In the last two days my newly purchased (2 weeks ago) 87 coupe 4+3 (my first Corvette) doesn't want to start without me giving it some gas. About a week ago, I noticed that after start up (usually starts with first try and no help from gas pedal) the engine RPMs swung between 400 and 1300 and settle at 800 or 900 after 30-60 seconds or so. If I depressed the gas, say to 1700 RPMs, after lifting my foot it went down to 1300 and stayed there. It no longer does this, but then again I am currently having to give it quite a bit of throttle. During the first week of ownership there was no problem (of course).

I checked the codes (intermitent Service Engine light) and got 13 (O2 sensor), 33 (MAF sensor ciruit), 36 (MAF burnoff ciruit) and 44 (exhaust is too lean). Then I cleared them, took the car for a 8 mile ride and let it set for 1 1/2 hours. I then had trouble starting it again and the SES light stayed on during the ride back. I checked and it now only shows a code 33.

Tomorrow I'm planning on checking if its just a dirty connector at the MAF sensor... but I doubt it somehow. It seems like something is failing. Any other things I should check / do? Could it be a problem with the throttle body?

I appreciate any help you can give. Thanks.



[Modified by Dutch W., 4:51 PM 10/5/2001]

 

First of all, I think your problem has to do with exceeding the redline...17k rpms and I would worry about the engine grenading, not an idle problem :D

The MAF connector is a place where a lot of bad connections are found. It is a 5 wire pigtail, so you have 5 chances of a bad connection. After checking this, I would do a tap test on the MAF. Take a normal screwdriver, hold the shaft, and tap the MAF with the handle of the screwdriver with the car running. Don't smack the ever-living heck out of it, just a firm tap. If you notice an idle change, your MAF is suspect. If this test passes, do a forum archive search on burnoff relays and MAF relays. There are 2 of em and a lot is archived about them (i.e. replace them in pairs).

As far os the O2 codes, this can be considered 'normal' when you have problems with your MAF circuit. Good luck, and try to keep it at 1700 rpm instead of 17000 from now on. -Matt-

 

Thanks for the response. You got me, Matt; in my previous post I did move the decimal place over one. I'll edit that, try your suggestions and report back.

 

My car passed Matt's MAF tap-test, so I replaced out both MAF relays and now (after the second time out) only an intermittent SES comes on (Code 44; exhaust lean). No more MAF codes 33 or 34 or O2 sensor code 13 (not yet anyway). :cheers:

Strangely(?), the idle problem has gotten better particularly in that after I give it gas, it doesn't stay at 1300 RPMs. It still has problems starting on the first start up (left overnight in garage, tried it while the tempature outside was a little over freezing. We've had a coldsnap since the problem began); second time was a charm. Would that be normal though?

I don't think its just my imagination since I heard it can happen, but MPG seems up by 3 or so after the relay change. By the way, I'm using 91 octane.

I had thought the bad MAF circuit relay was causing the O2 sensor trip (like Matt said), but after the switch-out I've got a Code 44 which could be something regarding the O2 sensor.

Any ideas what I should do to get rid of the cause of the code 44? Would a dirty or faulty O2 sensor be a more likely cause than a (vacuum) leak somewhere? Previous to the start-up problems, I had been leaning toward cleaning up the throttle body / IACs, but now I'm not sure. Maybe there is something simpler to do regarding a lean exhaust?

Thanks for any help you can give; I'm still awfully new to all of this, but learning.

 

You have mail! :flag

 

ttt

 

Dutch, you have it running any better yet?

 

Replace the O2 sensor. For about $25 it will probably improve your gas mileage too. For the high idle, you might want to check if the throttle body shaft has slop. This will cause your throttle to stick. For the hard start, clean the idle air control valve. Hope this cures most of the problems.

 

I removed the TB on my '87. Removed the TPS and IAC. Removed the top and bottom plates and soaked the TB in K9 parts cleaner that I purchased at Autozone. The varnish and carbon just lifted off and the thing looked new. I purchased a new TPS and IAC from my Chevy dealership. I set the voltage on the TPS to .054 volts. I just made sure the IAC measured correctly according the Haynes manual (from pintle top to base). I did not re-set the minimum idle air. My '87 idles consistently at 600 rpms. Smooth as silk. Just a thought. :yesnod:

Good luck,

Bob

 

Thanks to everyone for their responses.... I'll give your suggestions a try. :)