'98 Olds 3800, tries to die at idle, no MIL

blowout preventer · 2011-09-20T00:02:20+00:00

'98 Olds Intrigue 3800, 175K miles, having issues beginning a coupledays ago. Seems to only happen after it's warmed up (so far). At idle it will try to die, RPM's will dip way down, then it willflare up to about 2000 RPMs. No MIL during these episodes, and the only stored code scanner gave mewas one of the O2 sensors was out of range at some point. It hasn't exhibited this condition any other time, like going down thehighway, or when it's started cold. Only seems to be after it's warmedup. Since there's no MIL, I suspect the fuel pump. I doubt the fuelfilter is the culpit since it doesn't act up at or going up to highwayspeeds, when the engine is calling for more fuel. I don't want to go to the expense or hassle of changing the fuel pumpwithout being as sure as I can be that's the problem. The problem is intermittent, which in my experience is how fuel pumpscan be when they're beginning to fail. And that also makes it difficultto catch by putting a pressure gauge on it. I don't know if the fuel pump has been replaced in the past, and ifnot, it's about due. Given the conditions I described, and no MIL, does this point stronglyto the fuel pump? Or is there anything else I should look at first?

Sep 20, 2011 25 Replies

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blowout preventer 14 years ago

I bought a Delco crankshaft position sensor and went to change it out, but decided I wouldn't be able to get the harmonic balancer off, as my puller probably wouldn't fit right to pull it. Figuring that the labor wouldn't be that much with the correct puller, I took it to the GM dealer (I was right -- an hour labor to change.) They said they would rather diagnose it themselves to ensure they weren't changing the part that didn't need it, and I gave them the go-ahead. They diagnosed it using a tech 2 and said everything points to the MAF. My Innova scanner said the same thing.

HOWEVER, after MY scanner had indicated the MAf, I unplugged the MAF, and the engine still cut out, flared, etc. aferwards. I n other words, it exhibited the exact same problem in open loop without the MAF even in the equation.

SO... Should I just have them change out the Crankshaft Position Sensor, like I originally was going to have them do anyway ( since it has 175K on it and is probably due -- plus the engine dies ect. without the MAF plugged in, thus indicating something other than the MAF)?

OR... just change the MAF myself, which costs $200 and might not change the problem?

In other words, if scanning it with both my Innova, AND a Tech II by a pro, and they both indicate the MAF -- but the engine still acts up without the MAF even plugged in... What would you do?

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Steve W. 14 years ago

I would change the MAF!

Why? Because if you unplug it and NOTHING changes then it isn't working.

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Paul in Houston TX 14 years ago

I second Steve's opinion. Change the maf. If maf is plugged or unplugged and it does the same thing, then that means its not working at all. Especially after two scanners say the same thing.

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Ed Pawlowski 14 years ago

"blowout preventer" wrote

I'd expect that if it was not working.

If your TV, toaster, or washing machine don't work, do they act differently if you unplug them? If not, you'd have to assume what?

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PeterD 14 years ago

Yep, there is the correct diagnosis, and three cheers for the dealer who suggested more diagnostics were in order before replacing parts that may not fix the problem.

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