hi guys,

have an 89 formula with a 305 TPI engine. exhaust smells like raw fuel, car overheats if left idling too long, and when press the accelerator there is a noticeable lag in RPMs before it revs up. The lag is only there after it's warmed up.

getting desperate, any thoughts?

 

A factory service manual.

bad injs, leaking fuel psi reg

What is the temp of your over heating? They run at 240 degs

 

I have the same problem with my t/a the richness is soo bad it makes your eyes burn, but instead of lag my car will just fall on its face when I give it gas. I have replaced parts with no luck..

 

240? No way thats normal operating temp...it usually runs around 190.

How could you tell if it's a leaky FPR? I was thinking o2 sensor or MAF?

 

I think stock they usually run around 220 degrees. Sometimes you can tell the FPR is leaking by disconnecting the vacuum hose and seeing if there is raw fuel leaking through. You can check if the injectors are leaking by clamping off the return line, jumping the fuel pump, and clamping off the feed line. If it holds pressure and your injectors ohm out ok then they are probably fine. Also, if you can build or get your hands on a ALDL->USB cable, it's really a great tool for all sorts of problems. Being able to see what the computer is seeing really is an invaluable tool.

 

The stock T-stat is a 195. The second fan (if you have that) comes on at 239* or so.
So I should have said, the normal operating range can be from 200 to 240+ degs.

 

Thanks, all good info. My fuel lines are all steel so I can't pinch them

I think it is some sort of sensor though, none of the symptoms are there on the first start up, when the car is cold (and in closed loop mode?) I think when it flips to open loop and starts reading feedback from the various sensors is when I notice the lag especially and the fuel smell. When does it flip to open loop?

 

If it's a 305 TPI then it should have rubber lines near the steering box which connect the lines from the engine to the lines on the body. You can pinch these assuming they are not dry-rotted (which if they are you should replace them anyway). And for clarification, open loop is when the car is cold and it enters closed loop when it heats up and the O2 starts working.

 

You can check to see if you have leaky injectors by pulling the plugs after the engine runs for a couple of minutes. If you have a wet cylinder you have a leaky injector. Also you might want to check the regulator diaphragm they sometimes have a tendency to dry out and crack. Check your 02 sensor as well.

 

I have the exact same issue right now and I am 99.9% sure its a plugged cat. (Mine also runs rich and falls on its face when WOT) I am hearing some rattling around coming from the cat. I am replacing this week with high flow cat or test pipe and will report back if that was it.

 

tks for clarifying open vs close. Are there any other sensors besides o2 that the computer reads from in open loop? and how would i test an o2 sensor?

Kaotik - that is interesting i hadn't considered that, let me know what you find!...i have dual cats and they are hi flow off an audi S4 supposedly so not sure that's it

 

Any luck kaotik?

Would a bad o2 sensor cause overheating?

 

Check 02 . ....if it's running rich it's getting a lean signal calling for more fuel too much fuel and a clogged cat will cause a possible fire and/or over heat

 

how do you test an 02 sensor? i have a multimeter...

or do i need to get a laptop and plug into the cars computer?

 

You need to put your vom on vdc once the engine is warmed up and the O2 is 5-600f it will swing. 450mv is dead or inactive higher voltage toward 1v is richer below the swing point is leaner. The best way to see it swing is a analog vom.

 

Ok just to clarify as i am not an expert with a multi meter...i need to put it on voltage setting, assuming i back probe the wire and watch the voltage.

so 450mv or below is dead...too close to 1volt is running rich.

where is the sweetspot?

 

You right unplug the purple wire. One side of your vom red to the o2 wire. Blk to battery negative or good ground. A active o2 will be fluctuating up and down . Often time with header swaps a 3 wire heater o2 is needed to get the o2 hot enough to start functioning. Another test to see if the o2 is working is called field service mode. This is when the aldl is jumpered a to b. With the engine running it will blink rapidly for closed loop operation. Slower when not in closed loop.

 

Sry if i misunderstood but if i unplug the wire, how am i going to get a reading from the sensor?

also, the field test you mentioned is essentially only good to make sure the car is flipping in to open loop, correct? Is it okay to run the car with it jumped? i always thought it wasnt

 

Yes... I replaced the cat with a test pipe and she runs great and pulls strong. There was a HUGE chunk plugging the outlet. Runs great now... thanks