Schrecken

I tried searching around, but I couldn't really find what I was looking for (sorry if this has been covered multiple times)...

When I bought my car, the seller told me that the previous owner before him didn't drive it much and it had been sitting for a while. He talked about how when he first got it, he was having trouble with the motor kinda "hicuping" at random rpms and speeds. He said he changed the fuel filter and it looked pretty nasty, and he was planning on cleaning the tank since it had been sitting, but he noticed a big difference right away. Well, now that I have the car, it seems to be doing this a little bit to me. Does it sound like it is probably the fuel filter again? What are some things I should do to clean the fuel system?

edit: it is a 1990 GXL, stock.

boosted1205

iTrader: (9)

Well, anytime you pick up a car there's no telling WHAT the previous owner did to it. Try a full tune up and check the TPS. It sounds a little out of whack. When that is off, it does all sorts of weird things when driving.
If you suspect bad/old fuel, drain it out and change the filters (fuel pump and near the engine).
Take a day off and clean out the connections such as the engine grounds.

Schrecken

Thanks, pretty much what I figured from what I had read, just wanted to see if anyone else had a solution to this specific problem. I am sure that stuff will take care of it though.

SureShot

Using test lights or voltage at idle readings will get your idle setting perfect, but you could still have a worn out TPS resistor.
-The golden test:
Pull the TPS connector off.
Get an analog (needle type) VOM set to the 1K scale.
Connect it to the pins for the orange & green wires.
Open the throttle enough so you can test the TPS plunger through its full stroke.
As you work the TPS plunger in & out, the meter needle must swing smoothly from ~0 to ~5K ohms.

As the TPS wears, it can give non-linear or inconsistent signals to the ECU.
A worn out TPS may give 1K ohms at idle, but have a drop out further up the scale.
A drop out at mid scale will tell the ECU to idle at that point & give a fuel cut hesitation.
I had one go open at the top which made the S5 ECU go nuts, giving random fuel cuts.

I have fixed a dirty TPS with spray contact cleaner, but after 6 more months it wore out completely.

Schrecken

I don't think it is the TPS because it seems to happen so randomly... it isn't happening at the same point every time. That, and it happens pretty rarely, maybe twice each time I go driving... but it isn't major, it kind of feels like the fuel gets cut for a split-second. That is why I was thinking it had something to do with the fuel system, especially since the car was sitting for a long time. I will try to test the TPS this weekend though, thanks.