Running Rough/Misfire

Tiny
INDYRJC1
  • MEMBER
  • 1991 FORD TEMPO
  • 2.3L
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 108,000 MILES
We have a low mileage (108K) for its age 1991 Ford Tempo (2.3L 4 cylinder). It has run great for a long time. However, within the last few years it has exhibited some strange starting behaviors. Sometimes the engine will start immediately and sometimes you can crank it for ten or fifteen seconds and it won't start. However, if you simply shut off the key and try again it usually starts right away. The car then runs just fine. At least it did.

We took the car on a long trip recently and everything was fine until we stopped for gas. As soon as we pulled out of the station the car started bucking under acceleration and running rough. It did keep running, however, and we were able to complete the trip in spite of the problem; again running at highway speeds although it was hard to get back up to speed after a stop. At first, we assumed that we had gotten some bad gas and I added a can of Heet in case we had picked up some water when we refueled. I also replaced the under the hood fuel filter just as a precaution (I cut the old one apart and didn't really see anything out of the ordinary). The car ran fine for a day or two and then we started home. Just like before the car ran smoothly until we stopped for fuel. After filling the tank the car started acting just like it had before. And just like before even though the car was bucking and misfiring we were still able to drive at highway speeds and get home safely.

We have no "Service Engine" light but I went ahead and ran the test and got "11" as the code which means there is supposedly nothing wrong with the EEEC-IV system. And as a point of reference I had replaced the Fuel Pressure Regulator at 86K miles in an attempt to help with the earlier staring issue. It did seem to help at the time. And I also replaced the EGR Valve Sensor at 76K miles after getting a code for that problem.

And today my wife got in the car for a short trip and the car died in the driveway as she backed out. She put the transmission in neutral and tried multiple times to start the car but it would not run. However, I got in the car and turned the key to the OFF position, Turned it to ON while listening for the fuel pump to come up to pressure and shut off (which it did), and then moved the key to START. The engine started immediately and I was able to put it back in the garage so I could try to figure out what is going on. We've always done all of the required service on the car regularly (oil changes, air filters, etc.) And just before the trip where the problems started put in new spark plugs.

I have wondered about the EEEC-IV Engine Control Module itself. Could it have some intermittent circuit issue that makes it sometimes not allow the car to start, or maybe make it run rough. Or maybe the two issues aren't related at all. At this point I'm open to any new ideas that might make the car reliable and on the road again.

Thank you.
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Sunday, December 7th, 2014 AT 5:02 PM

8 Replies

Tiny
HOMER1967
  • EXPERT
Based on the symptoms and the info you have provide, I would suggest a fuel pressure test. The fuel pressure with the key on engine off ( koeo) should bebetween 50-60 psi. And with the engine running it should be 45-60 psi.
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Sunday, December 7th, 2014 AT 6:43 PM
Tiny
INDYRJC1
  • MEMBER
Fuel pressure with the engine off (koeo) is 55 psi. However, after about 30 seconds or so (no more than a minute) the pressure bleeds off to zero. With the engine running at idle the pressure is right at 45 psi. If I pull off the vacuum hose to the fuel pressure regulator with the engine running the pressure goes up to 55 psi again.

Thanks.
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Monday, December 8th, 2014 AT 4:07 PM
Tiny
HOMER1967
  • EXPERT
The rise in pressure when disconnecting the regulator is normal. The drop off is not though, I would have to say either you have a bad fuel pump assembly or one or more of the injectors are leaking down.
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Monday, December 8th, 2014 AT 5:27 PM
Tiny
INDYRJC1
  • MEMBER
I went ahead and put in a new fuel pump. The fuel pressure numbers are about the same as before (KOEO 55 PSI and KOER 45 PSI). However, when I shut off the key on KOEO there is very little leakdown now. After nearly an hour the pressure gauge still showed 15 PSI. Before the fuel pump change pressure would go to zero in no more than a minute.

And the fuel pump change seems to have cured the starting issue. So far, the engine has started instantly without any long cranking every time.

However, the car still has the hesitation/miss when being driven. There will be periods where it seems to run just fine only to start jerking again. This is very noticeable from a dead stop although it can occur at any speed. I'm starting to think that the long cranking at start was mostly a separate issue from the missing problem.

Does it still make sense to check out the individual injectors even though the leakdown rate has improved? Or is there another direction to go based on your experience with this kind of problem?

Thanks again.
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Sunday, December 14th, 2014 AT 1:41 PM
Tiny
HOMER1967
  • EXPERT
Have you checked the sperk plugs yet?Do you know how old they are.
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Monday, December 15th, 2014 AT 3:05 PM
Tiny
INDYRJC1
  • MEMBER
The spark plugs were new about a month ago.

Thanks.
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Monday, December 15th, 2014 AT 4:17 PM
Tiny
JP2175
  • MEMBER
Had same issues with a 1990 tempo. Only under load would it misfire. Couldn't get to speed safely. Chased problem and couldn't find answers online. Turned out the throttle body had a lot of buildup on the back end. Had it taken apart and cleaned. Car runs great now
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Wednesday, March 21st, 2018 AT 2:19 AM
Tiny
KEN
  • ADMIN
Great addition to this thread! Please feel free to help out whenever you are on the site :)

here is a guide to the repair you did

https://www.2carpros.com/articles/throttle-actuator-service

Cheers, Ken
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Friday, March 23rd, 2018 AT 10:19 AM

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