I own a 91 bonneville LE, a wonderful reliable car, has 164,000
miles on it with all the routine maintainance done with no major problems till yesterday, I drove it all day and stoppe at a grocery store and when I got back in to start it, it turned over but wouldnt start, after several attempts it still wouldnt. I waited a few minutes and tried again and it started up fine, but when I got home it wouldnt start again. a family member tried a little later and it started several times and then refused to again. I took it to a local garage, thinking it was probably the fuel pump. they put on an engine analyzer and it showed no codes, but it did act up @ the garage, they checked the pump and the fuel pressure and it was fine, they put an ignition module on it, thinking that was it, Now the car misses like crazy, They said it could aso be the crank sensor or the ecm, please help, what would cause the missing and running rough after the ignition module was put in? I have a limited budget so I am desperate.

Do you have a SES light now? You really need a good scan. It also sounds like the ignition module is not the right one or not working right.

Are all mechanics incompetent ? You see this all the time. Sounds like they crosssed up the wires on the coil packs. There is tests for everything on that car. You need to go to a shop that has a competent mechanic that know how to test the sensors and make sure they are working right. Make sure they have had lots of experience with the Buick V6 engines, there has been enough cars on the road the last 15 years with that engine. It could be any one of many parts causing this problem. Some will just start replacing parts untill they finally get it. At your expence of course. Others know the process to eliminate certain possibilities and replace the right piece.

I asked them to check the coil pack, they said it was wired right, put a new crank sensor, it still missed, they then put a new ignition module( they just put one in on Friday) on it, it still missed, new plugs and wire, it still missed, then a new coil pack it still missed, then 2 fuel injector, still missing, they are talking harmonic balancer and I dont think it is that. This
thing sound fishy to me. This car ran fine before they worked on it, just had starting problems, please help I am desperate

Oh my you gotta be kidin me. It sounds like they are about to get rich and your car is headed for the junk yard. Get the car out of there and dont give them a penny. Sounds to me like you just reeled off nearly 600.00 in parts. Get your car and run, never look back.

Please reread my last post on this , I beleive I predicted your future to the T.

Its called "throwing parts at a car", they are not mechanics they are part throwers.

Does sound like they are just throwing parts at it, there is a, eight page troubleshooting tree in the factory service manual for "cranks but does not start". OTOH you seem to have an intermittant which can drive even a good mechanic nutz.

If it is starting but missing occasionally and giving no codes, I would let it warm up enough to go into closed loop and see if it smooths out. If not, I would pull the plug wires one by one. If one wire makes no difference then I'd be looking at the plug wire and plug. If two adjacent, the coil. If two or more non adjacent, the ESC (does your 91 have the triple square coilpack or the triple oval pack ?).

That said have seen a 3800 start and sorta idle with two plug wires swapped. So if more than one cyl is messed up I would check that the plug wires are on the right coilpack terminals. From the radiator & going toward the firewall, 1 and 4 are on the first coil, 2 and 5 on the second, 3 and 6 on the third.

Are 1 then 3 then 5 moving away from the coilpack on the radiator side of the engine and 2 then 4 then 6 on the firewall side. Is easy to get confused

Since you must R&R the plug wires to replace the ESC, I tend to be a bit suspicious - is power way down also ?

Are a lot of other possibilities including a bad injector (is a test light procedure to check for that) but would need to (not certain what the right word is but can tell a lot by the "feel" of the miss). Grok ?

A cam sensor will throw an immediate code 41. A bad crank sensor will not start at all. Starts *sometimes* is generally the Electronic Spark Controller (under the coilpack) and can really make a mechanic tear hair out (I try to keep a good spare around & if swapping cures the problem then...) - you have to catch it when not working.

That said, with no codes the first test should always involve an inductive spark light, a test light on an injector, and a pressure guage on the fuel rail. Takes a bit of setup but can generally tell immediately where to look next

Would suggest having someone who knows what they are doing just start from step one.

Where in WV are you ?

The ECM was badit was fixed no charge because of all the crap they put on it yesterday,
the owners dad it turns out is a dialysis patient and that is what I do for a living. He said fix the car no charge and he is going to throw in fixing my electic window and my loose steering wheel. It cost $567.00 dollars and a lot of parts that I didnt need and some that I did. but you live and learn valuable lessons all the time, I printed all the replys and gave them to the mechanic and that is how he narrowed it down.

Oh, the mechanic loves you now!

Yes but if he had tested everything protocal first it would not have cost nearly that much. You just paid for his education and I bet he still doesnt know how to test the ECM. He just decided to change that also right ?

Must admit that the ECM is generally the last thing I expect unless there is no ALDL stream. Sounds like you have quire a few spare parts now though - is never bad to have a spare ESC and coilpack or cam and crank sensors.

Good to hear it is now fixed.