Expert opinion

renegadeslave

Obsidian Salamander
Okay, I know it's hard to diagnose a car without experiencing the symptoms, but I was hoping some of you might be able to offer a few suggestions on the next course of action.

About a month an a half ago, my friend's 1990 Cavalier starting missing during acceleration. He was told it could possibly be the ignition coils (no distributor), and so he had new ones put on. This worked wonderfully for a few days, until it started happening again. And I noticed the brilliant "mechanics" who had worked on the car left the spark plug wires touching the exhaust manifold. He put new spark plug wires on. Worked great for about a week, then starting missing AGAIN. We moved the wires further away from the engine (they were getting incredibly hot and possibly crossfiring). Worked for a couple weeks, now it's acting up once again. He pulled the plugs and they weren't gapped correctly so he put new ones in. Still doesn't run right.

Is it possible the wires are messed up just from running with incorrectly gapped plugs? Or is there a larger problem we're overlooking?
I checked his computer, and it says everything's fine.

Any help would be very much appreciated!
 

willie

Well-Known Member
Look at the wires/coils while it is running in the dark. If that doesn't show any leakage then spray it with a very fine mist of water. It definitely sounds spark related.
 

dustin

UAIOE
Make sure the spark plug wire insulation isnt melted from touching the hot exhaust manifold too...

Does it miss during all RPM's under acceleration or only during a certain RPM range?

Does it miss regardless if you are easy on the gas pedal or smash it to the floor?
 
R

rhumbpunch

Guest
Not an expert, but maybe you ouught to investigate other areas besides, Plugs/wires.

Assume its Fuel Injected: check injectors to see if all operational, dirty/clogged

Egr valve
Throttle Posistion Sensor (TPS)
Oxegen Sensor
Maybe something as simple as a fuel filter

Good Luck and Cheers
 

Broke90GSX

New Member
Originally posted by rhumbpunch
Not an expert, but maybe you ouught to investigate other areas besides, Plugs/wires.

Assume its Fuel Injected: check injectors to see if all operational, dirty/clogged

Egr valve
Throttle Posistion Sensor (TPS)
Oxegen Sensor
Maybe something as simple as a fuel filter

Good Luck and Cheers
That is the route I would check. My fiance' had an old 90 Cavalier. Did the exact same problems you talked about. I picked up a can of BG44k (search) & it worked wonders. Also I'd check the TB to see how clean it is.

Rob
 

renegadeslave

Obsidian Salamander
Okay, let me see if I can answer all these questions....

It misses mostly during acceleration. If it sits too long, it tries to cut out.

It's carborated.... or TBI... I think. That part has been replaced, and he did put a new fuel filter on when he first had problems. How do we check the EGR valve, TPS, and oxygen sensor? I think I know where the EGR and oxygen sensor are. Can you tell me where I might find the TPS?

The air filter seems to be getting a gas smell-- Maybe the air/fuel mixture isn't right?

Thanks for all the suggestions, guys!!
 

renegadeslave

Obsidian Salamander
Okay, we replaced the Throttle Position Sensor and the oxygen sensor today. There's a slight improvement because of the new oxygen sensor, but it still jumps. I think the EGR valve is good because the service manual says that if the diaphragm can move freely then it's alright.

What does the BG44K stuff do and where can I get it?
 
R

rhumbpunch

Guest
Couple more thoughts on your problem.

In many cases the TPS, once installed has some alignment procedures you need to perform. If you have a Haynes, or Chiltons manual for the car ( which by the way, aren't always the best for pin-pointing problems) the procedure should be in there.

With the EGR, a good test is to manually depress the diaphram of the valve while at idle. It should cause the motor to stumble, or least a noticeable drop in RPM. This can be done by locating he holes on the back of the EGR, and insert your finger or some blunt object that will fit, and push in on it. If the car is up to normal temp, do not use your fingers, hot, hot, hot !

I know how frustrating it can be trying to troubleshoot an older vehicle, spend money on parts, replace, and that dosen't fix the problem.

One other good source of car repair/troubleshooting is the site:

www.alldata.com You have to pay ($14.95) for each vehicle you want info on, but the info is comprehensive.

Again Good Luck
 

Broke90GSX

New Member
Originally posted by renegadeslave
What does the BG44K stuff do and where can I get it?
BG44k is a fuel additive that clears out any junk or build up in your fuel system. I got mine at Southern Tire. Basically any location will carry it. There's one also in Charlotte Hall I believe now.

Rob
 

renegadeslave

Obsidian Salamander
Here's the latest update....

We replaced the TPS, Oxygen sensor, EGR valve, MAP sensor, fuel pump, and cleaned out the gas tank. All the cylinders are getting fire. The diagnostic check shows everything electrical is okay. The engine idles fine, but as soon as the accelerator is pressed, it starts jumping.

I'm thinking the timing is off, which can only mean the computer is bad since it is a distributor-less ignition.

Anything I might be missing?

Thanks again for the help... I'll look for the BG44K when I get tires put on my car in a few days.
 
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