Skip the auto shop - Our mechanics make house calls

Q: Car hesitation from stop to acceleration

asked by on

I put a new fuel pump and filter in my SUV after the old one went bad. It then started to give me a code 35 IAC. I replaced my IAC and idle was normal and not super high anymore. No more codes. I have put a new MAP sensor, throttle body sensor, spark plugs and wires (in correct firing order), vacuum lines, distributor cap, and rotor. However, it is still hesitating hard while accelerating and has miner surges like less than 50rpm and its noticeable while driving with small jerks like its trying to catch up. Any advice? Also, the spark plug gap says it should be .035 and I bought the iridium plugs that are pre gapped at .055 as advised by the auto shop.

My car has 193352 miles.
My car has an automatic transmission.

Hi, thanks for writing in. Prior to further diagnostics you should install the spark plugs that are referred to in the factory service manual and/or obtain the plugs from a GM dealer. Installing alternative aftermarket plugs with different gaps, materials, heat ranges, and what have is OK if you are set up as laboratory to do testing but if not you have to go with OEM on plugs. GM has already agonized over the correct plugs for the vehicle and has spent millions of dollars on testing. Benefit from their experience. If an auto parts store tells you to use a part that is materially different that which is clearly documented in the Factory Service manual, 10 times out of ten the store is wrong and the Manual is right.

Given the age of the vehicle, I would consider the fuel injectors (remove and send to a lab for cleaning, for example Mr. Injector), vacuum leaks, and ignition wiring issues as a cause of the hesitation. But before checking those, install the plugs recommended by GM for the vehicle because that is the only way to eliminate a misspecification there as even a part cause of the hesitation. On a 20 plus year old vehicle, I would have the injectors professionally cleaned and tested no matter what symptoms you are having, but particularly if it is hesitation.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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: No palus to injectors

Hi there. If you are not getting a power indicator from a probe to a specific fuel injector, there are usually two reasons. First, the wiring harness connected to it is damaged or two, the connection to the engine control...

Q: Car cranks over but won't start - 1994 Toyota Camry

Hi there. If the Check Engine light is illuminated, the first thing to do is to retrieve any problem codes from the engine management system (yes, it has on-board diagnostics). If there is no Check Engine light, the problem may...

Q: Check Engine Light is flashing. My truck only starts after 5 seconds - 2006 Dodge Ram 1500

Hi and thanks for contacting YourMechanic. When the Check Engine Light flashes, it means that there is an intermittent problem making the light flash on and off. When the light flashes, it is best to pull off the road and...

Related articles

P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.