1992 4.6 liter engine surges under load

I have a 1992 Ford Crown Victoria 4.6 Litre with 200000 KMS. Idles perfectly, but under a load the engine surges (ex. Hold break and give it moderate to heavy gas) Also under moderate to heavy accelertation the engine will also surge until it picks up alot of speed. Then when it reaches desired speed, the engine will then buck. Have changed coils, wires, plugs, fuel filter, air filter, fuel pump, and even changed the computer but after that didn't work put the old one back in. And by the way it made no difference, going crazy triing to figure this out, please help.
Do you
have the same problem?
Tuesday, November 6th, 2007 AT 6:31 PM

1 Reply

Sounds like you have a deeal of mechanical ability and have replaced a bunch.

It sounds like you have a steady miss.
We need to find out which cylinder it is from.
You can load the engine like you described (with a helper) and cancle out cyclinders until you find the one.
You can cancel out one at at time in two ways. Either take the connector off of each fule injector one at a time at the load it misses the most.
Or take a wire off a spark plug one at time with it running.

Wear a thick glove if you do plug wire as it might try to bite spark you). Not harmful to most. But annoying as heck.
Hold the load at the point it misses/surges the most. And cancel one cylinder at at time.
It will miss much worse as you cancle one out. Then as you hook that one back up. It will get back to its normal miss.
When you cancle one out and it makes almost NO DIFFERENCE. You have found your culprit cylinder.

I have had 3 spark plugs recently that were good and all of a sudden went bad. And caused a deaed miss.2 of the 3 when engine up to temp only.
I actually swapped out a known good injector on one before I tried the plug.
I don't think plugs quality control is 100%.

After you find the missing one. You can swap that plug with another one and see if that cylinder now misses. If so you know the plug is bad.
I have had new plugs miss in less than a week. Remember how easiy is it to drop and damage them before you even buy them.

Also make SURE you have the plug wires on the correct plugs. Two crossed wires will give your smptoms exactly.
The 92 has coil packs up front and they are numbered but they can be used in two patterns.
You will see two numbers on each wire post.
I thik one is in white and one in brown.
Use the same set. Get a firing order diagram and make sure they are on correctly.
Remember fords cylinder numbering is strange for the GM and Dodge fans.
Passenger side is 1-2-3-4 from front to back and driver side is 5-6-7-8 front to back. IIRC
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Friday, November 16th, 2007 AT 5:32 PM

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