can touch in the interface but don't know any tricks. Also with no stored codes, I'm not sure which "actual values" to check when cranking the engine.
Probable red herring: engine oil was in the middle between the high/low marks until I went through a few cycles of tying to start the engine. After the 4th or 5th cycle, and after disconnecting and reconnecting the battery, the key-on oil measurement showed a blinking bottom bar. (!) This was confirmed by the dipstick. I suspect that the few starts-but-doesn't-run cycles on the engine pumped all of the cold oil up into the engine and now it's very slowly draining back down into the pan. Just checked again and the bottom bar is solid now, so I'm guessing in a few hours the oil level will be back to normal. Which is fine since I'm out of ideas now!
Ideas welcome!
Everytime I had your issue, it was something related to the Idle Air Control Valve. Either a cracked hose or a stuck valve.
I had this exact issue on my '95 M3 two days ago. It was a cracked hose from the intake boot to the IACV.
Thanks for the suggestion. My car has e-gas and best I can tell there is no idle air control valve. For sure it's not present on the throttle body on the usual place. I will keep looking!
Sounds like a big air leak to me too. It may not be an IAC but you have unmetered air by the sound of it. Check every hose, clamp and anything removed from mass air meter to the engine and all hoses going to the intake manifold.
Ok so time to investigate for air leaks. No obvious disconnected hoses or lines. I think maybe I�ll disassemble again back to the first throttle body inspecting along the way for anything suspect.
Thanks guys for the pointer to air leaks. I took off the throttle body and it was clear I hadn't centered the rubber boots correctly on the first throttle body plenum. Now I can see that right boot (passenger side) has a ridge to align that side and there are little marks on the plenum itself to show where the boots should be seated on the plenum.
All is well again (and no more coolant leak either...)!
Cheers!
Darn it. Did not get here in time. I was going to suggest exactly that. It is difficult to get the plenum centered in the rubber boots and clamps tightened. Also, there is the vacuum hose that connects to the left rubber boot from underneath. Don't forget to reconnect that vacuum line.
I�m glad all is well. I want to service the AOS and hoses this winter in my car so now I know another thing to watch for. I was worried it could be an AOS hose which would be hard to get to.
OP, I was experiencing the same kind of problem. I took the advice of some clown here on Rennlist and covered my snorkel while washing it. I forgot and left it on. Tried to start it. It would fire up, but stalled pretty quickly. I then then started it again while rev'n the hell out of it and it was struggling but I started down the road until... UNTIL!!!! I realized my mistake. Holy CRAAAAP! Pulled over quickly and removed the plastic snorkel condum and all it right with the world again.
LOL! I remember that thread and the advice to cover the snorkel was suggested in sarcasm...You bit
Should water ever get in (very unlikely) the air box is full of hole on the bottom and will drain out faster than it could ever enter.
Unfortunately, I'm not familiar with code P0507. The issue in my case was that I had installed the throttle body plenum incorrectly and left some airgaps where the rubber boots attached to the intake manifolds. Once I remove and reinstalled the plenum the car ran perfectly.
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