rough idle and timing doesn't advance

[Boss Hugg]

So we got Dad's 5.0 buttoned up yesterday in between a few other more important projects. We fired it up and it sounded great. However, we ran into problems.

We pulled the SPOUT and set the timing at 10 BTDC. Shut it off, replaced the SPOUT, fired it back up. Now, it idles at about 20 btdc, but retards on revving.

I came here, researched, found that we had constant 12v start condition on the TFI. We fixed that, but in the meantime, I had made some other changes and had left the connection off the MAF and we tried to crank the engine without it three times. It cranks and runs for about four seconds and dies.

Hooked the MAF back up, started the engine with 12V only on start, and now it idles rough, timing now sits at 20 without SPOUT and does not advance...

1. Could the TFI be damaged causing timing and spark problems like we're having?

2. Could the system be screwed up seriously because I left the MAF sensor unplugged and started it three times?

Hope to hear from some folks soon!

Could the constant 12V to the TFI have damaged the TFI?

 

[Boss Hugg]

most issues ironed out except..

timing doesn't advance on throttle up. Also, there are some codes such as MAF and TP voltages either high or low. We found female pin connectors at the ECU were spread wide open and probably not making contact. Fixed this and the motor idles normally now, but at 21* BTDC. (I think this is too much, but it seems to go with everyone else...)

Any ideas? Dad's pretty convinced his computer is fried. I'm not sure what to think.

 

[rustbucket]

EFI should be set at 10* before TDC without SPOUT connected. The computer controls the advance from that. What harness are you using? What's the idle speed?

 

[Boss Hugg]

Harness from 93 mustang. All circuits check out ok according to forfuelinjection site documents. Timing is set correctly. Idle speed around 650 rpm. (we dont have a tach so cant be exact. Also we tested the circuits on the tfi and it checks out fine.

 

[mattt]

My local Autozone has a test box for the tfi module. If yours does, have them check it. I would expect your timing to be jumping around at idle. I just started mine last week and it's jumpy with the spout connected. With it out, I now have a solid 10*. At first, I couldn't get mine to run at 10*, it was really surgey. However, now that it has run for a little while 15-20 minutes total, it's idling smoother. With the MAF disconnected, there is a huge difference in idle quality as I found out.

 

[Boss Hugg]

Matt you're exactly right. Timing is jumpy at idle. Did you put a new tfi on. Autozone here doesnt have a tester. Will a new one fix this problem? I've thought all along that its the tfi but following the test instructions it shows to be good.

 

[rustbucket]

In my experience, TFI's either work, or they don't. When they don't, the engine won't start. Check your TP sensor to see if that's out of range. Then check the MAF. There are some videos on YouTube that show you how. Another thing to check is if you have vacuum leaks. Those can cause all kinds of problems.

 

[mattt]

Matt you're exactly right. Timing is jumpy at idle. Did you put a new tfi on. Autozone here doesnt have a tester. Will a new one fix this problem? I've thought all along that its the tfi but following the test instructions it shows to be good.

Try a different Autozone. Not all stores have that test box. I had mine tested to track down a problem that ended up not being the TFI. My problem was the brand new out of the box stator in the distributor....it was dead right out of the box. Distributor rebuild shop replaced it n/c and I was good to go.

 

[ransil]

timing doesn't advance on throttle up. Also, there are some codes such as MAF and TP voltages either high or low. We found female pin connectors at the ECU were spread wide open and probably not making contact. Fixed this and the motor idles normally now, but at 21* BTDC. (I think this is too much, but it seems to go with everyone else...)

Any ideas? Dad's pretty convinced his computer is fried. I'm not sure what to think.

did you pull codes after fixing the pins??

 

[Viperwolf1]

What ECU and TFI module color?

 

[Boss Hugg]

A3m comp. Gray tfi. Everything but the maf and bp sensors came off the mustang. Codes involved egr, Maf voltage and tp voltage. Stator could be worn i guess... Dad says he's puttin this on the back burner so he can catch up on work. I'd like to see him get it right. He's been without his bronco for about 6 or seven years now.

 

[mattt]

If it runs, your stator is most likely good. The stator and tfi module are both typically good if your engine runs like Rustbucket said. Have you checked your timing light for proper function? What does it sound like if you blip the throttle? Does it sound correct or does it sound like it is in fact retarding?

 

[Boss Hugg]

I can't imagine the timing light being bad....

I've never heard an engine retard on acceleration.. Everything I've ever worked on had vacuum or mechanical advance on it...

When you open the throttle, it sounds pretty good to me. But I think dad expects a little more out of it..

I told him we should get some brakes hooked up on it, and get it out on the road to let the computer learn how to run again. If this doesn't fix it, we should keep working.

 

[ransil]

A3m comp. Gray tfi. Everything but the maf and bp sensors came off the mustang. Codes involved egr, Maf voltage and tp voltage. Stator could be worn i guess... Dad says he's puttin this on the back burner so he can catch up on work. I'd like to see him get it right. He's been without his bronco for about 6 or seven years now.

If you still have maf & TP codes fix them first..

 

[Boss Hugg]

I have not seen it with my own eyes but the ol' man says he's got the thing running right with no codes... How? Well i'll tell you.

He took the harness completely off and cleaned and checked every connection, opening up pins where necessary. Put back on, cleared codes, and run the engine for a while. Now, among other codes, we still have a TP code. So we ran the voltage test on the tp sensor finding that it put out between 2 and 2.5 volts from throttle closed to wide open. So i pulled one off his parts truck and put on and tested it. It showed almost 0 at closed position and i saw an increase in voltage with open throttle. I left him with it to set to the right voltage while i went home to help with a sick child. He called later and said he has no codes, No CEL, and the timing is advancing as it should.

So my thoughts are that the computer was reading 2 volts when throttle was closed which made it think the throttle was open, so it was already advancing timing OR it just didn't know what to do because other sensors weren't agreeing.

Now its time to get the brake bracket ordered and floorboards welded in so we can ride!