i have been working on this 1992 pontiac gran prix for some time replaced the 3.1 engine and car starts and runs fine until it warms up then it starts to idle very rich ,turn off ignition start back up goes through same senerio, i have changed every thing including computer car is in great shape just got this problem with it running right anyone can help im tired of working on it
Check the fuel injectors.
brand new as everything else is
Maybe test your crankshaft position sensor and wiring.
A failing crank position sensor may send inaccurate information to the fuel injectors, resulting in lean or rich fuel mixtures which can create excessive emissions, cause hesitation while accelerating and engine stalling when idling.
(A cold engine can tolerate a rich mixture. Like when you start an older lawnmower. You close the choke plate and the engine starts fine on the rich mixture. But as it warms up, if you don't open the choke plate, the engine dies on that same rich mixture.
Maybe do 2 tests. The 1st to check the voltage and 2nd to test CPS resistance.
1st test:
- Put multimeter in AC Volts mode.
- With Connector 2 disconnected or connected to the ignition control module.
- Connect the test leads of the multimeter to either of the two wires with suitable tools (the polarity of the multimeter's test leads don't matter on this test).
- Have an assistant crank the engine while you observe the multimeter (or oscilloscope).
- The multimeter's AC reading should fluctuate from 0.3 V AC to 1.0 V AC continuously as the engine is cranking (the maximum AC voltage attained will depend on the temperature of the engine, oil viscosity and battery charge condition).
2nd test:
- Put your multimeter in Ohms (Ω) mode.
- Disconnect connector 2 and:
- Connect the test leads of the multimeter to either of the two wires with suitable tools (the polarity of the multimeter's test leads don't matter on this test).
- These two wires are labeled with the letter A and letter C.
- The multimeter's Ohms reading should read 500 to 900 Ohms
If both tests are good, I'd start looking at the ignition control module
thanks ill give it another try as i already replace these parts
1st test 0.5 to 1.8 volts 2nd test 978 volts
Alright..I know the feeling what your going thru but don't get pist if I ask you things you know....but I don't know or confirm alright?
HOW do you know its running rich..is it the gas smell or is the exhaust black..engine stumbles...need your observation to be specific. Another is if its running rich you should be getting some codes...what are they ? Check engine lite should be on..is it? When you say ..warm - we mean operating temp correct...around 190 degrees ?
Right off the bat..I am thinking that your EVAP system is pulling gas fumes from the gas tank to the engine as one idea. and another is @yaser had mentioned...injector malfunction- too much fuel. But in that case their would be a missfire and a code for that.
Did you extract any codes yet ever ? This is OBD1 so using a paper clip will give the blink codes - Ever try it?
the temp is probaby 190 deg ,replaced injectors ,tps,ics,plenem gaskets ,egr, pvc gas tank with new pump black smoke comes from exhaust also presure regulator replaced kicked tires still runs rich
no codes no engine light no more hair on my head
also replaced plugs, gas filter air filter,havent tried the canister yet the only thing left but figured i would pick some brain power before i continue down this path
when i accerate motor from under hood it is very reponsive sound great but idle sucks
it might be caused by gunked up throttle body/intake/valves.
rebuilt throttle body
new gas also
Have you checked the fuel pressure regulator. Remove the regulator hose and see if it spits fuel while running. Sometimes you have to give it a minute or two, don't ask me why. If it spits fuel replace it.
regulator is new thats what ruined old engine got good preassure
Off the top of my head.....with no codes....its no help but first I would look into fuel fumes being sucked into the intake promoting a rich mixture....NOW usually that gives you a code that its too rich and this is the 2nd ECM. so I'm scratching my head....But we have to start being creative here. Another is can the ECM detect faults...have you tried this trick? Disconnect one O2 sensor and lets see if it brings up a fault or easier would be the MAP sensor....Also do you have a scanner and if so what make/model ?
i dont have a scanner, replaced map but have not gotten any codes with this other computen machine install as of yet this beast has turned into a nightmare .this whole problem started with the oil presure switch shorting an kick on the fuel pump filling the engine with gas, threw a rod them i changed motors replaced everything so i wouldnt have any problems this gm product says hold my beer
started it today wont idle tons of black smoke coming from tail pipe running so rich animals in forest came out with their eyes watering
I'm thinking ...the fuel leak got into the crankcase and washed out the piston rings...The problem remains in that you have a rich running idle because of low compression. Have you done a compression check on this motor ? If the compression on all cylinders is up then theirs cause for hope but if its down...this engine is also history now.
155 to 160 in all cylinders really good engine thats after engine warm up and not putting anything in cylinders like oil or wd40 this thing is posesed
Okay those compression numbers are great so we will rule out the engine being defective, However what bother me is that you do not get any codes when you disconnect sensors.... Without a scanner to verify that it does get live DATA we could do the other way I think the scanner cannot get any data at all...I think the LAST part you need to purchase is a good scanner I am afraid to get to the bottom of this problem.... and solve it once and for all.
cant afford a new scanner but have a friend who has a shop that has one last resort tried to find problem myself but guess ill bite the bullet ill let you know what turns up does arson sound like a good cure lol
Thats good you a friend you can access for this problem.. Hes going to find out real quick if his scanner powers up can access data and displays data. But if the scanner powers up..but cannot access data...we have a problem there for sure. You mentioned you replaced the ECM..do you still have it ? If so bring it with you. By the way when you replaced the ECM did you just slam dunk it in hook it uo and fires it up OR did you transfer the MEMCAL chip from old to the new ECM?