I measured intake manifold vacuum yesterday and it was 15 at idle and 17 at 1000-1500rpm. Is that normal or is it too low? I can't find from Haynes nothing about that...

Oops, I forgot, the car is '87 Camaro with 2,8L MPFI.

[This message has been edited by max87Camaro (edited July 19, 2001).]

 

That's quite good!
My 3.4 with now 45,000 pulls 20 at idle and 15-17 in gear.
I still have not cleaned the IAC yet.
Permamently instll one all the time driving. REALLY HELPS GAS MILAGE.
You see when you are wasting it.

------------------
Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

I forgot measure vacuum in gear...

My problem is, that engine idles very low and roughly and stalls, if I take my foot from gas. If engine goes warmer, it stalls less, only at breaking and steering sometimes if I do not press gas pedal. It's very annoying and don't know, where is the problem. At cold engine is nightmare.

I have checked:
- IAC moves,
- I have reset ECM
- TPS is OK
- no error codes
- EGR is closed (pipe near the TB)
- timing is 10 (with unplugged connector) at idle (with plugged connector 16)
- MAT (IAT) ~2,5k ohm @ temperature ~20 degrees Celcius, so it's OK
- plugs and wires was some time ago OK. It seems, that fuel mixture was little rich???
- Vacuum = 15 at idle
- I look at the plate inside the MAF, it's seems to be OK. MAF voltage was ~2,5V. I can't measure freguency. I tried disconnect MAF and car runs worse, so MAF is maybe OK.
- o2 sensor voltage. At fully warm engine it gives ~0,25V (idle) and if rpms was over 2500-3000, the O2 gives ~0,75V. Is that OK? Can O2 sensor cause idle problems at cold engine (less at warm engine)?
- fuel flow is checked according to the Haynes.


Can you give some advice? I don't know any more, what may be problem...

[This message has been edited by max87Camaro (edited July 19, 2001).]

 

Well, an O2 sensor won't work until the engine and exhaust have heated up... the bit of radioactive (or whatever the hell's in there!) piece in the sensor won't work until it's hot. The computer decides to read the Oxy sensor when a few things happen-

1. Engine run time is for a certain amount, like a half minute or so
2. Coolant temp above 80 degrees
3. Engine senses a changing value from oxygen sensor

When the oxy sensor's dead cold, it's value won't change; it'll stay the same. When it warms up and starts to work, the voltage it returns will vary... the computer then checks #1 and #2 to see if it'll use the oxy sensor's output.

Have you checked ignition timing yet?


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

What is could be a a weak fuel pump or low fuel when ay turn.
Sometimes that happens to me, when I have low fuel and I turn, car shuts down.
Try a fuller tank and some Liquid Gumout, two bottles, preminum gas & a heavy foot to combat dirty fuel injector or dirt in the fuel.

------------------
Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

Max87Camaro
I have this same problem, my car is a nighmare when it is cold, I have to either let it warm up for 5 minutes or drop it in gear at atleast 1500 to get it moving, once I get going I am fine, but it won;t idle, and it would die randomly, I did the dreaded thing and adjusted my Throttle screw, so I don't stall in traffic.

My car Throws a Code 32 (but the EGR Valve is fine), and thats it, and I think mine might be in the vacuum lines somewheres but I don't know. I've had it running like this now for 3 months and still can't find the problem.

Anyway lets compare problems, maybe we can find somthing that is wrong with our cars...

 

Thanks for your responses!

I have checked timing, it is 10. When I measured voltage from O2 sensor, it was fully warm and gives that voltage, what have described above.

I does not depends of fuel level in tank. fuel flow was OK. Does engine (or fuel pump or smth) temperature affect to the fuel flow?

Maybe can someone measure vacuum at stock 2,8L MPFI and then we can compare it? I have code 32 too, but after connecting vacuum to the EGR, this code is gone.

Today morning I started the car, rpms was normal but after few second they going less until engine stalls. Idle is too low and it seems, that at very low idle some cylinders does'nt work (idle is very rough and engine stalls). I must hold rpms at 1000, then is all OK and after warming engine is problem not that big - engine stalls only sometimes at idle).

Maybe we can somehow solve this strange problem?

Btw., I try build scantool. If it's ready, then can we get more information about engine sensors.

 

Be prepared for ignition failure.
I'll bet your spark is weak and when it rains, you have same symptoms.
Your spark NEEDS TO BE WHITE LIGHTENING!

------------------
Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

Last time, when I checked spark plugs, they all were little black and dirty (I replaced all plugs before that), they all looks same, no extra dirty plugs. I think, that's because fuel mixture is too rich or smth. But why this problem is almost only at cold engine???

I'll check plugs again... soon, because I don't have garage.

How can I know/check, is my spark weak or not? I have'nt noticed, that at wet weather my car runs worse..

[This message has been edited by max87Camaro (edited July 20, 2001).]

 

Max87, where'd you hook the vacuum gauge into? I'll dig up my dad's old gauge, and hook it into the same spot you did, and get an idle reading. I've never checked vacuum before; should be interesting!

Do you know if your car was hot or warm or cold or etc? Just started after sitting a few hours? I'll try to duplicate your car...

[edit] Oh & hey, did you ever clean the IAC motor's tip and the IAC passageway inside the TB, or did you just check to see if the motor moved?

------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

[This message has been edited by TomP (edited July 20, 2001).]

 

I hooked vacuum gauge to the hose, that comes from intake manifold to the heating system or smth. There is also power brake vacuum hose, near that hose (smaller).

I cleaned all TB and IAC valve.

Yesterday, I checked plugs, they all were OK.

Yesterday I reset also ECM and after that my engine works great, no rough idle and much more power. After heating up and some driving it's starts again - idle problem and lack of power.

Tomorrow morning: no idle at all (very rough and low), normal power. After heating up: less power and idle is little higher, but engine stalls sometimes at stopping (breaking) the car in traffic.

I'm out of thoughts, no error codes, all seems to be alright...

 

So, if I'm looking at your engine, you tapped the vacuum line into the back of the upper plenum, on the passenger side? Did you use a t-connector to measure vacuum, or did you just plug the gauge right into the plenum port and left the other hose unhooked?

Any exhaust manifold leaks that might be appearing when the pipes heat up (and expand)? Did you check the timing with a cold or hot engine? The engine should be warm... don't burn yourself tho! Hm, heat, heat... what about the coolant temp sensor for the computer? How about "stupidly easy stuff", like the air & fuel filters?


------------------
-Tom P (Hot rodded 1986 Firebird 2.8l) from http://www.f-body.net/mailbag/3rd/3rd_mailbag.html message boards
---Think your car could be pic of the week? Visit http://www.f-body.net for details!

 

I just plug the gauge right into the plenum port and left the other hose unhooked. I understand, what do you mean, that hose may leak, what I left unhooked... I'll check that.

My driver-side exhaust collector leaks a little (between engine and collector), because one bolt (right-down) is broken. Is that problem?

I drive before timing check 20-30 min and then engine stays about 10-15 min and then I check timing. Is it OK with that or I must check timing with fully hot engine?

I changed all filter not very long time ago (problem was still here) and fuel flow was OK.

Coolant sensor shows about 0,7k ohm (30 min. after driving) and it changes little. I think, it was OK.