mauijerky

I also recently acquired a 91 RS. Went through everything trying to fix a high idle issue, then a similar issue to what you are experiencing. High idle was a bad pcv valve allowing to much vacuum past the valve, also the grommets on the valve covers were hard and dried out. Then the erratic idle and basic running like crap was the short rubber hose that attaches the fuel pump to the hanger assembly. The hose was very mushy and had a slit down the side of it. The pump was working fine but most of the fuel was just going right back in the tank. Since I had it all apart I put in a new pump. My 91 RS runs awesome now!! Although, you probably already pulled out the fuel pump by the time you read this.

morgsie

iTrader: (1)

Get AC Delco p/n EP241. This is the TPI pump and an excellent upgrade from the stock TBI pump. Always install a new sock and fuel filter. It's amazing how much easier troubleshooting this era of car is when you can hook up a fuel pressure gauge. Good luck.

Barlow8869

iTrader: (1)

had the same trouble with my 2.5l s-10, like some others said, i dropped the tank and found that little piece of hose split ... had i not taken apart my injectors and forgotten to put a seal back in one, i may have been looking for a long time ... lol

joerotelli

I just bought a 91 rs with 305 tbi changed plugs,wires,battery,fuel pump,fuel filter. Started the car it wouldn't idle by itself had to hold throttle half way after about maybe 3 minutes finally got it to idle on its own idled extremely rough and then just died, car won't restart wait 20 min the car finally restarts idles rough but on its own then it was like a switch turned on and the car ran very rich. Also I hooked the car up to scanner pulled electronic spark timing should I check timing on distributor also car pops from exhaust

joerotelli

I just bought a 91 rs with 305 tbi changed plugs,wires,battery,fuel pump,fuel filter. Started the car it wouldn't idle by itself had to hold throttle half way after about maybe 3 minutes finally got it to idle on its own idled extremely rough and then just died, car won't restart wait 20 min the car finally restarts idles rough but on its own then it was like a switch turned on and the car ran very rich. Also I hooked the car up to scanner pulled electronic spark timing should I check timing on distributor also car pops from exhaust please help wife is screaming

mauijerky

I'd start with the ignition module inside the distributor. Pull it out and you should be able to have it tested at your local parts store (the one I work at does). If that checks out then you might have a bad EST module.

IrishGreen

UPDATE:

I did not want this to be yet another "dead thread" so I am posting our latest update. My son and I (both novices) tried to replace the fuel pump ourselves, but with just jack stands, a little knowledge and cheap tools, we surrendered and towed it to a local garage. They are putting in a new AC Delco pump and sock for $125. That's a deal to me.

One thing we discovered was that if we dump a lot of starter fluid into the throttle body the car idles and can actually be driven. But as soon as the starter fluid is burned up it goes back to its old ways of the loping idle. So is this indicative of a bad pump causing the idle problem? The evidence seems to point that way. As I stated in a previous post, our fuel pressure held steady at 5psi when it was last checked. At idle or dumping the throttle, it never moved.

Anyway..... we hope to have the pump replaced by the end of the week and will post what the results are. My son has learned to be patient when working on an older car, but he is ready to take his prize out for a spin. Wish us luck.

Caveman305

iTrader: (8)

If it will run smooth on starting fluid, fuel delivery is your problem

Sucks you guys had to throw in the towel but its understandable if using hand tools with 20+ year old rusty bolts to fight with

Thats definitely a steal if that is the install price!

IrishGreen

UPDATE:
I don't want to get too excited, but the car is running great after the new fuel pump installation. I am currently putting in new plugs/wires and cap and rotor. They all had signs of wear and needed done. So if it all holds together, I believe that our loping idle has been solved (this time).

So to Recap:

New MAP Sensor $68
New IAC Valve $32
New EGR Valve/Selenoid $82
New O2 Sensor $16
New CTS $18
New TPS $38
New Fuel Filter $27
New Fuel Pump/Sock $91 + Labor $125
New Cap/Rotor $47
New Plugs/Wires $130 + Labor $60

Grand Total= $539 + Labor $185 = $725

All that is left is new brakes (pads/rotors/calipers) which should bring us in right around our $1000 budget total. Thanks and major respect to all the people who helped us along the way. I am sure we will call on your talents again.

Caveman305

iTrader: (8)

glad you got it straightened out!

you guys are really going to enjoy this car

IrishGreen

The car is running very good although the idle is a bit high. I'll have to try to figure that out soon. Couple small issues popped up of course as soon as we fixed the loping idle. The heater fan doesn't work anymore and a couple times the ignition key won't start the car. After you wait a while it works again. Any input or should I start a new thread? Merry Christmas to you all.

mauijerky

High idle is caused by vacuum leaks, bad IAC, or bad CTS. You already replaced the IAC and CTS. So maybe vacuum leaks. Although, there is a IAC reset process that will ensure the pintle is positioned properly. Short the two pins on the ALDL connector to put the car in diagnostic mode. Turn the key to the on position. The IAC will bottom its self out and hold it there until you take it out of diagnostic mode. If you unplug the IAC while bottomed out, it will stay there after being taken out of diagnostic mode. Leave IAC unplugged and start car after removing jumper from ALDL connector. Car should idle 500-600rpm. If idle is still high then you have vacuum leaks. Turn off engine, plug IAC back in. Next time you start, the IAC will be properly positioned. My vacuum leak was the pcv system. My idle dropped down when I temporarily plugged off the PCV vacuum line.

As for heater fan, I am assuming you mean the blower motor for the vents. If the fuse and circuit is good, then you either have a bad blower motor resistor or a bad blower motor. The resistors tend to go out more often than the motors. Or it could just be corrosion at the resistor connector.

My car is also being a little wonky with the Ign switch, I haven't dealt with it yet, though. I'll just bump the key a few times and it works. The cause is either the switch, connection, or bad solenoid. Also, chevy starters are known to have problems when hot.

Hope this helps