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Old 02-24-2012, 16:23   #1 (permalink)
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1994 Topaz - Starting / Stalling / Throttle Response

Hey guys,

Got a few problems going on here with the Topaz. I'll start from the beginning and try to keep it brief ...

- Tune up last year (Spark plugs and wires, cap and rotor, fuel filter): Starting problems began soon after... coincidence? Seems like the the car is not getting any gas when its first started. Have to leave the key in in the on position for 5-10 seconds before starting for the engine to catch.

- Few months later: Started to surge at idle when in drive, simple solution was to put it in park or neutral at stops

- Month later: Surging problem became worse and now have to rev to keep from stalling, even in neutral

- Couple months later: Driving around, car bogs down even with wide-open throttle. Can only get up to about 20 km/hr and gear changes are rough. This is intermittent at this point, sometimes the throttle doesn't respond - sometimes it does. Once it stalls out, it fires right back up and runs well for a couple minutes before happening again. Idle problem is now constant.

- Few weeks later: Car sits as we try to diagnose issues. Runs like shit as seen in the video links:
: Startup, rough idle and eventual stall
: Nasty noise from the rear-end, throttle is floored and no response

Here is what we have looked at so far…

-OBD tests (KOEO) with the Ford tester: No current codes, continuous codes were:
122 (TPS below min. voltage)
157 (MAF sensor)
172 (Oxygen sensor fault/lean)
186 (Fault Injector Pulse)
211 (Profile Ignition Fault)
332 (Insufficient EGR Flow)
556 (Fuel Pump Relay Fault)

-OBD test (KOER) – code 412 (unable to control RPMS) Guessing the idle is too rough for this test

-Checked for spark and plug condition: plenty of spark, plugs are relatively clean (bit of oil), gap is perfect

-Cleaned egr (pin was seized), throttle body (very gunky), and IAC in hopes of a smoother idle

-Checked TPS sensor with a multimeter: ~5V reference, ~ 1V at closed, ~5V fully open. Test checked out perfectly. We put a brand new one in to make sure and nothing seems to have changed.

So basically, my best guess is a fuel problem or maybe a vacuum leak? Maybe a bad fuel filter or air trapped in the system when it was changed? Fuel pressure regulator? Could be a million things... My head is spinning with the possibilities, so hopefully somebody can maybe point me in the right direction from previous experience.

Is there a way to test the MAF sensor, or just buy a new one and hope for the best?

Thanks a lot!
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Old 02-24-2012, 17:17   #2 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Unplug the MAF and see how it runs. If better, the MAF is dirty or needs replacement. What's the fuel pressure? Leaving the key on only feeds pressure from the pump for the first few seconds. Turning it on and off and on again wil run the pump every time.
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Old 02-24-2012, 17:32   #3 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Hey Bert,

The car runs worse with the MAF unplugged, pretty much stalls instantly.

Fuel pressure is the next thing on my list to check. I'm thinking that since all the problems started soon after the filter was replaced that this may be fuel related. I'm still looking around for a good guide to follow when testing this.

Oh, and now that you mention it. The key does need to be cycled on and off in order to start properly.
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Old 02-24-2012, 18:37   #4 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

The MAF is probably okay then. Check the Autozone website for a free online manual. You may get all you need there. Post what you can't and we may be able to help. What engine is it?
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Old 02-24-2012, 19:33   #5 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Right on, I'll check there.

Its a 1994 Topaz, 2.3L, Auto trans, only ~150,000 km. Ran great before these problems came up...

Thanks again for the help man, much appreciated! Lookin forward to the test.
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Old 03-01-2012, 08:14   #6 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Just checked the fuel pressure...

-Key on, engine off: ~ 25 psi
-Key on, engine on: ~40 psi on startup (for about 10 seconds it runs nicely). Starts to surge and idle roughly when the pressure drops to ~30 psi. Eventually stalls out at 20-25 psi.
-Bleed-off: When engine is turned off or stalled, the pressure bleed-off is minimal

I read that when idling if you pull the vacuum line on the regulator, the pressure should rise 5-10 psi. When I pulled the line, the pressure stayed constant.

Changed the fuel filter in case of clog -- runs the exact same.

These numbers look a bit low to me, what do you guys think? Also, from this, can we say whether its the pump or regulator?

Thanks alot!
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Old 03-01-2012, 17:20   #7 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

The fuel pressure should be 50-60 PSI KOEO and 45-60 PSI at idle. You could try pinching the return hose to see if it jumps up.
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Old 03-01-2012, 18:37   #8 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Yeah definitely not seeing that high of pressures. Highest so far is 40 psi immediately after startup followed by a drop in pressure as it begins to idle roughly. Even cycling the pump with the engine off ~25 seems to be the max.

Tried pinching the return line as it was idling like you suggested as well. No change at all in fuel pressure. This leads me to believe its the fuel pump rather than the regulator, any thoughts.

Thanks
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Old 03-01-2012, 19:21   #9 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

I thnk you're on to it. The first reading I posted is KOEO. I forgot to add that.
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Old 03-02-2012, 07:07   #10 (permalink)
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Re: 1994 Topaz - Starting / Stalling / Throttle Response

Right on, thanks bert.

I'm going to swap it out tonight, I'll post back up with the results.
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