95 Gmc Not Running Well Misfire

unioncoug · August 26, 2009

My engine is running horrible last month I changed the filters plugs cap and rotor and wires. 2 weeks ago I pulled my horses up to a friends about 10 miles when i got back into town I pulled up to the light and I could barely keep it running. by the way its an auto I've done the test that the chiltons book tells me to on the ignition module and stuff like that it finally threw some codes it did the tps low voltage and the map sensor so i tested them. we changed the map sensor but it still runs like crap. the book says when the ignition is on it should test around .5 volts it is reading 3.945. when you start it at an idle it is at 3.945 then when you give it some gas it'll go down where it is supposed to be. Is it the ECM that is bad or am i missing something?

bill190 · August 26, 2009

Check the battery voltage with a multimeter.

The battery should read 12 something volts with just the ignition on (not started).

Then start it and it should then read 13/14 volts at the battery. This is the alternator kicking in and charging the battery.

Then measure the voltage inside the vehicle as well. Check from the center of the cigarette lighter to ground and you should get about the same voltage as at the battery. Check with just the ignition on and also with the vehicle running like above.

Also if you can give us the exact codes, that would help.

unioncoug · August 26, 2009

the codes that have come up are 22 32 33 34 42 and 44

bill190 · August 26, 2009

And did you check the battery voltage with a multimeter as described above?

unioncoug · August 26, 2009

not yet I had to go to work i will tonight when I have more time to mess with it

unioncoug · August 28, 2009

So I checked it tonight the voltage is just fine. Now the codes are gone but it still runs like crap. I was messin with it and if I held my foot on the gas petal around 2500 it would die unless I pumped it. I tried it at a higher rpm it would want to die but would just drop about 500 rpms then go back up then drop after about 2 seconds again. It won't stay running at an idle. I have know idea what to check now.

2COR517 · August 29, 2009

Was it running fine, then started running poorly suddenly? Check your fuel pressure, and you might need to do a compression test.

txab · August 29, 2009

+1 on the fuel pressure

unioncoug · August 29, 2009

It was running fine until I got back into town and hasn't ran well ever since I've changed the fuel filter and map sensor. the map sensor still reads at 3.9 when the ignition is on this is checking the a and c terminal I have 5 volts at a and b. The feed back terminal should read around .5 volts and go up from there when you give it gas. so its dumping gas in and changing the timing at an idle until you give it gas. But when I give it gas and hold it it wants to die unless I pump the pedal. or if it is above 3000 rpm it'll drop down about 500 rpm then go up then down and so forth. The spark is strong according to chiltons the ignition module test fine. If I unplug the vacuum then the codes appear. of 22 32 33 34 42 and 44. then they go away after I mess with it and plug the vacuum back in. it runs a bit better when the vacuum is unplugged from the map sensor but won't really stay idling. I'm at a loss of what to check and do.

bossier62guy · August 29, 2009

It was running fine until I got back into town and hasn't ran well ever since I've changed the fuel filter and map sensor. the map sensor still reads at 3.9 when the ignition is on this is checking the a and c terminal I have 5 volts at a and b. The feed back terminal should read around .5 volts and go up from there when you give it gas. so its dumping gas in and changing the timing at an idle until you give it gas. But when I give it gas and hold it it wants to die unless I pump the pedal. or if it is above 3000 rpm it'll drop down about 500 rpm then go up then down and so forth. The spark is strong according to chiltons the ignition module test fine. If I unplug the vacuum then the codes appear. of 22 32 33 34 42 and 44. then they go away after I mess with it and plug the vacuum back in. it runs a bit better when the vacuum is unplugged from the map sensor but won't really stay idling. I'm at a loss of what to check and do.

Do like the guys above you stated and check the fuel pressure.....

unioncoug · August 29, 2009

Is there a port some where for a tbi to check the fuel pressure or do i have to rig up a fitting

bossier62guy · August 29, 2009

Is there a port some where for a tbi to check the fuel pressure or do i have to rig up a fitting

http://www.actron.com/product_detail.php?pid=16175

2COR517 · August 29, 2009

The new MAP sensor could be bad. And Autozone should have that fuel pressure gauge too.l

pennzoil29 · August 30, 2009

Code 32 is the EGR valve, Have you checked it? That would also cause you're symptoms you are describing. Dirty fuel injectors, oxygen sensor. I would replace the tps. I have a friend, who has a '92 van and replaced everything but that, because his was doing exactly as you describe your's is doing. I told him to replace the tps and see what happens. I saw him the other day, and asked him how it was running. He told me like a top since he replaced the tps. jmo

unioncoug · September 3, 2009

Well i'll pull the o2's and check the egr valve. I also just checked my brothers lumina tps and it is reading the same as the truck at almost full throtle it drops volts then comes back almost in the same spot. wondering if its the fluke 87 that is making it test bad I am just checking the volts I haven't checked the using the it on a ohms is that a better way to check it?