Rough Idle, terrible cold starts

TWRViper · Jun 1, 2005

My idle sucks and it takes 3-5 starts for the engine to even idle when cold. I usually have to give it some throttle to keep it from dying when the engine is cold.

I tried replacing my IAC to no avail. When I disconnect the IAC the engine RPMs surge. I thought it was supposed to die.

My EGR was removed with no CEL. Only code 33. I don't see any vacuum leaks. I've got 36lb injectors, 36psi fuel pressure, PRO M maf, vortech 12 psi sc, AC removed.

I checked my TPS signal it reads 0.6V when the key is on and the engine is off. I guess that is low. But I don't have a CEL. No engine running codes.

I can't turn the TPS on the two screws enough to get the .9v. Is the low TPS signal causing the rough idle. The only way I can get the .9V is by turning the idle up to 2000 RPMs.

Any ideas?

Thanks
Tom

stang22 · Jun 1, 2005

The TPS should be between .95 to 4.50 at WOT. You may have to use a dremmel or a drill bit hollow the holes in the TPS so you can adjust it. It doesn't take much to get the .30volts difference.

Tim

TWRViper · Jun 1, 2005

Would that explain why RPMs surge when I disconnect the IAC plug?

stang22 · Jun 1, 2005

Not necessarily. The IAC is responsible for keeping the idle in check (or it's supposed to). You disconnect it and there goes your idle.

Tim

IDLE AIR CONTROL VALVE (IAC)

Definition: An electrically-operated valve which allows air to bypass the throttle plate in a fuel injected engine to regulate engine idle speed.

jrichker · Jun 1, 2005

See the sticky "Help me create the Surging Idle Checklist" at the top of the forum. There will be some helpful information in the posts.

HISSIN50 · Jun 1, 2005

FWIW, code 33 is an EGR code (last time I checked).

I would go through and reset the idle from scratch - what you have is just not right and it has been played with enough that things might not be in concert.

Here is a link with some info on doing this:

http://www.muscularmustangs.com/iac.php

good luck.

RYC CUKR · Jun 1, 2005

I went through the idle setting procedure that HISSIN put up in the link and I still had issues. I couldn't figure out what it was. I had checked everything and couldn't see where I could have a vacuum leak but that is what I had. At the TB/EGR spacer, in my case delete plate.

I got a can of starting fluid and went around the engine and sprayed starting fluid on all of the gaskets and vacuum connection and that is how I found it. With the starting fluid the engine will idle itself up when you find the vacuum leak. Went through and tightened everything down and the car starts and runs 10x better.

TWRViper · Jun 2, 2005

Ok I replaced the IAC it seemed the old IAC was only working sometimes.. but I'm not sure on that. Some times my vacuum is 10 psi while some times it is 0-1 psi. Would that be due to the supercharger?

I also adjusted the throttle and the TPS to .95V. It seems it is idling better but it dies after a few seconds when starting cold (after 4-6 hours). It takes a few starts to allow it to idle.

Anyone with a supercharger have this problem?

TWRViper · Jun 3, 2005

I just realized that the AFPR's vacuum connecter was never hooked up (no vacuum leak, just didn't have a hose for it). Is that normal? Would that be a problem?

What does the vacuum connection do for the AFPR?

HISSIN50 · Jun 4, 2005

The vac connection helps regulate the fuel pressure. at idle (high vac) the FPR puts out less pressure than it does at WOT (little manifold vac). The puter assumes the regulator is connected to vac.

good luck.

TWRViper · Jun 4, 2005

Ok today I tried hooking the AFPR up to the vacuum. It seems that the fuel pressure decreases when I rev the engine. Would that be because of the supercharger?

TWRViper · Jun 4, 2005

In addition the guy before me capped off the EGR valve on the back of the throttle body. The reason this was done was probably because the aftermarked exhaust did not have the holes for the emmissions stuff.

The colored vacuum tree (red, green, white, and black) on the passenger side of the was left dangling but the electronic sensors and vacuum valves are still connected. No CEL, but code 33. To those of you who have successfully removed the EGR, do I need to connect any of those colored vacuum lines on the passanger side?

TWRViper · Jun 14, 2005

I readjusted my TPS to the minimum voltage (~.55V) to decrease the amount of fuel added during idle.

I got the idle air bypass kit from 50resto.com. Seems to be a little rough in the mornings but doesn't die. Much better!

Still looking for EGR vacuum lines to reconnect my EGR again...

stang22 · Jun 14, 2005

TWRViper said:
I readjusted my TPS to the minimum voltage (~.55V) to decrease the amount of fuel added during idle.

What was you reasoning for setting it so low?

Tim

TWRViper · Jun 14, 2005

It seemed it was running to rich before the o2 sensors were warm and not enough air was getting in. Even before I installed the idle air bypass kit it seemed to idle better.

stang22 · Jun 14, 2005

The seems a little low to me. I believe the object is to get to 4.5v (WOT) the quickest, therefore setting your base TPS setting to .99v or close to that.

Tim

dvs bullet · Jun 14, 2005

If you are running rich at an idle, then your prblems are somewhere other than the tps sensor, I still suspect a leak some where check you pcv and see if it is plugged, also you could have a leak on the inside of the engine. just some thoughts

HISSIN50 · Jun 14, 2005

The TPS reading is zeroed-out upon start up, if it can. If not, it should toss a code. The puter knows to expect a reading around one volt, and it will zero out that reading as a baseline.

I would be lookin elsewhere. If it starts running poorly till the O2's light off, that is only 30 seconds to 2 minutes of decent operation, which is not too great. If you wish for ideas on what else to check, a sig might help.

Good luck.

TWRViper · Jun 14, 2005

Ok I just made a sig. Let's see if it works...

The PCV is replaced by a breather filter. The inlet on the TB is capped.
The EGR has been capped, so that might be causing a little bit of a problem... if anyone has any of the vacuum lines for the emissions stuff let me know. I want to reinstall it.

I plan on recalibrating the TPS to .99V to see if it gets any better. I'll let you know.

I have no CELs.

Tom

jrichker · Jun 14, 2005

See http://www.veryuseful.com/mustang/tech/engine/ for vacuum & wiring diagams. Add this site to your favorites, since there is lots of good stuff on it.

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