1992 Toyota Tercel loping when idle and fuel pressure

DLMILA0727

MEMBER
1992 TOYOTA TERCEL
4 CYL
2WD
MANUAL
134,000 MILES

I am needing to find out what is causing my car to have a DEAD SPOT when it is just idling? Also why did the fuel pressure drop when throttle pressed? Is it the fuel pump? What should the fuel pressure reading be with car running? I anxiously await your reply. If you help to solve this mystery, I will then make a donation.

5 Replies

MASTERTECHTIM

MECHANIC
4,750 POSTS

If you have a fuel pressure gauge on rail and pressure drops when stepping on the gas, what you need to do is crimp off the return fuel line and see if the pressure goes way up. If with the return line crimped and fuel pressure still drops then replace your fuel pump. The way the system is supposed to operate is when you accelerate the fuel pressure should rise. Check this then get back to us.

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Friday, February 15th, 2008 AT 4:29 PM

RASMATAZ

MECHANIC
75,992 POSTS

The fuel pressure should be 41-42psi when the +B to Fp terminal at the diagnostic check connector when jumpered.

The regulated pressure should read when engine is running should be 33-37psi and without vacuum at the pressure regulator should read again 41-42psi.

Might also want to test the coolant temperature sensor/idle air contol valve/throttle position sensor.

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Friday, February 15th, 2008 AT 4:39 PM

DLMILA0727

MEMBER
3 POSTS

I previously asked the question listed below. We have checked the regulated pressure when engine is running and it is 33psi. When we check it without vacuum the pressure regulator reads 42psi. When we crimp off the return fuel line the fuel pressure jumps up, indicating it is not the fuel pump. We have put new plugs in, wires with distributor cap, rotor, fuel filter, fuel pressure regulator and even checked the timing, but we still have a lope or dead spot when idling and when you stomp on the gas, the engine bogs down to the point of not running or even dies. When we pulled the #1 plug out to check it, it showed signs of fuel running to RICH. This has us puzzled. What is going on? What do we do next?

Question previously asked:
I am needing to find out what is causing my car to have a DEAD SPOT when it is just idling? Also why did the fuel pressure drop when throttle pressed? Is it the fuel pump? What should the fuel pressure reading be with car running? I anxiously await your reply.

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Thursday, February 21st, 2008 AT 11:52 AM

RASMATAZ

MECHANIC
75,992 POSTS

Clean out the idle air control valve and test the throttle position sensor closed and open voltages.

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Thursday, February 21st, 2008 AT 1:49 PM

DLMILA0727

MEMBER
3 POSTS

Sorry to say it was not the idle air control valve or the throttle position sensor. Come to find out it was the coil. The coil had a small crack which was allowing it to ark and caused a small burn mark on the crack. Once the coil was replaced, the car started on the very first crank, purr's like a kitten and has the get up and go it hasn't had in a long time. My lady bug is back and more beautiful than before. I do want to thank you all for your help, it was just unfortunate that you didn't get the problem solved before I discovered it. Sorry. I will let all my friends know of this website for their future reference. Keep at it car guys. :P