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1992 Ford Tempo Runs/Idles Rough, Low Power


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KRipp
New User

Sep 12, 2011, 8:06 PM

Post #1 of 10 (8389 views)
  post locked   1992 Ford Tempo Runs/Idles Rough, Low Power  

My father and I have spent the past two weeks attempting to pinpoint the problem with a 1992 Ford Tempo with a 2.3L 4 cylinder HSC engine with no luck. We are completely baffled as to what it could be, and would love it if somebody here had an idea.

The car starts fine when cold but will sometimes require two or more attempts if it was running recently. It runs rough and lacks power at all times, but gets worse when it is hot, to the point of stalling at idle. I can push the gas pedal to the floor and it doesn't accelerate any faster than if it were at half or less. The check engine light does not come on and there are no stored OBD-I codes. The exhaust also tends to smell of unburned gas.

Also, the radio sometimes dies at random and then works again. I don't think that's relevant, but I'll be complete.

We have tested the following things and determined that they are working properly:

MAF Sensor - When disconnected, check engine light came on and car ran worse, multimeter tests were fine.
Throttle Position Sensor - Smooth resistance increase
Fuel Pressure Regulator
Air Bypass Valve
EGR Valve - Blocked off from intake manifold and noticed no improvement
Ignition Control Module - Tested out with multimeter
Ignition Coil
Engine Compression - all 4 cylinders were 150 +/-5 psi, which is within the acceptable range
Fuel Injectors - These were ridiculously dirty and squirting fuel in a straight line, but did not improve performance at all after being cleaned.
Fuel Pump - Pressure at test port is correct, can hear it running when applying 12V
PCV Valve - Not blocked
Vacuum Hoses - Checked for leaks with stethoscope
Ignition Timing - Used timing light, marker lined up with 10 degrees BTDC, exactly the correct value.
Spark Plugs and Wires - Checked wires. Spark plug #1 was significantly worse looking than the others and the gap might have been a bit small. We had replaced the spark plugs before this and it didn't seem to help.
Plugged Catalytic Converter/Exhaust Backpressure - Ran car with exhaust connection to EGR Valve disconnected, no change
Air Filter - Checked/replaced

We have taken off the distributor cap and visually inspected it and the rotor and all appears fine. We have not replaced any distributor parts.

We also tested the intake manifold pressure and it was 16 in-Hg, which is on the low end of acceptable. It tested at 12 at one point, but I'm pretty sure we had something disconnected at the time.

Finally, about a month ago, the alternator failed and had to be replaced.

I have no clue what could be going on, and I'd be grateful if someone could come up with an idea.


(This post was edited by KRipp on Sep 12, 2011, 8:08 PM)


zmame
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zmame profile image

Sep 13, 2011, 4:37 AM

Post #2 of 10 (8348 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

what was your fuel pressure when it was acting up?


KRipp
New User

Sep 13, 2011, 4:13 PM

Post #3 of 10 (8340 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

Could you please clarify what you mean by "when it was acting up?" Do you just want the numeric fuel pressure reading we got when we checked it, or do you mean the fuel pressure coinciding with when we had a low manifold pressure?

Also, thank you very much for replying.


zmame
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zmame profile image

Sep 13, 2011, 4:19 PM

Post #4 of 10 (8338 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

Key on engine running, What is your fuel pressure?.


KRipp
New User

Sep 13, 2011, 5:12 PM

Post #5 of 10 (8334 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

~48 psi off the test port. The repair manual claimed it should be from 45 to 60.


zmame
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zmame profile image

Sep 13, 2011, 7:02 PM

Post #6 of 10 (8325 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

45-60PSI Engine Running
50-60PSI Engine off key on

When it's hot and not running good try to hold @ 2500 RPM with a vacuum gauge and see if the vacuum slowly lowers on the gauge.

Key on engine off backprobing the center pin on the MAP is it between 1.39 and 1.59V
remove vac line from vacumm and Apply 18 in-Hg to map sensor and make sure it holds.
Check vac tee at MAP and make sure there is Vacumm there.
Take off EGR and make sure it's properly seated.

Thats some things to try.


Discretesignals
Ultimate Carjunky / Moderator
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Sep 13, 2011, 8:07 PM

Post #7 of 10 (8321 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

What are the ohms on the fuel injectors? How did you clean them?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


KRipp
New User

Sep 18, 2011, 6:53 PM

Post #8 of 10 (8289 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

Sorry for the lack of a prompt response, this is the first day in a while I've had a chance to work on/check the car.

The injectors were between 11-12 ohms, with an expected reading of 10-18. They were cleaned by connecting a syringe with the needle removed to the injectors, filling the syringe with carb cleaner, and applying power in a short tap several times.

So, the tempo has a MAF rather than a MAP, I believe 1992 was the first year it was changed over. That said, you inspired me to do a more thorough test of the MAF and I got some very interesting results. While I said that the car ran worse with the MAF sensor disconnected, we may have gotten a bad result at that time (possibly because it was in the middle of a sequence of other tests, possibly for some other reason. We repeatedly tested the MAF tonight, and whether or not it was connected does not seem to have any impact on how the car runs. We then examined it, cleaned it, and tested it electronically. It gives a signal that starts at 1V and climbs smoothly with increased RPM, so it seems like it's working properly.

My current understanding is that this implies that the issue is either a) a vacuum leak that we have failed to find or b) the car is stuck in limp in mode for some reason. If it's b, my thought is that it could be a bad Engine Control Module, though it seems unlikely that the ECM would fail "just a little bit," since it properly lights up the check engine light in other cases when I would expect it to come on. Could a problematic sensor that we didn't test because it didn't seem relevant to our problem be triggering limp-in mode without lighting the check engine light? Is it possible for the car to be in limp-in mode without a check engine light at all?

I'm going to go and do some more testing, will update if I notice something new.


jeb1470
New User

Feb 24, 2012, 6:23 PM

Post #9 of 10 (7816 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  

Hey, sorry to bring this back from the dead... but I am having the exact same problems and have made pretty much the same checks.

Did you ever happen to fix your problem? Or does anyone have any more suggestions?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 24, 2012, 6:39 PM

Post #10 of 10 (7813 views)
  post locked   Re: 1992 Ford Tempo Runs/Idles Rough, Low Power  


Quote
Hey, sorry to bring this back from the dead.


Then don't............ If you need help with something, then you need to start a new question. Don't respond to old threads and don't hijack someone else's question.



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