Engine Haunted, Need EFI Exorcist

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Jul 30, 2004 | 12:00 PM

jerrybro

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Engine Haunted, Need EFI Exorcist

88 302 stock EFI, automatic trans, 120K miles

After driving for a while, idle goes wild. May go real high, then suddenly drop to real real low, has stalled once or twice. During an episode, may buck while driving/accelerating.

Do I have a TPS gone awry? Is my MAP sensor wacky? Has my Idle Air Bypass developed an attitude? Wiring harness been eaten by mice?

It's in a car, not a truck, but this forum seemed to have some real knowledge flowing through the posts, and its like a truck to me.

Thanks
Jerry

ps We own 2 kinds of vehicles at my house, German ones and big Fords. Nothing else is allowed in the driveway.

Jul 30, 2004 | 12:49 PM

Kemicalburns

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Joined: Jul 2002

Posts: 14,285

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From: Bend,OR

take off your IAC , its on the side of throttle body. clean it up good and reinstall, might also take the TPS off and clean or replace there not to spendy. have the battery disconnected during all this so that when your done reconnect battery and go for a drive. this will get the ecu to relearn and make proper corrections.

good luck.

Jul 30, 2004 | 01:28 PM

ratstang

Cross-Country

Joined: Jan 2003

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If it's not the idle air bypass, it's likely the EGR position sensor (EPS). 18 bucks at autozone.

Jul 30, 2004 | 04:52 PM

EPNCSU2006

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Joined: Nov 2002

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From: Concord, NC

Try pulling the codes before you start flinging parts at it. Go to http://fordfuelinjection.com and click on "Getting Codes" if you don't know how.

Aug 3, 2004 | 10:55 AM

jerrybro

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Update.

I dumped the codes last night. 11,11,51,54,53,35,29,51,54,53,35,29. From what I've read, this is telling me that the KOEO test passed, and that the stored codes all point to higher than expected voltage readings on the PFE/EVP, ECT, TPS and ACT sensors. I'm gonna clear all the codes, take it for a drive and dump them again when it acts up, but it sure is looking like a rodent chewed harness to me.

Thoughts, suggestions, incantations and drink recipes as all welcome.

Aug 3, 2004 | 12:38 PM

Phinxter

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Joined: Feb 2004

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From: Saratoga, NY

If the KOEO passed its safe to assume the wiring is good. SStart with the lowest code and work your way up. Good idea on clearing them first though. If you have and know how to use a DMM you can test the sensors to see if they are working, instead of playing swaptronics.

Aug 3, 2004 | 03:54 PM

EPNCSU2006

Lead Driver

Joined: Nov 2002

Posts: 9,557

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From: Concord, NC

Check to see what the reference voltage is. If someone hooked it up to 12V then there will be a problem. The reference wire should be only 5V (key on).

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Aug 5, 2004 | 06:48 PM

Dannym

More Turbo

Joined: Jun 2004

Posts: 690

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From: Sweden

I had the exact same problem, '87 Ford E150 van with 302, and buttloads of code errors. Idle surged, got worse until it died at low speeds. It was due to massive vacuum leaks, the vac actuators cannot control the engine.

Problem is, Ford used these hard plastic vac lines. At least the way they were routed on the van, the ones on the passenger side caught enough heat that they became brittle and cracked apart in my hand. Also the vac reservoir "coffee can" partially rusted through.

Get a whole roll of ordinary rubber vac line and replace everything. The ones coming off the intake manifold seemed OK from one end to the other so I let them be. I epoxied the vac reservoir's rust spot closed. Engine got much better!

Aug 8, 2004 | 04:35 PM

#10

jerrybro

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Epilogue

Upon inpsection I found a mouse nest between the upper and lower manifolds (and you thought I was joking, didn't you) which I vacuumed out. Inspected all connectors and wiring. Found the hard vacuum line to the egr broken. Connected a rubber vac line from the break to the egr, used rtv to ensure the rubber to plastic connection sealed. Filled the tank and took it out, so far, so good.

Thanks all, now I'm gonna buy that Ford Fuel Injection book I saw at borders.

Cheers

Aug 8, 2004 | 05:45 PM

#11

Dannym

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From: Sweden

Quote:

Originally Posted by jerrybro

Connected a rubber vac line from the break to the egr, used rtv to ensure the rubber to plastic connection sealed.

Um, just replace the whole line! The nipples on both sides were designed to take std vac line. They had to add special rubber boots to the tiny hard plastic line to make them fit (which is really silly when you think about it). Why leave portions of the failed line in place and add a makeshift joint to boot? In fact, replace all the lines in that area, they're going to break on you sooner or later and will likely stop the vehicle. Be sure to check the reservoir too- it's a big "coffee can" behind the battery.