idle stumble in gear

[thor]

hi everyone.
It's been a while since i've posted last. My last Talon (94) came together with the help of everyone here that replied to my last inquirys, and I thank you.

Long story short, my girlfriend was driving it in november and rear-ended someone, which totalled the car. I have since purchased a non turbo 93 Talon for 400 bucks that had a blown head gasket which I have just finished changing.

The problem I have is this: When putting car in any gear, (car is automatic) the car stalls or if it doesn't, it runs real rough at 600rpm. It does NOT idle surge though thankfully. The part I don't get is it idles fine at 750-800. I did have a bad idle stepper motor which i've since changed and cleaned so it's working properly per test specs in manual.

I have set the base timing and Biss adjustment per the manual, and the car idles great. I installed new autolite 63 plugs and wires, and i've checked all sensors per the manual and all are within spec. It does seem to be running rich though. I want to add I changed my biss o-ring too if that matters.

I noticed too that when putting any load on the engine (headlights, ac, blower) the idle drops and doesn't recover much. But like I said, I did have a bad idle stepper motor, so that can't be the cause of this.

could this possibly be a bad injector or fuel problem? I've checked for vacuum leaks with starting fluid spraying on everything and the idle is rock solid. I was concerned that this engine was pretty filthy as I pulled it apart there was a lot of crusty buildup on everything and the head was varnished pretty bad with old oil. the car only has 102k on it. If you are interested, i've documented the buildup of the 94 then the 93 here- http://www.phantomaudio.net/Talon.htm Please forgive my bad commentary.

I have another throttle body and fuel rail to try but i'd like to get this one going and sell the entire engine out of the other car as a whole. I hate not being able to fix something this small after changing a timing belt.

any help is appreciated. Thank you!

 

[thor]

just revisiting this because I haven't seen any replies.

could it be the o2 sensor being out of spec? it seems to test ok in the car, but I'm looking to see if anyone has experience with this.

 

[xioca]

Your idle dropping when you turn on your accesories could be a bad alternator. Check you battery with all the accesories off with a volt meter and it should be around 14.5v. Then have somebody turn on your lights and a/c and it should drop but quickly recover. If it doesn't you could have a bad regulator in the alternator.

Also are you saying your idle is still ruff or only when the accesories are on, I didn't quite understant. By the way I believe the 1g auto idle should be set at 800 rpm.

Another Idea on your idle issue, it could be a bad ground. Search and read up on a grounding kits, there were a couple of threads on it not to long ago and some stated that it helped with the idle drop when accesories are turned on, or there car idled better. Just an idea, good luck with the car.

 

[thor]

thanks for the information! to answer your question- no, the idle is rough under 800. I took it out and have been trying to drive it, and the power is there no problem, there aren't any dead spots in the powerband, and it shifts ok. It's just the damn idle that's getting me. Surprisingly it has lots of power for an automatic non turbo car.

The voltage checks out ok. The alternator is fairly new too.

to recap now that i've driven it a bit- When I put the car in drive, if it doesn't stall, it seems to run rough at 600 rpm or so. Once I get it going, it won't stall at a light, but it shakes the car at idle. The tach stays steady though. It acts like it's "loading up" with gas. The plugs look as new as when I put them in.

things i've done already-
new head gasket with resurfaced head (main problem when I got it)

swapped throttle bodys- made no difference
changed ignition module- no change
changed coil pack- no change
changed fuel injectors no change
changed fuel return regulator no change
new o2 sensor- no change
new idle air motor helped with startup only
changed air unit in airbox- no change
fresh autolite plugs and wires- no change
checked all grounds- all good (southern car too)
set the biss screw per manual idle at 800 in park
set base timing per manual at -5 btdc
sprayed starting fluid on areas looking for vac leaks- nothing.
checked temp sensor- within range

the only one I haven't changed is the cam sensor but I figured since the car is running, it's working. I also haven't changed the computer. I don't know if the 94 is compatible.

like I said before, I have a complete 94 here that was running perfectly before it crashed, and the engine is intact and undamaged. So I have a lot of spare parts i've been using

Please anyone I'm desperate! I'm banging my head against the wall about this. I've been working on cars for a long time and I have 2 saab turbos that i've got going, but this one is literally making me lose sleep. If there's anyone in the buffalo, NY area that is well versed in the 4g63, i'd be willing to pay your time to stop by and help out.

EDIT- I just got in it 5 minutes ago after it has sat for over 2 hours and it idled smooth at 700 in gear, but wen't back to the old way in less than 1 minute. ok now i'm baffled more!! I understand FAIV plays a hand here, but I didn't think it was that fast.

 

[thor]

ok, I'm here trying a few things and I stumbled across this concern-

I did a compression check and it's as follows- 70-80-80-90.. wouldn't the car not start or run if it was that low? keep reading though...

I wanted to point out something I noticed too that didn't register until now after those atrocious readings... When assembling and rotating the engine with the timing belt and head on, I noticed that the valves were slightly open (springs slightly compressed) even though the cam lobes were off of them. not all valves did this, and it seemed to be random. Is this a sign of bad lifters??? I cleaned them per spec but they were mighty dirty. could they be stuck at max height?
the car does not burn oil so I don't suspect rings and it runs at normal temp so it shouldn't be head gasket again. no water in oil and not burning water..

I just did a vacuum check and it's at 15hg at 800rpm. I read somewhere that it should be a min 18? When I bump up the rpm's to 3000 it's around 20hg

would this explain why it runs like ass at low rpm's but seems ok at highway speeds? has anyone experienced this before?

ugh! no human should have to suffer this much working on a car! and I loved the last talon which is why I got another one!

 

[thor]

I guess i'm not going to get any replies so i'll state what i've found at this point:

something is wrong with the head whether it be cams, springs, cracked head, valve damage.. etc. I changed the lifters and there is no change in the problem. It can't be rings because it doesn't burn any oil running or idling. The spark plugs are as clean as they come out of the box (changed to NGK)

i'm at a loss. for now i'm just going to drive it until something happens more severe. I just look retarded sitting at a light with a car that sounds like it's going to die any second