EFI 302 erratic idle when cold

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Mar 15, 2002 | 02:09 PM

caguru

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EFI 302 erratic idle when cold

:-X23
Well, I have a little problem with my 88 ford f150. It has a EFI 302 / 5-speed. For the first few minutes when it is running the idle constantly goes from 1500 to 500 rpm. If you try to drive during this period it will stall out when you start slowing down.

So far the following have checked out fine:
battery/connections
alternator
That's all I have tested mainly because I first thought it was an electrical problem. Plus after driving GM for so long the Ford set up is new grounds for me.

Any suggestions? Thanx

Mar 15, 2002 | 07:16 PM

bgblktruk

Tuned

Joined: Mar 2001

Posts: 383

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From: California

EFI 302 erratic idle when cold

Hi, so my first impression is that it would be the idle air bypass valve, the throttle position sensor, or a build up in the throttle body. This seems to be common complaint, so you could do a search here and check others suggestions. The other thing I would suggest is try and pull the codes. If you have any other ideas or troubles post them and we'll see if we can do anything else. Good luck.

Mar 18, 2002 | 08:13 PM

pittmike

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Joined: Jan 2002

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From: Pittsburgh USA

EFI 302 erratic idle when cold

Hi,

had similar problem and took a warm Saturday to fix it:

- Remove the Throttle Body from the intake manifold
- Unbolt the Idle Air Bypass valve that is part of the throttle body
- Hold it so that the Throttle Position Sensor is looking skywards
- Clean the throttle body with throttle body cleaner and wipe it clean
- Same for the bypass valve
- Check if gaskets are ok, better replace them with new ones
- Bolt everything together

- Check the EGR Valve too, unbolt it and see if the valve body is burnt a lot, if it is better replace that thing

Hope this helps.

Mar 24, 2002 | 07:07 AM

86F150PAT

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Joined: Mar 2002

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EFI 302 erratic idle when cold

had a similar problem....not anymore...

RIPPED ALL THAT CRAP OUT AND BOUGHT A CARB!!

Mar 29, 2002 | 01:22 PM

caguru

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EFI 302 erratic idle when cold

Sorry about not responding. I finally got a chance to look into it. I was checking the TPS sensor as described in the tech articles section when I realized everything seemed a bit wet under the hood. I started it up and realized I had a fountain going! no joke. There was water shooting straight up into the hood (and distributor) from the intake.

I am guessing right now that water shooting up into the distibutor is causing some problems with firing. just a guess. I am just totally surprised to see a little hole in my manifold. Especially that when I got this truck it had a hole in the timing chain cover (that thing is a real bear to replace).

So now that I am putting a new intake on is a performance swap I can make that will work with the existing MFI 5.0? Is that what they call the FOrd version? I am used to GM MPI 350, 305.

Well time to get my hands dirty.

By the way, what is it with this truck and aluminum parts? They all seem to have holes in them.

Apr 3, 2002 | 09:24 PM

caguru

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EFI 302 erratic idle when cold

Well, finally got the new manifold in and still having problems. (at least its not leaking anymore.) It still idles funny. Here's what I've checked.
TPSensor is good.
Idle air bypass valve is good.
No codes in computer (just 11).
EGR is temporarily non functional. Someone put a BB in the vacuum hose!
Spark and ignition is good.
Injectors seem fine. Fuel pressure too.
That's all I have checked so far. Any ideas?
btw, it's no longer just a cold run problem. It also happens upon decelaration as i noticed to today. It just hates idling.

Apr 4, 2002 | 04:30 PM

Matt_W

Senior User

Joined: Jan 2002

Posts: 140

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From: CT USA

EFI 302 erratic idle when cold

the holes could have been caused if someone ran a bad coolant mix through it for a while. It will eat right away at the aluminum. You should watch that engine very carefully. other things might start to go.