94 Ls400 With Loss Of Power And Trouble Ideling

[stovetoppings]

I was driving home the other day and hit a couple moderate bumbs. All of a sudden I had a loss of power and trouble accelerating. It was fine if I accelerated very slowly but the engine still sounded like it wanted to cut out. Check engine light never came on the first day but I noticed that there was a strong sent of gas coming out of the tale pipes. The next day I started it up and the trac control and check engine light came on. Has anyone else had this problem?

[SRK]

So now you have a check engine light, and that means a code is stored, and that's what you need to find first. The TRAC system turns off when a code is tripped. Not really worth guessing at, but if I had to it's an O2 sensor. But don't be replacing any without further diagnosis.

[stovetoppings]

Code's 25 and 26 come on which is the air fuel ratio to lean/rich error. Strong sent of gas coming out of the exhaust pipes. Saw another post with same issue. They ended up replacing both O2 sensors and still had the same problem. Not saying this is my situation but something to consider.

[SRK]

There are four O2 sensors - two pre-cat, and two post-cat. I'd suspect it's one of the pre-cat ones, and the code will indicate the one. Otherwise you have a faulty ignition coil if both O2's are triggered. I don't know the codes off by heart - that's for you to figure out. Diagnose it.

[stovetoppings]

http://www.lexls.com/tutorials/intro/codereading.html

None of the O2 errors popped up. Only 25 and 26

[landar]

If it were me, I would be looking for a loose connection to the air flow sensor. Code 25 and 26 are lean and rich codes which are opposing mixtures. Since you hit some bumps, *maybe*, its as simple as a connector that jarred loose. Maybe...if you have lived a clean life thus far. Or perhaps the air flow sensor has failed.

With your strong scent of gas, it sure sounds like the ECU is making the mixture too rich as if it thinks the engine is still cold when it really is warm. You might also want to check the temp sensors.

If the engine is running really rough then it could also be a coil that is out or going out , as SRK suggests.

[curiousB]

I'd start by seeing if one of the coils and/or associated wiring is bad.

These cars are famous for problems with ignition coils so its a high probability place to start. The fact it runs rough sounds like you might be running on 4 cylinders and dumping a lot of unburnt fuel into a heated exhaust stream. The CATs are probably red hot after a drive... Take a look at them after driving at night. If they are glowing red this supports bad ignition theory.

Could be O2 sensors too but that wouldn't explain dramatically bad running engine. It would explain poor gas mileage and some loss of power but even in open loop mode engine should run reasonably. Also its not likely you'd get more than a single O2 sensor failure at a given time. The two secondary O2 sensors exist to see if the CAT is performing so they wont effect performance. The two O2 primaries are used to trim fuel mixture but as I said even if one is not working the car should run somewhat OK.

[shoob]

if it was a coil it wouldnt be a lean mix......less fire means more un burned fuel. check all the hose connections going to the afm. could be cracked or have a slight vacuum leak.

[VBdenny]

Had a problem with mine, same thing. Hit a bump and upon further inspection. I foun the vacuum line which I had plugged from the power steering pump, had come off.

[SRK]

if it was a coil it wouldnt be a lean mix......less fire means more un burned fuel. check all the hose connections going to the afm. could be cracked or have a slight vacuum leak.

The O2 sensor measures oxygen, not fuel. So a hard misfire sends more oxygen, not consumed in combustion, down the exhaust, and the O2 sensor interprets that as lean. Assuming that's what's happening.