Big time lag?!?!?

havoc13 · Post by **havoc13** » December 2nd, 2006, 5:10 pm

My car lags big time while i'm driving sometimes i will have my foot all the way down but it wont be accelerating fast any one have any opinions what it could be

Yoda · Post by **Yoda** » December 2nd, 2006, 5:21 pm

Try this. If the engine is idling normally. Will the car accellerate faster if you slowly increase the throttle than if you try to floor it? Chance are that the Cat is dead or has been poisoned with some sort of contamination blocking exhaust gas flow.

Nd4SpdSe · Post by **Nd4SpdSe** » December 10th, 2006, 11:45 am

cooper_9 · Post by **cooper_9** » December 15th, 2006, 2:55 pm

my car did this for a bit. I did i tune up (wires, plugs, cap, rotor) and its fine now

OROutdoors · Post by **OROutdoors** » December 18th, 2006, 8:28 pm

Lag can also be caused by a partially obstructed air intake; perhaps you should change the air filter. Another thing to check is to run a vaccuum test on the system to check for leaky vacuum hoses. If your car is old, this may be a high possibility.

FYI, Baxter Autoparts has Overkill silicone vacuum hose kits available for $28.00 US, good till the end of 2006. So, not only could you fix that lag, but add some color too.

nolig2278 · Post by **nolig2278** » December 29th, 2006, 11:31 pm

how do you run a vacuum test?

Bumpysbro · Post by **Bumpysbro** » December 30th, 2006, 2:54 pm

rent/but a vacuum gauge and hook it up to a vacuum port on your intake manifold and see the what the readings are and compare them to either the online manual or a repair manual. not too hard just need a tester

nolig2278 · Post by **nolig2278** » January 1st, 2007, 10:51 pm

a boost gauge would do this?

i thought maybe there was a tool to test with the car off as idle is erratic so that effects vacuum levels

OROutdoors · Post by **OROutdoors** » January 2nd, 2007, 2:08 pm

I'm not familiar with boost gauges, I suspect they are specific to forced induction (I run normally aspirated). A vaccuum test kit tests many parts of your car. The manner of the reading while operating the car (at rest) helps diagnose the problem. Some reulsts that you will want to observe, if present along with minimum and maximum readings: wild erratic needle, a calm erratic needle, is the needle steady but low, does the needle start high and then steadily fade. Further, take some reading as different throttle positions. Also, if the needle is wildly erratic, you can help find out at which cylinder the problem exists by using a timing light on the gauge) triggered by different spark plug wires (though there may be enough delay that the results would be incorrect).

Consult with a good manual; or use a Hayes or Chiltons.

I take it you have done some basics first, such as checking the sparkplugs for clues into your engine. Maybe you are running plugs that are too cold, while using the car as a daily driver -- and thus aren't burning off the carbon. This is fine if you are racing the car and routinely bring the car up to high RMP and create a lot of heat. If you are using the car for both racing and daily driving, I'd suggest getting two sets of plugs, and swapping in the racing plugs when you get to the track.

Do you have any other clues from what you've found?

I got my vaccuum gauge from JC Whitney a while back, it wasn't much. It is a good tool to keep around. Then again, I'm a firm believer in useing the right tool for the right job. JCW currently has one for $21.00 -- it looks like the one I have.

http://www.jcwhitney.com/autoparts/Prod ... cuum+gauge

OROutdoors · Post by **OROutdoors** » January 2nd, 2007, 2:28 pm

I'm a firm believer in running tests so that I don't spend a lot of money (and time) replacing parts that are good. In the case that Havoc13 was talking about, we don't have very much information, so I have some things to test and try:

1. vaccuum test (see prev msgs).

1.5. check for leaky vaccuum lines.

2. examine spark plugs for signs and the gap.

3. while plugs are out, test the compression.

4. use a jumper cable to temporarily improve grounding to the block.

5. check the throttle position sensor.

6. add fuel injector cleaner to a tank of gas to see if the injectors were clogged.

7. check air filter.

8. take the car to parts store such as Schucks and get them to dump the codes to their tester.

9. bad gas? try premium.

10. test spark plug wires and coil wire for resistance levels.

11. what color is the oil on the oil cap.

12. check fuel pressure - does fuel filter need to be replaced?

I hope this helps. Havoc13 -- if you get some more results from some test, please post them.