94 grand am gt sport V6 (sputtering)

:confused:I have a 94 grand am Gt sport V6 with 202,000 miles. I am haveing trouble with starting it, when i crank it, it spits and sputters and back fires. sometimes i have to crank it a couple times and them it will run fine. i have done the wires, sparkplugs, air filter, fuel filter, fuel pump, oil change. also when i put it in netural it kills the fuel pump relay.

Please help i am almost at my end with it and have no idea what to do with out spending a fortune on trial and error. i have heard it could be the TPS(throttle position sensor), the CPS (crank position sensor), the coil packs, the electronic spark control module. and many other electrical devices. i can not afford to spend alot of money so i am trying to narrow it down.:banghead:

Welcome to AF!!

The first thing to do is check the fuel pressure at the rail. There should be a fitting on the rail to attach the fuel pressure gauge. With the pump running you should get between 35 and 45 pounds. Anything less indicates a problem with the fuel pressure regulator. Another thing to do is to check compression on the engine. You will need to remove all plugs and do the check. You should be within a few pounds across the board. Also try unplugging the MAF sensor and see if it will start and run. If the engine starts and runs it may be bad and will need replace. Not cheap. Finally replace the fuel pump relay with a new one from a dealer or parts store. Don't use a cheap one make sure it is good quality. A cheap relay won't hold up.

All of these tests can be done for a few dollars as you can rent the compression tester and the fuel pressure tester from an autoparts store like Autozone.

Finally if you find everything in good shape you may want to remove the cat as they will fail and choke off the engine especially at start-up and cause poor performance when running.

Good luck and let us know what you find.

Also, check coil output with a spark tester....check for vac leaks...

Compression is good, there is no MAF sensor on this vehical. I have not been able to check the cat because its a welded exhaust system and dont have the money now to cut it apart. The mufflers are rusted off could that cause it to sputter sometimes?



what should the coil output be? Like i said it will run fine sometimes and other times it spits and sputters. Could a coil pack about to go bad cause intermediate spark? or would it be the spark control module? I have checked for vac leaks but am unable to see any, does a Haynes manual have a vac diagram in it?


On a seperate note my water pump is now leaking from around it not sure if it is the seal around the shaft or the pump itself any notes on how to make it easy to replace. (look hard) side motor mount in the way

Coil output can be intermittent if it is going bad. Also the ground to the coil can be an issue so check to make sure it is well grounded. As for the water pump you will be better off replacing it. I know it costs money but it is good insurance should it fail while driving.

As for the w/p, it is probably one of the easiest w/p's to replace, ever....

Relieve coolant pressure(just remove rad cap when cool).....Leave belt on to break the 4 bolts on the pulley....then remove belt, pulley bolts, 5 w/p bolts, w/p, scrape off gasket.....have pan underneath to catch coolant....

Checked the fuel pressure comes out to be about 38-40 key on engine not running, with engine running about 32-35. Unplug pressure regulator jumps to 40-42. Can a busted charcoal can (evap canaster) cause problems?

should i ground the plate that the coils are mounted to? or should i just add a couple more grounds from the battery to the motor\frame?

Add a ground wire to the plate the coils are mounted on. I would run the wire directly to the battery terminal. A bad evap canister will usually cause a check engine light to come on and should be replaced with a new one so that the system operates properly.

Don't understand the ground to the plate, if the four bolts are tight...but I guess anything is possible......

You say compression is good....that means the plugs had to be out....how did they look? Are the plugs old? how old are they? Are they A/C Delco?

Did you ever check coil output with a spark tester? how are the wires? If you pull a wire off a coil terminal(one at a time), are any of the terminals corroded?

Thanks for the help i will put some ground wires in when i get home.

i put in new plugs not to long ago and they are not fouled, the wires are new too, the terminals on the coil packs are clean and have dielectric grease on them, i have not checked the coil output, can i stick and ohm meter on the wire to check? what should the reading be? I have some spark because when the car is running i can pull the wires off (one at a time) and get a shock.

new plugs don't mean they are better than the old one.

Cheap plugs are really cheap... Weirdly, sparkplugs is one of the few part where you should really NOT use another brand or model...

Ex: on some engine, using bosh plugs result in a worse condition than worn out ac delco ones... And bosh are supposed to be "good", so imagine with the even cheaper one...

As for the ground wire... personally, I'ld just remove the bolts, remove the pack, give a quick sand paper pass on both the coil plate and where it mount as to remove any rust or corosion...
The wire is a dirty way to put a plaster on the problem.