Rebuilt my engine, now it won't idle

[jasonbierschwale]

Hey guys,
I rebuilt my motor... it's got great power now! Not that I've abused it... I am completely failiar with rebuild break in procedures. You can just tell it's got all of it's old power back.
Now, the car won't idle. It runs great above 1500 RPM. Below 1500, it's kinda rough (like it's missing) and if you let it drop below 1000RPM, it dies. I have an old battery in the car, so I cannot crank too much before the battery dies. Once the car has run for 5 minutes or so, it doesn't want to start back up. If you crank it and throttle it at the same time, it farts and acts like it wants to start, but won't start unless it sits for awhile. Here are some things I have noticed in the 25 total minutes of running time since the rebuild:

It smells like it is running rich.
The car starts very easily when cold.
The car will not start after it has been running for 5 minutes - just cranks and farts.
it will not idle.
Runs great above 1500RPM.

I had a vacuum leak in the line to the pressure regulator from the front valve cover - it's been fixed. The check valve for the VRIS broke off - I blocked the vacuum lead from the intake, and blocked the vacuum line that the check valve attached to. As far as I know, there are no more vacuum leaks. I removed the negative battery cable and stepped on the brake for 30 seconds to reset the fuel map (I had the problem before this too). Any ideas you guys could throw out would be great. Thanks!

Jason B

[jasonbierschwale]

OK, took of the intake hose, and tested the MAF for resistance. Everything checked out (I think). There wasn't much difference from E2 to VS with the MAF open or closed, but apparently it makes a difference. Anyway, I plugged the MAF back in without replacing the air hose and held the MAF open - VOILA! The engine idles like a champ. So, my air hose is torn. Apparently it's leaking in other places as well. I guess I have to go the dealer.

[Steeb]

duct tape is a good temp fix for many things
it happens to everyone eventually, our cars are equipped with crappy intake piping from the factory

[jasonbierschwale]

OK,
turns out my air hose is sealed up just fine. This is the third or fourth time I have started the car since I rebuilt the motor. I called the Mazda Dealership and talked to a tech - he seems to think that I may have my cams out one tooth. He says he had one that would start and idle just fine but had no power. This one is exzactly the opposite. It will not start and idle (I have to put the pedal on the floor to start it, and then keep the revs above 1500), but it has plenty of power above 1500RPM. I thought maybe the timing was out, so I played with the distributor. Apparently the computer controls the timing, because I turned the distributor a full 90 degrees with very little effect. I thought I had a leak in my intake hose, but I plugged everything and still have the problem. I took the top of the air box off and held the MAF open about 1" and can start the car if I put the gas pedal on the floor. It will actually idle somewhat smoothly if the MAF is held open 1", but if you rev the motor (even just a little bit) then the car does not slow back down to an idle... it dies.

OK, I need some advice.

Has anyone had MAF go bad? Does it sound like mine is bad? I don't want to and cannot spend $230 for a new one, so I need to know for sure if that's it. I tested the resistance, and it looks fine.

Has anyone redone their timing belt and had the timing out by one tooth? Does it act like this? It's a pain to adjust the belt, so I'd like some input before I tear back into it. THanks!

Jason B

<small>[ December 26, 2003, 10:32 PM: Message edited by: Trinity23T ]</small>

[stang67fb]

ok im going to throw some ideas at you although im sure you already tried them. when i first did my swap i had about the same probs as you, in a way. first see if it runs without the VAF sensor plugged in, it should but very rich.

do you get any CEL's?

other than that pressing the pedal down to the floor is nuts to start it. you either have a bad fuel pump,clogged filter,intake manifold leak, or some other vaccum line down the line not working right.

other than that maybe just maybe your belt is off that one tooth but i think if it was the car would have some kind of backfire or prolly wouldnt even run.

hope this helps

[jasonbierschwale]

I did get some CEL's - 09 and 10 (Coolant Sensor and Intake Air Temp Sensor).

I did unhook the MAF and run the engine without it - same problems, only worse.

I have the Haynes manual, and it has the vacuum diagram in it. I checked all connections. The only thing that's not hooked up right is the vacuum line that hooks into the check valve under the intake (on top of the rear valve cover). I broke the check valve off during the rebuild, so I blocked one side off with RTV, and blocked the intake bung with a cap.

Clogged filter sounds promising, but that doesn't explain the fact that it starts fine when cold (still won't idle, though). One of the original things that I thought it could be was timing. I messed with the disty only to find that the ECU controls spark advance. But then I realized that there was a mechanical way to alter the timing - if the cams are not timed right. I remember putting the timing belt back on, and the instructions say to turn the crank one tooth CCW, and then turn it back after the belt is routed (to preload the 'pull' side of the belt before adding the tensioner. I DO NOT remember turning the crank back CW in order to load the belt. I bet the timing belt is one tooth off. Keep those suggestions coming, just in case. Thanks!

[jasonbierschwale]

No more thoughts on this?