Problem - 92 RS 3.1 takes 3+ times to catch when cold starting (Strong starter, just won't catch). Once warm it starts first try. Drops idle and hesitates when accelerating from a stop. At cruising speed, slight hesitation when you accelerate, takes off great after a few secs.

Already did the following: plugs, wires, cap and rotor. TPS, IAC, CTS, PCV, oil and filter, MAP sensor. Replaced all vacuum lines that were rotted. Trying to get old O2 sensor off to replace (any tips would be appreciated).

I am guessing one or more of the following:

1. O2 sensor (heard that this can be problem but I thought the sensor only signals the ECM at operating temp).
2. Fuel filter (previous owner supposedly replaced the fuel filter but no guarantees).
3. Ignition coil (starts fine warm so I don't think this is the problem).
4. Fuel pump (I really don't want to drop the fuel tank to pull the pump. I hope someone tells me that it is not as big a problem as it sounds).
5. ECM (been wondering if my ECM is bad, I have a cooling fan problem too, I had to jump the cooling fan relay to keep fan on all the time).
6. Fuel injectors (probably need to be pulled and cleaned or replaced, but would this cause my problems?)

I have been reading the forums and I am really impressed with all of the great information and positive feedback everyone has. Seems like there are alot of really experienced people here. Thanks for the feedback.

 

I'm thinking FPR, or maybe you hooked it to the wrong vacuum source, otherwise probably pump, injectors or ignition timing.

 

Start by checking the fuel pressure when running and not. Should be between 37 and 47 PSI and should hold for 20 minutes with the pump not running. I've had a set of injectors that would bleed off the fuel pressure in less than 5 seconds, and it would require starting fluid to start sometimes. That set of injectors is being kept as spares (I'm sure there is at least one good one in there).

 

Thanks. I'll check the FPR. The manual says that the fpr is not serviceable, just to replace the whole setup. Is that true or can I just pick up the regulator?

I plan to take the injectors out and clean/ evaluate them next. Thanks for the advice. Keep it coming and I'll keep updating.

 

FPR is serviceable. You have 2 options doing this, either get a security T10 torx bit and potentially break the head off in one of the screws, or punch the pins flat in the screws and use a regular T10 bit. However, like I said above, you won't know anything about what could be wrong with the fuel system if you don't check the fuel pressure,

 

OK, an update.

Checked fuel pressure. 0 with ignition on. approx 20 with engine running.

Turn engine off, almost immediately back to 0! Started looking around and found oily gas on one of the fuel lines in the back. I assume it is leaking and thats where i am losing pressure. I guess I will get the fuel lines replaced.

Changed FPR and had no effect. Double checked and I have all of the vacuum lines replaced.

 

Yeah if the FPR and pump are good, which the fpr definitely is since you replaced it, and the pump probably is from the sound of things it would be a leak, if you know the location of it you CAN just splice in some rubber fuel line, though if you can afford to I suggest simply replacing both lines all the way up to the engine bay.

 

I wouldn't just patch the fuel lines unless you're in a real pinch... Unless someone did something to damage the lines, they're probably rusted, and there may be rust in other spots along the lines (under the clamps, especially).

 

Hence my suggestion to completely replace if he can afford to, some of us have to cut corners sometimes unfortunately

 

And you may get hosed for clamps and body brackets... The brackets are a pain and may end up broken when the lines are removed.

 

Thanks for the help guys. Plan to replace the fuel lines this weekend. Gonna try to be careful with the clamps, but i have made some custom clamps to replace them if needed.

still trying to track down where the hesitation and stalling is coming from. I have a exhaust leak close to the engine I think. I've been trying to get the O2 sensor off, but it is stuck hard. Any ideas on removing it? The car is running pretty rich, so I think the O2 sensor is a problem.

Keep the advice coming folks, I would love to get this job moving to body work and paint before the summer is out.

 

With a fuel pressure of only 20 PSIG, that will cause a lot of driveability problems.

If you have a fuel leak, start by fixing that. Repair all known problems before replacing anything that is questionable. You just may repair all the ails, by fixing the known bad items.

If the repaired fuel line doesn't fix it, and I'm sure it won't, because losing 203 PSIG, due to a leak would be extremely noticeable, as in large amounts of fuel on the ground when ever the pump is running, replace the fuel filter. I'm sure you'll replace the fuel filter when you're replacing the fuel lines anyway, but this had to be said.

If you still have low pressure, I would perfoem the dead head test, which is to close off the return the line, while the engine is running, and watch the fuel pressure, if it doesn't go up, well beyond 43 PSIG, (should be closer to 80 PSIG or so when dead headed!), then look at the pump being the culprit.

It wouldn't hurt to inspect the injectors, to make sure they are functioning properly, but I haven't personally seen a problem with injectors very often.

 

about your O2 sensor,theres a product that i use for just these kinds of things,its called "PB blaster" it works very well .you may also CAREFULLY use a torch to heat the manifold around the sensor,not the sensor itself.sometimes i just have to remove the manifold itself and go at it.either way be sane ,be safe and dont burn down your car

 

Oh yeah, I got so into the fuel side, I forgot about the O2 sensor.

If the sensor won't come out when cold, then I will run the car so that the exhaust is nice and warm, then using what ever wrench, socket, combination, etc, crack it loose, then let it sit and cool for a bit. The hard part is getting the sensor broken loose, once that is done, it will come out when the exhaust is cool. You can take it completely out with teh exhaust warm, but sometimes the threads will cool quickly and tighten on the sensor, causing it to jam or worse, strip the threads out. It's a delicate touch, to know when this is happening.