Reoccurring miss and will not accelerate smoothly

JERRY LAITINEN

MEMBER
1990 MERCURY MARQUIS
5.0L
V8
2WD
AUTOMATIC
140,000 MILES

Engine will only idle for less than a couple of minutes before shutting off. I have narrowed it down to the spark ignition system shutting down. When driving it jerks and bucks violently when you try to accelerate. Driving or idling the ignition system has a dead miss on all cylinders. I have replaced the entire ignition system, checked the timing, replaced every sensor, fuel filter and the fuel pump. I’ve ran the codes and it shows 18 and 33. I’m down to inspecting the wiring harness by individual wire. What could it be?

3 Replies

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

This could be a vacuum or intake leak. I would check the entire vacuum system, paying special attention to the intake manifold. Here is a link below explaining how to do this below:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go through this guide and get back to us with how everything turns out.

Thanks,
Alex
2CarPros

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Sunday, November 17th, 2019 AT 6:50 PM

JERRY LAITINEN

MEMBER
5 POSTS

Thank you, however I failed to mention that I had already thoroughly checked the manifold and vacuum system for a leak. I do have an update from today though. I swapped the ignition coil on the brand new distributor and the car idles smoothly for about a minute before it shuts off. It starts and drives accelerating normally but shuts off every 4 to 5 minutes. I have to wait for about 2 minutes before it will start again. It will not accelerate at full throttle, it acts as if you have only pressed the accelerator down gently. The parts store has ordered me a completely new distributor to replace the one I bought from them last week. I should have another update tomorrow night.

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Monday, November 18th, 2019 AT 4:39 PM

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello again,

Okay, sounds good. In the mean time in the diagrams down below I have included the list for possible problems for your vehicle stalling from the vehicle manufacturer. Please go over this list and it might give you a different way to go if the ignition system fix doesn't do it. Please let us know how turn out.

Thanks,
Alex
2CarPros

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