cooling issues

[SouthwestSpider]

I replaced the sensor, it looked like the readings were off at the high end, under 200 ohms. I replaced the connector because it was old and loose.
Started it - ran it to hot, and disconnected the fan to confirm that the fan wasn't interfering. No change no problems. Reconnected the fan let it run. Then shut the car down and left it for a half hour.
Started it and it wouldn't let me throttle up. It would idle but with a slight rise and fall of rpms. Eventually - without touching the throttle (because it would stall out if I gave it any throttle) the rpms climbed to 950 and it smoothed out. Once at the smooth running stage it would allow me to throttle up and it ran great.
I sprayed a little silicone lubricant into the throttle positioning switch. I wonder if there is a problem at the MAF with the door not opening up or opening too soon. It acts as though it's choking out (when it's idling rough and I give it gas).

[RRoller123]

You can just see the marks in this pic where the AFM door was dragging on mine. A little judicious sanding with 400 grit paper took care of it, and the car ran noticeably better afterwards. You can also do surgery on the innards if necessary, but maybe check the door first for free swinging.

[SouthwestSpider]

Terrific help there RRoller. I'll take it apart and see what's up. Thanks!

[RRoller123]

The surgery is not as bad as it looks. Basically, clean up the thick film resistor tracks, and adjust the wiper arm down to push the contact points further out onto the TF. It made an amazing difference in how smoothly my car runs. It used to buck intermittently and it was not very smooth.

Pull the top and here are some pics that may help. Ask as many questions as you would like, there are many here who have done this AFM surgery successfully.

Loosening this bolt (single yellow arrow) and sliding the wiper arm down a little pushes the contact wiper out onto new TF resistive material. You can see the worn tracks (2 yellow arrows)

[SouthwestSpider]

Okay - I have the MAF off and there is a little oily residue, but no marks to indicate that the door drags. The top is held together with what looks like silicone. Do I cut through that silicone to remove the top. And when I do - is there a specific silicone I use to reattach it?
I will wait for your answer before I take it apart further.
Much thanks for your time and patience!
Would the heat and cutting out during a high temp evolution have anything to do with the MAF?
Just recently I shut the car down, it hadn't completely cooled down but when I shut it off the fan was running (as they do) and approximately a half hour or less later, I started it. It started and ran at idle but would not let me apply any throttle. After running roughly (up and down rpm) it smoothed out and I could use the throttle. It then behaved as per normal, running like a little champ. This confounds me.

[Indyandy]

Maybe I am off, but have you checked the fuel filter. This seems like a fuel issue to me.

[So Cal Mark]

I'd check rest fuel pressure and see if the system holds. If not you might have injectors that are leaking and getting spark plugs wet.
Just so you know, you have an Air Flow Meter, not a MAF. Big difference in how they work

[SouthwestSpider]

Darn it - I put the M in the wrong place. Thanks Mark.

[RRoller123]

Check the door swing mechanically by moving it through its full motion to make sure it is not dragging anywhere. Hold it in the same orientation that it is in when it is installed in the car while doing this. The cap is held on by some sort of silicone, yes. I used hi-temp RTV (black if you don't want it to show) when reinstalling it. Careful cuts with a razor knife and prying with an awl or small screwdriver will get it off, but there is a lip that you need to be careful not to damage. I biffed mine up a little before I realized how it was shaped.

[majicwrench]

I'm always concerned to see people take thing apart when really, they have no clue if it is the issue or not. Dinking with afm is likely to cause more problems than solutions. When car is acting up you need to TEST SOME THINGS. Fuel pressure would be a good start.
Just me,
Keith

[RRoller123]

Yep, I agree, but it is probably a given in this particular instance that every one of our cars, being this old, would benefit a great deal from moving the wiper out onto new TF material. But this may be a side issue, and you are right that it is better to diagnose first.

[SouthwestSpider]

I would be delighted to check my fuel pressure. If I knew how. Where do I start?
The other question I have is - how is it that the car runs roughly, stalls - as if it's choking out, when it's hotter than normal - how does that relate to fuel flow? Wouldn't it run rough if it was cold also?

[majicwrench]

Any one trying to maintain their FI cars should have a good fuel gauge. Then T it into the line at the cold start valve.
Obviously something changes tween hot and cold. Could be many many diff things, that is why you need to start testing to see what is lacking. If fuel pressure is fine, then you look elsewhere. Shotgun approach will likely create more issues than solutions.
A quicky test, pull vac line at pressure regulator with car running rough, does it get better?? Now with vac line still off, get can of carb cleaner with little hose and piss into line, again with car running rough. Better?? or Worse??
Keith

[rlux4]

First off let me say that I'm not disagreeing with you Keith, I appreciate the benefit of your knowledge that you freely give here.
That said, I would add a caveat; If it's not cold you wouldn't need to rig a T into the cold start line, by disconnecting it at the valve you can put the pressure gauge straight on the fuel line using a standard barbed nipple fitting on the gauge. You know, but others may not, the cold start valve is only a factor in the first few seconds of a cold start.
A pressure tester for liquids is what's needed guys. NAPA should have them, I forget where I got mine. Here's a picture of it;

Notice the clear plastic tube. It's a bleed off line. Getting one like this is the safest. You don't get the burst of pressurized fuel
when you go to disconnect it. Be aware that when you disconnect the line from the cold start valve you'll have to be careful because of this. I wrap a rag around it to contain the small amount of fuel spray.
Ron

[RRoller123]

Harbor Freight Tools has an inexpensive combination vacuum gauge/fuel pump pressure tester that I just bought for use as a vacuum guage. I think the kit was like 20 bucks, with a bunch of fittings and a vacuum T.