Hesitation @ 2k RPM

[Darkgh0st]

I bought a cable and I'm running the datamaster software demo. I checked the TPS sensor and it seems to have a clean signal. Not sure what else to check. It runs fine cold, and pulls hard @ WOT. The only problem is 2,000RPM where it starts bogging down and hesitating. Any suggestions?? TIA

[pletner]

I've got the same problem! Anyone know what the heck this is?

[STL94LT1]

Sounds like a closed loop problem, check your o2 voltage.

[tjwong]

Originally Posted by STL94LT1

Sounds like a closed loop problem, check your o2 voltage.

Scan your ECM and check the o2 voltages when the car is in open loop and when the problem shows up. It sounds to me like the car is leaning out for some reason, and if it is then the o2 sensor voltage will dive down well below .450mV. If it does that then we have to address why. It could be a MAP sensor that is giving an eroneous load signal, for instance if its bad it could report an lower than normal output which would indicate a higher than normal vacuum which to the ECM would mean a lighter engine load. which would mean that the ECM would fuel much leaner. Also it would be a good idea to check your fuel pressure at the problem RPM. MAP sensors are typically a very robust sensor, they don't go bad very often.

Just remember high vacuum = <45 Kpa and that also means <2.50 Volts. Low vacuum = > 45 Kpa and > 2.50 Volts. If the MAP sensor is the problem it would show up hot or cold in closed or open loop. The MAP sensor is they primary control element in a speed density strategy. If you have a MAF strategy then that sensor is the primary control element for engine fueling.

[rick lambert]

I had a similar problem in my 87, at 1800 RPMs. I used a noid light to make sure all the injectors were getting the signal...turns out I had one bad injector pigtail. Up to that point I had done an enormous amount of TS.