[tamathumper]

I've been noticing a few things lately about how the car runs - the most significant is a heavy stumble at low RPMs when cold. Once it's warmed up, everything is A/OK, but when cold, the stumble is now severe, and it can take literally a couple of seconds before the engine recovers and starts to climb again. It's actually enough to be dangerous if I was pulling out into traffic.



I've also been noticing a "burble" in the exhaust note when the car is coming off acceleration, and once I thought I heard a backfire. This is not when the car is under load, but more when the car is coming down to idle - or even more when the car is right at that point between load and engine-braking, kind of in the "coast" zone. I can just barely hear a "bum, ........ bum" note in the exhaust that was never there before. The idle itself seems steady, though.



I bought the bits this morning to make a pressure-tester, and I pressurized the whole vacuum system to look for leaks. There were none that I could find anywhere, and the system was still pressurized a bit after several minutes.



I'm wondering if the ICV (Idle Control Valve) would be causing something like this?

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[Lear35A]

When you had stuff off to put in the SC, did you give the ICV a good internal cleaning? It's probably impossible to get to with the SC installed, but when I had mine out and flushed it with brake clean there was gunk in it. Your diagnosis may be correct.

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[tamathumper]

No, I didn't mess with it at the time, but it's no harder to get at now with the SC than before, in fact it might be a little easier. I see Clark's Garage calls for a good cleaning with carb and choke cleaner, which I'm assuming is OK for my O2 sensor and cat?

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[Lear35A]

You need to take it off to clean. By the time it's back in that spray cleaner will have evaporated. Won't do anything to the O2 sensor and cat.

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[tamathumper]

Ok, it's on the list.

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[Lear35A]

I cleaned mine with the engine out. I took a look in my engine compartment today. Getting that ICV out of there with everything else installed will be a challenge. Good look.

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[tamathumper]

Yeah I took a look today too, it's tucked under there pretty tight. <img src="/forum/images/smilies/968/sad.png" class="smilie" alt="" />

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[tamathumper]

And now, in addition, I've had two occurrences in the last day where I try to start the car and it acts like it's not firing - it turns and turns for several seconds, then stumbles, turns and turns some more, then finally catches. WTH?! DME Relay?

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[flash]

i just changed mine, with everything in place. it can be done. you have to loosen the big clamp that holds it to the bracket. then it gets fairly straightforward.



i don't think this is your problem though it could be. i tend to think you have a hall sender on the fritz or something like that. what does the durametric say?

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[banditsc]

Ya, I'm thinking either hall sender or crank position sensor, Both of which go bad and the connectors to them go bad before the sensors themselves.



I may have an alternative to the costly ICV, will know later this week when I get my car back together.

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[flash]

yeah - i'm waiting to see how that works out myself. might help solve a different problem of mine

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[tamathumper]

Would one of those cause all three symptoms, e.g. the stumble at low RPMs, the bubbling exhaust note, and the crank-no-start for 3-4 seconds?

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[banditsc]

I would pull apart the connectors to both sensors and make sure that the connectors are at least still good. The crankshaft reference sensor is one of the main inputs to the ECM and without knowledge of speed and crank position the computer can't decide when to spark and / or pulse injector. The hall sender will not prevent the car from starting, but will cause a lower power situation and stumbles, I've only seen that one cause me issue at higher revs or slights higher then cruising revs.

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[tamathumper]

Can't find the crank sensor online or in the part's manual,... still looking,... it must be on the bell housing somewhere?

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[banditsc]

It's located on the top of the bell housing. http://www.pelicanparts.com/More_Info/94...Each%20%20

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[Lear35A]

It's position 5 on illustration 901-05

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[Lear35A]

Here's a pretty good picture of it.

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[tamathumper]

Aha, "pulse sender", no wonder "crank" or "position" or "sensor" wasn't finding it!



Thank you both! 944-606-115-00



Why do I have the feeling it's not going to be that easy to get to?

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[banditsc]

It's an easy one, much easier then the hall sender.

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[Lear35A]

But be very, very careful about dropping a screw or (more likely) the washer down one of the holes. Tape them over before starting.

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