"flat spot" accelerating

SW96 · 04-01-2008, 01:24 PM

We recently got a 1996 SW2, automatic. When we got it, the MIL was on, and a scan showed TPS out of range. The test drive seemed to confirm the diagnosis of a bad TPS, so I replaced it when we got home. I cleared the code, which hasn't come back, but the "flat spot", or hesitation when first stepping on the gas, remains.
Has anybody else had this issue, and what fixed it?

RC1488 · 04-01-2008, 05:05 PM

Quote:

Originally Posted by SW96

We recently got a 1996 SW2, automatic. When we got it, the MIL was on, and a scan showed TPS out of range. The test drive seemed to confirm the diagnosis of a bad TPS, so I replaced it when we got home. I cleared the code, which hasn't come back, but the "flat spot", or hesitation when first stepping on the gas, remains.
Has anybody else had this issue, and what fixed it?

Perhaps since its a new car a Tune up will give you a nice clean start for any diagnosis. This will also give you a begining point for furute maintenance.

I say this bc my first questions would be the following:
Have you cleaned the Throttle body?
Have you replaced the Engine Coolant Temperature Sensor?
Do you have copper spark plugs (NGK seem to work the best)?
etc etc

If you want a tune up list i can post it for you

SW96 · 04-01-2008, 10:54 PM

I know the plugs are new, as are the wires. Looks like they tried to maintain the problem away, and when they couldn't, they dumped the car. I think it would be a very good idea to clean the throttle body (NO air filter!). It also stalls when putting it in gear with the a/c on. It's my wife's car, and we work slightly different shifts, so getting time to diagnose and work on it is going to be a problem. Next time I will get to poke around under the hood will be (maybe) Saturday afternoon...

SW96 · 04-06-2008, 01:42 AM

Okay, just because I don't like Champion plugs, I put a set of platinum NGK's in the car, cleaned the throttle body, cleaned the AIC, performed an induction service, and replaced the O2 sensor.
Still has the problem. I've replaced the TPS, and hooked up a Genesys scanner to the car so I could view live data. Everything looks good, but it seems almost like I turn the ignition switch off momentarily when I step on the gas pedal. ECT sensor looks like it's working as it should, with relatively accurate temp data.

**Ssicarman** · 04-06-2008, 05:06 AM

You can't really tell if the temp sensor is any good from scan tool temp readings as the temp sensor is what sends that info. Have a look at the sensor connector and the sensor it self.
Corrosion in the connector terminals and or cracks in the plastic nose of the sensor all the reason you need to replace one or both.

RC1488 · 04-06-2008, 07:50 AM

Quote:

Originally Posted by Ssicarman

You can't really tell if the temp sensor is any good from scan tool temp readings as the temp sensor is what sends that info. Have a look at the sensor connector and the sensor it self.
Corrosion in the connector terminals and or cracks in the plastic nose of the sensor all the reason you need to replace one or both.

+1^^^

Also get rid of the Platinum plugs. Copper plugs are what you want. Any of the iridium, platinum, etc will just cause problems with the waste spark system the s-series uses. Ive seen where a car wont start all bc they had platinum spark plugs.
Simple = happy car = happy driver

SW96 · 04-09-2008, 10:24 PM

I am going to try the CTS Sunday (next time I can work on it). I'll probably get a set of Delco plugs while I'm there. The CTS is pretty inexpensive, and while I'm at it, I'm going to get the low side A/C hose (fitting on compressor leaking).

SW96 · 04-12-2008, 12:02 PM

Okay, my wife and I both got home from work a bit early, so I replaced the CTS, pigtail for it, and the spark plugs.
No joy.
It still "hiccups" when you first step on the gas pedal, sometimes even stalling.
Any further suggestions? Anybody had this happen, and if so, what was the fix?