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Discussion Starter · #1 ·
I just got done putting a "new" engine in my 2001 ZX3. When I first started it up it revved a little but found idle and stayed there but when I tap the gas it would rev much higher than it should have then eventually go back down. the last time I started it, it up it revved up to around 3k rpm. After like 30 seconds it went back to normal idle but when I gave it a little gas it revved up to 4k and stayed there til I shut it off after like 10 seconds. I've done some searching about the problem and I read something about the power steering pressure switch being a possibility. The reason I suspect that is because when installing the pump I accidentally grabbed the switch and broke the connector off. The 2 prongs were still there so I just hoped I could still plug it in and be fine. But I dont know if it would make it rev that high. I know other problems could be the IAC and MAF. But my question is would that broken connector make the switch send the ECU wacky signals and make the engine rev like that? If not then what would.
 

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P/S pressure switch is for bumping up the throttle slightly to keep idle from dropping when excessive pressure is seen. A normal idle would mean this isn't the problem.

Check the throttle body first for smooth movement & return to closed when throttle pedal isn't pressed. Hose clamp too tight has been known to distort it enough to hang up.
 

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Discussion Starter · #3 ·
Ok ill have to check that. Its very possible that we tightened the clamp at TB too tight. Never thought about that being a problem. Cant get to my car for a couple days because its at a friends garage and I got work.
 

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Discussion Starter · #4 ·
Was able to stop by and check that clamp tonight. The throttle closes all the way and doesnt stick but it was doing the same thing when the clamp wasnt connected. I guess im just gonna throw parts at it. Take the TPS and IAC from my old engine and put them on or something. I dont know. This engine swap has been nothing but a nightmare and I thought it was almost over but I was wrong.
 

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Vince your Moderator
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Life is work....
 

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C2H5OH
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I guess im just gonna throw parts at it.

That will surely solve the problem.
[poke]



Engine basics 101,
More air = more RPM


Vacuum leak, sticking IAC ... and that's about it. Find/fix one of those 2 and you'll have the car running well.


ALSO, there is often a short learning period for new sensors and when the ECU looses power. During this time the car may not run as you think it should, it's running tests and relearning. To fully relearn the car must be driven.
 

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Discussion Starter · #7 ·
Checking over vacuum lines, I noticed the big one at the bottom of the manifold slid in and out easily. I looked at that hole on my old motor and noticed the round clip in there and said to myself "I guarantee thats not in the new motor." And sure enough, it wasn't. Put that in and it didnt rev like it was. It still has a rolling idle a bit but I feel like thats closer to what a learning ECU would act like. I could tap the gas and the RPMs would come back down now. I didnt have time to drive it yet but it was idling better. Check engine light came on before I found the missing clip so I have to check that yet.
 

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Sounds better, you may well have found the air leak causing the problem.

Next step after checkong the throttle itself as others mentioned.
 

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If different TB then the adjustment on it for aircrack could be off too as in too big, the IAC tries to correct lower for it but sometimes cannot. People just can't seem to leave those things alone thinking you can still adjust the idle speed like in the '70s.
 
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