NO idle!

Terra

Member
:
Mazda SP20
Hi everyone,

I'm battling wity this car following dropping a new engine in..

When I first dropped the engine in the car was idling, albeit very very rough, fluctuating up and down and occasionally stalling. Also worth noting when I fired it up a ton of smoke came out the exhaust, like a really crappy lawnmower.

So I took it for a test drive, seemed that as the car got warm it just wouldn't idle, period.

Since then the car won't idle at all, warm or cold air con off and on.
After the first drive I pulled the Egr out, cleaned and scrubbed it. Made absolutely no difference.

Before the engine replacement (previous engine shot a piston through the block) the car ran and idled perfectly. I've only replaced the bare block - starter, alternator, intake manifold etc are all from the old engine.

Anyone have any ideas? I'm thinking coils are the next place to look, and perhaps iac however given these were fine before i might be chasing dead ends...

Cheers
T
 
Bad idle or no idle are very common problems on this car. It's a total crap shoot.

A couple options:

1. Vacuum leaks.

2. Exhaust leaks,

*The above 2 things had the largest impact on how my car ran; in particular the idle.

3. Many blame the EGR when it comes to idle issues, but I think that's just convenient because it seems to make sense. And you're using your old EGR which is known to be good.

4. There's nothing wrong whatsoever - well, except for the fact that the engine management system is utterly moronic. If you leave it alone for a couple months / thousand miles, I bet it will fix itself. Just don't disconnect the battery.

Smoke on startup after installing a new or used engine block is not alarming.
 
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Yeah I'm pretty sure the vacuum lines are pretty good, I did notice a couple of nights ago the brass tube that runs from the intake round the block had a loose / not fully right nut on the intake end, but I don't think that would cause this issue, and have since tightened.

Exhaust seems good at the engine block and the spring loaded connector near the firewall seems tight - this might be a little different to other people's configuration as its a stainless aftermarket extractor set.

Yeah I agree with you on the Egr, if all these things like Egr, iac and coils were sweet before there's little reason they would go bad now.

I'm going to try and take the car for a drive today and see if there is any noticeable improvement to the idle afterwards. I'm actually moving 800kms away in 5 days so if it just needs to be run that should be a good distance.
 
Keep in mind that whenever the battery is disconnected, the ECU needs to relearn how to idle the car.

My car runs like complete crap and nearly stalls after the battery is disconnected.

It takes about 100 miles to settle down.

The ECU needs a bunch of attempts to hand over idle control to the IAC at different temperatures and conditions.
 
Yep took it for a 30 min drive around my neighbourhood today and the idle has definitely come back to somewhat normal, I guess after more driving (once I sort out the road user / licenecing tax stuff) it should be running sweet!!

Is it driving like acceleration and deceleration that trains the computer or can I just leave it idling in my driveway? I left it today for about 20mins after my drive and it seemed that the idle was improving slowly.
 
Is it driving like acceleration and deceleration that trains the computer or can I just leave it idling in my driveway?...

I'm kinda guessing but I'm pretty sure the ECU needs to try to handover idle control to the IAC a bunch of times.

Idling in the driveway should help but it needs more practice... Keep hitting the gas so it can bring it back to idle.

Driving around the neighborhood is probably best... Lots of stop signs for the car to go to idle as it warms up.
 
Just thinking... It might help to turn your AC on and off while it's idling to give your car some practice at idling under load.
 
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