Thread: 1991 G.P SE 3.1 runs sluggish when cold??

Hello, I have a 1991 GP 3.1, I recently replaced the Fuel Pump & Filter Proactively, and installed new Plugs and wires, new TPS and knock sensor
also this summer. Now, when the Car is Cold, it has a very distinct Miss
to it... until it warms up. I thought maybe the Fuel regulator might be bad,
but checked the pressure and it's within tolerances. I sprayed Brake Clean
around Intake Gasket/ Vacuum lines...Nothing. The Fuel Economy is really
Bad, since the new Pump was installed. (15 mpg)
It is not throwing a code out either??
When it hesitates Cold, I can Mash her down, and it will take off.
Any Ideas on what else it could be??
(I checked the Temp sensor also.)
It runs great, when warm!
Thanks, Matt.

I ran 2 Tank Fulls of Injector cleaner through it already.
This Morning, when it was Cold, I sprayed it with Brake Clean,
and there was No change again. (while running.) (Possible Vacuum leak?)
I drove it and it ran Great!?
I replaced the TPS, this Summer, with a cheap one from O Reilly's
and I am wondering if this isn't the culprit?? (No Codes though.)
I am thinking either it is a Intake Gasket leak or something with
the TPS.?

change the ECT sender.

you said its only when cold and fine when warm...

If the Coolant Temp sensor was bad , wouldn't it through a code?
"SES"
There are no codes being thrown?

Mine didn't throw a code.

Read low when at running temp.

Car had misfires at idle. Ran great once warm.

Now its smoother just by changing the ECT sender.

Thank You for that Information, Matt!
When I get a Day off from Work, I'll try replacing it.

I disconnected it, to Test it, and it sent a "15" code...
so I thought that it wasn't the problem... but you are telling
me that it might just be weak.

I'll let ya know the results, when I replace it.

I dont think OBD lets you do this but with OBD II you can see what the PCM reads as the engine temperature.

Mine was reading 4* to low. Misfired when cold as a result.

If the car has a FPR i'd suggest putting vacuum on it. Although that would result in misfires regardless of running temp.

Also does this vehicle have a vacuum advance?

Well, I replaced the Coolant temp. sensor, and it still
runs like crap when Cold. :-(
It doesn't throw a code.

Did you tap on your MAF when its acting up?

I'm wondering if a plugged Cat. could be my problem??
It has the original Cat. on it.
??????

you could unbolt the downpipe and see how it runs.