86 camaro stalls

[ghettopenny]

Hey Im pretty new to this site and sounds like you guys offer a lot of help. I have an '86 camaro w/2.8 and it began stalling at idle last fall. I first cleaned the upper intake and replaced plugs, wires, cap, and rotor and there was no improvement. I then replaced MAF sensor and IAC valve. Still no improvement. I have checked as well as I can for vacum leaks, found none. I replaced the EGR valve and o2 sensor and still no improvement. It idles smooth with a little gas at 1100 rpm but when I let it drop to 750 it will stumble and then surge trying to recover and then stall eventually. It has a little valve chatter but otherwise runs very well. It has 170,000 on the original motor and trans and I'd like to bleed every mile I can out of it. Ive rebuilt a 2.8 in a trooper 5 or 6 years ago and I'm not really in a hurry to do it again. Im all ears.

Chris

[bszopi]

Does it stumble at any other RPM? How long since the fuel filter has been changed?

[ghettopenny]

It doesnt miss or stumble at all anywhere above idle and I just replaced the fuel filter in November.

[ghettopenny]

I have another concern also. I'm taching 3000 to 3500 rpms at highway speeds. My old celebrity eurosport didnt have a tach so I have no frame of reference. Is that high or normal?

[hatebur2001]

I have a 92 camaro 3.1 5-speed with a ton of miles. The idle is alittle bit ragged, but with a 5-speed I can just let it rev up. I also had a 92 Firebird 3.1 Auto with a similar problem, unstable idle. Never solved the problem as the wife told me to get rid of it.

Did you check the fuel pressure? If it is too low at idle, it will run lean and act like a vacuum leak.

Did you replace the injector o-rings? Also, the 2.8/3.1 fuel injectors are known to clog up and/or short out.

I found this link awhile back

http://www.lindertech.com/dirty_dzn.htm

1. Application: GM 2.8L, 3.1L vin”T” and 3.3L up to 1993.
Original Design Multec

Type: This is the original design Multec.
Symptom: It is prone to electrically shorting out. We have heard a couple of reasons, too much bronze mixed in with the coil windings and the winding wires are not shielded where they come off the bobbin to the terminals. Which ever the case may be, they short out.
Resistance: The minimum resistance of this injector is 12 ohms. We usually see then 12 – 13 ohms at room temperature.
Recommendation: Our fix is to replace them with a Bosch DRI (Deposit Resistant Injector).

The tach maybe off due to age. I have the "newer" dash design, so my tach is different. In my case, a factory cut resistor slowly increases in resistance until it open circuits. Then the tach pegs. The fix is to solder in the correct resistance to re-calibrate. Right now, my tach used to read 3500, but now reads 4000 rpm at 70 mph. When it finally open circuits, I will fix it.

Also search the archives at www.thirdgen.org, if you haven't already.

[gpse3400]

Yeah you could check the injectors as mentioned but since you also mentioned the valvetrain you might want to readjust the rockers.

[ghettopenny]

I really appreciate the info. I havent dug all the way down to the injectors yet looking for the problem, but being such an expensive part, I just wanted to rule out any other more simple possibilites. About the heads..... I know they need work. They sound like a can full of bbs when I kick it down to passing gear or when Im accelerating onto the interstate. I really need to do a couple of simple things before I dive into valve adjustment or injector o-rings. I need to do a compression test to make sure any of this work is worth it. If my compression is fair and is not improved by adding a little oil in the cylinder before the test, it is my understanding that the heads are the source or lowered compression. If that is the case would tightening the rockers improve my compression?

[gpse3400]

wel testing th injectors just for resistance is somthing that you'll want to do and verifify that they are the same resistance. should be about 12 ohms. but before you do the compression test you will want the get the valvetrain squares. who knows you might actually find something wrong up there. but yeah get the vavle train adjust so you will get a proper reading

[ghettopenny]

How do I get the injectors tested for resistance? Do I remove them and take them somewhere or can it be done in car? Im thinking in car is impractical since theyre buried.

[gpse3400]

well yeah you'll have to remove the upper intake manifold and then unplug the injectors and test them with a multimeter. No need to send them out. If they are not within range just replace them. Junkyard would be a place to go.