'87 IROC cutting up again - Team Camaro Tech
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post #1 of 16 (permalink) Old Feb 22nd, 07, 01:51 PM Thread Starter
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'87 IROC cutting up again

Well, the old '87 has a new ailment and I'm wondering if any of you guys can help; On the way to work this morning the engine (TPI) cut off--dead in the road--but fired right back up and I made it in fine. Then, on the way home it did it again and the Check Engine light came on and stayed on. The car now tried to run, sputtered a couple of times, then smoothed out and ran fine all the way home. Has anyone had this experience with TPI, and what was the fix? We're having some nice, sunny days and I want to drive the car, but now I don't trust it. Any help would be greatly appeciated.


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post #2 of 16 (permalink) Old Feb 22nd, 07, 05:36 PM
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Re: '87 IROC cutting up again

flaky maf sensor...sucks cuz its kinda tough to test...see if you can get it scanned...the comp will retain codes as long as you dont disconnect the battery...(even if the light goes back off)

sometimes you`re the windshield and sometimes you`re the bug...
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post #3 of 16 (permalink) Old Feb 22nd, 07, 06:29 PM
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Re: '87 IROC cutting up again

I've known a bat throttle position sensor to cause a sudden stall, but it usually happens at the moment you let off the throttle to stop at a light or something. The bottom 1/3 of the TPS wiper will get worn to the point where it occationally cuts out when the accellerator pedal is an that range. And as you can imagine when this happens (or any other sensor flakes for that matter) it can really confuse the computer and make it over compensate causing a stall. You need to get the diagnostic codes and go from there. But beware that generation of engine control can throw all sorts of funky codes, so you kind of have to reason your way through to a root cause.

Dave
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post #4 of 16 (permalink) Old Feb 22nd, 07, 06:31 PM Thread Starter
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Re: '87 IROC cutting up again

Thanks a mil, Mike!


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post #5 of 16 (permalink) Old Feb 22nd, 07, 06:32 PM Thread Starter
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Re: '87 IROC cutting up again

and Dave


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post #6 of 16 (permalink) Old Mar 2nd, 07, 10:05 PM Thread Starter
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Re: '87 IROC cutting up again

It came up a Code 34--dang MAF sensor. Good news is I got a reman Delco sensor for $150, with the improved wire design. Working at a dealership has its advantages...chuckle. Thanks again, guys.


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post #7 of 16 (permalink) Old Mar 3rd, 07, 10:37 AM
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Re: '87 IROC cutting up again

Jim, there is a simple way to test the MAF sensor. Instead of spending that $150.00 right away, you should check your old one out first. Your ECM will sometimes throw out a trouble code and it doesn't necessarily mean that the sensor is bad.

Start the car and let it idle. Do the "tap test" on the MAF sensor. Gently tap the MAF sensor (not too hard) with the butt end of a screwdriver. The idle should not change on the engine. If it does, you can safely say that the sensor is bad.

67 RS Camaro 327/ 350 Holley 650cfm > Edelbrock Performer Intake > Pertronix Ignition > Accel Super Stock Coil and Wires > Hedman Hedders > Hotchkis Performance Springs > 15" Rallys all around


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Last edited by Camaro Dave; Mar 3rd, 07 at 07:07 PM.
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post #8 of 16 (permalink) Old Mar 3rd, 07, 03:27 PM
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Re: '87 IROC cutting up again

that test usually works well on a map sensor, but i`ve not used the tap test on a maf sensor...the maf senses airflow past the wire in the intake path by heating the wire and sensing the temp change of the wire as the air passes over it...usually whan a maf sensor goes bad, the wire breaks at a point in the sensor, and will not read to the computer...tapping on the sensor shouldnt make the idle change, as the temp of the sensor wire wont change with the tapping action...there is a ton of great info on tuned port injection on www.chevythunder.com...

sometimes you`re the windshield and sometimes you`re the bug...
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post #9 of 16 (permalink) Old Mar 3rd, 07, 07:05 PM
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Re: '87 IROC cutting up again

Quote:
Originally Posted by kustomwerker View Post
that test usually works well on a map sensor, but i`ve not used the tap test on a maf sensor...the maf senses airflow past the wire in the intake path by heating the wire and sensing the temp change of the wire as the air passes over it...usually whan a maf sensor goes bad, the wire breaks at a point in the sensor, and will not read to the computer...tapping on the sensor shouldnt make the idle change, as the temp of the sensor wire wont change with the tapping action...there is a ton of great info on tuned port injection on www.chevythunder.com...
There is a Tap test for the MAF sensor as well. I did a search on testing the MAF sensor and came up with this.

http://www.autoclassroom.com/engine_performance/

It's been awhile since I have done a MAF sensor check. I had it backwards though. If the engine idle changes.....the MAF sensor is bad.....not good. Just wanted to make that correction.

67 RS Camaro 327/ 350 Holley 650cfm > Edelbrock Performer Intake > Pertronix Ignition > Accel Super Stock Coil and Wires > Hedman Hedders > Hotchkis Performance Springs > 15" Rallys all around


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post #10 of 16 (permalink) Old Mar 3rd, 07, 10:03 PM
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Re: '87 IROC cutting up again

OH!!

I just remembered something about a 87 TPI with a MAF code (sensor voltage too high I believe it was). The problem was the connector to the MAF. Although we replaced a couple of MAFs before we found the real problem. After back-probing the connector to the MAF, we found the sensor line to be at +5V always. The voltage wouldn't fluctuate with air flow as it should have. In fact, at idle I think you're suppose to see something like 1.5 volts or there-abouts.

The problem turned out to be the connector pins were sprung open a bit after 20 years of heat and oxidation. A little rolled-up piece of sand paper removed the oxidation. A pick-probe closed up the connector sockets to make them snug again. A little dielectric grease prevented future problems with corrosion.

You may have very well fixed the problem, but I encourage you to give the connector a good look to make sure you aren't headed for the same issue. This same deamon can lurk in other connectors as well so consider the possibility if other gremlins show up.

Dave
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post #11 of 16 (permalink) Old Mar 3rd, 07, 11:21 PM
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Re: '87 IROC cutting up again

right on dave...like i said, i didnt know of the tap test...thats not to say that it doesnt work...dnult has a good point too...crappy connections can baffle the best techs!!!

sometimes you`re the windshield and sometimes you`re the bug...
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post #12 of 16 (permalink) Old Mar 6th, 07, 07:54 PM Thread Starter
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Re: '87 IROC cutting up again

Okay, guys...did the "tap test" and the idle didn't change, so I took the car out and really leaned on it--trying to get it to act up. I drove it hard for several miles, and the Check Engine light flickered just as I pulled into my driveway. So I put the new MAF sensor on. The car started up with the new sensor, ran about a minute and cut off. After the 3rd time cutting off, it ran like a watch with the new sensor. I drove it a few miles and everything was great, so I'm driving it to work tomorrow. I didn't disconnect the battery cable when I changed the sensors--could that have fooled the computer for a bit with the new sensor, then it read everything was okay? Also, where is the MAF sensor relay, and could it be the culprit if it does act up again? I really, really appreciate all the feedback I've gotten on this. Thanks again, guys.


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post #13 of 16 (permalink) Old Mar 7th, 07, 01:28 PM
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Re: '87 IROC cutting up again

I would disconnect the negative battery cable, for about a minute, to clear the ECM of any trouble codes that might be stored in the memory. Start the car and drive it around for a while. If the MAF sensor was the sole problem, then the check engine light should stay off. If not.....recheck the trouble code and search for the problem.

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post #14 of 16 (permalink) Old Mar 7th, 07, 06:26 PM Thread Starter
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Re: '87 IROC cutting up again

Guess what? It did it again--cut off on the way home, then started back up with the check engine light on and ran good all the way home. That's with the new MAF sensor on it. It came up Code 34 again. I haven't taken the battery cable off yet--the code is still in the ECM. Will that make it still act as if there is a problem if the code hasn't been cleared? All the pins in the connector were tight with no corrosion, no bare wires, and there is no vacuum leak at the MAF sensor. Thanks, guys.


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post #15 of 16 (permalink) Old Mar 10th, 07, 07:25 AM
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Re: '87 IROC cutting up again

you should clear codes whenever changing a suspect part...that way, you start off fresh with your code history...check for a faulty ground at the back of the head...(clean up the head, and star washer with sand paper)also by the waterneck there could be a pigtail for ground...(i work on so many different things, its tough to remember where things are)lol...i suppose if the relay was flaky, it too could cause the problem you`re having...i`d get the haynes manual for the location of the spacific relay...if you dont have one, repost, and i`ll dig out mine...

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