Q: Car misfires after distributor, rotors, plugs, plug wires replacements. 1999 GMC Savana 3500

asked by on

I purchased my car from a public auction and then had my mechanic examine it. He told me that it was misfiring and should have a tune up. He changed the distributor cap, rotors, plugs, and plug wires. After those replacements, the car is still misfiring. Even though the check engine light is not on, he still hooked up the hand-held computer to the van but there was not any code. He had me drive the car for 30 minutes, he re-tested it, but no check engine light ever appeared. Now, he is speculating the it might be the fuel filter, fuel pump, intake manifold gasket, or something else. He also suggested that perhaps I should take my van to the muffler shop so that they can change the intake manifold gasket. He is a good mechanic and usually can spot the problem right off and fix it, but this one has him puzzled as to what the solution should be. I’m wondering if perhaps I should take the car to a dealership for a diagnostic. Before I spend more money on replacements, would you give me your assessment of the misfiring problem and how it can be fixed?

Although the person who serviced your vehicle the first time did not repair the issue, I think he might be correct about the fact that it could be an intake manifold gasket or a fuel pump issue.

You may want to consider having another mechanic look at the vehicle to get a second opinion on this. This inspection would include testing of the fuel pressure to determine whether or not it is within the specifications set by the manufacturer. If the fuel pressure is low, the fuel pump is very likely having an issue.

If the fuel pressure is within specification, I would recommend having a vacuum test performed on your vehicle to determine whether or not the vacuum level is within specification. If the vacuum level is low, the intake manifold gasket may be the issue. Another way to confirm the intake gasket issue would be spraying some brake cleaner around the area where the intake manifold connects to the engine. If the engine revs up when the brake cleaner is sprayed in a certain spot, the intake gasket is most likely the problem. Once the problem has been verified, the mechanic will be able to give you a list of parts that may be needed in order to resolve the misfiring issue.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Car misfires after distributor, rotors, plugs, plug wires replacements. 1999 GMC Savana 3500

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: Takes 3-7 tries before engine stays running

Hello. The symptoms you are experiencing, hard starting and an unstable idle speed, can be caused by a variety of issues. You mention that you replaced a few parts, namely ignition components, so they should be alright. The next things...

Q: When carrying a load, van rough idles and loses power - 2001 GMC Savana 3500

Hello. There may be an issue with your fuel injectors. If the fuel injectors are clogged, this will not usually throw a Check Engine Light code but will prevent the engine from running properly. If a fuel filter becomes overfilled...

Q: Oil leaking out and I keep replacing gaskets

The valve cover gasket is a rubber type seal that keeps oil from coming out of the engine. When the mechanic replaces the seal, they must clean the head surface thoroughly, wipe it down with brake cleaner, and dry the...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.