1995 bonnieville skips when running

[rtm1165]

i have a 1995 bonnie,,it was running good but about 3 months ago it would be running fine then all of a sudden it would just skip the the rpm would just drop ,,i kept driving is and it progressively got worse to the point where it woold only run for about a 100 ft at a time,,my mechanic put it on the computer and ran the codes it showed the heating sensor and the crank sensor bad. we check the fuel pressure it was good we changed all of the bad sensors and took the air filter out,,it ran fine for about 2 weeks then the problem started again,but one thing the computer wouldn't let the convential machines scan it it would not let them in to read it.it seemed to me to be a firing problem and the computer seem to either be getting a bad message or it is not any good at all... how hard a job is it to fine a computer and put it in ?or could there be another problem?.please help!!!!!

[richtazz]

Being a 95, your car has a hybrid computer system. It is still OBD-I, but doesn't have the standard 12-pin OBD-I connector. Most if not all 94-95 GM vehicles require a special scan tool to pull codes. The cheapo, DIY handheld scan tools cannot pull codes from these vehicles.

[rtm1165]

the saga continues,after replacing the cam sensor and the dtank sensor the car ran fiine for about 550 miles then stared acting up again,,,my mcdhanic said we need to replace the computer,,thats my next move,,i got 2 concerns when i put the ecm in by putting the old prom from the orginial computer into the new one does this reprogram the computer??? the other condern is i went to the dealer and told them of the problem stated thed there is a magnet on the timimg chain pully that the crank sensor reads and send the message to the computer,,she said thet if the magnet is moving around it is sending an inproper message to the sensor...has any one ever heard of such a thing????,,,or repaired one,???,,do the motor have top come out to replace this magnet??? PLEASE HELP!!!!!!!

[maxwedge]

Originally Posted by rtm1165

the saga continues,after replacing the cam sensor and the dtank sensor the car ran fiine for about 550 miles then stared acting up again,,,my mcdhanic said we need to replace the computer,,thats my next move,,i got 2 concerns when i put the ecm in by putting the old prom from the orginial computer into the new one does this reprogram the computer??? the other condern is i went to the dealer and told them of the problem stated thed there is a magnet on the timimg chain pully that the crank sensor reads and send the message to the computer,,she said thet if the magnet is moving around it is sending an inproper message to the sensor...has any one ever heard of such a thing????,,,or repaired one,???,,do the motor have top come out to replace this magnet??? PLEASE HELP!!!!!!!

You are bouncing all over the place here with the diagnosis of this problem, has anyone who knows what's what checked this out? The cam sensor magnet is on the cam gear in the front cover, the sensor must be removed and the engine cranked over slowly to see if the magnet is still in it's retainer on the cam gear, a mirror will needed to do this. Yes the prom will set up the program in the new pcm. What does acting up mean, any codes?

[Byron11234]

This may sound stupid, but about a year ago my 94 Bonn started doing the same thing, but just when it was going up a hill or under a pull. I put in new plugs and it fixed it for about two weeks and it started it again. Turned out to be a plug wire was touching the radiator and was almost burned in two. When I changed the plugs, I unknowingly turned the wire away from the bad spot and after a while it slowly turned backed and started shorting out again. I guess I'm just saying it's pretty easy to overlook the easy fixes.

[rtm1165]

maxwedge,,by acting up i mean the car started doing the same thing again,,rpm drop, not maintaining a idle, and not starting in mornings,,only after about 20 mins of trying,,, the codes were a bad cam sensor, crank sensor, heating sensor, right now i am going with a new ecm and see if it works,, i talked to another tech at the poinac dealer and he stated that the magnet was a safety measure to keep the car from cranking if it jumped time,,,,,,,,what is the fail rate of the obdm i computer????

[maxwedge]

Originally Posted by rtm1165

maxwedge,,by acting up i mean the car started doing the same thing again,,rpm drop, not maintaining a idle, and not starting in mornings,,only after about 20 mins of trying,,, the codes were a bad cam sensor, crank sensor, heating sensor, right now i am going with a new ecm and see if it works,, i talked to another tech at the poinac dealer and he stated that the magnet was a safety measure to keep the car from cranking if it jumped time,,,,,,,,what is the fail rate of the obdm i computer????

The cam sensor is there to time the injector firing process, it will still start if bad, but will require extended cranking, pcms of that time frame were usually reliable. Heating sensor meaning coolant temp sensor?, if scanned the cts should read engine temp cold to hot, does it. Also the egr was known to be troublesome on this engine sticking and getting carboned up and not seating, could also cause some of your symptoms. Bad engine grounds can skew sensor readings.

[rtm1165]

how many ground wires should i be looking for???? i know they have to be cleaned every so often,,,,,i found the neg side of the battery under the front of the car.

[sixsmiles]

I had this problem on a 95 Bonny and checked engine to h frame resistance it was 20 MOhms. Ran a new wire from the engine to the h frame and it took care of all missing dying problems.

[rtm1165]

engine to the h frame???? is there a diagram for this???or is it just the wire from the neg side of the battery.

[maxwedge]

Originally Posted by rtm1165

engine to the h frame???? is there a diagram for this???or is it just the wire from the neg side of the battery.

Check the resistance from the engine block to the negative terminal on the battery, this assumes a good ground from battery cable, there should very little resistance if you are concerned about the engine grounds, also watch the sensor grounds usually on the top of the engine somewhere, black wires with a ring connector.

[rtm1165]

well the new computer didnt solve the problem ,,my mechanic and i have given up,,i have taken the car to another shop where the top mechanic is an electronic guru,,,,the local gm dealers send there cars to him when they cant figure out things,,,,who ever designed this car put too much 'protection features' on it...damn!!

[rtm1165]

well after a day of searching the guru has not been able to tell me anything he dosent know,,,,i asked him what am i to do if he cant find out whats wrong???he told me he dosent know,,,but give him another day,,

i have one question will the motor have to come out to replace the magnet on the timing chain gear???and will that gear have to come out to replace the magnet??????

please help!!!!!!!!!!!!!!!!

or do i have the only cr in america that cannot be repaired?????

[rtm1165]

oh well i talked to the guru again today he said he worked things where the car will start every time today but is still is skipping and not maintaining an idle,,,he told me to give him another day,,,i guess he eliminated the potential magnet problem by running the car without the crank sensor in it,,,,the car ran but the injectors did not work in squence,,,and it did the same thing,,he put the sensor back in and the injectors fired in squence,,,but the car did the same thing,,he said that some times you cant find what is wrong with the car,,,,, is this true???? shall i begin looking for another car or what????

[richtazz]

did the "guru" check engine to frame resistance?