Hesitation

[MichaelH]

I've been trying to get my '95 MTX to run like new. I'm almost there. I've replaced one O2 sensor, installed a new IAB/IAC and TPS, a new Walbro 190 LPH fuel pump, new fuel filter. It runs great, except for one annoying thing. It somtimes hestitates just a fraction of a second when I give it throttle. I don't think it's dirty injectors, because it runs great, otherwise. I have one expert opinion that it's a bad MAF sensor, or at least the sensors are dirty. That seems reasonable, as that wouldn't throw a code and I get no codes when running KOEO and KOER. The CPS and CID have less than 10K miles.
Any other ideas?

 

[NotSoSlowSHO]

plugs and wires?

 

[MichaelH]

NotSoSlowSHO:
plugs and wires?

They were new about 10K ago, too.

 

[SHO_Driver]

How about running with the MAF unplugged? See if it's better or worse.

 

[MichaelH]

SHO_Driver:
How about running with the MAF unplugged? See if it's better or worse.

Thanks. I'll try that. What should I expect? If it's better, then........? If it's worse?

Could a vacuum leak cause a hesitation?

 

[cyanmauve]

This may sound odd, and it most likely isn't your problem, but…

Take the plug wires off of the plugs. Look down the plug wells. If there is any oil, or liquid in the wells, this could be a source of the problem. Oil in the plug wells is indicative of bad valve cover gaskets.

Short of replacing the gaskets, you remedy the problem by can vaccuming all of the moisture out with a wet/dry vac and some small diameter tubing.

 

[MichaelH]

cyanmauve:
This may sound odd, and it most likely isn't your problem, but…

Take the plug wires off of the plugs. Look down the plug wells. If there is any oil, or liquid in the wells, this could be a source of the problem. Oil in the plug wells is indicative of bad valve cover gaskets.

Short of replacing the gaskets, you remedy the problem by can vaccuming all of the moisture out with a wet/dry vac and some small diameter tubing.

Thanks. I'll check that out, too.

 

[masho95]

You might want to check out the TPS sensor also. Check the voltage wire to see what you have at idle. I believe it should be as close to 1V as possible. Somewhere around .96V is good I believe. If it's way below, it could be causing that slight hesisitation at beginning throttle.

 

[SHO_Driver]

MichaelH:

SHO_Driver:
How about running with the MAF unplugged? See if it's better or worse.

Thanks. I'll try that. What should I expect? If it's better, then........? If it's worse?

Could a vacuum leak cause a hesitation?

If it runs better without the MAF plugged in you may have isolated the problem, meaning defective/dirty MAF. If it runs the same then look elsewhere.

Yes a vacuum leak could cause hesitation.