I have a 95 STS and when I give it half throttle, there seems to be some hesitation and it's a little jumpy. Do you think it's misfiring? Should I get a compression test? Possibly the fuel injectors? But when I mash the petal to the floor it takes off. Other than that it's money! Thanks for the help..


Hello? Anyone out thurr?

 

Hi
I am having the same problem as you have on my 93 STS.
In my case is the EGR valve, not that is brocken, but it is something to do with the connector or the wiring.
In the OBD you might find error P036 for that.
I have removed the valve checking for the alleged carbon clogging, it was clean, checked for sticky EGR valve, but it moved really free, but the replacing it back and cleaning the connector seemed to have taken away the problem until the engine started warming up to a typical operating temperature.
It was then that by doing the recommended testing via the PCM override turned out the valve wasn't raising to the required height and that it was clearly a problem with the contacts on the valve.
I will be cleaning these contacts and degrease them really well but if it is something do to with electric cables that are worn and have somehow melt does anyone know where the stated CKTS 1476 and 474 and PCM connectors "2C/2D" are?
The other effect of this problem, I really hope to sort out myself, is that the engine makes a HUGE va*** like noise when accellerating hard and small tiny explosions can be heard. That's anopther indication the pintle is not fully raised, but the small explosions coming from the exhausts?
Until I get this sorted, am I ruining the engine somehow?
PMPN8EZ, see if you get any error messages in the OBD.
If you've seen the orange light for the Service Engine Soon you'll be certain will be displayed.

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And excellent news!
It all turned out to be related to the EGR valve.
I have thoroughly cleaned the pintle shaft and it was back as new.
I think the EGR valve is bound to last forever if it is kept cleaned.
Then, you would not believe it, the spark plugs. Carefully cleaning them dissolving the carbon deposits without scratching them and guess what? This car is flying again.
The 2000rpm to 3000rpm hesitation went away with the cleaning of the EGR valve.
The 4000rpm to the 6500rpm backfire and mild start delay from cold went away with impeccably clean spark plugs.
No electrical problem in sight as I was worried.
My car has its 300hp back on track and after I have changed the oxygen sensors, at 60MPH I am even getting 14KM per litre and 8Km per litre stuck in traffic!
Better keep this quiet as people has to keep thinking I go around with a gas guzzler, which it's in itself a status symbol, you know.
You stay all well

 

Although it many not be the same problem I had in a 94 Fleetwood, I suggest that you use some carb cleaner and a small brush to clean the butterfly and the area around it in the air intake.