HELP!!!!! my car dose not want to stay running. seems to idle fine till it warms up then quits. when car is idling i throttle slowly and reaches just under 4000rpm. the it starts choking. when i hit the gas fast, it chokes. when the engine is hot it will not start again till it cools. i have tested the fuel pressure and it reads 38.5 to 40psi when idling. from a handfull of mechanics that is fine. tested for spark (that is good), also replaced gas filter. so i am wondering if anybody else has had this particular issue and what they did to fix it. please indicate if it is from the manual or not. thanks.. i will be posting new areas as i encounter them. ok, i said forget it and decided to replace the fuel pump. and results were fantastic. ran it GREAT peppy and responsive, drove it for a bit everything went well. i then parked it and an hour later decided to go out and get something to eat.. well, it started and ran just like it did before i replaced the fuel pump. i dont get it... keep in mind that it ran and drove like a dream when i replaced the pump and now runs like before... any answers?

Try checking the resistance of your fuel injectors. The resistance should be around 14 to 16 ohms. If a injector shorts out it will take down the bank and the car will run rough. I had a simular problem with my 92 Camaro and had 2 bad injectors. When it got warm the injector would short out and the car would die. I replaced all the injectors and it runs great now.

but it ran great after new fuel pump, better than it ran when the car was running good before all issues.. could it be a faulty fuel pump that just decided to loose pressure? because i think any other problem would have still accured as soon as the new fuel pump was put in.. wouldnt it?

You didn't check the ignition system. Most ignition problems tend to get worse when the engine is hot and then the problem magically disappears when the engine cools off.

Also, check the fuel injectors, as stated above. Z28 has given you the wrong numbers. According to the FSM, anything above 11.8 ohms per injector is acceptable. I've never had an injector test above 13.5. And, believe me, I have tested a couple dozen of those things.

ok, thanks so far. will check all of the above over the weekend, i will post my status as soon as i can.. thanks again

ok, brought it to the garage and ran a code check.. it pulled up seven different codes.. one of them being the ESM.. others they wouldnt tell me but i realize one problem could set off a chain of codes.. should i start there with the ESM or should i find out what all the codes are first?

Post the codes...

feul pressure check is at 45psi witch is good. replaced fuel regulator and it seems to stay running like crap a bit longer than last time. tried a new maps unit and that didn't do anything. tested injectors, IAC, TPS and all seems great. what could the problem be? i am thinking its the computer but if its not then i can not return it and its back to what could be the problem? gas lines are not blocked. no vacuum leaks.. i am running out of answers


PS, they still wouldnt give me the codes... or they really forgot.. dont know.. anything else to check?

After you replaced all of these parts, did you reset the ECM by disconnecting the battery for a minute? Or did you just let it rip and hope for the best? You should disconnect the battery before doing anything else.

But, BEFORE you do that, take a paperclip (or other piece of wire) and stick it into the 12-pin connector facing the driver by the fuse panel, in the upper right hand corner's hole and the one next to it. Turn the key on and the SES light will blink the codes. Sounds like either the shop didn't pull the codes (most likely) or they just don't want to tell you because it seems that they are a huge secret for some reason. The codes SHOULD be written on the work order if the work was done right.

John, I have a 91 3.1L firebird too and I'm having the same problem too. It only started doing this when it got hot and my car is dead, will crank as long as I want it to but not start to save it's life. It started and ran two weeks ago but now nothing. I have replaced the TB sensor, IAC sensor, engine coolant sensor, IAT sensor, ignition module and checked my engine vacuum and all checked out fine on mine. I'm going to try both coils and test my injectors then move onto my ECU and fuel pump and see what happens. If I should figure anything out I'll let you know and if you figure anything out please do the same? When I flashed my codes I got code 13 and 33, it's likely you have a code 33 too. And check your o2 sensor too, that's something I haven't looked into on mine yet.

Could be Mass air flow sensor.

this one dose not have the mass air flow sensor. i have also replace the EGR valve and no difference. Checked PCV as well and that is clean. not much more to do but a stick of dynamite and a good alibi. i am giving up.. i have just enough money to buy a cheap car and tell the garage to keep it. Also every post through this whole forum that has the same issue i have basically has no final "its running" scenario. why is that?

1. You didn't pull the codes yourself. At least, you didn't post them.
2. You didn't test the ignition system or have the module tested at a parts house.
3. You didn't reset the ECM by disconnecting the battery after replacing all of the parts that were replaced.
4. What was the resistance of the fuel injectors? ANY injector testing at less than 11.8 ohms needs to be replaced. And, electrical testing the fuel injectors doesn't test their ability to flow fuel properly.
5. When you replaced the FPR, did you put a rubber-tipped blow gun's tip into the brass fitting in the middle of the FPR and blow any crud out of the return line? Anything blocking that line will increase the fuel pressure to such a high level that the engine will flood out more often than not.

I had a similar problem the car would run for a few minutes then die and I could not get it to start I tore my hair out on this one it turned out injectors 1, 4 and 6 were bad. Check the ohms on the injectors to see if they are in spec.

i do have periods that it dose stay running and purrs like a kitten.. could it still be injectors?

the garage would not give me the codes.. they just said the first code that failed was the MAP sensor.. and replaced it and still ran the same. ignition was tested.. no prob there.. i dont think the injectors was Ohm tested.. I am pretty sure FPR was cleaned thoroughly.. i will check all in the morning.. thanks

I would check them. What happend to me was I would start the car it would idle perfectly I could let it sit idleing for 30 minutes easy no issues then I would drive the car a few blocks it would start stumbling and bucking then die. After letting the car sit for a few minutes it would start up and the same process would happen I had to have my car towed a whopping block yes 1 block to my apartment. Also check youg ignition module as well.

OK just answer me this. dose bad fuel injectors sometimes work then not work? will that also throw several codes? some of them being MAPS, IAC and TPS?

Honestly doesn't sound like injectors to me, take Maverick's word that its most likely ignition because he is probably right and even before I read up to his post I was thinking the exact same thing.
It is probably your ignition coil or module...first off, always assume everything sensor wise works and that if you have issues its fuel or spark, easy way to rule them out:
1. When it is hot and won't start pull a spark plug and check to see if its sparking or not, if its not then its most a bad IC or ICM.
2. Starter fluid sprayed into the air intake system when it won't start.

Only problem with that is that if the car is like mine was with the later harness installed, the engine will be fine by the time he gets the HOT plug out (:nono: ). I'd get my hands on a plug tester and hook it up to the coil when the engine is messed up (lots quicker to remove the coil wire from the dizzy cap than it is to fight with the plug boot and the hot areas around a plug).

i am definately getting spark.. sparks about 3 quarter of inch.. seems to be strong spark.. also had tested a new coil and that didnt help..

When it's hot?

yes sparks good cold and hot. i didnt really get an answer on the injector question... if they are bad could they run good one second and not the next? rarely dose it purr like a kitten but occasionally it will then die after 5 - 10 min.. most times it runs crappy, chug a lugging, shaking back and forth like crazy, then die.. i will ohm test them once i get a chance. just trying to have a little hope..


got in a bike accendent 2 months ago and been out of work , on temp disability "not much money". skiddish to ride bike to work and the F-Bird is my only car.. i am due to go back to work in 2 days.. arrrrgh... lol. injectors isn't cheap if i buy them, if it needs them then i hope that will be the issue..

I reset the computer and sterted it... ran like crap and it just and only gave me code 33 "map sensor" i had put a new on it and reset the computer and it still tells me something is wrong with the map sensor... any ideas?

Unplug the MAP with the key off and then turn the key on. Hook a voltmeter between the GREEN wire and ground at the MAP sensor connector (unplugged, of course). There should be NO power on this wire, as it runs FROM the MAP TO the ECM as the MAP output signal. If there is power, the MAP wiring is shorted and that is causing a number of issues.

i will check... and what would the chances of being the green wire not being connected to computer and not shorting out.. where would i find that wire incase i have to replace it "from where? to the map sensor"

ALL 3 wires in the MAP sensor circuit only have 2 ends. One is at the ECM (engine control module), which provides both the 5VDC reference signal and ground, and the other is at the MAP sensor. The wires pass through the body in the pass-through just to the front of the passenger's side lower door hinge. If you need to replace or bypass the factory wire, you will need to find a way to run all 3 wires through the right hand shroud and into the ECM in a way that can be disconnected, because taking that pass-through apart is a royal PITA (been there, done that) and takes FOREVER AND A DAY, and if something ends up happening that requires the harness to be removed, the wiring will need to be disconnected.

The MAP sensor wires at the ECM are in A4, B6, and F15 (in the green connector). There is either a short in the wiring or the ECM is bad, as according to my factory service manual (FSM). The ECM is under the passenger's side of the dash, behind the panel by the feet. It will be in a white bracket. Just slide it out of the bracket and check the wires.

:edit: If you don't find a wiring short (DO NOT use a resistance test on this or you could damage the ECM), the next step is to replace the ECM. Get a cheap one from a junkyard out of just about any FWD 60* MFI car produced after 87 (except a W-body, which used a different ECM). Most of the cars will have the ECM mounted in behind the glove compartment. Swap the chip out of your existing ECM into the other one (will probably have a 60* spark offset and will run even worse than it does now due to the coil firing after TDC).

60* spark offset? AAARRRGGGHH!!! you mean i have to adjust the timing?
never did that before... but anyway, the computer has been replaced. and the "grey green and black wire leads straight to the CPU? because i will just put a disconnect near the CPU and run new wire to rule out bad wires.. a friend of mine also thinks it could be the distributor and the coil that is inside it.. what are your thoughts on that.. should i just replace wire to the maps and hope for the best? i hope i dont have to set timming because i never did that before and dont know how.. kind of a beginner at this but i am good at some electrical..

You can't adjust the timing with the FWD chip, which is why you need to keep your existing one. You pull the 2 screws off of the long cover on the top with a 1/4" nut driver or socket, release the tabs holding the MEMCAL in place, and pull it out. The installation into the "new" ECM is just as easy, and then you plug the box in and try it.

Anyways, the FWD timing offset has the same initial spark as the RWD, but then the ECM will trigger a coil firing event 60* AFTER the piston reaches top dead center, instead of BEFORE, so the engine would run like crap. Unless you want to throw a distributorless ignition system on your engine.

Right now, your ECM is throwing a code for a defective MAP. Let's work on what the ECM knows or thinks is wrong BEFORE we do anything crazy like rebuilding or buying a rebuilt distributor (which won't help the MAP problem). And even if you were to rebuild the distributor, there seems to have been a problem in the ignition harness on the 90-92 cars. Which I don't think pertains to you at the moment, as the car is throwing a MAP code. And also the fact that the TSB states to clear any codes first.

Codes were cleared. disconnected battery and installed new maps.. after half hour reconnected batt and still ran bad and threw code 33 "maps"

Did you check the harness when you replaced the MAP, or did you just throw the sensor on there and hope it would work?

Have you checked the injector resistance again? Check them when the motor is hot and your having the problem. When I had injector problems the car would run good for a while but when it heated up the injectors would short out and the motor would stumble and die.

the car runs like crap from cold start.. when i first turn the key it sounds to run properly for 3 seconds then starts running crappy for about a minute then die.. about 10 people say "in my neighborhood" that it sounds like distribitor probs so i pulled one off a running motor and give that a shot.. in my adventure i will Ohm test the injectors once again..

I hear you. I thougt the same thing and installed a new MSD distribitor and it still ran like crap. It would startup and then stumble and die.

Well, you're still leaving yourself with a problem. Your car currently posts a code 33. You can replace the distributor and all six injectors, but you'll still have the code 33. And the code 33 is a good bet on what's causing the problem.

The 92 TSB for the 90-92 models was for problems with shorting and other damage in the ignition wiring. The MAP sensor wiring is in part of the ignition harness, IIRC, which means it could be damaged and shorting. However, you won't know this without testing for power on the MAP sensor's green wire. If the MAP and ECM were replaced with good ones, that leaves a problem with the wiring. But, without testing the wiring...

See what I'm getting at here?

Well, i just put in a whole distributor assembly, new coil and plugs just to make sure they were new "what the heck" that didn't work but fired a little longer so, i finally gathered the nuggets to take the plenum apart and Ohm test the injectors and to my surprise injectors 2, 5, 6, tested around 6.? others tested at 12.8. so witched leads to me buying new ones.. one question? would that throw a map sensor code? i will post my outcome after i put the injectors in.. feel free to post till then.... Thanks to everyone so far.

The only thing that will throw a code for the MAP sensor is a problem in the MAP sensor circuit... The ECM will not throw a code for defective injectors, no matter OBDI or OBDII.

i have tested the maps wiring and it is in perfect condition. i was thinking that if there were bad injectors and the car is having a rough time trying to leveling off the fuel\air mix, i would believe it would throw off the maps only because it cant perform its job under that condition so, in return the computer will think that is isnt functioning properly cause the car dosnt run right or even close.. in the meentime i have to replace injectors anyway.

i would also like to ad that 3 plugs on left side of engine were massively "DRY BLACK" and the 3 on the right were "WET GOLD".. it will be a few days till i get the new injectors so stand by

You should plan on replacing all the injectors and not just the ones that tested bad. You don't want to have to do the job twice because you tried to save a few bucks and only replace the ones that tested bad.

i thought the same thing.. if they are the same age then how long would i have on the other ones? replace them all and be done with it

What is the vacuum the engine is pulling ?

This isn't a test reserved for old carb'd cars and IS important to troubleshooting.

This post is painful to read through...

Based on ? You didn't even know how to pull the codes from the ECM... what is 'perfect condition' ?

well i didnt mention that i have gotten a repair manual and i am learning to do more things with it.. i have been trouble shooting and the last thing was to test the injectors because i didnt want to spend that much unless i had to.. so the i decided to test the injectors because i had ran out of things to check and despite the maps code, the injectors need to be replaced any way.. i am waiting for them to arrive and go from there. after they come in and i will put them in, i know from that point on "it will not be the injectors and ignition system being that they are all new". the injectors also pulse correctly so it is not the computer "also new". so, sparks good, pulses good, new injectors, then it should be running.. starter fluid also keeps car running.. looks to be that the injectors are definitely the cause.. please just wait and i will post after the injectors are in..

I take it I'm not the only one banging my head on the wall...

I didn't really mean it quite as derogatory as it comes off in my post but, the help-ee seems to be disregarding helpful information.

You're going about this in a piss away money at parts and hope it works pov.

Maverick has probably posted some of the more direct problem solving advice towards your problem yet, you still seem to just disregard it and keep throwing irrelevant parts at the source of the problem.

If the car is throwing a MAP sensor code, injectors, fuel filter, you farted in the car.... NONE of the is relative until you fix the MAP problem that is causing the code.

Wiring and vacuum are critical to them running right.

A high signal (voltage) from the MAP (or low vacuum for simply testing with a gauge) can easily indicate a vacuum leak or EGR problem with the car (granted, wiring is 100%). As the manifold vacuum drops, the MAP interprets that as load (or acceleration) on the motor. It will start dumping gas into the motor assuming it's doing work causing a rich condition. If the EGR is the source of the low vacuum, not only is the MAP telling the ECM.. 'more fuel, were' doing work'. the EGR gas is dumping nonburnable 'air' into the motor.

I've expected to read this post at some point and see you saying 'well... f-it... I couldn't get it to run so I just replaced the motor...'

Sometimes complex problems, have simple solutions.

And the truth shall set you free! Or your car, as the point may be.

i wasn't ignoring the help, i didn't have the nerve to dig in it that far. at the very last point i didn't care so i proceeded by myself.. many people tells me that its one thing and that it couldn't at all be another, i was confused.. so i got a manual and learned a little more then did it myself and now i have a running car.. a few bad injectors "in my case" did throw a MAPS code.. everything is back in perfect running order.. i also had to put a new distributor assembly in any way because the old one had too much play at the rotor and while i was at it why not throw a new coil in it too..

i would like to say "thank you everybody".. you were a big help.. and that garage i took it to, never again!!! lol..

Hello all,

Having exact same issue with my 91 305 TA. The garage swore to me it was the Distributor but I think I convinced him when I had it towed back to him. Will have them check ignition and fuel injectors. Thank you.

A LITTLE LATE BUT ?

I have a 1990 V6 3.1
I had the problem with the fuel injectors two different times

the new injectors were the ones that failed again

I went with a disc type injector from Racetronix
low cost !!
so far they clean up well land lasted 3 years so far running well

much better than any other injectors i used

Thanks to excellent advice from an Injector cleaning specialist.