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Followup To
Question -
Hey, I have a 89 daytona (5 speed) with the tbi 2.5L (non-turbo) enigine. About 2 weeks ago it started surging at idle. It "putts" and almost stalls then it picks it self up to 1500 rmp for a sec and does it again. If I rev the engine it takes about 10-15 seconds for the rmps to drop back down. Also, it hezitates on acceleration and it was "puttin" out the exhaust wen I used the engine to slow down while driving. Note that there is no vaccume leaks and I installed a new map sensor. Plus the check engine light isn't on and it runs the same hot or cold. I had some suggestions that it might be the idle air control motor or the o2 sensor but I wanted to ask you before I go replacing or extensively testing stuff. What do you think?
Answer -
Hi Morgan,
I have the same engine in an '89 LeBaron Coupe, with automatic. It is a great engine. Even though the check engine light is not 'on' that doesn't mean there are no faults stored in the engine controller memory. Only some of the faults actually turn on the "check engine" light. The most useful thing to do would be to try to get the fault codes that may stored in the engine controller memory to readout. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves.
Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the 2.5L and we can look up the possibilities of what is wrong based upon what fault codes you show.
There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair. And that it what the troubleshooting manual is good for. It could be the O2 sensor or the TPS, but getting the stored codes may avoid guessing.
It is good that you checked for vacuum leaks, because that is one sort of trouble that doesn't have a code specific for it.
Roland
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Hey again Roland, I figured I should leave our last conversation in because you probible help so many people I wouldn't blame you for not remembering everyones problem. Anyways I checked the code and came up with these " 12 21 33 and 55 " Also, I forgot to mention I have tested the TPS and it's worked perfectly within specs. Well, what do ya think boss?
AnswerHi Morgan,
The 12 means the battery supply to the engine controller was disconnected sometime in the past 50-100 key cycles; not important unless you haven't disconnected the battery recently in which case it might mean you have a loose battery or ground connection. The 21 points to the O2 sensor signal not varying, either because of a wiring fault or the sensor not putting out a signal. That code is very consistent with your surging idle speed and poor running. So I suggest that you look at the disconnect plug in the O2 harness to make sure it is clean and tight and look at the wires to the sensor and to the PCM of that harness for any damage. In the absence of any noticeable wiring problems and if the sensor is getting up in the mileage (100K miles as a target) then replacing the O2 sensor would be a good bet. Be very careful to not damage the tip of the new sensor where the wires come out. I can also give you a couple of tests to check out the wiring harness for a fault if you have an ohmmeter.
33 is about a problem with the AC clutch relay circuit which doesn't play a role in the present issue.
The other possibilities for your bad idle are the egr valve not being fully closed at idle or a vacuum leak (which you believe is not present). On the egr, try revving the engine while observing the stem inside the cage to see if it goes up and down in response to the throttle being opened and closed (the stem has a groove for visibility). If it doesn't move or seems sluggish you might want to remove the valve and clean the passageway and lubricating the stem.
But try to deal with the O2 sensor for sure. To clear the code from the controller, just detach the battery for 5-10 minutes and then it should be erasesd (check that out, only a code 12 should be in the memory). Then drive it for a while and check for any new codes.
Roland
