My son’s 1991 Honda Accord was running real rough. The temperature gauge did not budge from cold. I changed out the thermostat in an effort to help. When I tried to start it it started great then coughed and shuddered and then died. It keeps starting and then dying. I took off the IAC and flushed it with mass air flow cleaner. The screen over one of the ports was all crudded up. It cleaned up OK. However then I put it back it improved for a minute and then died again. I have checked for vacuum leaks but found none.
Thanks in advance for your help.
MikeM1954
It was running rough, then you replaced the thermostat, and now it won’t stay running at all?
It seems like the first goal should be to get it back running at least as well as it was before replacing the thermostat.
I think you must have inadvertently moved or disconnected something in the process and didn’t get it all back together correctly. The coolant level is ok, right? You checked that by looking in the radiator? Did you have to disconnect any electrical connectors to get access to the thermostat? Is the check engine light on? Have you used the car’s OBD I function to read any stored diagnostic trouble codes?
Edit: One other idea, maybe you got something wet while replacing the thermostat. Try opening the hood and let everything dry out maybe.
The problem might be with the ignition control module in the distributor.
http://www.rockauto.com/catalog/moreinfo.php?pk=951210&cc=1167106
These modules function in two modes. These are the start and run modes.
When starting the engine, the module is in the start mode. The module allows full battery voltage to the coil. This insures there’s hot enough spark to fire the engine when it’s cold and the fuel mixture is rich. Once the engine starts and ignition switch moves the run position the module drops the voltage to the coil. This is done because once the charging system comes on line the voltage is too high which would burn up the coil.
So the module may be working in the start mode, but failing in the run mode.
Tester
Tester will probably turn out to be right, but it’s also possible that the fuel pump is dying. You might want to check the fuel pressure. Fortunately, the engine doesn’t need to be running to do this… only the pump.
I let the car sit over night. When I tried to start it after work today it started up great (my son had left the lights on and the battery was dead). It started great and ran for about one minute. The RPMs were at about 1500. It ran like that for about one minute and then the RPMs fell off and the engine died again. It always starts up and will run for a few seconds. If you give it gas it just dies that much faster.
I did not use compressed air to blow out the IAC. Should I do that? Or is the IAC just a bad idea.
I disconnected the IAC and tried to start the car. It started and I was able to rev up the engine. It ran a lot better but it idled very low and had a tendency to stall. Can I assume that I have a bad IAC or can it be something else?
If depressing the accelerator causes the engine to die more quickly the IAC isn’t the cause. Mass air flow cleaner is for mass air flow sensors and won’t do much to clean the IAC, anyway. However, it might be the Mass Air Flow sensor that is failing but if you have any of the MAF cleaner left use it as it was designed and hope for a good result.
A good scanner which can access live data might get you to the bottom of the problem. If you can buy or borrow one first check for error codes and take care of them and then look at the air flow signal and throttle position signal when depressing the accelerator. Also watch the rpm signal. If increasing the throttle results in a decreasing airflow or a decreasing throttle angle or the rpm drops on the scanner before the engine rpms actually drop you can post back and someone here will likely help you track down the cause.
Absent any diagnostic trouble codes or real-time diagnostic data, given what you say OP – that it runs much better but simple idles w/a too low rpm with the IAC disconnected – I think replacing the IAC may be a good bet. What may be happening is the ECM is telling the IAC to open the throttle more, and then the ECM assumes that is happening and injects some more gas to compensate for the extra air. But the IAC isn’t actually opening more like it should, so the mixture gets too rich and the engine stalls. With the IAC disconnected the ECM probably knows that, and therefore doesn’t inject any extra gas, yielding the preferred mixture, but with a too-slow idle. How much does a replacement IAC cost?
I did the paper clip thing and got a # 14 trouble code. IAC … So I have ordered another IAC. I will keep you posted. Thanks for the help.