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Engine surges at idle and light throttle


airjeff
11-19-2010, 11:53 PM
I've got a '98 2.0 SPI 5-speed 220k. This problem has been getting worse over time. Sometimes at idle, but always just above idle the engine will bog and then surge up some and repeat the yo-yo process. It does not sound like an engine missing, more like it floods itself and then revs to clear it. Also, it smells very rich while it's happening. It almost always bogs coming off idle now. It can also happen while driving at very light loads also. Makes the car buck when it happens. No CEL and no pending codes.

I've checked the vacume lines, replaced the IAC, plugs are good and gapped, wires have less than 10k on the wires, MAF was cleaned with MAF cleaner, air filter is good.

I have not checked actual vacuum since I don't have a gauge, but if I increase the vacuum manually by blocking part of the IAC port it seems to solve it. But, I can't really drive with my thumb there. :) I'm not sure if increasing the vacuum is just masking my problem.

Here is one strange thing. I have an AutoEnginuity scan tool and the MAF reading is stuck at .19lbs/min always, never moves. I know the tools works in other cars. It isn't possible for a car to run like that is it? Like I said, no CEL and no pending codes.

So, any ideas? I'd hate to pay a shop to look at it, I don't want to sink much money into a car with 220k...then again, this is my first problem.

airjeff
11-20-2010, 09:19 AM
Forgot to say it all started this summer.

mightymoose_22
11-21-2010, 12:35 PM
Possibly a vacuum leak at the intake manifold rather than a hose. I have had similar problems with my 94 and solved it by replacing the intake manifold gasket.

danielsatur
11-21-2010, 09:05 PM
Even though you cleaned the MAF sensor, it could be bad MAF sensor without a DTC.
What about the upstream O2 sensor?

Because of Age/Mileage, I would consider a new MAF sensor, and a O2 sensor.

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